Nanofiltration in Combination with Limestone Filtration for Treating a Soft Spring Water Containing High Amounts of Humic Substances

The paper presented here describes experiments with a nanofiltration pilot plant treating spring water which contains high amounts of humic substances. With this process, water components such as humic substances, iron, manganese, and aluminum may be very well removed. However, the low pH value of the NF filtrate does not conform with the German standards. This is why the pH value will be increased in a second treatment step by limestone filtration. Prior to limestone filtration, CO₂ dosage is required in order to make sure that the pH value stays below the upper limit of the German standards of 9.5. With this treatment, a drinking water results which meets the German standards and has good chemical properties with respect to corrosion. The operation of the nanofiltration pilot plant for the treatment of the very soft spring water did not require the continuous addition of chemicals in order to prevent scaling. Although the spring water entered the NF without chemical pretreatment, there was no decrease in filtrate capacity observed over a period of six months. This is in contrast to other investigations involving colour reduction from very hard surface waters. When treating very hard waters by nanofiltration, the addition of complexing agents or acid is required in order to prevent scaling of the membranes. Such intricate pretreatment procedures cause doubt of the application of nanofiltration for the treatment of hard waters in large plants. However, in the case presented here, the application of NF in combination with the hardening step is quite simple, so that the full-scale plant may be operated mainly automatically and will require only little maintenance.     

Degradation of Acid Pharmaceuticals in the UV/H2O2 Process: Effects of Humic Acid and Inorganic Salts

The presence of acid pharmaceuticals in water environments poses a potential threat to ecosystems and human health. Recent research has shown that photo oxidation processes are much more effective for removing these pharmaceuticals. However, the existence of humic acid (HA) could inhibit the clearance efficiency of this process. In this study, we investigated the photochemical degradation of six selected acid pharmaceuticals in surface water and effluent from wastewater treatment plants using the UV/H₂O₂ process. The results showed that HA can act as a photo sensitizer or a ^. OH sink, and its concentration had a significant inhibitory effect on the degradation of acid pharmaceuticals. Most of these pharmaceuticals were inhibited during this process when HA was added to deionized water solutions. In addition, the effects of chloride, bicarbonate, and nitrate on the degradation of these pharmaceuticals were different. The removal efficiency of these acid pharmaceuticals is lower in natural samples than in deionized samples because of the complex constituents in the latter.     

Typology of Municipal Wastewater Treatment Technologies in Latin America

This paper presents an analysis of the wastewater treatment plants in six Latin American and Caribbean countries. Based on a sample of 2734 municipal treatment facilities, the applied processes are classified by sizes (influent flow) and type of technologies. The distribution of the technologies is also presented for each of the six countries. In addition, a representative municipal wastewater characterization, based on influent data from 174 treatment plants, is proposed. Results show that stabilization ponds, activated sludge, and the upflow anaerobic sludge blanket reactors represent 80% of the treatment facilities of the sample, providing treatment to 81% of the total flow considered. Moreover, 67% of the plants in the sample are small (flow <25 L/s) and the very small facilities (influent flow <5 L/s) are extensively applied in the region (34% of the sample), especially in Mexico and Brazil. The use of very small treatment plants may result in low energy efficiency systems and on possible incompliance of the discharge standards. This common practice in several countries in Latin America should be revised in order to improve the environmental performance of such facilities.     

Integrated stochastic modeling of pharmaceuticals in sewage networks

Pharmaceuticals and particularly antibiotics can harm sensitive aquatic species. Their occurrence in urban wastewater systems is the consequence of five successive processes: (i) ingestion of the substance, (ii) accumulation in the urine, (iii) excretion, (iv) degradation in the sewer system and (v) transport to the wastewater treatment plant (WTP). These processes were included in an integrated model that can be used to assess the dynamics of pharmaceuticals at a WTP inlet. First, information on sales data, posology, pharmacokinetics and toilet flushing frequency were combined to create a source model of pharmaceuticals entering a sewer system. This production function was then coupled with a transport/degradation model to simulate concentrations of pharmaceuticals at a WTP inlet. In an example application, the full model was applied to simulate the concentration of the antibiotic ciprofloxacin on an hourly time scale. In this application, the model was calibrated and validated for a case study at a WTP in Lausanne, Switzerland. Validation of the integrated approach was successful despite the high variability evident in the model results. This modeling approach has potential use in pollution management and epidemiology related to wastewater.     

