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Forward Osmosis Promoted in-situ Formation of Struvite with Simultaneous Water Recovery from Digested Swine Wastewater

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... Their finding demonstrated that the aquaporin FO membrane was effective to remove the Sb (>99.7% rejection) as well as other inorganic and organic contaminants (90%) during the treatment of real dyeing wastewater. In the context of resource recovery, several works regarding FO application to promote valuable resource recovery from saline wastewater was reported in the literature [43,75,76]. For instance, Wu et al. [75] studied the effect of MgCl 2 as the DS to obtain the struvite from agricultural wastewater (i.e., livestock wastewater) using the FO system. ...
... In the context of resource recovery, several works regarding FO application to promote valuable resource recovery from saline wastewater was reported in the literature [43,75,76]. For instance, Wu et al. [75] studied the effect of MgCl 2 as the DS to obtain the struvite from agricultural wastewater (i.e., livestock wastewater) using the FO system. The FO was proposed as an alternative treatment in their work since conventional livestock wastewater treatment such as anaerobic digestion can only reduce the organic concentration without realizing the nutrient recovery. ...
... Water flushing is one of the physical cleaning methods frequently used in membrane operation. For example, Wu et al. [75] flushed the FO membrane with deionized water (200 mL/min) to control the fouling during the struvite recovery process from pre-treated agricultural wastewater. It was claimed that no apparent fouling formation was observed in their study, and more than 50% water recovery was achieved. ...
Article
The saline wastewater from various sources including agriculture and industrial activities, appears to have high salt concentration, organic content and other pollutants which can harm the environment. Thus, saline waste-water treatment has become one of the major concerns in many countries. Membrane technology offers great potential in saline wastewater treatment due to its high permeate quality, flexibility, and desalination capability. This paper highlights the current development in various types of membrane processes such as pressure driven-based membranes, forward osmosis, membrane distillation, electrodialysis and membrane bioreactor, either as a stand-alone or integrated process for saline wastewater treatment. The membranes performance in terms of water reclamation as well as resource recovery is discussed. Besides, the membrane fouling issue is highlighted, and the efficiency of various fouling mitigation strategies when dealing with real/challenging saline wastewater are reviewed. Finally, the future challenges and outlook in the context of membrane application for saline wastewater treatment are discussed.
... The main ways in which FO is superior to conventional pressure-driven membrane processes are that (i) it generates high water flux at low or no hydraulic pressure, (ii) it has a high level of rejection of a wide range of contaminants, and (iii) it may have a lower membranefouling propensity than pressurized membrane processes (Lee et al., 2010). Nowadays, FO has been tested to recover nutrients from various types of waste streams, including municipal wastewater (Xue et al., 2015), activated sludge or sludge centrate (Hau et al., 2014;Ansari et al., 2016), livestock wastewater (Wu et al., 2018), and source-separated urine (Zhang et al., 2014;Volpin et al., 2018). However, nutrient concentration and recovery performance by FO process is largely contingent on feed and draw solution chemistry, membrane properties, and the feed concentration rate. ...
... In general, moderate N (>40%) and high P (>80%) retention was reported for most wastewater tested. The formation and precipitation of struvite with comparative quality of commercial products has been observed for several nutrient-rich wastewaters, such as swine wastewater (Wu et al., 2018) and human urine (Volpin et al., 2018). However, a knowledge gap remains regarding how FO performs for nutrient enrichment and recovery from domestic black water. ...
... Intensive P and Mg was detected on both used filters. It can be seen in Fig. 3 (A) that a clear overlap of Mg (13.6 wt%) and P (18.5 wt%) distribution together with a 1:1 molar ratio was obtained, similar to that of commercial struvite reported in previous studies (Volpin et al., 2018;Wu et al., 2018). In the case of HSBW, the peak of P was partly hindered by Au, resulting in an inaccurate estimation of the weight percentage of recovered P. Nevertheless, the element maps showed clear matching between Mg and P distribution, with a well-regulated crystal structure observed in the SEM image. ...
Article
A dual “waste-to-resource” innovation in nutrient enrichment and recovery from domestic black water using a sea salt bittern (SSB)-driven forward osmosis (FO) process is proposed and demonstrated. The performance of SSB as a “waste-to-resource” draw solution for FO was first evaluated. A synthetic SSB-driven FO provided a water flux of 25.67±3.36 L/m2 · h, which was 1.5–1.7 times compared with synthetic seawater, 1 M NaCl, and 1 M MgCl2. Slightly compromised performance regarding reverse solute selectivity was observed. In compensation, the enhanced reverse diffusion of Mg2+ suggested superior potential in terms of recovering nutrients in the form of struvite precipitation. The nutrient enrichment was performed using both the pre-filtered influent and effluent of a domestic septic tank. Over 80% of phosphate-P recovery was achieved from both low- and high-strength black water at a feed volume reduction up to 80%–90%. With an elevated feed pH (∼9), approximately 60%–85% enriched phosphate-P was able to be recovered in the form of precipitated stuvite. Whereas the enrichment performance of total Kjeldahl nitrogen (TKN) largely differed depending on the strength of black water. Improved concentration factor (i.e., 3-folds) and retention (>60%) of TKN was obtained in the high-nutrient-strength black water at a feed volume reduction of 80%, in comparison with a weak TKN enrichment observed in low-strength black water. The results suggested a good potential for nutrient recovery based on this dual “waste-to-resource” FO system with proper management of membrane cleaning.
... To reduce flow resistance, the pores in the support layer should be low in tortuosity [4]. FO is increasingly used in many fields of environmental engineering, including those related to water and wastewater treatment [5][6][7][8][9][10][11][12][13][14][15]. While there are many reports on the subject in the literature, at present there is relatively little information on the direct use of this process to treat the liquid fraction of the digestate. ...
... While there are many reports on the subject in the literature, at present there is relatively little information on the direct use of this process to treat the liquid fraction of the digestate. As an example, only the research presented by Wu et al. [10] shows that it is possible to use FO for water recovery and struvite precipitation from agricultural digestate. In the experiments described therein, more than 50% of water recovery was achieved, along with a 99% removal of phosphate and 93% removal of ammonium nitrogen. ...
Article
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The research undertaken in this paper was aimed at determining the effect of struvite precipitation, one of the potential products that can be obtained during digestate management, on the performance of the non-pressurized membrane process—forward osmosis (FO). The effect of using an integrated struvite precipitation—forward osmosis process to treat the digestate liquid on the changes in the properties of organic substances present in the treated solution (particle size distribution, ζ-potential) was analysed as well. The study was conducted for the liquid fraction of municipal waste biogas plant digestate. The obtained results demonstrate the suitability of this process for recovering water from liquid digestate. It was found that forward osmosis conducted for a digestate pre-treated by chemical struvite precipitation leads to higher water flux values and increased salt concentration in the receiving solution (from 0.5 to 3 mol/dm3 NaCl). There is practically no concomitant infiltration of organic substances into the receiving solution. Therefore, the use of 3 mol/dm3 NaCl as a draw solution results in the recovery of the highest volume of water per unit of time. An analysis of the particle size distribution shows that the removal of the macromolecular fraction of organic compounds from the digestate mainly takes place simultaneously with the chemical precipitation of struvite. It was found that an increase in the concentration of the draw solution, which allows for greater water recovery, resulted in the aggregation of the concentrated organic molecules.
... Dendritic cracks on the crystal surface were visible with further magnification to 10, 000 times ( Figure 4b). This type of cracks was also visible in the struvite crystal from swine manure (Wu et al., 2018). Dendritic cracks on a crystal's surface can be stated as cracks with an arranged branching orientation giving indication of its lattice arrangement. ...
... It is also an early indication of struvite-laden content in the sample (Xie et al., 2014). A commercial struvite is known to have P and Mg composition percentage of up to 32.9% and 22.2% (Wu et al., 2018). Therefore, from the result, the crystal deposit sample can be seen as almost similar to struvite in terms of its composition. ...
Article
Full-text available
The formation of struvite crystals or magnesium ammonium phosphate (MgNH4PO4) in palm oil mill effluent (POME) occurs as early as in the secondary stage of POME treatment system. Its growth continues in the subsequent tertiary treatment which reduces piping diameter, thus affecting POME treatment efficiency. Hypothesis. The beneficial use of the crystal is the motivation. This occurrence is rarely reported in scientific articles despite being a common problem faced by palm oil millers. The aim of this study is to characterize struvite crystals found in an anaerobic digester of a POME treatment facility in terms of their physical and chemical aspects. The compositions, morphology and properties of these crystals were determined via energy dispersive spectroscopy (EDS), elemental analysis, scanning electron microscopy (SEM) and x-ray diffraction (XRD). Solubility tests were carried out to establish solubility curve for struvite from POME. Finally, crystal growth experiment was done applying reaction crystallization method to demonstrate struvite precipitation from POME. Results showed that high phosphorous (P) (24.85 wt%) and magnesium (Mg) (21.33 wt%) content was found in the struvite sample. Elemental analysis detected carbon (C), hydrogen (H), nitrogen (N) and sulfur (S) below 4 wt%. The crystals analysed by XRD in this study were confirmed as struvite with 94.8% struvite mineral detected from its total volume. Having an orthorhombic crystal system, struvite crystals from POME recorded an average density of 1.701 g cm⁻³. Solubility curve of struvite from POME was established with maximum solubility of 275.6 mg L⁻¹ at pH 3 and temperature 40 °C. Minimum solubility of 123.6 mg L⁻¹ was recorded at pH 7 and temperature 25 °C. Crystal growth experiment utilizing POME as the source medium managed to achieve 67% reduction in phosphorous content. This study concluded that there is a potential of harnessing valuable nutrients from POME in the form of struvite. Struvite precipitation technology can be adapted in the management of POME in order to achieve maximum utilization of the nutrients that are still abundant in POME. At the same time maximization of nutrient extractions from POME will also reduce pollutants loading in the final discharge.
