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Treatment and Recycling of Wastewater from Oil Refinery/Petroleum Industry

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Abstract

Petroleum refinery effluents (PRE) are generally the wastes generated from industries primarily engaged in refining crude oil, manufacturing fuels, lubricants and petrochemical intermediates. These effluents or wastewater, generated, are considered as a major source of aquatic environmental pollution. The effluents are mainly composed of oil, grease and many other toxic organic compounds. The process of crude oil refining consumes large volume of water. Consequently, significant volume of wastewater is generated. The requirement of water depends upon on the size, crude products and complexity of operation. Petroleum refining units need water for distillation, desalting, thermal cracking, catalytic and treatment processes in order to produce useful products such as LPG (Liquefied Petroleum Gas), gasoline, asphalt, diesel, jet fuel, petroleum feedstock etc. Wastewater generated through petroleum refineries contains various hydrocarbons. It has been estimated that the demand for world oil is expected to rise to 107 mbpd (million barrels per day) in the next two decades. By 2030 oil will account for 32% of the world’s energy supply. The increasing demand of oil clearly shows that effluents produced from the oil industry will continue to be produced and discharged into the water bodies. The pollutants found in the effluent are seriously toxic and hazardous to the environment. Techniques used for effluent treatment include adsorption, coagulation, chemical oxidation, biological techniques as well as contemporary technologies like membranes and microwave-assisted catalytic wet air oxidation and Advanced oxidation processes (AOP) like heterogeneous photo-catalytic degradation which is based on its potential to completely mineralize the organic effluents beside being cost effective, readily available and the catalyst used itself is non-toxic in nature. The review provides a detailed description on nature of effluent or wastewater produced from the oil refinery units, its discharge into the water bodies, toxicological effects of the effluent on terrestrial and aquatic ecosystem and the various treatment technologies designed for the treatment and recycling of wastewater generated during operation.

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... A significant amount of steam is used in the distillation unit; resulting vapours get condensed that contain hydrocarbons products, hydrogen sulphide, ammonia, etc. (EI-Nass et al., 2014). Distillation unit produces sour water, usually contaminated with ammonia, chlorides, phenol, hydrogen sulphide, mercaptans, and suspended solids (Singh, 2019). ...
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... The process is conducted in the presence of hydrogen using metal catalyst (e.g., aluminium chloride activated with hydrochloric acid) at low temperature. This process generates caustic wash water (contain calcium chloride) and sour water (contain ammonia and hydrogen sulphide) (Singh, 2019). ...
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Petroleum hydrocarbons in the bilge water of small fishing vessels are continuously released into the environment. The bilge water samples usually contained low amounts of oil-degrading bacteria; therefore, this study examines application of polyurethane foam (PUF)-immobilized Gordonia sp. JC11, a known lubricant-degrading bacterial inoculum, for the treatment of bilge water. Batch microcosm experiments showed that the PUF-immobilized bacteria were more efficient at removing oil than indigenous microorganisms and were able to remove approximately 40–50 % of the boat lubricant (1,000 mg L−1). The immobilized PUF samples rapidly adsorbed oil from the bilge water inside a small fishing vessel; however, the uninoculated PUF contained more oil than the inoculated PUF at most time points. The hydrocarbon components were also different when comparing inoculated and uninoculated PUF. These results indicate that the oil accumulated inside the PUF containing immobilized bacteria was being degraded by the Gordonia sp. JC11. However, these bacteria gradually die off after repeated oil exposure, and it is suggested that PUF-immobilized cells be replaced at timed intervals. This technique is considered simple and cheap; thus, it could be used to reduce chronic oil pollution from the release of bilge water.