Production of Drinking Water from Highly Contaminated Surface Waters: Removal of Organic,Inorganic, and Microbial Contaminants Applying Mobile Membrane Filtration Units

In military out of area missions of the Bundeswehr, it can be necessary to produce drinking water even from highly polluted surface waters containing a variety of organic, inorganic, and microbiological contaminants. Thus, mobile drinking water purification systems must be able to remove such contaminants as far as possible to meet the requirements of the German and European drinking water regulation/directive. Presently, two novel drinking water purification units applying membrane filtration undergo intensive long‐term trials carried out by the Bundeswehr. If these trials positively proof the functionality of these units and their ability to remove all possible contaminants they shall substitute so far available devices which use large amounts of chemicals and charcoal filtration for water purification.In the course of a research project, the functionality of the new devices and their efficacy to remove high amounts of algae, microbes, and organic and inorganic pollutants are additionally tested in “worst‐case” field studies. In September 2000, the first mobile drinking water purification unit was tested at the Teltowkanal in Berlin, Germany.This canal was chosen because it carries high burdens of municipal sewage effluents. The results from the fatigue test confirmed the ability of the water purification unit to reduce the concentrations of all contaminants meeting the maximum tolerance levels set by the German/European drinking water regulation.The pre‐filtration device was very effective in removing algae and solid particles to protect the membranes from clogging and to enable an almost maintenance‐free operation. Residues of pharmaceuticals and some other organic contaminants have almost totally been removed from the surface water where they were detected at individual concentrations up to the μg/L‐level.     

Occurrence and Distribution of Organic Contaminants in the Aquatic System in Berlin. Part I: Drug Residues and other Polar Contaminants in Berlin Surface and Groundwater

Several polar contaminants were found in screening analyses of 30 representative surface water samples collected from rivers, lakes, and canals in Berlin. Residues of pharmaceuticals and N-(phenylsulfonyl)-sarcosine originating from various sewage treatment plants effluents were found at concentrations up to the μg/L-level in the surface water, whereas the concentrations of polar pesticides such as dichlorprop and mecoprop were always below 0.1 μg/L. The pharmaceuticals most frequently detected in the surface water samples include clofibric acid, diclofenac, ibuprofen, propiphenazone, and two other drug metabolites. Additional investigations of groundwater wells of a drinking water plant have shown that polar contaminants such as drug residues or N-(phenylsulfonyl)-sarcosine easily leach through the subsoil into the groundwater aquifers when contaminated surface water is used for groundwater recharge in drinking water production.     

Surveillance of Invasive Bacterial Pathogens and Human Enteric Viruses in Wastewater Final Effluents and Receiving Water Bodies – a Case Study from Durban,South Africa

The physico‐chemical characteristics and microbial composition of the final effluents of two municipal wastewater treatment plants in South Africa were assessed between July and September 2009. The impact of the treated final effluents on the receiving water bodies was also evaluated. The temperature across all sampling points ranged between 14 and 22°C, while pH varied from 6.9 to 7.6. High levels of turbidity, chemical oxygen demand (COD), ammonia, nitrate, nitrite and orthophosphate (PO₄) were observed in many cases. Turbidity of the samples was in the range of 2.2–288.6 NTU. The concentrations (mg/L) of other physico‐chemical parameters are as follows: COD (9.33–289); ammonia (0.000340–45.4); nitrate (0.062–539); nitrite (0.021–22.6); PO₄ (5.3–33.2). The microbial quality of the effluents discharged from the plants did not comply with the limits set by the South African guidelines with respect to pathogens such as Salmonella, Shigella, Escherichia coli, total coliform, faecal coliform, enterococci, faecal streptococci, and viral particles for effluents intended for discharge into receiving watersheds. This study revealed an undesirable impact on the physico‐chemical and microbial qualities of the receiving water bodies as a result of the discharge of inadequately treated effluents from the wastewater treatment facilities. This poses a health risk to several rural communities which rely on the receiving water bodies primarily as their sources of domestic water and recreational purposes. There is therefore a need for the intervention of appropriate regulatory agencies in South Africa to ensure compliance of treatment facilities with wastewater effluent quality standards.     

Behavior of Steroid Hormones and Conjugates During Wastewater Treatment – A Comparison of Three Sewage Treatment Plants

The fate of the steroid hormones 17 β‐estradiol, estrone, estriol, 16 α‐hydroxyestrone, and β‐estradiol 17‐acetate, the hormone‐conjugates β‐estradiol 3‐sulfate and estrone 3‐sulfate, and the oral contraceptives 17 α‐ethinylestradiol and mestranol were studied during wastewater treatment as wastewater treatment plants are the major source contamination of urban surface waters with steroid hormones. The elimination efficiencies of three different concepts of WWTPs, i. e., activated sludge versus trickling filter, were compared over four weeks at different weather conditions. While larger WWTPs operating on activated sludge eliminated hormones more constantly than smaller WWTPs, heavy rainfall events led to a collapse of the elimination efficiency. By using trickling filter techniques for the treatment of wastewater an elimination of the steroid hormones could not be observed. Additionally, mass flows on a per person basis are compared. In the three experiments, which ran continuously for four weeks each, it turned out that the concentrations of ethinylestradiol and mestranol were below 6 ng/L in all samples. The inflow concentrations were 70 to 82 ng/L (estrone), 17 to 44 ng/L (estradiol), 61 to 130 ng/L (hydroxyestrone), 189 to 255 ng/L (estriol), 10 to 17 ng/L (estrone‐3‐sulfate) and about 28 ng/L (estradiol‐3‐ sulfate). While in the activated sludge treatment plants the elimination of estrone was 90 and 50%, respectively, estrone was formed from precursors in the trickling filter plant. A similar situation occurred for 17β‐estradiol, estrone 3‐sulfate, and estradiol 3‐sulfate. Hydroxyestrone was eliminated with similar efficiencies in all wastewater treatment plants (64 to 82%), as well as estriol (34 to 69%). Accordingly, the emissions of the wastewater treatment plants differed largely and were not attributed to the size of the respective plant, only.     

