Article

Enhancing the removal of ammonia in nitrifying biofilters by the use of a zeolite containing expanded clay aggregate filtermedia

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Abstract

Pilot plant experiments were carried out on a nitrifying biofilter with a zeolite containing expanded clay aggregate filtermedia (Filtralite ZL). The filter removed ammonium from domestic wastewater by a combination of nitrification and ion exchange. An identical filter material, but without sorptive capacity with respect to ammonium, was used as a reference (Filtralite). The experiments demonstrated that Filtralite ZL removed more ammonium at high ammonium loading rates than Filtralite. This was caused by ion exchange of ammonium in addition to nitrification. Under low ammonium loading rates, nitrification of already sorbed ammonium took place. This combined effect of ion exchange and nitrification of ammonium in Filtralite ZL was demonstrated in experiments with constant ammonium loading for periods up to 10 days and as well as in experiments with daily variations in ammonium loading rate. No chemical regeneration was necessary in addition to the biological regeneration during the experimental period of four months.

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... De la même façon, l'adsorption de NH4-N a été estimé à 33% dans la matière organique accumulée dans le 1er étage d'un FV française classique alimenté en effluent brut (Morvannou et al., 2014). De même il a été aussi observé que la régénération biologique a eu lieu dans un filtre garnis de matériaux poreaux (Leca®) et zéolite dont l'adsorption de NH4-N a été suivie d'une régénération de sites d'adsorption en continu par nitrification, sans besoin de l'ajout de produits chimiques pour la régénération (Gisvold et al., 2000). ...
... Thus, to improve NH4-N removal the use of natural zeolite as a medium support in single HF with artificial aeration increased efficiency above 90% compared with conventional materials (Araya et al., 2016). In addition, to enhance NH4-N by zeolite, it was reported that adsorption sites were continuously regenerated by nitrification without adding chemical products for material regeneration (Gisvold et al., 2000). Similarly, the analysis of microbial activity showed that zeolite is capable of providing growth support for nitrifying bacteria favored by aerobic conditions (Beebe et al., 2013). ...
... Another possibility is the use of zeolite which promote ammonium adsorption (Wang and Peng, 2010). The media is then regenerated by nitrates release produced during rest period or between batch feeding (Gisvold et al., 2000). ...
Thesis
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Discharge limits are becoming increasingly stringent for small communities and sensitive eutrophication areas. The objective is to established new community obligations by setting environmental quality targets (up to 15 mgNGL.L⁻¹ and 2 mgPtot.L⁻¹) especially to the improvement of wastewater treatment in small communities (<2000 p.e). In France, the use of Treatment Wetlands to treat domestic wastewater from small communities (<2 000 p.e.) has increased exponentially in recent years. The classical Vertical Flow Treatment Wetland (VFTW) enable very good performances removal in terms of TSS, COD and TKN, nevertheless denitrification (TN) and phosphorus removal (Ptot) are limited. The aim of this work was to develop innovative solutions, allowing the reduction of the footprint and the improvement of the classical French VFTW in terms of nitrogen (N) removal. An integrated approach was followed with pilot scale experiments and full scale systems using real wastewater during 26 months. A comparison between results of pilots and full-scale was also carried out.The use of zeolite allowed to improve the performances by the adsorption of NH₄-N, with lower concentrations in summer (15 mg.L⁻¹), using a compact filter (95 cm) with passive aeration pipes. However, fluctuations were observed at low temperatures decreasing the removal performances.Similarly, a configuration based on the combination of unsaturated-saturated conditions for NGL removal was evaluated. The zeolite was used in the unsaturated layer to improve the NH₄-N removal and nitrification. Indeed, it has been observed that the zeolite improves the purifying performance compared to a filter filled only with gravel. The outlet concentrations were 40 and 52 mgNGL.L⁻¹ for zeolite and gravel filters respectively.The use of recirculation in full scale systems has improved removal performances in unsaturated / saturated single stage. However, these are preliminary results as these stations are in the start-up and maturation period, few 24 h samples were available, which makes the comparison difficult.
... At the same time, the nitrifying bacteria that grew on the surface of the activated carbon filler and among the roots of the water spinach and the activated sludge that formed at the bottom of the devices converted NH 4 + -N into nitrate or nitrite nitrogen [16]. The nitrification process can be described with the following equation [17]: ...