Article
Anaerobic ammonium-N removal from modified greenhouse turtle breeding wastewater with different chemical oxygen demand (COD) strengths (194.0-577.8mgL(-1)) at relatively fixed C/N ratios (∼2) was investigated using a lab-scale up-flow anaerobic sludge blanket (UASB) anammox reactor. During the entire experiment, the total nitrogen (TN) removal efficiency was about 85% or higher, while the average COD removal efficiency was around 56.5±7.9%. Based on the nitrogen and carbon balance, the nitrogen removal contribution was 79.6±4.2% for anammox, 12.7±3.0% for denitrification+denitritation and 7.7±4.9% for other mechanisms. Denaturing gradient gel electrophoresis (DGGE) analyses revealed that Planctomycete, Proteobacteria and Chloroflexi bacteria were coexisted in the reactor. Anammox was always dominant when the reactor was fed with different COD concentrations, which indicated the stability of the anammox process with the coexistence of the denitrification process in treating greenhouse turtle breeding wastewater.
Article
To combine the advantage of the oleaginous yeast Yarrowia lipolytica with the high activity of some fungal lipases for oily wastewater treatment, an effective lipase-displaying arming yeast was constructed using the flocculation functional domain of Saccharomyces cerevisiae as the protein anchor. To estimate the effect of the whole-cell oily wastewater treatment, the lipase-displaying arming yeast was added into an open activated sludge bioreactor. Within 72h of whole-cell treatment, 96.9% of oil and 97.6% of chemical oxygen demand (COD) were removed, while only 87.1% of oil and 91.8% of COD were removed in control A (Y. lipolytica Polg was added), 45.1% of oil and 67.5% of COD were removed in control B (no cell was added) in 72h. The lipase-displaying arming yeast exhibited remarkable oil removal and COD degradation effect compared with the control samples, exemplifying its application potential.
Article
A novel approach was developed to enhance the efficiency of the dissolved air flotation (DAF) for biodiesel wastewater by acidification and coagulation. Firstly, Grease & Oil and Chemical oxygen demand (COD) removal efficiencies of biodiesel wastewater using acidification with pure hydrochloric acid and pure sulfuric acid at pH=3 and 1day retention time were more than 80%, and 50%, respectively. Secondly, Grease & Oil and COD removal efficiencies of biodiesel wastewater using alum, polyaluminum chloride and ferric chloride coagulants without acidification at 1.0g/L were more than 90% and 30%. Thirdly, DAF alone and DAF with acidification could not separate Grease & Oil from biodiesel wastewater. Thus, DAF with the acidification and coagulation is suggested for biodiesel wastewater treatment. Biodiesel wastewater treatment by acidification before alum coagulation allowed the alum concentration to be reduced by 60–90% compared to treating without acidification. In addition, the efficiency of Grease & Oil removal from biodiesel wastewater by DAF with alum and acidification was 85–95%. It can be concluded that the efficiency of Grease & Oil removal from biodiesel wastewater using DAF with acidification and coagulation was 10% greater compared to other processes.
Article
The Kinneil intertidal area, situated in the middle reaches of the Forth estuary, eastern Scotland, has been subject to the effects of industrial discharges, principally from petro-chemical industries (oil refinery and chemical works) since the 1920s.The intertidal fauna has been studied annually since 1976 using consistent methodology (90 stations, each with two samples of 5 × 5 × 5 cm, through a 250 μm sieve). The study continues, now providing over 20 yr of data.During the study period the discharges from the industrial sources have been reduced substantially through a combination of plant closure and modernization and the installation of effluent treatment works. Furthermore, the River Avon which flows across the area has experienced substantial improvements in water quality, attributed to improvements in waste treatment works at localities upstream from the estuarine site.Fluctuations of the faunal composition of the mudflats have been studied over the period. Some species, such as Hydrobia ulvae, Cerastoderma edule, and Nereis diversicolor show substantial fluctuations but no clear trend, whilst others such as Corophium volutator, Macoma balthica and Eteone longa show clear increases in abundance.Overall, however, the clearest trends have been increases in diversity, expressed either as mean number of species per station, or as diversity indices. These increases in diversity are shown to be a clear community response to the improvements made to the petro-chemical wastes discharged to the area.