... Dendritic cracks on the crystal surface were visible with further magnification to 10, 000 times ( Figure 4b). This type of cracks was also visible in the struvite crystal from swine manure (Wu et al., 2018). Dendritic cracks on a crystal's surface can be stated as cracks with an arranged branching orientation giving indication of its lattice arrangement. ...
... It is also an early indication of struvite-laden content in the sample (Xie et al., 2014). A commercial struvite is known to have P and Mg composition percentage of up to 32.9% and 22.2% (Wu et al., 2018). Therefore, from the result, the crystal deposit sample can be seen as almost similar to struvite in terms of its composition. ...
... FO is born with high selectivity, low fouling propensity, and high fouling reversibility, and small energy consumption when the draw solution is appropriately handled [23]. Wu et al. [24] demonstrated that the cellulose triacetate (CTA) FO membrane could concentrate digested manure centrate to trigger spontaneous and insitu struvite formation with 0.5 M magnesium chloride as the draw solution to contribute a water flux of 3.12 L/m 2 h. A higher water flux (5 L/m 2 h) was observed by Kedwell et al. [25] who used the thin-film composite (TFC) FO membrane for phosphorus recovery from digested manure centrate. ...
... It is noteworthy that the increased alkalinity of the feed solution could also result in the deprotonation of the membrane polyamide layer, augmenting the exchange of monovalent cations between the feed and draw solution [50]. In addition, the decreased NH 4 + -N content in the feed solution could also be ascribed partially to the spontaneous and in-situ struvite precipitation in the feed stream with enhanced concentration of relevant ions [24]. ...
Article
We compared the performance of conventional and aquaporin thin-film composite forward osmosis (FO) membranes (denoted as HTI and AQP membrane, respectively) for concentration of digested manure centrate. Results show that the two FO membranes were capable to concentrate digested centrate for resource recovery. During concentration of digested manure centrate, a cohesive fouling layer formed on the HTI membrane surface, resulting in more dramatic flux decline and less fouling reversibility in comparison to the AQP membrane. The two FO membranes exhibited effective and comparable rejection of bulk organic matter, total phosphorus, and heavy metals, leading to their notable enrichment in digested manure centrate. By contrast, ammonium nitrogen (NH4⁺-N) was only retained by approximately 40% using the two FO membranes with a slightly higher retention by the HTI membrane, since it was less negatively charged. As a result, total nitrogen was ineffectively rejected by the two FO membranes. It is noteworthy that the HTI membrane also contributed to higher rejection of most antibiotics than the AQP membrane, possibly due to enhanced retention by the fouling layer and retarded forward diffusion. Results from this study evidence the outperformance of the AQP membrane as a new generation FO membrane over its conventional counterpart with respect to antifouling property, while further improvement in membrane selectivity, particularly of monovalent cations (e.g. NH4⁺-N), is needed to advance FO applications in resource recovery from challenging waste streams.
... Several nutrient recovery methods from swine wastewater have already been reported, such as air stripping [4,5], adsorption and ion exchange [6,7], membrane [8][9][10], and electrochemical oxidation [11,12]. The chemical precipitation of struvite (MgNH 4 PO 4 ⋅6H 2 O) is a promising ammonium recovery technology from swine wastewater that has already been explored in many studies [13][14][15], resulting in ammonium removal efficiency of up to 92 %. ...
... Water in the feed stream can be transported across the FO membrane to the draw solution, while some of the draw solute also transfer to the feed stream due to reverse salt flux (Yan et al., 2018). Many of the recent studies have explored the capacity and efficiency of FO on retaining and concentrating P in wastewater, urine and sludges (Ansari et al., 2016;Wu et al., 2018;Xie et al., 2014). Cellulose triacetate membrane, thin film composite membrane and surface modified polyamide NF membranes have been constructed in FO membranes, which can recover more than 90% of P from the feed (Jafarinejad, 2021;Xie et al., 2016). ...
Article
Phosphorus (P) as an essential nutrient for life sustains the productivity of food systems; yet misdirected P often accumulates in wastewater and triggers water eutrophication if not properly treated. Although technologies have been developed to remove P, little attention has been paid to the recovery of P from wastewater. This work provides a comprehensive review of the state-of-the-art P removal technologies in the science of wastewater treatment. Our analyses focus on the mechanisms, removal efficiencies, and recovery potential of four typical water and wastewater treatment processes including precipitation, biological treatment, membrane separation, and adsorption. The design principles, feasibility, operation parameters, and pros & cons of these technologies are analyzed and compared. Perspectives and future research of P removal and recovery are also proposed in the context of paradigm shift to sustainable water treatment technology.
... Meanwhile, NH 4 + can be converted into NH 3 , which is also one of the reasons for the low concentration ratio of NH 4 + [37]. In addition, previous investigators have suggested that the reduction in NH 4 + content in the feed solution may also be partly attributable to struvite precipitation due to increased concentrations of related ions [38]. The treatment of MgCl 2 treatment had a weak concentration effect on NH 4 + compared with other treatments, which was affected by the higher recovery rate. ...
Article
Full-text available
Biogas slurry poses a severe challenge to the sustainable management of livestock farms. The technology of the forward osmosis (FO) membrane has a good application prospect in the field of biogas slurry concentration. Further research is needed to verify the effects of different draw solutions on FO membranes in biogas slurry treatment and the related membrane fouling characteristics. In this study, three different draw solutions were selected to evaluate the performance of FO membranes for biogas slurry concentration. Membrane fouling was investigated by characterization after FO membrane treatment to identify fouling contaminants. The result showed that FO membrane treatment can realize the concentration of biogas slurry and MgCl2 as the draw solution has the best effect on the concentration of biogas slurry. The different draw solutions all contributed to the efficient retention of most organics and TP while each treatment was ineffective at retaining nitrogen. The cake layer that appeared after the biogas slurry was concentrated covered the surface of the FO membrane. Some functional groups were detected on the surface after membrane fouling, such as C-O and C=C. Moreover, the C element accounts for 57% of the main components of the cake layer after the membrane fouling. Membrane fouling is caused by both organic fouling and inorganic fouling, of which organic fouling is the main reason. This study provides a technical reference for the high-value utilization of biogas slurry.
... Struvite recovery is a mature technology, mostly involving the addition of Mg (MgO/MgCl 2 ) to a solution containing soluble PO 4 -P (ortho-P) and ammonium, thereby adjusting the pH to 8.3-10 and inducing the precipitation of struvite, MgNH 4 PO 4 · 6H 2 O [248]. Even though these processes have the ability to remove and recover over 80-90% of the soluble P in the wastewater or effluent flow, yet only 10-40% of the NH 4 + -N can be captured [253][254][255] and suit for specific N/P ratio. Extensive literature reported that biochar, stripping and struvite methods can be carried out for ammonium recovery with efficiencies varying between 50%-95% [122,256]. ...
Article
Full-text available
Sustainable provision of chemicals and materials is undoubtedly a defining factor in guaranteeing economic, environmental and social stability of future societies. Among the most sought-after chemical building blocks are volatile fatty acids (VFAs). VFAs such as acetic, propionic and butyric acids have numerous industrial applications supporting from food and pharmaceuticals industries to wastewater treatment. The fact that VFAs can be produced synthetically from petrochemical derivatives and also through biological routes for example anaerobic digestion of organic mixed waste, highlights their provision flexibility and sustainability. In this regard, this review presents a detailed overview of the applications associated with petrochemically and biologically generated VFAs, individually or in mixture, in industrial and laboratory scale, conventional and novel applications.
... Even if manure CF was limited to two in most cases, the effective concentration of nutrients was achieved. P rejection was high in all cases (>95%) but the very variable rejection of nitrogen was observed from less than 40% in some cases and up to nearly total rejection without clear explanation [190][191][192][193]. P can be recovered as struvite if precipitation is controlled; otherwise, it may lead to a scaling issue [192,194]. ...
Article
Full-text available
In the past few years, osmotic membrane systems, such as forward osmosis (FO), have gained popularity as “soft” concentration processes. FO has unique properties by combining high rejection rate and low fouling propensity and can be operated without significant pressure or temperature gradient, and therefore can be considered as a potential candidate for a broad range of concentration applications where current technologies still suffer from critical limitations. This review extensively compiles and critically assesses recent considerations of FO as a concentration process for applications, including food and beverages, organics value added compounds, water reuse and nutrients recovery, treatment of waste streams and brine management. Specific requirements for the concentration process regarding the evaluation of concentration factor, modules and design and process operation, draw selection and fouling aspects are also described. Encouraging potential is demonstrated to concentrate streams more than 20-fold with high rejection rate of most compounds and preservation of added value products. For applications dealing with highly concentrated or complex streams, FO still features lower propensity to fouling compared to other membranes technologies along with good versatility and robustness. However, further assessments on lab and pilot scales are expected to better define the achievable concentration factor, rejection and effective concentration of valuable compounds and to clearly demonstrate process limitations (such as fouling or clogging) when reaching high concentration rate. Another important consideration is the draw solution selection and its recovery that should be in line with application needs (i.e., food compatible draw for food and beverage applications, high osmotic pressure for brine management, etc.) and be economically competitive.
... Forward osmosis (FO), the most common osmotically driven membrane process, stands out as the most promising alternative for RO processes due to its inherently low fouling tendency, easier fouling removal, and energy efficiency when compared to pressure-driven-type membrane processes [16][17][18][19]. Owing to these attractive inherent features, FO has been used as a concentration and dilution process in diverse areas including food processing [21][22][23][24], wastewater treatment [25][26][27], desalination [28][29][30][31], and power generation [3,32]. In medical application, FO assists in controlling the release of drugs with low solubility [33,34] and in preserving properties of feed (nutrition, taste, quality, etc.) when it comes to the pharmaceutical industry [35]. ...