... Denitrification is a result the reduction of NO 3 --N to N 2 or N 2 O by denitrifying bacteria under anaerobic conditions [17]. The reaction equation is as follows [22]: NO 3 -+ 4g COD + H + → 0.5N 2 + 1.5g sludge (3) The spray interval time in QW3 was the longest such that the anaerobic reaction time was sufficient. ...
... The common ammonium removal processes are air stripping, chemical treatment, selective ion exchange and biological nitrification-denitrification [1][2][3]. An attractive process for removal of ammonium is ion exchange [4][5][6][7][8][9]. The ion exchange method usually employs organic resins, which are selective but very expensive. ...
... As shown in Fig. 4, three isotherms had been obtained at 20, 40 and 60 • C. According to linear regression, the relation of ln K c and A c can be got, then the value of K a can be calculated in terms of Eq. (5). The free energy ( G • ) of the exchange reaction can be obtained from Eq. (6). The values of H • and S • were determined from the slope and intercept of the plots of ln K a versus 1/T according to Eqs. (7) and (8). ...
Article
The paper concerns the removal of ammonium ions from aqueous solution using a modified clinoptilolite-Ca(2+)-formed clinoptilolite (CaY) prepared from natural clinoptilolite. The batch study results show that the pH has an effect on ammonium adsorption capacity as it can influence both the character of the exchanging ions and the clinoptilolite itself; the CaY has a high selectivity to NH(4)(+) and the exchange decreases with increasing temperature; ammonium ion uptake onto CaY was suitably described by the Langmuir model. The column results indicated that the effluent of simulated wastewater treated with CaY could meet the integrated wastewater discharge standard of China, and CaY can be circulated through regenerating by Ca(OH)(2).
... Therefore, the use of zeolites in a fixed-bed adsorber serves two purposes: they remove NH 4 + while simultaneously acting as a NH 4 + -reservoir to buffer fluctuating inlet concentrations. Furthermore, Gisvold et al. demonstrated that no chemical regeneration was necessary during a four-month operational period of removing NH 4 + from domestic wastewater by nitrification and zeolites [35]. These studies demonstrate enhanced nitrogen removal rates and establish sustainable regeneration methods for extending the filter's run-time. ...
Article
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The ever-increasing consumption of ammonium fertilizer threatens aquatic environments and will require low-power water treatment processes. With a focus on the treatment of drinking water, the scope of this study was to investigate the feasibility of a sequential Anammox zeolite-biofilter with an anaerobic river and tap water mixture (NH4+: 4.3 mg/L; NO2−: 5.7 mg/L). When the filter velocity was set to 0.032 m/h, NH4+ and NO2− were removed with efficiencies of 86% and 76%, respectively. Remarkably, lowering the substrate concentrations and operating temperatures only resulted in a minor reduction in the efficiencies of nitrogen removal compared to wastewater treatment plants. The coupling of the zeolite and Anammox processes influenced the NO2−/NH4+-ratio as the zeolites removed NH4+ at a higher rate. Reliable process monitoring can be achieved by correlating the electrical conductivity and the removal of nitrogen compounds (R2 = 0.982). The WHO threshold values of all nitrogen compounds could be met using this setup, and thus, it could lead to a significant improvement in drinking water quality around the world. Thus, the Anammox zeolite-biofilter is promising as a cost-effective and low-power technology, especially for decentralized use in threshold and developing countries, and should therefore be the subject of further investigation.
... The use of zeolite in a single horizontal flow wetland with artificial aeration increased the NH 4 -N removal efficiency between 25 and 60% compared to conventional materials (Araya et al. 2016). In an experiment lasting ten months, Gisvold et al. (2000) found a continuous biological regeneration of the NH 4 -N sorption capacity of zeolite in a filter column charged with wastewater with strongly fluctuating inflow concentrations. ...