Article
High rate algal ponds (HRAPs) are an efficient treatment for controlling wastewater pollution by reducing the organic matter and the inorganic nutrient content. An experimental HRAP was set up in Mèze (France) and sampled over 24 months. A model simulating orthophosphate (PO4) evolution was constructed using Stella II software. It was thought that deterministic modelling of the temporal evolution of PO4 might provide a rational basis for pond management policies. In hardwater, two processes have to be taken into consideration: PO4 uptake by algae and PO4 precipitation. The model also has to take into account the fact that the latter process is very sensitive to nycthemeral variations in pH.Simulated PO4 concentrations over a two-year period show that about 10% of total input is removed by precipitation whereas about 30% is removed by absorption. These results are of critical importance for the management of this type of wastewater treatment system.
Article
A novel rotating biological contactor (RBC) with biodrum was designed to remove hydrocarbons in wastewater from industrial discharges, and its performance was investigated. The biodrum, a cylindrical mesh drum, filled with random packing of polyurethane foam cubes retaining petroleum-degrading achlorophyllous micro-alga Prototheca zopfii cells, was approximately 40% submergence in the culture. The amount of algal cells, immobilized in the 10-mm-cube pieces, was greater than in pieces of smaller pore size under the experimental conditions studied. A mixture of n-alkanes (C14, C15 and C16) was used as a model oil, and the influent hydrocarbons were removed by immobilized cells in the biodrum. The single-stage RBC system was operated at 25°C and at pH 7.0 in a batch mode. The removal rate for n-alkanes in the RBC with biodrum system was significantly increased as compared to those in the RBC system with polycarbonate biodisk.
Article
Chitosan is a partially deacetylated polymer obtained from the alkaline deacetylation of chitin, a biopolymer extracted from shellfish sources. Chitosan exhibits a variety of physico-chemical and biological properties resulting in numerous applications in fields such as cosmetics, biomedical engineering, pharmaceuticals, ophthalmology, biotechnology, agriculture, textiles, oenology, food processing and nutrition. This amino-biopolymer has also received a great deal of attention in the last decades in water treatment processes for the removal of particulate and dissolved contaminants. In particular, the development of chitosan-based materials as useful coagulants and flocculants is an expanding field in the area of water and wastewater treatment. Their coagulation and flocculation properties can be used to remove particulate inorganic or organic suspensions, and also dissolved organic substances. This paper gives an overview of the main results obtained in the treatment of various suspensions and solutions. The effects of the characteristics of the chitosan used and the conditions in solution on the coagulation/flocculation performance are also discussed.
Book
This book presents the techniques, technologies, regulations, and strategies that define pollution prevention. The subject is addressed from many perspectives by prominent experts. In many ways pollution prevention, rather than being a specialty field itself, is actually a convergence of fields drawing upon knowledge in a wide variety of more typical fields of expertise. Individual chapters have been processed separately for inclusion in the appropriate data bases.
Article
Pseudoxanthomonas sp. RN402 was capable of degrading diesel, crude oil, n-tetradecane and n-hexadecane. The RN402 cells were immobilized on the surface of high-density polyethylene plastic pellets at a maximum cell density of 10(8) most probable number (MPN) g(-1) of plastic pellets. The immobilized cells not only showed a higher efficacy of diesel oil removal than free cells but could also degrade higher concentrations of diesel oil. The rate of diesel oil removal by immobilized RN402 cells in liquid culture was 1,050 mg l(-1) day(-1). Moreover, the immobilized cells could maintain high efficacy and viability throughout 70 cycles of bioremedial treatment of diesel-contaminated water. The stability of diesel oil degradation in the immobilized cells resulted from the ability of living RN402 cells to attach to material surfaces by biofilm formation, as was shown by CLSM imaging. These characteristics of the immobilized RN402 cells, including high degradative efficacy, stability and flotation, make them suitable for the purpose of continuous wastewater bioremediation.
Article
This research investigated the application of Bio-Amp, a commercial bio-additive for the treatment of fat, oil, and grease (FOG) in a grease trap, and evaluated potential impacts of treated effluent on downstream collection system and treatment processes. Results show that after Bio-Amp treatment, FOG deposit formation was reduced by 40%, implicating a potential reduction of sewer line blockages. Chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP) and total fatty acids were reduced by 39%, 33%, 56%, and 59%, respectively, which represents an overall loading reduction of 9% COD, 5% TN and 40% TP received by the treatment plant from all the dining halls. On the other hand, readily biodegradable COD fractions significantly increased, which implies a potential improvement on Bio-P removal. Overall, the results showed that application of Bio-Amp in grease trap provides potential reduction of sewer line blockages, and can also alleviate downstream treatment burden.