Article
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Forward osmosis (FO) has been recognized as the preferred alternative membrane-based separation technology for conventional water treatment technologies due to its high energy efficiency and promising separation performances. FO has been widely explored in the fields of wastewater treatment, desalination, food industry and bio-products, and energy generation. The substrate of the typically used FO thin film composite membranes serves as a support for selective layer formation and can significantly affect the structural and physicochemical properties of the resultant selective layer. This signifies the importance of substrate exploration to fine-tune proper fabrication and modification in obtaining optimized substrate structure with regards to thickness, tortuosity, and porosity on the two sides. The ultimate goal of substrate modification is to obtain a thin and highly selective membrane with enhanced hydrophilicity, antifouling propensity, as well as long duration stability. This review focuses on the various strategies used for FO membrane substrate fabrication and modification. An overview of FO membranes is first presented. The extant strategies applied in FO membrane substrate fabrications and modifications in addition to efforts made to mitigate membrane fouling are extensively reviewed. Lastly, the future perspective regarding the strategies on different FO substrate layers in water treatment are highlighted.
... The FO membrane used in this study was the cellulose triacetate (CTA) membrane manufactured by Fluid Technology Solution (FTS) and purchased from Sterlitech Corporation, USA. This membrane was selected because it has been widely used for several wastewater studies and has excellent stability in harsh wastewater environments due to its high chlorine tolerance, low reverse salt flux, and good water flux (Phuntsho et al. 2013, Wu et al. 2018. Before using the membrane, it was soaked in DI water overnight at laboratory temperature (21±3 o C) to ensure complete wettability. ...
Article
This study presents systematic investigations to evaluate the performance, rejection rate, fouling, cleaning protocols and impact of physical and chemical cleaning strategies on the performance of commercial cellulose triacetate (CTA) membrane. The treatment of landfill leachate (LFL) solution was performed in the active layer facing feed solution and support layer facing the draw solution (AL-FS mode), and active layer facing the draw solution and support layer facing the feed solution (AL-DS mode). Compared to the AL-FS mode, a higher flux for AL-DS mode was achieved, but membrane fouling was more severe in the latter. In both membrane orientations, the rejection rate of the FO membrane to heavy ions and contaminants in the wastewater was between 93 and 99%. Physical and chemical cleaning strategies were investigated to recover the performance of the FO membrane and to study the impact of cleaning methods on the membrane rejection rate. Physical cleaning with hot water at 35 °C and osmotic backwashing with 1.5 M NaCl demonstrated excellent water flux recovery compared to chemical cleaning. In the chemical cleaning, an optimal concentration of 3% hydrogen peroxide was determined for 100% flux recovery of the fouled membrane. However, slight membrane damage was achieved at this concentration on the active layer side. Alkaline cleaning at pH 11 was more effective than acid cleaning at pH 4, although both protocols compromised the membrane rejection rate for some toxic ions. A comparison of the membrane long-term performance found that cleaning with osmotic backwashing and hot water were effective methods to restore water flux without comprising the membrane rejection rate. Overall, it was found that physical cleaning protocols are superior to chemical cleaning protocols for forward osmosis membrane fouled by landfill leachate wastewater.
... As mentioned above, this phenomenon could be attributed to the small radius of NH 4 + -N and its positive charge to be electrostatically attracted by the negatively charged FO membrane surface. Nevertheless, Wu et al. [36] demonstrated that the rejection of phosphorus and NH 4 + -N by the FO membrane was more than 99 and 93%, respectively, due to the in situ struvite formation during the concentration of digested swine manure effluent when magnesium chloride was used as the draw solution. The in situ struvite formation was triggered by the reverse diffusion of magnesium ions from the draw solution, which is a notable example to switch the inherent drawback of FO, reverse solute flux, for beneficial application. ...
Article
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Purpose of Review Membrane techniques have been employed to concentrate livestock manure effluent from anaerobic digestion to produce highly concentrated liquid organic fertilizer. This review aims to provide a comprehensive understanding on the opportunities and challenges of membrane processes in the concentration of digested effluent for their further implementation. Recent Findings Anaerobic digestion has been deployed to convert livestock manure into biogas (energy) and digestate with high potential as biofertilizer. Digestate can be separated into a solid and liquid fraction to reduce required capacity for onsite storage. The liquid fraction, known as digested effluent, remains a vexing challenge to digestate management due to the contradiction between its continuous production and seasonal application to farmlands, particularly in developing countries. Recent investigation has demonstrated the promise of membrane techniques for the concentration of digested effluent to recover recycling water and produce nutrient-rich liquid fertilizer. These techniques mainly include hydraulically driven membrane processes (from microfiltration to reverse osmosis), forward osmosis, membrane distillation, and electrodialysis. In most cases, these membrane techniques are hybridized to enhance the concentration efficiency. Nevertheless, the practical application of these membrane processes is hindered by several technical challenges, which mainly include membrane fouling, contaminant enrichment, ammonia volatilization, and high economic input. Summary In this paper, we critically reviewed the performance of different membrane processes in the concentration of digested livestock manure effluent. Key technical challenges and their potential countermeasures were elucidated. Furthermore, future perspectives were provided to shed light on further development of membrane concentration techniques in the field.
... To evaluate the SRR and ReR for solute removal via chemical precipitation, we used one of our prior studies as a case study, which formed struvite precipitates from a direct FO system used to dewater pig wastewater (Fig. 4A). 56 To calculate the SRR and ReR, only Mg 2+ that migrated via RSF and was precipitated into struvite was considered "removed". This case study utilized a batch operation with 60% water recovery. ...
Article
Forward osmosis (FO) has shown advancement towards recovery of useful water from various waste streams. A major issue that arises is the accumulation of salts due to reverse solute flux (RSF) from a draw solution into a feed solution that can result in several negative effects such as decreased water flux and inhibiting biological activities. This paper aims to provide a concise discussion and analysis of methods that can help to alleviate the effects of solute build up. New parameters, solute removal/recovery rate (SRR) and removal/recovery ratio (ReR), are proposed to help better define the performance of reducing solute buildup and employed in case studies to evaluate the selected reduction methods. Solute removal can be accomplished by physical separation, chemical precipitation, and biological removal. Recovery of solutes, one step beyond removal, is discussed and demonstrated by using bioelectrochemical systems and electrodialysis as examples. This work has highlighted the concerns associated with solute buildup and encouraged further exploration of effective tools to mitigate solute buildup for improved performance of FO-based water/wastewater systems.
... Therefore, the advantages of in situ recovery/recycle of solvents with membranes should be considered, even though more work is needed on the in situ processes with NF, which have significant potential. Recent examples of this trend of employing membranes for in situ recovery have been reported in the literature in a number of fields (Ch avez-Castilla and Aguilar 2016; Fodi et al. 2017;Wu et al. 2018;Didaskalou et al. 2018). ...
Article
Membrane engineering is currently classified as an eco-friendly cleaning technology in various fields, especially for wastewater treatment, and its use is increasing due to the growing interest in water environment protection and preservation. In this study, a new approach to improving membrane performance is proposed by using polyethersulfone (PES) as a polymer blend with polyphenylsulfone (PPSU). PPSU-PES ultrafiltration membranes were prepared using the classical phase inversion method to remove dyes from simulated wastewater of the leather tanning industry. Four concentrations of PES were studied (i.e. 0, 4, 5, and 6 wt.%), while keeping the concentration of PPSU constant at 20%. A scanning electron microscope (SEM) and atomic force microscopy (AFM) were used to characterize the surface structure of the cross-section, top, and bottom membranes. It was found that the structural morphology of the membrane varied with the PES concentration. The addition of PES helped significantly decrease the contact angle and increase the porosity of the PPSU/PES/N-methyl-2-pyrrolidinone (NMP) blend membranes by approximately 15.2% and 280%, respectively, and to decrease the thickness of the membrane compared with neat PPSU. The effects of black dye (i.e. acid black 210, MW = 938.017 g mol⁻¹) concentration (i.e. 35, 45, and 65 ppm), feed temperature, and pH on the permeate flux and dye removal were also investigated in this study. It was found that there is a minor effect of the feed temperature and no effect of pH on the permeation flux. Also, it was discovered that the performance of the membranes improved from 5.77 to 27.7 and 3.46 to 19.62 for distilled water and feed solution of 35 ppm, respectively over those prepared from the neat PPSU membrane, while the dye removal was higher than 99.65% for all of the membranes studied.
... In addition, longterm operation and membrane autopsy studies have been conducted in real municipal wastewater reclamation plants. These studies concluded that natural organic matters (OMs) and soluble microbial products are the main influencing foulants [3,15]. ...
Article
Forward osmosis (FO) can extract water from a solution with a low chemical potential (feed solution, FS) and transport it to a solution with a high chemical potential (draw solution, DS) through natural osmotic pressure. For wastewater reuse via FO, an identifying the foulants and understanding the fouling and transport mechanisms are important. An element-scale spiral-wound FO (SWFO) system and a laboratory-scale FO module tests were conducted with a cellulose triacetate-based FO membrane. Secondary wastewater effluent was used as the FS. To determine the main foulants in FO, the element-scale SWFO was operated at a wastewater plant for 36 d, and a detailed characterization of the foulants (particularly organic matters; OMs) and a membrane autopsy were conducted. The results were verified via a laboratory-scale demonstration. Hydrophilic and large-molecular-weight OMs was the main foulant. It was transported to the DS from the FS through the membrane. The water flux, reverse solute flux, and related parameters (type, concentration, and valence of the draw solute) affected the transport of OMs through the FO membrane. Therefore, further study is needed to develop strategies for reducing the transportation of OMs through the membrane in the wastewater reuse by selecting a suitable draw solute or properly arranging the elements.