Article
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The scope of this study was to investigate if using zeolite as a reactive material in a vertical-flow wetland under field conditions improves ammonium removal from domestic wastewater in the long term. The experimental setup consisted of two pilot-scale first stage French vertical flow treatment wetlands (2.3 m2 surface area each), which were implemented under field scale conditions inside a wastewater treatment plant in the central region of France (L'Encloitre, 37360). The filters were operated during 27 months. A compact pilot containing Leca® as a main filtration layer (Ø 1–5 mm) was compared to a similar one filled with natural zeolite (Ø 2–5 mm). The pilots were fed according to regular feeding/resting periods (3½/7 days) and the nominal loading rate was of 300 g COD m−2 d−1 and 33 g·N·m−2·d−1 during operation. In both pilots, results showed a removal efficiency of more than 90 and 85% for TSS and COD, respectively. They also showed an increased NH4-N removal of 9% on average (total removal efficiency of 84%) with the use of zeolite compared to Leca®. The ion exchange capacity of zeolite seemed not to be affected after 27 months of experiments; however, the material was compacted and more friable after operation. HIGHLIGHTS A zeolite layer in a French Vertical-Flow Wetland improved the ammonium removal.; Seasonal effects impacted the removal efficiency.; Material compaction of the zeolite during the trial period needs to be further investigated.;
... Sieves were installed at the top of the airlift bioreactor in order to keep the carriers in the bioreactor. Expanded clay has been proven to be a good surface for nitrifying microorganisms (Gisvold et al., 2000;Patroescu et al., 2016). Its low density (1030 kg/m 3 ) makes it applicable for low energy fluidization in airlift bioreactors and therefore we used it in this study. ...
Article
In this study, a 1000 L pilot scale internal loop airlift bioreactor was operated and compared to a mathematical model to determine the best design for optimal supply of oxygen for nitrification and sufficient air for biomass fluidization. The design model is based on parameters such as geometry, carrier density, and airflow of the 1000 L pilot scale bioreactor. The model predicts a range of superficial air velocities (0.009–0.013 m/s) under which the airlift bioreactor was fluidized. Three superficial air velocities (0.009 m/s, 0.011 m/s and 0.013 m/s) were experimentally tested in the pilot plant and the obtained circulation velocities were compared with the predicted design scenarios. The predicted velocity was in agreement with the measured velocity. The aim of the mathematical model and the calculations of different geometry scenarios was to define the optimal geometry design for the physical model. The results show that the ratio of the cross-sectional area between the riser and the downcomer of 1.33 resulted in the lowest superficial liquid velocity of 0.076 m/s in the riser at a relative low superficial air velocity of 0.011 m/s and a carrier density of 1030 kg/m³. This bioreactor design enabled longest retention time of particles in the oxygenated riser.
... At the same time, the nitrobacteria growing on the surface of zeolite can promote the oxidation of NH4 + -N to nitrate nitrogen. The equation for the nitrification process is given by [23]: ...
Article
The efficiency of bio-tricking filter used for domestic sewage, livestock wastewater, food wastewater, etc. was universally dependent on zeolite size distribution, however its influence rule for black water treatment is still unclear now. In this study, we constructed five kinds of bio-trickling filters loaded with different size distribution of zeolite to systematically investigate the removal characteristics of turbidity, ammonia nitrogen (NH⁴⁺-N), total nitrogen (TN), total phosphorus (TP) and chemical oxygen demand (COD) of black water. The results showed that under the same hydraulic loading and influent water quality, the filter filled of small (5mm or less) size zeolite and another one covered with large-size (15-30mm), medium-size (5-15mm), small-size in sequence were better than those filled with large and medium size zeolite respectively or the mixture of three size on the removal efficiency of turbidity, NH⁴⁺-N, TN, TP and COD. Although the removal efficiency of the filter filled of small size zeolite was similar to layered model, layered model gave optimal performance for treating water considering the issues of cost and clogging. When the average concentrations of turbidity, NH4⁺-N, TN, TP, COD were 286.5 NTU, 116.1 mg/L, 159.8 mg/L, 14.9 mg/L, 742.4 mg/L in black-water, the layered model reached them reduction of 88.6%, 97.3%, 70.5%, 22.5%, 77.2%.
... In Norway, "zeolite containing expanded clay aggregate filter media" was used to remove ammonia from domestic wastewater by a combination of nitrification and ion exchange. No chemical regeneration was necessary in addition to the biological regeneration during the four-month experimental period [23]. Zeolites used for stripping ammonium in reactors are typically sand-sized aggregates combining a relatively large exterior surface area with ease of handling. ...