Article
An agricultural waste, barley straw, was chemically modified using a cationic surfactant hexadecylpyridinium chloride monohydrate (CPC) to obtain a biosorbent for removal of emulsified mineral oil from aqueous solution. The physical and chemical properties of the raw and surfactant-modified barley straw (SMBS) were characterized by N2 adsorption, bulk density, Fourier transforms infrared spectra and the composition of cellulose, hemicellulose and lignin. The adsorption tests were performed using a standard mineral oily wastewater in a batch adsorption system. The effects of contact time and pH of solution on the emulsified oil uptake were investigated and discussed. It was found that the removal efficiency of emulsified oil increased with the increase in contact time. Biosorption was found to be less favorable at high acidic condition and a maximum removal was obtained at about neutrality. The isotherm study indicated that emulsified oil adsorption on SMBS was fitted well with the Langmuir model rather than the Freundlich model. The maximum adsorption capacity determined from the Langmuir isotherm was 518.6 mg g−1 at 25 °C. The kinetic study revealed that equilibrium time was achieved in less than 40 min and the kinetic data were fitted well to the pseudo-first-order model. Copyright © 2010 Curtin University of Technology and John Wiley & Sons, Ltd.
Article
The slightly polluted wastewater from oil refinery contains some COD, oil pollutants and suspended solids (SS). A small-scale fixed film biological aerated filter (BAF) process was used to treat the wastewater. The influences of hydraulic retention time (HRT), air/water volume flow ratio and backwashing cycle on treatment efficiencies were investigated. The wastewater was treated by the BAF process under optimal conditions: the HRT of 1.0 h, the air/water volume flow ratio of about 5:1 and the backwashing cycle of every 4–7 days. The results showed that the average removal efficiency of COD, oil pollutants and SS was 84.5%, 94.0% and 83.4%, respectively. And the average effluent concentration of COD, oil pollutants and SS was 12.5, 0.27, 14.5 mg·L−1, respectively. The experimental results demonstrated that the BAF process is a suitable and highly efficient method to treat the wastewater.
Article
The aim of this research is inspecting the efficiency of physical-chemical and biological processes with the active sludge method in the wastewater of the Pars Oil Refinery Company. This research was done from 26th, January 2007 and continued up to 27th, May 2007. The main operation in Pars oil refinery is to produce lubricants. This research tries to examine and evaluate the performance of treatment system at the refinery to decrease microorganism in the industrial wastewater in a laboratory scale pilot. The pilot has two sections; physical-chemical section, including Dissolved Air Flotation system, and biological section, including active sludge reactor and clarifier. This investigation carried on a 10 liter Dissolved Air Flotation reactor and an active sludge reactor in a laboratory scale. The volume of the aerireactor (aeration reactor) was 10 liters, and the volume of the secondary sediment was 3.5 liters. The waste water of the refinery was used as inlet flow of the pilot and necessary sludge was obtained at first from the Shahrak Ekbatan waste water treatment system. After analyzing the test results, it was concluded that the average percentage of excluding oil, Chemical Oxygen Demand and Biological Oxygen Demand was 29.7, 49 and 27.8 respectively. This indicates the effective role of physical treatment in decreasing oily emulsion material that would result in decreasing organic density in untreated wastewater. In biological system, the efficiency of excluding Chemical Oxygen Demand and Biological Oxygen Demand is 73.4 and 84.7, respectively. This confirms high efficiency of this unit. The samples taken from entering (influent) and exiting (effluent) wastewater of both units were tested. Standard Methods were applied to determine the considered physical and chemical parameters. Keywordsactivated sludge–aerireactor–dissolved air flotation–oil refinery
Article
In this study, waste water of Kιrιkkale Refinery (Turkey) was treated with coagulants (alum, ferric chloride, ferrous sulfate and lime) and coagulant aids (polyelectrolytes: anionic, cationic, nonionic) and some Turkish clays namely Samaş, Çanbensan, Ceylan, Hasandede and Keskin in order to see their effects in clarifying the waste water before biopurification. The results showed that local clays (Hasandede and Keskin) are as efficient as bentonites (Samaş, Çanbensan and Ceylan). The clarifying efficiency of clays in combination with coagulants shows almost the same results of about 90%. The effect of coagulants, FeCl3, FeSO4 and CaO, was similar to that obtained with Al2(SO4)3. The efficiency of polymeric materials especially cationic and anionic polymers was found to be better than that obtained with clays.