... In terms of the organic materials enrichment, fouling control, and membrane cleaning efficiency, the cellulose triacetate membrane performed better than the polyamide one. Wu et al. (2018) implemented a proof-of-concept FO process for in situ formation of struvite from digested swine wastewater. The FO system utilized a drawback, reverse solute flux (RSF), and made use of the reverse-fluxed Mg 2+ to precipitate struvite, thus recovering both water and nutrients. ...
Article
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The review scans research articles published in 2018 on physico‐chemical processes for water and wastewater treatment. The paper includes eight sections, that is, membrane technology, granular filtration, flotation, adsorption, coagulation/flocculation, capacitive deionization, ion exchange, and oxidation. The membrane technology section further divides into six parts, including microfiltration, ultrafiltration, nanofiltration, reverse osmosis/forward osmosis, and membrane distillation. Practitioner points • Totally 266 articles on water and wastewater treatment have been scanned; • The review is sectioned into 8 major parts; • Membrane technology has drawn the widest attention from the research community.
... Despite great promise and much progress of FO-based technologies, a major challenge and also an impediment remain to be solved in the fourth (current) stage is the salinity buildup on the feed side, resulted from both reverse solute flux (RSF, a major contributor) and concentrating effect by FO membrane rejection (Hancock and Cath, 2009). RSF is defined as the cross-membrane diffusion of DS to the feed side driven by solute concentration difference and has been utilized for process intensification, such as supplying substrate or buffer reagents in an osmotic microbial fuel cell (Bowden et al., 2012;Wu et al., 2018), enhancement of anti-scaling resistance (Zhang et al., 2017), or facilitating struvite precipitation from sludge centrate/digestate (Wu et al., 2018b;Xie et al., 2014). Still, the detrimental effects of RSF include gradual loss of DS, reduced osmotic driving force (i.e. ...
Article
Forward osmosis (FO) has emerged as a potentially energy-efficient membrane treatment technology to yield high-quality reusable water from various wastewater/saline water sources. A key challenge remained to be solved for FO is reverse solute flux (RSF), which can cause issues like reduced concentration gradient and loss of draw solutes. Yet no universal parameters have been developed to compare RSF control performance among various studies, making it difficult to position us in this “battle” against RSF. In this paper, we have conducted a concise review of existing RSF reduction approaches, including operational strategies (e.g., pressure-, electrolysis-, and ultrasound-assisted osmosis) and advanced membrane development (e.g., new membrane fabrication and existing membrane modification). We have also analyzed the literature data to reveal the current status of RSF reduction. A new parameter, mitigation ratio (MR), was proposed and used together with specific RSF (SRSF) to evaluate RSF reduction performance. Potential research directions have been discussed to help with future RSF control. This review intends to shed more light on how to effectively tackle solute leakage towards a more cost-effective and environmental-friendly FO treatment process.
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The concerns regarding the reactive nitrogen levels exceeding the planetary limits are well documented in the literature. A large portion of anthropogenic nitrogen ends in wastewater. Nitrogen removal in typical wastewater treatment processes consumes a considerable amount of energy. Nitrogen recovery can help in saving energy and meeting the regulatory discharge limits. This has motivated researchers and industry professionals alike to devise effective nitrogen recovery systems. Membrane technologies form a fundamental part of these systems. This work presents a thorough overview of the subject using scientometric analysis and presents an evaluation of membrane technologies guided by literature findings. The focus of nitrogen recovery research has shifted over time from nutrient concentration to the production of marketable products using improved membrane materials and designs. A practical approach for selecting hybrid systems based on the recovery goals has been proposed. A comparison between membrane technologies in terms of energy requirements, recovery efficiency, and process scale showed that gas permeable membrane (GPM) and its combination with other technologies are the most promising recovery techniques and they merit further industry attention and investment. Recommendations for potential future search trends based on industry and end users’ needs have also been proposed.
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Thesis
Στην παρούσα Διπλωματική Εργασία διενεργείται ανασκόπηση και συγκριτική αξιολόγηση του συνόλου των σύγχρονων προηγμένων τεχνολογιών που επιτρέπουν τη συμμόρφωση της διαχείρισης των Υγρών Αποβλήτων με τις αρχές της Κυκλικής Οικονομίας. Στο πλαίσιο αυτό, εξετάζεται η μετάβαση από το συμβατικό σύστημα της «Ενεργού Ιλύος», σε ένα μοντέλο ολοκληρωμένης διαχείρισης των λυμάτων που στοχεύει στη μείωση του ρυπαντικού φορτίου με ταυτόχρονη παραγωγή νερού, για επαναχρησιμοποίηση σε διάφορες χρήσεις, στην παραγωγή ενέργειας και στην ανάκτηση συστατικών υψηλής προστιθέμενης αξίας. Η επαναχρησιμοποίηση του νερού, επιτυγχάνεται με μια πληθώρα τεχνολογιών. Ωστόσο, οι σύγχρονες τεχνολογικές εφαρμογές, πέραν άλλων κριτηρίων βιωσιμότητας, θα πρέπει να επιτυγχάνουν και έναν υψηλό βαθμό απομάκρυνσης των ιδιαιτέρως επιβλαβών αναδυόμενων οργανικών ρύπων. Συγκριτική αξιολόγηση, που διενεργήθηκε μεταξύ ώριμων τεχνολογιών (TRL>6), έδειξε ότι οι μεγαλύτεροι βαθμοί απομάκρυνσης (80-100%) επιτυγχάνονται με τον οζονισμό, τις προηγμένες διεργασίες οξείδωσης και τη διήθηση μεμβρανών (NF/RO). Ωστόσο, ο οζονισμός απαιτεί τη χαμηλότερη ειδική κατανάλωση ενέργειας (0,1-0,2 kWh/m3). Η ανάκτηση των θρεπτικών συστατικών από τα λύματα, κρίνεται επιτακτική για την προστασία του περιβάλλοντος από το φαινόμενο του ευτροφισμού και για την εξασφάλιση των μη-ανανεώσιμων φυσικών πόρων. Η χημική κατακρήμνιση, για την ανάκτηση των Ν και P μέσω του σχηματισμού στρουβίτη, βρίσκει τη μεγαλύτερη εφαρμογή λόγω της υψηλής απόδοσης και σταθερότητας της διεργασίας. Ωστόσο, η ανάκτηση ποιοτικότερων θρεπτικών συστατικών επιτυγχάνεται με διεργασίες μεμβρανών, μεταξύ των οποίων προκρίνονται τα συστήματα ώσμωσης (FO), λόγω της συνδυαστικής χαμηλότερης ενεργειακής απαίτησης και τάσης για ρύπανση στην επιφάνεια της μεμβράνης. Τα αγρο-βιομηχανικά απόβλητα είναι κατάλληλα για ενεργειακή εκμετάλλευση, λόγω του υψηλού βιο-διασπάσιμου οργανικού φορτίου που περιέχουν. Εφαρμόζεται αναερόβια χώνευση και ανάλογα με το είδος των λυμάτων, είναι δυνατόν να παράγονται 0,17 – 0,35 L CH4/g COD. Η επεξεργασία της εκροής, για την ανάκτηση των βιο-δραστικών ουσιών, αυξάνει το κόστος της διεργασίας, το οποίο αντισταθμίζεται από την εμπορική αξία των ανακτηθέντων ουσιών (10.000-20.000 €/kg).
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Forward osmosis (FO), considered as a promising separation process for nutrient enrichment in wastewater, is attracting increasing interest in integration with chemical precipitation and other technologies for recovering nutrients in wastewater treatment. In this chapter, the processes of nutrients recovery via FO‐based systems are introduced in terms of mechanisms and influencing factors. Additionally, the key challenges related to the recovery systems are discussed and some approaches are proposed to resolve these challenges. Roadmaps for future research and development on the nutrients recovery using FO‐based systems are identified. Compared to aerobic FO‐based systems, anaerobic FO‐based processes need more investigations into their integration's efficiency in the context of nutrient recovery from wastewater. Emphasis is given to carry out more economic assessment and pilot‐ and plant‐scale evolutions of the recovery systems, which makes the nutrients recovery via FO‐based technologies more sustainable in wastewater treatment.
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The depletion of phosphorus resources and the excess discharge of phosphorus into waste streams are contrasting problems. The key to solving both problems is to recover phosphorus from the waste streams. Current phosphorus recovery technologies require high phosphorus concentrations and lack the ability to separate toxic substances from recovered phosphorus products. Membrane separation processes such as nanofiltration, forward osmosis, and electrodialysis are examples of effective methods for solving some of these issues. In this paper, the mechanisms, performance, and influential factors affect phosphorus recovery from membrane separation are reviewed. Membrane fouling, energy consumption, and the selectivity of toxic substances in membrane separation processes were evaluated. This work will serve as a basis for future research and development of phosphorus recovery by membrane separation processes and as a response to the increasingly pressing issues of eutrophication and the growing depletion of phosphorus resources.
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There has been increasing attention in osmotically driven membrane processes (ODMPs), which include forward osmosis (FO) and pressure retarded osmosis (PRO). They provide a sustainable solution against water and energy scarcity issues by utilizing the osmotic pressure difference between two water bodies, feed (low salinity) and draw solution (high salinity), across a semipermeable membrane. Indeed, their main applications, water treatment (e.g., desalination and wastewater treatment) and power generation, facilitate resource recovery from wastewaters. This review updates the recent development of FO and PRO by providing a comprehensive review on their fundamentals, membrane properties, potential applications as well as advanced techniques. In addition, economic analysis and environmental impacts are critically reviewed to highlight their feasibility and sustainability. Resource recovery from wastewaters (e.g., water, nutrient and energy) using FO and PRO is also discussed followed by their commercialization and future trends in order to push forward laboratory research to full-scale commercialization.