Article
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Water quality in San Francisco Bay has been adversely affected by nitrogen loading from wastewater treatment plants (WWTPs) discharging around the periphery of the Bay. While there is documented use of zeolites and anammox bacteria in removing ammonia and possibly nitrate during wastewater treatment, there is little information available about the combined process. Though relatively large, zeolite beds have a finite ammonium adsorption potential and require periodic re-generation depending on the wastewater nitrogen loading. Use of anammox bacteria reactors for wastewater treatment have shown that ammonium (and to some degree, nitrate) can be successfully removed from the wastewater, but the reactors require careful attention to loading rates and internal redox conditions. Generally, their application has been limited to treatment of high-ammonia strength wastewater at relatively warm temperatures. Moreover, few studies are available describing commercial or full-scale application of these reactors. We briefly review the literature considering use of zeolites or anammox bacteria in wastewater treatment to set the stage for description of an integrated zeolite-anammox process used to remove both ammonium and nitrate without substrate regeneration from mainstream WWTP effluent or anaerobic digester filtrate at ambient temperatures.
... On the other hand, biological regeneration of spent media in a fluidized bed reactor seems to be a more attractive option. Gisvold et al. (2000) investigated the biological regeneration of a natural zeolite used to adsorb ammonia from municipal wastewater. Xing and Hickey (1994) bioregenerated successfully a GAC in a fluidized bed reactor treating BTX from groundwater (FBR). ...
... Later processes exploited the ability of the bacteria to directly strip the ammonium from the zeolite, thereby simplifying the process (Jung et al., 2004). For example, in Norway ''zeolite containing expanded clay aggregate filter media'' was used to remove ammonia from domestic wastewater by a combination of nitrification and ion exchange, and no chemical regeneration was necessary (Gisvold et al., 2000). Zeolite has been used in nitrifying biofilms (or reactors) to provide a dampening effect for peak or variable loads (Hedström, 2001; Inan and Baykal, 2005; McVeigh and Weatherly, 1999). ...
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The current article focuses on chemical oxygen demand (COD) and nitrogen (ammonium and nitrate) removal performance from synthetic human wastewater as affected by different substrate rocks having a range of porosities and cation exchange capacities (CECs). The aggregates included lava rock, lightweight expanded shale, meta-basalt (control), and zeolite. The first three had CECs of 1 to 4 mequiv/100 gm, whereas the zeolite CEC was much greater (-80 mequiv/100 gm). Synthetic wastewater was gravity fed to each constructed wetland system, resulting in a 4-day retention time. Effluent samples were collected, and COD and nitrogen species concentrations measured regularly during four time periods from November 2008 through June 2009. Chemical oxygen demand and nitrogen removal fractions were not significantly different between the field and laboratory constructed wetland systems when corrected for temperature. Similarly, overall COD and nitrogen removal fractions were practically the same for the aggregate substrates. The important difference between aggregate effects was the zeolite's ammonia removal process, which was primarily by adsorption. The resulting single-stage nitrogen removal process may be an alternative to nitrification and denitrification that may realize significant cost savings in practice.
... [34] The same effect was observed in a pilot-scale biofilter with biomass immobilised on zeolite containing expanded clay aggregate filtermedia. [35] Furthermore, it was found that the experimental data of ammonium adsorption obtained in the present work fitted well to both the Langmuir and Freundlich isotherms for the three zeolite particle sizes studied. To be specific, the highest determination coefficients (R 2 ) were achieved with the Freundlich isotherm with values of 0.96, 0.98 and 0.93 for zeolite particle sizes of 0.5, 1 and 2 mm, respectively. ...
Article
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An evaluation of natural zeolite as a microorganism carrier in nitrifying reactors operated in batch mode was carried out. Specifically, the influence of zeolite particle sizes of 0.5, 1.0 and 2.0 mm in diameter on microorganism adherence to zeolite, ammonium adsorption capacity and the identification of microbial populations were assessed. The greatest amount of total biomass adhered was observed for a zeolite particle size of 1 mm (0.289 g) which was achieved on the 12th day of operation. The highest ammonium adsorption capacity was observed for a zeolite particle size of 0.5 mm, which was 64% and 31% higher than that observed for particle sizes of 1.0 and 2.0 mm, respectively. The maximum de-sorption values were also found for a zeolite particle size of 0.5 mm, although when equilibrium was reached the ammonium concentrations were similar to those observed for a zeolite particle size of 1.0 mm. It was also found that the experimental data on ammonium adsorption fitted very well to the Freundlich isotherm for the three particle sizes studied. Finally, the nitrifying reactors showed similar microbial populations independently of the particle size used as microorganism carrier. The dominant bacterial community was Gammaproteobacteria making up 80% of the total population found. Betaproteobacteria were also identified and made up 12% approx. of the total population. Ammonium Oxidant Betaproteobacteria and Nitrobacter were also detected.