Article
As an alternative to the conventional activated sludge (CAS) process, this paper investigates the use of B350M and B350 group microorganisms immobilized on carriers in a pair of Biological Aerated Filter (BAF) reactors to pre-treat oil field wastewater before desalination. By operating the biodegradation system for 142 days with a hydraulic retention time (HRT) of 4 h and volumetric load 1.07 kg COD (m3 d)−1 at last, the reactor immobilized with B350M achieved mean degradation efficiencies of 78% for total organic carbon (TOC) and 94% for oil, whereas that with B350 only reached 64% for TOC and 86% for oil. The influent wastewater contains organic substances from C13H28 to C32H66, and a total of 16 polycyclic aromatic hydrocarbons (PAHs). The degradation efficiencies of PAHs in the BAF immobilized with B350M and B350 microorganisms are 90% and 84%, respectively. It is observed that the biological diversity of microorganisms in the reactor containing B350M (seven more strains of bacteria survive) is richer than in that containing B350. A large quantity of filamentous microorganisms developed in both reactors without causing foaming or bulking.
Article
Species of Suillus produce fleshy, pored mushrooms. They are important symbiotic (ectomycorrhizal) partners of many coniferous trees. The genus includes several putative eastern Asian and eastern North American disjunct species, i.e., the S. americanus–S. sibiricus and S. decipiens–S. spraguei complexes. Phylogenetic relationships among the groups were determined to further understand the biogeographic pattern. Analyses were based on 40 sequences of the ITS region of the nuclear ribosomal RNA tandem repeats, representing 18 distinct species/populations. Our phylogenetic analyses suggested that: (1) Chinese and United States' (U.S.) S. spraguei plus S. decipiens form a strongly supported monophyletic group, with North American S. decipiens and Chinese S. spraguei being sister taxa; (2) S. americanus, Asian and U.S. S. sibiricus, plus S. umbonatus form a clade supported by a high bootstrap value; and (3) little ITS sequence divergence exists within the latter group compared to the S. decipiens–S. spraguei clade. Phylogenetic patterns revealed by this study imply a close phylogenetic relationship between eastern Asian and eastern North American disjunct population/species of Suillus. These fungi display relatively high host fidelity (at least to the host subgenus level), suggesting potential coevolutionary/comigratory trends.
Article
This paper presents a review of the procedures to design and retrofit water networks. Although the emphasis is in showing results for refineries, the methods are valid for any process plants. It is first shown that the problem has been decomposed into the design of two interacting subsystems. One problem is the freshwater and wastewater reuse allocation and the other is the wastewater treatment problem. It is also shown how the wastewater treatment problem was modeled as a distributed and decentralized treatment. The roadmap towards zero liquid discharge and energy integrated solutions is then discussed. Several solution approaches are briefly outlined emphasizing the main trend leaning towards the use of mathematical programming. The major claim made is that mathematical programming can produce globally optimal solutions and practically important sub-optimal solutions when conceptual insights are employed to build the models. Although the paper intends to be comprehensive, it emphasizes the author's recent work. Finally, a few of the existing challenges of the area are outlined.
Article
Phosphorus removal by the activated algae process was studied in laboratory scale under various conditions of hydraulic loading. Phosphorus removal ranged from 70% at 4 h hydraulic retention time, to 95% at 12 h hydraulic retention time. Chemical precipitation was found to be the predominant mechanism for phosphorus removal. An optical device for introducing light to the process was used which, based on theoretical consideration, significantly increases the efficiency of light utilization by algae cultures.