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Biofouling caused by the growth of the biofilm is the main bottleneck that limits the effective operation of thin-film composite (TFC) membrane in the forward osmosis (FO) process. This study investigated the combined effects of graphene oxide (GO) immobilized thin-film nanocomposite (TFN-S) membrane and Pseudomonas quinolone signal (PQS)-based quorum quenching on biofouling mitigation, especially under the operation of pressure-retarded osmosis (PRO) mode, and the influence of methyl anthranilate (MA) inhibitor on the composition and structure of biofilm was also evaluated. Synthetic wastewater was used as the feed solution, in which the model strain Pseudomonas aeruginosa was added to simulate biofouling. The results showed that GO modification and MA addition both efficiently mitigated flux decline and EPS secretion, but the interference of PQS pathway on biofouling control was better than GO embedding. TFN-S membrane with MA addition exhibited superior anti-biofouling performance based on the combined effects of GO and MA. The alleviated concentration polarization and enhanced hydrophilicity of the TFN-S membrane reduced the flux decline in the early stage. Additionally, the antibacterial property of GO inhibited the viability of the attached bacteria (under PRO mode) and MA further mitigated the EPS secretion and biofilm development in the later stage. In the presence of PQS inhibitor MA, live/total cells ratio was 15% and 13% higher than that of TFC membrane in FO and PRO modes, respectively. Furthermore, exogenous addition of MA led to a relatively loose biofilm structure, resulting in high membrane permeability in the biofouling formation process.
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In recent years, the concept of nutrient removal/recovery has been applied as a sustainable solution to develop and design various modern wastewater treatment technologies for recovering nutrients from waste streams and is one of the high-priority research areas. Forward osmosis (FO) technology has received increasing interests as a potential low-fouling membrane process and a new approach to remove/recover nutrients from wastewater and sludge. The main objective of this review is to summarize the state of FO technology for nutrient removal/recovery from wastewater and sludge in order to identify areas of future improvements. In this study, nutrient removal processes, FO membrane technology, main factors affecting the FO process performance, the source water for nutrient recovery, the previous studies on the FO membrane process for nutrient removal/recovery from wastewater and sludge, membrane fouling, and recent advances in FO membranes for nutrient removal/recovery were briefly and critically reviewed. Then, the proposed possible designs to apply FO process in conventional wastewater treatment plants (WWTPs) were theoretically presented. Finally, based on the gaps identified in the area, challenges ahead, future perspectives, and conclusions were discussed. Further investigations on the properties of FO associated with real wastewater, wastewater pre-treatment, the long-term low fouling operation, membrane cleaning strategies, water flux and the economic feasibility of the FO process are still desirable to apply FO technology for nutrient removal/recovery at full-scale (decentralized or centralized) in the future.
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This study aimed to investigate pollutant concentration and membrane fouling characteristics of a forward osmosis (FO) process using aquaporin biomimetic membrane (ABM) for concentrating black odorous water. The membrane cells were operated in active layer facing feed solution (ALFS) mode with 2 M NaCl solution as the draw solution. The system was continuously performed for 64 batch cycles, and each cycle duration was 24 h. At the end of each cycle, physical cleaning with deionized water was employed as the membrane recovery strategy. The results showed that the rejection ratios of chemical oxygen demand (COD), total phosphorus (TP) and nitrate (NO3⁻-N) could reached 97.2%, 98.0%, and 85.0%, respectively, while most NH4⁺-N penetrated into the draw solution due to cation exchange. The total nitrogen (TN) rejection ratio was largely dependent upon the NH4⁺-N/TN ratio. At high NH4⁺-N/TN ratio, the successions of ammonia oxidizing bacteria (AOB) communities enriched in the biofouling layer in different experimental stages would affect the transformation degree of NH4⁺-N, and thus lead to much fluctuations of TN rejection. The average initial water flux reached 9.84 L/(m²·h), and the average water flux of each cycle kept stable especially in the later stage of the experiment. In the biofouling layer, polysaccharides enhanced while proteins decreased in the later period. P, Mn, Fe and Na also accumulated on the surface. Norank_f__Reyranellaceae, Erythrobacter, SM1A02, Pirellula, and Hydrogenophaga were the predominant genera enriched in the fouling layer, which would lead to complex pollutants transformations, especially nitrogen transformation, during the FO process.
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A forward osmotic membrane bioreactor for sludge anaerobic digestion (ad-OMBR) could realize high-solid digestion via drawing moisture out by forward osmosis (FO). Methane production and microbial community evolution were monitored in an ad-OMBR as the total solids (TS) content was gradually increased. With magnesium chloride (MgCl2) and cellulose triacetate (CTA) membrane as a draw solution and FO membrane, respectively, the ad-OMBR exhibited better performance than the conventional digester, with higher solid content, organic degradation and methane content in biogas. The conductivity of the ad-OMBR did not increase, potentially because of the formation of struvite crystals aided by the reverse-fluxed Mg2+ ions. Microbial diversity increased along with the increase in solid content based on the Shannon index, while the most operational taxonomic units were obtained in the 8% TS sludge Although phylum Firmicutes decreased when the TS content was raised to 11%, the relative abundance of Proteobacteria, Chloroflexi, Actinobacteria, and Bacteroidetes, which could also degrade organic matter, increased with increasing TS in ad-OMBR. FO membrane fouling in ad-OMBR was highly reversible.
Chapter
In the twentieth century, wastewater has emerged as one of the most appalling problems facing mankind. In recent times, numerous steps have been taken to conserve the water bodies, and a variety of wastewater treatment strategies have been developed to treat wastewater in order to make it reusable. The high operational cost associated with these strategies makes the process economically unfeasible. Therefore, looking into the high nutrient content of wastewaters from domestic and industrial establishments, it has been proposed that these treatment plants may be integrated with energy generation (bioenergy) and resource recovery (N, P, K fertilizers and molecular intermediates as value-added products) for making the overall process self-sustainable. Overall, the man-made problem caused due to wastewater can be used as an opportunity for economic benefits through technological advancements. The present chapter evaluates technical and economic aspects of various wastewater treatment strategies with special emphasis on energy and value-added product recovery. It will not only highlight crucial features of each process but also suggest probable areas of improvements keeping in mind the future prospects for establishing self-sustainable wastewater treatment plants.
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An emerging osmotically driven membrane process, forward osmosis has attracted growing attention in the field of desalination and wastewater treatment. The present study provides a critical review of the forward osmosis process for wastewater treatment focusing on most recent studies. Forward osmosis is one of the technologies that has been widely studied for the treatment of a wide range of wastewater because of its low fouling and energy consumption compared to conventional techniques for wastewater treatment. To date, forward osmosis has limited applications in the field of wastewater treatment due to several technical and economic concerns. Although membrane cost is one of the critical issues that limit the commercial application of forward osmosis, there are other obstacles such as membrane fouling, finding an ideal draw solution that can easily be recycled, concentration polarization and reverse salt diffusion. Innovative technologies for in-situ real-time fouling monitoring can give us new insights into fouling mechanisms and fouling control strategies in forward osmosis. This study evaluated recent advancements in forward osmosis technology for wastewater treatment and the main challenges that need to be addressed in future research work. GRAPHICAL ABSTRACT Forward osmosis process for wastewater treatment. KEYWORDS Wastewater; forward osmosis; waste-water treatment CONTACT Ali Altaee
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The liquid digestate has been regarded as a potential organic fertilizer for its benefit in nutrients recovery. However, the potential risk of hazardous substances remaining in the wastewater was still one of the main obstacles for the wastewater application in the circular agriculture. The pretreatment is important to remove pollutants with relatively satisfied results. Ferric coagulation was a feasible way to simultaneously remove various contaminants in the wastewater with few residuals of ferric ions under alkaline and neutral conditions. In special, it could reduce the residues of sulfide and arsenic compounds. We gained insights into the mechanism of ferric coagulation in removing sulfide and arsenic compounds. Redox reaction and precipitation were the reasons resulting in removing sulfide. The formation of precipitate by combining with iron(III) contributes to the removal of arsenic compounds. Toxicity tests using Scenedesmus obliquus and Chlorella pyrenoidosa showed an obvious reduction of toxicity for the liquid digestate after ferric coagulation. Besides, ferric coagulation could efficiently remove turbidity, reduce COD and eliminate dissolved organic matters correlated with the fate of heavy metal and antibiotics. Therefore, this paper could give basic data and technique supports for the secure utilization and pollution control of liquid digestate. This article is protected by copyright. All rights reserved.
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Electrolytic manganese residue (EMR) contains large quantities of manganese (Mn ²⁺ ) and ammonia nitrogen (NH 4⁺ -N). Phosphogypsum (PG) contains plenty of phosphate (PO 4³⁻ ), fluorine (F ⁻ ) and some heavy metals. Separate storage of EMR and PG could seriously damage the ecological environment. In this study, synergistic stabilization/solidification (S/S) of EMR and PG was studied. The effects of EMR:PG mass ratio, S/S pH, solid-liquid ratio and temperature on the concentrations of NH 4⁺ -N, PO 4³⁻ , Mn ²⁺ and F ⁻ in the leaching solution, and the characteristics of EMR and PG were studied. Meanwhile, the synergistic S/S mechanisms of EMR and PG, and leaching test were investigated. The results showed that the concentrations of F ⁻ , PO 4³⁻ , NH 4⁺ -N and Mn ²⁺ in the leaching solution were 4.5 mg/L, 13.6 mg/L, 55.5 mg/L and 0.8 mg/L, respectively, when the mass ratio of EMR to PG was 1:2 and the pH was 9.0 adjusted by MgO after 20 days S/S. Manganese was mainly solidified as Mn 3 (PO 4 ) 2 ·7H 2 O and Mn(OH) 2 , and ammonia nitrogen was mainly stabilized as struvite; fluorine was mainly stabilized as (Mn, Ca, Mg)F 2 , and phosphate was mainly solidified as (Mn, Ca, Mg) 3 (PO 4 ) 2 and (Mn, Ca, Mg)HPO 4 . The leaching test results showed that PO 4³⁻ and NH 4⁺ -N were reduced to 13.6 mg/L and 55.5 mg/L, respectively, and the concentrations of all the measured heavy metals and F ⁻ were within the permitted level for the GB8978-1996 after 20 days S/S.