... The success of ammonium removal through ion exchange with clinoptilolite under various conditions, including various types of wastewater characteristics, peak loads of ammonium, and ammonium removal from relatively unpolluted water, had been documented in the literature (Koon and Kaufman, 1975;Beler Baykal and Akca Guven, 1997;Hedstrom, 2001;Beler Baykal et al., 2003;Cinar and Beler Baykal, 2004). Previous work had also indicated that simultaneous use of clinoptilolite together with nitrifiers in the combined process of ion exchange and partial nitrification was even more successful and beneficial in terms of control of ammonium discharges (Beler Baykal et al., 1994, 1996Beler Baykal, 1998;Gisvold et al., 2000aGisvold et al., , 2000bHedstrom, 2001). ...
Article
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Ammonium selective natural zeolite clinoptilolite is suggested as a possible support material for nitrifying biofilms to help improve effluent ammonium quality through its high capacity of ammonium removal in the process of ion exchange. This will especially be helpful in cases where the biofilter receives peak or variable loads routinely or occasionally. At the time of peak loads or shocks of ammonium, ion exchange capacity will provide a buffer for the effluent ammonium quality. Data to support this suggestion is presented.
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On-site sewage treatment and disposal systems (OSTDSs) are oftentimes used to treat human waste accruing from nearly one-third of the U. S. population. Operation of OSTDS contributes a large fraction of nutrient loads to groundwater aquifers. This article aims to develop and present a new "green sorption medium,'' which has not been fully tested before, to be placed in the vadose zone of the OSTDS underground drain fields. This green sorption medium is comprised of recycled materials with "green'' implications for nutrient absorption and adsorption. The composition or recipe of the new material mix was derived based on a thorough literature review. Technical coverage of this study includes material characterization, batch isotherm identification, and a microcosm study leading to improve the application potential of these new material mixes. Batch absorption isotherm data was well fitted by the Langmuir and Freundlich isotherm models. Under the hydraulic retention time of 24 h in a laboratory-scale microcosm of unique functional design, removal efficiencies were found significant for all pollutants of concern. Running as a continuous system, the microcosm, filled with the preselected recipes, was dosed with septic effluent containing 1.76mg L(-1) of ammonia, 0.166mg L(-1) of nitrite, 0.352mg L(-1) of nitrate, and 1.498mg L(-1) of orthophosphorus. This study confirmed 55% removal efficiency of nitrates and 89% of phosphorus under a hydraulic retention time of 24 h. With the aid of Langmuir isotherm data, the theoretical life expectancy of the proposed sorption media mix used in the microcosm was estimated to be 1.2 years for phosphorus sorption. Results obtained largely complement current knowledge on the use of green sorption media for nutrient removal. These findings should also elaborate full-scale field studies in the future.
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The use of source separated human urine as fertilizer is one of the major suggestions of the new sanitation concept ECOSAN. Urine is rich in nitrogen, phosphorus and potassium which act as plant nutrients, however its salinity is high for agricultural and landscape purposes. Moreover, characteristics change significantly throughout storage where salinity increases to higher values as the predominant form of nitrogen shifts from urea to ammonium. Transferring nitrogen in human urine onto the natural zeolite clinoptilolite and using the subsequently recovered ammonium from the exhausted clinoptilolite for agricultural/landscape purposes is suggested as an indirect route of using urine in this work. Results reporting the outcome of the proposed process together with characterization of fresh and stored urine, and preliminary work on the application of the product on the landscape plant Ficus elastica are presented. Up to 97% of the ammonium in stored urine could be transferred onto clinoptilolite through ion exchange and about 88% could be recovered subsequently from exhausted clinoptilolite, giving an overall recovery of 86%. Another important merit of the suggested process was the successful elimination of salinity. Preliminary experiments with Ficus elastica had shown that the product, i.e. clinoptilolite exhausted with ammonium, was compatible with the synthetic fertilizer tested.