Article
Pollution of the aquatic environment occurs from many different sources including from oil refineries. Oil refinery effluents contain many different chemicals at different concentrations including ammonia, sulphides, phenol and hydrocarbons. The exact composition cannot however be generalised as it depends on the refinery and which units are in operation at any specific time. It is therefore difficult to predict what effects the effluent may have on the environment. Toxicity tests have shown that most refinery effluents are toxic but to varying extents. Some species are more sensitive and the toxicity may vary throughout the life cycle. Sublethal tests have found that not only can the effluents be lethal but also they can often have sublethal effects on growth and reproduction. Field studies have shown that oil refinery effluents often have an impact on the fauna, which is usually restricted to the area close to the outfall. The extent of the effect is dependent on the effluent composition, the outfall's position and the state of the recipient environment. It is possible to detect two effects that oil refinery effluent has on the environment. Firstly it has a toxic effect close to the outfall, which is seen by the absence of all or most species. Secondly there is an enrichment effect which can be distinguished as a peak in the abundance or biomass. These effects are not limited to just oil refinery effluents, which makes it difficult to distinguish the effects an oil refinery effluent has from other pollution sources. The discharge from oil refineries has reduced in quantity and toxicity over recent decades, allowing many impacted environments in estuaries and coasts to make a substantial recovery.
Article
This article sets out to survey the remarkable development that has taken place in catalysis in the refining and petrochemical industries since the middle of the 20th century, and more especially since the 1970s, highlighting what appears to be the most significant progress. It then attempts to outline the energy and environmental context for the coming decades which will govern the trend in industrial catalysis in the 21st century. Although the reduction of CO2 will eventually require the decarbonization of energy carriers, oil will still remain the principal source of liquid motor fuels for a long time. However, the share of gas will gradually increase and hydrogen is destined to play an important part as an energy carrier. The use of biomass will develop, but at a modest level. Within this framework, catalysis will still play a leading role in technical and economic development in the 21st century, even though it is far from being an emerging discipline.
Article
Aerobic degradation of a crude oil (sample P1), collected from a deep water reservoir from the Pampo Sul Field (Campos Basin, RJ) at 82 °C and 2405–2588 m, by indigenous bacteria in the oil and formation water was monitored for 60 days. Degradation parameters, measured using gas chromatography–mass spectrometry (GC–MS) of the crude oil degraded in the laboratory for periods of 0, 30, 50 and 60 days, were compared with those of a naturally biodegraded oil (sample P2). The analyses revealed that the n-alkanes were totally depleted by the 60th day when the crude oil (P1, degradation level 2) was transformed into petroleum of biodegradation level 6 (P2).
Chapter
The expression “best available techniques” is defined in Section 5 of the U.S. Environmental Protection Agency Acts, 1992 and 2003, and Section 5(2) of the Waste Management Acts, 1996 to 2005, as the “most effective and advanced stage in the development of an activity and its methods of operation, which indicate the practical suitability of particular techniques for providing, in principle, the basis for emission limit values designed to prevent or eliminate or, where that is not practicable, generally to reduce an emission and its impact on the environment as a whole, where best in relation to techniques means the most effective in achieving a high general level of protection of the environment as a whole, available techniques means those techniques developed on a scale which allows implementation in the relevant class of activity under economically the technically viable conditions, taking into consideration the costs and advantages, whether or not the techniques are used or produced within the State, as long as they are reasonably accessible to the person carrying out the activity, and techniques includes both the technology used and the way in which the installation is designed, built, managed, maintained, operated and decommissioned” (EPA, 2008).
Article
An internal loop airlift bioreactor containing chitosan-immobilized Sphingobium sp. P2 was applied for the removal of automotive lubricants from emulsified wastewater. The chitosan-immobilized bacteria had higher lubricant removal efficiency than free and killed-immobilized cells because they were able to sorp and degrade the lubricants simultaneously. In a semi-continuous batch experiment, the immobilized bacteria were able to remove 80-90% of the 200 mg L(-1) total petroleum hydrocarbons (TPH) from both synthetic and carwash wastewater. The internal loop airlift bioreactor, containing 4 g L(-1) immobilized bacteria, was later designed and operated at 2.0 h HRT (hydraulic retention time) for over 70 days. At a steady state, the reactor continuously removed 85±5% TPH and 73±11% chemical oxygen demand (COD) from the carwash wastewater with 25-200 mg L(-1) amended lubricant. The internal loop airlift reactor's simple operation and high stability demonstrate its high potential for use in treating lubricants in emulsified wastewater from carwashes and other industries.