Article
Biogas slurry, also called liquid digestate, refers to the liquid part of the anaerobic digestate produced from the anaerobic digestion process, which is an environmental pollution source if it is discharged without proper treatment. To recover the nutrients in the biogas slurry, a membrane system was designed to concentrate in the work. The effects of pre‐treatment technology including gravity settling and ultrafiltration process were studied via analyzing the chemical oxygen demand (COD), ammonia nitrogen (NH3‐N), total nitrogen (TN), and conductivity. Reverse osmosis was applied in the biogas slurry concentration. The performance of reverse osmosis membrane used in the concentration process was studied by analyzing the permeate and concentrate (retentate), the volume reduction factor and the concentration factor. The suitable parameters were selected as 20.0‐25.0°C for influent temperature, 0.8‐1.0Mpa for operating pressure, and 6.0‐8.0 for influent pH. Furthermore, the feasible concentration factor was evaluated as 4. The economic, environmental, and social benefits could be gained if (concentrated) biogas slurry was used as an alternative to chemical fertilizers. This article is protected by copyright. All rights reserved.
Article
During the struvite (MgNH4PO4·6H2O) recovery from agricultural or industrial wastewater, the extensive existence of heavy metals would pose great threats to the planting and environment. This work revealed the association of kinds of heavy metals, as possible substances in the wastewater, with the struvite. The struvite has been synthesized in situ and employed to contact with both high and low concentration heavy metal (including Cu, Ni, Pb, Zn, Mn, Cr(III)) wastewater. The heavy metal precipitation rates under different pH values from 6.0 to 10.0, and under a series of struvite addition amount have been investigated. The precipitation of heavy metals without addition of struvite is functioned as control experiments. The struvite's presence can enhance the heavy metal precipitation rate under all pH values. The Ni and Mn have relatively lower precipitation rate compared with other metals. For extremely low heavy metal concentration the precipitation rate is 99.1%, 97.9%, 99.9%, 98.9%, 96.9%, and 98.3%, which is much higher than that of control group (10.5%, 8.7%, 13.2%, 14.1%, 6.7%, and 10.5%). Through XPS and TEM & EDS analysis, the heavy metal hydroxides is found to be precipitated on the struvite surface. Based on TEM observations, it has been found the copper hydroxides had nucleation and growth on the struvite's surface. The heterogeneous nucleation mechanism has been proposed, which provides relationship model of sorption, nucleation, and precipitation of heavy metals in the form of hydroxides on struvite surfaces. It has been calculated that the △Gi value that thermodynamic activation energy barrier constraints on the metal hydroxide formation can be intensively abated through heterogeneous nucleation on struvite.
Article
Forward osmosis is a low-energy water treatment emerging technology, which has demonstrated improved solute rejection and low fouling propensity. In this study, the applicability of aquaporin-based forward osmosis membranes during separation of biogas digestate liquid fractions was investigated. The results showed that Total Ammonia-Nitrogen rejection was higher than 95.5% in all experiments, independently of the type of draw solution (NaCl and hide preservation effluents), experimental period and the use of feed acidification. The results also confirmed that high draw osmotic pressures (i.e. 3.5M sodium chloride and hide preservation wastewater) combined with feed acidification had a negative effect on the membrane water permeability. Membrane rinsing after fouling was also successful in recovering the membrane initial water flux as well as removing the remaining foulants on the membrane surface. The membrane inspection results from Scanning-Electron Microscope, Energy-Dispersive X-Ray analysis and Fourier Transform Infrared– Attenuated Total Reflectance showed that fouling in this application was mild and reversible after membrane rinsing. The applicability of aquaporin-based forward osmosis membranes during separation of biogas digestate liquid fractions has been demonstrated. The results showed the potential of this technology to achieve enhanced ammonia-nitrogen rejections and low-fouling propensity.
Article
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Forward osmosis (FO) is one of the evolving membrane technologies in desalination with recent expanded new interest as a low energy process. The most significant parts of FO process are the membrane and draw solution since both play a substantial role in its performance. Hence, the selection of an appropriate membrane and draw solution is crucial for the process efficiency. Improvements in the development of membranes and draw solutes have been recorded recently. However, limitations such as fouling of FO membranes, reverse solute flux, concentration polarization, and low permeate flux in standalone FO systems. This work targets the review of recent progress in FO, aiming on the prospects and challenges. It starts with addressing the advantages of the FO process. The crucial part of this review is a thorough discussion of hybrid FO systems, different FO membranes, and draw solutes available coupled with their effects on FO performance. Finally, the future of FO for sustainable desalination is also discussed.
Article
Full-text available
In the present study, struvite decomposition was performed by air stripping for ammonia release and a novel integrated reactor was designed for the simultaneous removal and recovery of total ammonia-nitrogen (TAN) and total orthophosphate (PT) from swine wastewater by internal struvite recycling. Decomposition of struvite by air stripping was found to be feasible. Without supplementation with additional magnesium and phosphate sources, the removal ratio of TAN from synthetic wastewater was maintained at >80% by recycling of the struvite decomposition product formed under optimal conditions, six times. Continuous operation of the integrated reactor indicated that approximately 91% TAN and 97% PT in the swine wastewater could be removed and recovered by the proposed recycling process with the supplementation of bittern. Economic evaluation of the proposed system showed that struvite precipitation cost can be saved by approximately 54% by adopting the proposed recycling process in comparison with no recycling method.
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Full-text available
In the past four decades, membrane development has occurred based on the demand in pressure driven processes. However, in the last decade, the interest in osmotically driven processes, such as forward osmosis (FO) and pressure retarded osmosis (PRO), has increased. The preparation of customized membranes is essential for the development of these technologies. Recently, several very promising membrane preparation methods for FO/PRO applications have emerged. Preparation of thin film composite (TFC) membranes with a customized polysulfone (PSf) support, electorspun support, TFC membranes on hydrophilic support and hollow fiber membranes have been reported for FO/PRO applications. These novel methods allow the use of other materials than the traditional asymmetric cellulose acetate (CA) membranes and TFC polyamide/polysulfone membranes. This review provides an outline of the membrane requirements for FO/PRO and the new methods and materials in membrane preparation.
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Full-text available
This study aims to evaluate the use of oxidation reduction potential (ORP) to regulate the injection of a small amount of oxygen into an anaerobic digester for reducing H2S concentration in biogas. The results confirm that micro-oxygen injection can be effective for controlling H2S formation during anaerobic digestion without disturbing the performance of the digester. Biogas production, composition, and the removal of volatile solids (VS) and chemical oxygen demand (COD) were monitored to assessment the digester's performance. Six days after the start of the micro-oxygen injection, the ORP values increased to between -320 and -270mV, from the natural baseline value of -485mV. Over the same period the H2S concentration in the biogas decreased from over 6000ppm to just 30ppm. No discernible changes in the VS and COD removal rates, pH and alkalinity of the digestate or in the biogas production or composition were observed.
Article
Abstract Landfill leachate contains substances that can be potentially recovered as valuable resources. In this study, magnesium in a landfill leachate was recovered as struvite with calcium pretreatment; meanwhile, the leachate volume was reduced by using a submerged forward osmosis (FO) process, thereby enabling significant reduction of further treatment footprint and cost. Without pretreatment, calcium exhibited strong competition for phosphate with magnesium. The pretreatment with a Ca2 +: CO32– molar ratio of 1:1.4 achieved a relatively low loss rate of Mg2 + (24.1 ± 2.0%) and high Ca2 + removal efficiency (89.5 ± 1.7%). During struvite recovery, 98.6 ± 0.1% of magnesium could be recovered with a significantly lower residual PO43 −-P concentration (< 25 mg L− 1) under the condition of (Mg + Caresidual): P molar ratio of 1:1.5 and pH 9.5. The obtained struvite had a similar crystal structure and composition (19.3% Mg and 29.8% P) to that of standard struvite. The FO process successfully recovered water from the leachate and reduced its volume by 37%. The configuration of calcium pretreatment - FO - struvite recovery was found to be the optimal arrangement in terms of FO performance. These results have demonstrated the feasibility of magnesium recovery from landfill leachate and the importance of the calcium pretreatment, and will encourage further efforts to assess the value and purity of struvite for commercial use and to develop new methods for resource recovery from leachate.