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In recent years the nutrient levels of the Upper Floridan aquifer have been increasing (USGS, 2008). An example of this is found in Ocala, Florida where Silver Springs nitrate concentrations have risen from 0.5 mg/L in the 1960 s to approximately 1.0 mg/L in 2003 (Phelps, 2004). Because stormwater is a contributor to surficial and groundwater aquifer recharge, there is an increasing need for methods that decrease nitrogen and phosphorus levels. A laboratory column study was conducted to simulate a retention pond with saturated soil conditions. The objectives of the column studies reported in this thesis were to investigate the capabilities of a natural soil and soil augmentations to remove nitrogen and phosphorus for a range of concentrations at three different temperatures. An analytical attempt to model the columns through low order reaction kinetics and derive the corresponding temperature conversion constant to relate the rate constants is also presented. The Media Mixes were selected through a process of research, preliminary batch testing and then implemented in column studies. Three columns measuring three feet in length and 6 inches outer diameter were packed with a control and two media mixes. Media Mix 1 consisted of 50% fine sand, 30% tire crumb, 20% sawdust by weight and Media Mix 2 consisted of 50% fine sand, 25% sawdust, 15% tire crumb, 10% limestone by weight. The control column was packed with natural soil from Hunter s Trace retention pond located in Ocala, Florida. The reaction rates for nitrate are best modeled as first order for Media Mix 1, and zero order for the Control and Media Mix 2. The reaction rates for orthophosphate are best modeled as zero order, second order and first order for the Control, Media Mix 1, and Media Mix 2 respectively. The best overall media for both nitrate and orthophosphate removal from this study would be Media Mix 1. Media Mix 2 does have the highest average orthophosphate removal of all the mixes for all of the temperatures; however Media Mix 1 outperforms Mix 2 for the other two temperatures. The best column for Nitrate removal is the Media Mix 1 column. The temperature conversion factors for nitrate were found to be 1.11, 1.1, and 1.01 for Media Mix 1, the Control and Media Mix 2 respectively. The temperature conversion factors for orthophosphate were found to be 1.02, 0.99, and 0.95. As well as temperature conversion factors, the activation energies and frequency factors for the Arrhenius Equation were investigated. Average values corresponding to each column, species, and temperature would be inaccurate due to the large variation in calculated values.
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It had previously been shown that ammonium selective natural zeolite clinoptilolite may be used successfully as an ion exchanger for ammonium removal and nitrogen control from domestic wastewater. The process had been reported to be acceptable either by itself alone or as an upgrade. In this work, the possibility of using clinoptilolite for ammonium removal from fertilizer production wastewater was investigated. The fertilizer plant under consideration was rather a non-typical one with a lower ammonium strength than what is normally expected, and a variable effluent concentration. Batch experiments were performed to assess the capacity of clinoptilolite towards ammonium removal from an industrial wastewater at two different pHs. Flow experiments for the characterization of system behavior under continuous feeding conditions at different contact times were conducted for breakthrough analysis. Both real and simulated fertilizer wastewater samples were investigated and the results have shown that the real one may successfully be represented by the simulated one. Experimental results have shown that surface capacities exceeding 14 mg ammonium g(-1) clinoptilolite could be attained, complete removal of ammonium may be achieved with empty bed contact times of 10 min or higher and ion exchange with clinoptilolite could be used successfully to comply with the effluent standards given for the fertilizer plant.
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Possibility of using natural zeolites for water softening was investigated. Quantitative data regarding separation of calcium from water at various levels of hardness through ion exchange with the ammonium selective natural zeolite clinoptilolite is reported. Capacity of the zeolite towards calcium removal in the presence of ammonium at low concentrations and calcium at higher concentrations, and breakthrough characteristics are presented. The results have revealed that removal of calcium, and hence hardness, through ion exchange with clinoptilolite under those circumstances is a promising alternative, with surface capacities reaching 11 mg calcium/g clinoptilolite.
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Utilizing preferential ion exchange of zeolite to ammonium, the conventional contact stabilization activated sludge process (CS) can be upgraded to a new type nitrogen removal process, zeolite enhanced contact-adsorption regeneration-stabilization process (ZCS). For municipal wastewater, the effluent ammonium concentration of the ZCS process was around 6.83 mg/L, indicating that ammonium removal efficiency was enhanced over 27% when the influent ammonium concentration was between 24.7 and 50.5 mg/L in the same hydraulic retention time (HRT) and sludge retention time (SRT) conditions as those of the CS process. The results of PCR-DGGE technology showed that the microbial diversity, uniformity and abundance of the ZCS process were all higher than that of the CS process. In addition, anoxic/oxic (A/O) process with the volumetric ratio of oxic tank to anoxic tank being 2:1 was preferred for the regeneration process. The pilot scale ZCS process with the capacity to treat up to 72 m(3)/d of municipal wastewater was also monitored. The test results revealed that ammonium saturated zeolite could be biologically regenerated effectively and in time. The daily zeolite powder addition was limited to the amount that made up the loss due to the sludge excluding. Furthermore, the orthogonal experiments results showed that the most significant effects on nitrogen and ammonium removal were zeolite powder dose and external recycle ratio, respectively.