Article
An upflow anaerobic sludge blanket (UASB) bioreactor was successfully used for the treatment of petroleum refinery effluent. Before optimization, chemical oxygen demand (COD) removal was 81% at a constant organic loading rate (OLR) of 0.4 kg/m(3) d and a hydraulic retention time (HRT) of 48 h. The rate of biogas production was 559 mL/h at an HRT of 40 h and an influent COD of 1000 mg/L. Response surface methodology (RSM) was applied to predict the behaviors of influent COD, upflow velocity (V(up)) and HRT in the bioreactor. RSM showed that the best models for COD removal and biogas production rate were the reduced quadratic and cubic models, respectively. The optimum region, identified based on two critical responses, was an influent COD of 630 mg/L, a V(up) of 0.27 m/h, and an HRT of 21.4 h. This resulted in a 76.3% COD removal efficiency and a 0.25 L biogas/L feed d biogas production rate.
Article
A circulating photocatalytic reactor was used for removing aliphatic and aromatic organic pollutants in refinery wastewater. The TiO(2) added wastewater samples, while saturating with air, were irradiated with an immersed mercury UV lamp (400 W, 200-550 nm). Optimal catalyst concentration, fluid pH and temperature were obtained at amounts of near 100 mgL(-1), 3 and 318K, respectively. A maximum reduction in chemical oxygen demand of more than 90% was achieved after about 4h irradiation and hence, 73% after about only 90 min; significant pollutant removal was also achievable in the other conditions. The identification of the organic pollutants, provided by means of a GC/MS and a GC analysis systems, equipped with headspace injection technique, showed that the major compounds were different fractions of petroleum aliphatic hydrocarbons (up to C(10)) and the well-known aromatic compounds such as benzene, toluene and ethylbenzene. The results showed a high efficiency degradation of all of these pollutants.
Article
Spirulina platensis was cultivated in a bench-scale airlift photobioreactor using synthetic wastewater (total nitrogen 412 mg L(-1), total phosphorous 90 mg L(-1), pH 9-10) with varying ammonia/total nitrogen ratios (50-100% ammonia with balance nitrate) and hydraulic residence times (15-25 d). High average biomass density (3500-3800 mg L(-1)) and productivity (5.1 g m(-2) d(-1)) were achieved when ammonia was maintained at 50% of the total nitrogen. Both high ammonia concentrations and mutual self-shading, which resulted from the high biomass density in the airlift reactor, were found to partially inhibit the growth of S. platensis. The performance of the airlift bioreactor used in this study compared favorably with other published studies. The system has good potential for treatment of high strength wastewater combined with production of algae for biofuels or other products, such as human and animal food, food supplements or pharmaceuticals.
Article
Although highly diverse and specialized prokaryotic and eukaryotic microbial communities in soil degrade polycyclic aromatic hydrocarbons (PAHs), most of these are removed slowly. This review will discuss the biotechnological possibilities to increase the microbial dissipation of PAHs from soil as well as the main biological and biotechnological challenges. Microorganism provides effective and economically feasible solutions for soil cleanup and restoration. However, when the PAHs contamination is greater than the microbial ability to dissipate them, then applying genetically modified microorganisms might help to remove the contaminant. Nevertheless, it is necessary to have a more holistic review of the different individual reactions that are simultaneously taking place in a microbial cell and of the interactions microorganism-microorganism, microorganism-plant, microorganism-soil, and microorganisms-PAHs. Elucidating the function of genes from the PAHs-polluted soil and the study in pure cultures of isolated PAHs-degrading organisms as well as the generation of microorganisms in the laboratory that will accelerate the dissipation of PAHs and their safe application in situ have not been studied extensively. There is a latent environmental risk when genetically engineered microorganisms are used to remedy PAHs-contaminated soil.