Article
Recovery of nutrients, water, and energy from high-strength sidestream centrate offers benefits such as reusable resource, minimized discharge and cost-savings in mainstream treatment. Herein, a microbial electrolysis cell - forward osmosis (MEC-FO) hybrid system has been investigated for integrated nutrient-energy-water (NEW) recovery with emphasis on quantified mass balance and energy evaluation. In a closed-loop mode, the hybrid system achieved recovery of 54.2 ± 1.9% of water (70.4 ± 2.4 mL), 99.7 ± 13.0% of net ammonium nitrogen (8.99 ± 0.75 mmol, with extended N2 stripping), and 79.5 ± 0.5% of phosphorus (as struvite, 0.16 ± 0.01 mmol). Ammonium loss primarily from reverse solute flux was fully compensated by the reclaimed ammonium under 6-h extended N2 stripping to achieve self-sustained FO process. The generated hydrogen gas could potentially cover up to 28.7 ± 1.5% of total energy input, rendering a specific energy consumption rate of 1.73 ± 0.08 kWh m−3 treated centrate, 0.57 ± 0.04 kWh kg−1 COD, 1.10 ± 0.05 kWh kg−1 removed NH4+-N, 1.17 ± 0.06 kWh kg−1 recovered NH4+-N, or 5.75 ± 0.54 kWh kg−1 struvite. Recycling of excess Mg2+ reduced its dosage to 0.08 kg Mg2+/kg struvite. These results have demonstrated the successful synergy between MEC and FO to achieve multi-resource recovery, and encouraged further investigation to address the challenges such as enhanced hydrogen production, reducing nutrient loss, and optimizing MEC-FO coordination towards an energy-efficient NEW recovery process.
Article
Abstract Forward osmosis (FO) is an alternative approach for treating landfill leachate with potential advantages of reducing leachate volume and recovering high quality water for direct discharge or reuse. However, energy consumption by FO treatment of leachate has not been examined before. Herein, the operational factors such as recirculation rates and draw concentrations were studied for their effects on the quantified energy consumption by an FO system treating actual leachate collected from two different landfills. It was found that the energy consumption increased with a higher recirculation rate and decreased with a higher draw concentration, and higher water recovery tended to reduce energy consumption. The highest energy consumption was 0.276 ± 0.033 kW h m−3 with the recirculation rate of 110 mL min−1 and 1-M draw concentration, while the lowest of 0.005 ± 0.000 kW h m−3 was obtained with 30 mL min−1 recirculation and 3-M draw concentration. The leachate with lower concentrations of the contaminants had a much lower requirement for energy, benefited from its higher water recovery. Osmotic backwashing appeared to be more effective for removing foulants, but precise understanding of membrane fouling and its controlling methods will need a long-term study. The results of this work have implied that FO treatment of leachate could be energy efficient, especially with the use of a suitable draw solute that can be regenerated in an energy efficient way and/or through combination with other treatment technologies that can reduce contaminant concentrations before FO treatment, which warrants further investigation.
Article
Due to the residues of tetracyclines (TCs) in swine wastewater, recovering phosphate as struvite (slow-release fertilizer) from swine wastewater may pose TCs-pharmacological threats to the agricultural planting and human health. However, limited information has been reported on the relevant works. In this study, the transport of TCs in the process of struvite crystallization was examined, and the influencing parameters, including pH value, Mg/P molar ratio and initial TCs concentration, were investigated. Results revealed that the maximum TCs adsorption capacities onto struvite crystals ranged from 1494.7 μg/L to 2160.0 μg/L. The mechanism of TCs adsorption onto struvite crystals was electrostatic adherence. The presence of Mg²⁺ interfered TCs adsorption through complexing with TCs, which was also determined by pH variation. TCs adsorption onto struvite crystals evolved three phases, including quick increase phase, fluctuation phase and steady phase, which were dominant by electrostatic adherence, dissociation and equilibrium, respectively. Furthermore, the simulated equilibrium data exhibited a Freundlich adsorption isotherm, indicating that TCs adsorption took place on the heterogeneous surface of struvite crystals.
Article
Using liquid fertilizer as a draw solute in forward osmosis (FO) to extract high-quality water from wastewater is of strong interest because it eliminates the need for regenerating draw solute, thereby requiring less energy input to system operation. However, energy consumption of such an approach has not been evaluated before. Herein, a submerged FO system with all-purpose liquid fertilizer as a draw solute was studied for energy consumption of water recovery from either deionized (DI) water or domestic wastewater. The results showed that a higher draw concentration led to higher water flux and lower energy consumption, for example 0.25 ± 0.08 kWh m⁻³ with 100% draw concentration, but reverse salt flux (RSF) was also more serious. Decreasing the recirculation flow rate from 100 to 25 mL min⁻¹ had a minor effect on water flux, but significantly reduced energy consumption from 1.30 ± 0.28 to 0.09 ± 0.02 kWh m⁻³. When extracting water from the secondary effluent, the FO system exhibited comparable performance of water flux and energy consumption to that of the DI water. However, the primary effluent resulted in obvious fouling of the FO membrane and higher energy consumption than that of the secondary effluent/DI water. This study has provided important implications to proper evaluation of energy consumption by the FO system using liquid fertilizer or other non-regenerating draw solutes.
Article
Using fertilizers as draw solutes in forward osmosis (FO) can accomplish wastewater reuse with elimination of recycling draw solute. In this study, three commercial fast-release all-purpose solid fertilizers (F1, F2 and F3) were examined as draw solutes in a submerged FO system for water extraction from either deionized (DI) water or the treated wastewater. Systematic optimizations were conducted to enhance water extraction performance, including operation modes, initial draw concentrations and in-situ chemical fouling control. In the mode of the active layer facing the feed (AL-F or FO), a maximum of 324 mL water was harvested using 1-M F1, which provided 41% of the water need for fertilizer dilution for irrigation. Among the three fertilizers, F1 containing a lower urea content was the most favored because of a higher water extraction and a lower reverse solute flux (RSF) of major nutrients. Using the treated wastewater as a feed solution resulted in a comparable water extraction performance (317 mL) to that of DI water in 72 h and a maximum water flux of 4.2 LMH. Phosphorus accumulation on the feed side was mainly due to the FO membrane solute rejection while total nitrogen and potassium accumulation was mainly due to RSF from the draw solute. Reducing recirculation intensity from 100 to 10 mL min−1 did not obviously decrease water flux but significantly reduced the energy consumption from 1.86 to 0.02 kWh m−3. These results have demonstrated the feasibility of using commercial solid fertilizers as draw solutes for extracting reusable water from wastewater, and challenges such as reverse solute flux will need to be further addressed.
Article
The knowledge we have gained in recent years on the presence and effects of compounds discharged by wastewater treatment plants (WWTPs) brings us to a point where we must question the appropriateness of current water quality evaluation methodologies. An increasing number of anthropogenic chemicals is detected in treated wastewater and there is increasing evidence of adverse environmental effects related to WWTP discharges. It has thus become clear that new strategies are needed to assess overall quality of conventional and advanced treated wastewaters. There is an urgent need for multidisciplinary approaches combining expertise from engineering, analytical and environmental chemistry, (eco)toxicology, and microbiology. This review summarizes the current approaches used to assess treated wastewater quality from the chemical and ecotoxicological perspective. Discussed chemical approaches include target, non-target and suspect analysis, sum parameters, identification and monitoring of transformation products, computational modeling as well as effect directed analysis and toxicity identification evaluation. The discussed ecotoxicological methodologies encompass in vitro testing (cytotoxicity, genotoxicity, mutagenicity, endocrine disruption, adaptive stress response activation, toxicogenomics) and in vivo tests (single and multi species, biomonitoring). We critically discuss the benefits and limitations of the different methodologies reviewed. Additionally, we provide an overview of the current state of research regarding the chemical and ecotoxicological evaluation of conventional as well as the most widely used advanced wastewater treatment technologies, i.e., ozonation, advanced oxidation processes, chlorination, activated carbon, and membrane filtration. In particular, possible directions for future research activities in this area are provided.
Article
Forward osmosis (FO) is one of the evolving membrane technologies in desalination with recent expanded new interest as a low energy process. The most significant parts of FO process are the membrane and draw solution since both play a substantial role in its performance. Hence, the selection of an appropriate membrane and draw solution is crucial for the process efficiency. Improvements in the development of membranes and draw solutes have been recorded recently. However, limitations such as fouling of FO membranes, reverse solute flux, concentration polarization, and low permeate flux in standalone FO systems. This work targets the review of recent progress in FO, aiming on the prospects and challenges. It starts with addressing the advantages of the FO process. The crucial part of this review is a thorough discussion of hybrid FO systems, different FO membranes, and draw solutes available coupled with their effects on FO performance. Finally, the future of FO for sustainable desalination is also discussed.
Article
This paper proposes a novel process for the simultaneous removal of ammonia-nitrogen and phosphate from simulated swine wastewater using modified zeolite. The natural zeolite was modified by magnesium salts as the adsorbent material for ammonia-nitrogen from wastewater. Mg2+ released from the adsorption process served as the magnesium source in struvite crystallization. The treatment of simulated swine wastewater using modified zeolite at pH 8-9.5 showed much better efficiencies of ammonia-nitrogen and phosphate removal than those by natural zeolite at the same pH. The high nutrient-removal efficiencies were mainly achieved because of cooperation between adsorption by modified zeolite and struvite crystallization. When the reaction condition was controlled at 110 g/L of modified zeolite and 40 min of reaction time, the ammonia-nitrogen and phosphate-removal efficiencies reached 82% and 98%, respectively. The individual presence of K+, Ca2+, Na+, and Mg2+ had a significantly negative effect on the removal of ammonia-nitrogen in the order of preference of Ca2+ > Mg2+ > K+ > Na+ at identical molar concentrations. Nevertheless, the presence of these ions, except for Na+, had a positive influence on the removal of phosphate. In addition, investigation of the effects of organic acids on the process showed that the removal of nutrients could be significantly reduced by inhibiting struvite crystallization by citric acid present in the simulated swine wastewater. However, the presence of acetic acid had no effect on the proposed process. An economic evaluation revealed that the treatment cost of the proposed process was 3.65 $/m(3) of simulated swine wastewater.