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A dynamic modeling approach was used to estimate in-situ model parameters, which describe the degradation of methyl tert-butyl ether (MTBE) in a laboratory packed bed reactor. The measured dynamic response of MTBE pulses injected at the reactor's inlet was analyzed by least squares and parameter response surface methodologies. Response surfaces were found to be statistically significant and thus suitable for estimating the global minimum as well as the 95% parameter uncertainty regions. The linear parameter uncertainty estimates for the half-saturation constant (K(S)) and the maximum growth rate (micro(max)) were: 0<K(S)<10 mg COD/L and 0.12<micro(max)<0.25 d(-1). Obtaining reliable parameters is a necessary step towards model application in order to study practical reactor operational problems such as the competition between the relatively slow growing MTBE degraders and the oxidizers of other groundwater co-contaminants such as ammonium, benzene, toluene, ethylbenzene and xylenes.
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Post equalization of peak ammonia loads in a filter with biological activity in combination with an ion exchanger is proposed as an alternative to the classical large volume equalization basin for wastewater treatment plants receiving variable influent concentrations. The results obtained indicate this modification to be very promising to dampen peaks of 2–5 times the averag value. As such the system is not only useful for plants to be newly designed and constructed, but also for existing systems especially with such filters. Current systems which cannot handle peak loads successfully by themselves, can be upgraded just by the addition of the correct amount of the ion exchanger into the filter bed.
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A new concept for ammonium removal from secondary effluent by zeolite followed by bioregeneration has been studied. In contrast to other studies of hybrid biological-ion exchange multireactor systems, the proposed process uses the ion exchange material, zeolite, as a carrier for the nitrifying biomass. Therefore, the entire process is carried out in a single reactor. Since all the ammonium from the original effluent is concentrated in the zeolite and released gradually during regeneration, nitrification is carried out in a small volume reactor in an almost batch mode where optimal conditions for nitrification can easily be maintained. Moreover, the conversion of ammonium cations to nitrate anions allows for regenerate recycle, where the amount of chemicals added for desorption is reduced to the amount of sodium bicarbonate added as a buffer for nitrification. As a result, operational costs and production of large volumes of brine are minimized. To achieve sufficient NH4+ concentration in the solution to allow for high rate nitrification, the cation-rich regenerant solution (or part of it) is reused from one cycle to the next. A theoretical model including ion exchange and bioregeneration modes, indicates that the total cation concentration and each cation in the recycled regenerant should reach constant values after several cycles of adsorption–regeneration and remain constant as long as the influent characteristics and operation conditions stay similar. Experiments results verified the predicted values.
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The potential of ammonia removal through ion exchange with clinoptilolite was investigated under constant and variable loads. Clinoptilolite, by itself and in combination with a filter with biological activity was studied. Special attention was given to peak loads of ammonia. It has been demonstrated that ion exchange is a very promising tool for this purpose both for new plants to be designed and as upgrades in existing facilities.
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In this study the use of zeolites as ion-exchangers for equalization of ammonia peak loadings in aerated biological activated filters was investigated. For this use zeolites were mixed with a filter medium and the nitrifying filter was loaded with ammonia peaks for two hours at different flow rates. It could be demonstrated that during the phase of higher inflow concentrations the zeolite was collecting ammonia. When the influent concentration decreased ammonia was desorbed from the zeolite and could be nitrified by the bacteria growing on the filter medium. It was shown that additional zeolites can equalize variations of ammonia, especially in filter units which are working at a high nitrification rate and which are very sensitive to varying influent conditions. During the operation time of the filter no separation of the zeolite by higher hydraulic loading or by backwashing could be recognized. So the upgrading of nitrifying filters with zeolite represents an additional security for effluents containing oscillating ammonia concentrations.