Article
The total ammonia nitrogen (TAN) was removed from swine wastewater using MgO-saponification wastewater as the source of magnesium for struvite precipitation. The experimental results indicated that pH regulators had a significant effect on the extent of struvite precipitation. The effect of pH regulators on the TAN removal ratio was as follows: K2CO3 > KOH > Na2CO3 > NaOH at identical pHs. The corresponding order for the removal of phosphate was KOH > NaOH > K2CO3 > Na2CO3. When struvite crystallization occurred in the presence of ferric ions at 0–500 mg/L concentration, the TAN removal ratio decreased from 89.7% to 82%. Nevertheless, the removal ratio could be remarkably improved by intermittent addition of magnesium source. The pilot-scale experiments revealed that an average of 93% (±3%) TAN removal could be achieved in a continuous-flow reactor by dosing the MgO-saponification wastewater at Mg:N:P ratio of 1.1:1:1 via seeding crystal technique. An economic evaluation showed that the cost for struvite precipitation could be reduced by approximately 12.4% using the combined treatment of swine wastewater and MgO-saponification wastewater as compared with the use of pure magnesium salts.
Article
We demonstrate the simultaneous extraction of phosphorus and clean water from digested sludge centrate using a forward osmosis (FO)–membrane distillation (MD) hybrid process. In this FO–MD hybrid process, FO concentrates orthophosphate and ammonium for subsequent phosphorus recovery in the form of struvite (MgNH4PO4·6H2O), while MD is used to recover the draw solution and extract clean water from the digested sludge centrate. A decline in water flux was observed during the FO process, but fouling was largely reversible after a brief, simple membrane flushing using deionized water. The FO process also provides an effective pretreatment capacity to the subsequent MD process, which exhibited stable water flux. The use of MgCl2 as the draw solute for the FO process is another novel aspect of the system. The reverse salt flux of magnesium to the concentrated digested sludge across the FO membrane and the diffusion of protons away from the digested sludge create favorable conditions for the formation of struvite crystals. The precipitates obtained in the hybrid process were verified to be struvite crystals by examining the crystal morphology, element composition, and crystal structure. Results reported here highlight the potential and robustness of the FO–MD hybrid process for extracting phosphorus from wastewater.
Article
Cellulose triacetate/cellulose acetate (CTA/CA)-based membranes for forward osmosis (FO) were prepared by immersion precipitation. Casting composition and preparation conditions — 1,4-dioxane/acetone ratio, CTA/CA ratio, substrate type, casting thickness, evaporation time and annealing temperature — were tested for their effects on formation and subsequent performance of membranes. Membranes were characterized by various methods, and their performances were tested against commercially available membranes. The FO membrane prepared under optimized composition and conditions had a smooth surface and showed higher water flux and salt resistance than the commercial membranes. Annealing improved the membrane performance by removing residual additives and solvents. The computerized image processing of optical microscopy images was shown to be useful for assessing the membrane substrates.
Article
Membrane cleaning efficiency depends on many parameters such as hydrodynamic conditions, concentration and temperature of chemical cleaning solution, as well as sequence of cleaning. Various studies and industrial applications show that factorial design is an efficient method in optimization of operational parameters. In this study, a statistical factorial design was employed to identify more accurately the key factors as well as their interactions in both physical and chemical cleaning of ultrafiltration (UF) and reverse osmosis (RO) membranes in municipal wastewater reclamation. It was found that significant factors affecting physical cleaning of both UF and RO membranes are production interval between cleans, duration of backwash and pressure during forward flush. In chemical cleaning of both membranes, temperature and concentration of high pH cleaning solution and backwash after chemical cleaning play important roles. By using the optimized membrane cleaning methods, the cleaning efficiency was significantly improved, which can cause higher membrane filtration capacity and efficiency.
Article
Osmosis is a physical phenomenon that has been extensively studied by scientists in various disciplines of science and engineering. Early researchers studied the mechanism of osmosis through natural materials, and from the 1960s, special attention has been given to osmosis through synthetic materials. Following the progress in membrane science in the last few decades, especially for reverse osmosis applications, the interests in engineered applications of osmosis has been spurred. Osmosis, or as it is currently referred to as forward osmosis, has new applications in separation processes for wastewater treatment, food processing, and seawater/brackish water desalination. Other unique areas of forward osmosis research include pressure-retarded osmosis for generation of electricity from saline and fresh water and implantable osmotic pumps for controlled drug release. This paper provides the state-of-the-art of the physical principles and applications of forward osmosis as well as their strengths and limitations.
Article
Air-cathode single chamber microbial fuel cells (MFCs) were operated with swine wastewater. The maximum power density, the maximum current density, the average value of COD-removal efficiency, and the coulombic efficiency were 1-2.3 W/m(2), 6.0-7.0 A/m(2), 76-91%, and 37-47%, respectively. During operation, 70-82% of the phosphorus was removed from the influent, and some precipitations were observed on the surface of the liquid side of the cathodes. The amount of phosphorus contained in these precipitates was estimated to be equivalent 4.6-27% of the influent. The main component of these precipitates was revealed by X-ray diffraction analysis to be struvite. Furthermore, our results indicate that phosphorus in suspended solid form was first dissolved, and then precipitated on the cathode. By scanning electron microscope observation, the morphology of the precipitates was irregularly shaped, including crystals with hexagonal cross-section surfaces, and was different from the familiar needle-like ones. These results indicate that simultaneous recovery of electrical power and phosphorus from wastewater by microbial fuel cell is possible.
Article
Forward osmosis (FO) is a membrane separation technology that has been studied in recent years for application in water treatment and desalination. It can best be utilized as an advanced pretreatment for desalination processes such as reverse osmosis (RO) and nanofiltration (NF) to protect the membranes from scaling and fouling. In the current study the rejection of trace organic compounds (TOrCs) such as pharmaceuticals, personal care products, plasticizers, and flame-retardants by FO and a hybrid FO-RO system was investigated at both the bench- and pilot-scales. More than 30 compounds were analyzed, of which 23 nonionic and ionic TOrCs were identified and quantified in the studied wastewater effluent. Results revealed that almost all TOrCs were highly rejected by the FO membrane at the pilot scale while rejection at the bench scale was generally lower. Membrane fouling, especially under field conditions when wastewater effluent is the FO feed solution, plays a substantial role in increasing the rejection of TOrCs in FO. The hybrid FO-RO process demonstrated that the dual barrier treatment of impaired water could lead to more than 99% rejection of almost all TOrCs that were identified in reclaimed water.
Article
Anaerobically digested swine wastewater contains high concentrations of phosphorus (P) and nitrogen (N). A pilot-scale experiment was carried out for nutrients removal and recovery from anaerobically digested swine wastewater by struvite crystallization. In the pilot plant, a sequencing batch reactor (SBR) and a continuous-flow reactor with struvite accumulation devices were designed and employed. The wastewater pH value was increased by CO(2) stripping, and the struvite crystallization process was performed without alkali and Mg(2+) additions. Results of the long-term operation of the system showed that, both reactors provided up to 85% P removal and recovery over wide ranges of aeration times (1.0-4.0 h), hydraulic retention times (HRT) (6.0-15.0 h) and temperatures (0-29.5°C) for an extended period of 247 d, in which approximate 30% of P was recovered by the struvite accumulation devices. However, 40-90% of NH(4)(+)-N removed was through air stripping instead of being immobilized in the recovered solids. The recovered products were detected and analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD) and chemical methods, which were proved to be struvite with purity of more than 90%. This work demonstrated the feasibility and effects of nutrients removal and recovery from anaerobically digested swine wastewater by struvite crystallization without chemical additions.
Article
Recent legislation on the removal of nutrients from wastewater has led to a number of operation problems with struvite scaling. Struvite is MgNH4PO4 x 6H2O and this paper reviews the formation, control and recovery of struvite from primarily municipal wastewater and other waste streams. Treatment options for control and technologies for recovery are discussed.
Article
The building of a sustainable society will require reduction of dependency on fossil fuels and lowering of the amount of pollution that is generated. Wastewater treatment is an area in which these two goals can be addressed simultaneously. As a result, there has been a paradigm shift recently, from disposing of waste to using it. There are several biological processing strategies that produce bioenergy or biochemicals while treating industrial and agricultural wastewater, including methanogenic anaerobic digestion, biological hydrogen production, microbial fuel cells and fermentation for production of valuable products. However, there are also scientific and technical barriers to the implementation of these strategies.
Article
Ammonia losses during swine wastewater treatment were examined using single- and two-chambered microbial fuel cells (MFCs). Ammonia removal was 60% over 5 days for a single-chamber MFC with the cathode exposed to air (air-cathode), versus 69% over 13 days from the anode chamber in a two-chamber MFC with a ferricyanide catholyte. In both types of systems, ammonia losses were accelerated with electricity generation. For the air-cathode system, our results suggest that nitrogen losses during electricity generation were increased due to ammonia volatilization with conversion of ammonium ion to the more volatile ammonia species as a result of an elevated pH near the cathode (where protons are consumed). This loss mechanism was supported by abiotic tests (applied voltage of 1.1 V). In a two-chamber MFC, nitrogen losses were primarily due to ammonium ion diffusion through the membrane connecting the anode and cathode chambers. This loss was higher with electricity generation as the rate of ammonium transport was increased by charge transfer across the membrane. Ammonia was not found to be used as a substrate for electricity generation, as intermittent ammonia injections did not produce power. The ammonia-oxidizing bacterium Nitrosomonas europaea was found on the cathode electrode of the single-chamber system, supporting evidence of biological nitrification, but anaerobic ammonia-oxidizing bacteria were not detected by molecular analyses. It is concluded that ammonia losses from the anode chamber were driven primarily by physical-chemical factors that are increased with electricity generation, although some losses may occur through biological nitrification and denitrification.
QC guidance for sampling and analysis of sediments, water, and tissues for dredged material evaluations
  • Us Epa
US EPA, QA/QC guidance for sampling and analysis of sediments, water, and tissues for dredged material evaluations, Office of Water, Washington, DC (1995) 297.