Magnetically Separable Water Treatment Technologies and their Role in Future Advanced Water Treatment: A Patent Review

Magnetic separation has been recognized as an important property for the simple deployment of micro and sub‐microparticles into solution in the field of water treatment. Many materials with desirable properties for water decontamination are hindered due to the difficulty inherent in removing them from solution post‐treatment. By securing these materials to magnetic compounds, this important issue can be solved as removing active materials from wastewater requires only the application of a magnetic field. This review article presents and discusses many recent technologies, in the form of patents, which exploit the property of magnetic separation for advanced water treatment, including methods of adsorbing pollutants from wastewater and magnetically separating them, as well as methods of deploying active materials for the degradation of contaminants, then magnetically retrieving these catalysts. The requirement for advanced wastewater treatment methods becomes more essential as new, persistent contaminants arise as a result of pharmaceuticals, pesticides and industrial processes which cannot be addressed by traditional water treatment procedures. Magnetic separation promises to be a critical factor in these advanced methods, allowing the safe deployment of active materials which would otherwise be unusable, opening the gate to more efficient, economic and environmentally friendly water purification.     

Designing river water quality policy interventions with scarce data: the case of the Middle Tagus Basin,Spain

ABSTRACT

Anthropic pressures deteriorate river water quality, so authorities need to identify their causes and define corrective actions. Physically based water quality models are a useful tool for addressing physicochemical pollutants, but they must be calibrated with an amount of data that is often unavailable. In this study, we explore the characterization of a model to design corrective interventions in a context of sparse data. A calibration indicator that is both simple and flexible is proposed. This approach is applied to the Middle Tagus Basin in central Spain, where the physicochemical concentration of pollutants is above legal standards. We quantify the effects of the main existing pressures (discharge from wastewater treatment plants, agricultural diffuse pollution and a major inter-basin water transfer) on the receiving waters. In particular, the study finds that wastewater treatment plant effluent concentrations should be reduced to up to 0.65 mg/L of ammonium and 0.55 mg/L of phosphate to achieve the environmental goals. We propose and prioritize a set of policy actions that would contribute to the good status of surface water bodies in the region.     

Water availability for the greening of Kuwait

Water resources for agricultural development and landscape enhancement in Kuwait are very scarce; the quality is saline (brackish), and the soil texture is sandy, incapable of holding nutrients and moisture. Most of the rainfall in Kuwait either evaporates due to the high temperatures or percolates through the soil. The rainfall is not sufficient to recharge the underground water supply. A variety of alternative water sources have been studied, including seawater desalination and wastewater treatment. Wastewater treatment proved to be convenient due to the relatively low salinity detected in the treated water. Furthermore, the amount of wastewater is expected to increase as more residential areas are connected to the sewage system as the population increases.

The development of a greenery plan for Kuwait requires intensive water management. This goal can be achieved through manpower training in landscape development, selection of plants tolerant to arid environments, usage of appropriate irrigation and drainage systems, promotion of greenery programs within public and the governmental agencies for their direct participation in urban area beautification, and extension of wastewater treatment techniques.     

Livestock wastewater treatment by a mangrove pot-cultivation system and the effect of salinity on the nutrient removal efficiency

The present investigation compared the capacity of greenhouse pot-cultivation systems under two salinity conditions (freshwater and saline water) with two mangrove species (Bruguiera gymnorrhiza and Kandelia candel) to remove nutrients from livestock wastewater. During the whole treatment period there were relatively stable leachate TOC concentrations for wastewater-treated pots. Leachate NH4(+)-N concentration of B. gymnorrhiza pots was generally lower than that of K. candel pots. Leachate PO4(3-)-P concentration of pots receiving wastewater under freshwater condition was higher than that under saline water condition. Soil inorganic N content was more than two times higher for the wastewater treatments than that for the controls under low salinity condition and slower rate of increase under saline water condition. Soil P nutrients of both total and extractable inorganic forms significantly increased for both systems due to the discharges of livestock wastewater under both salinity conditions. The rate of increase in P contents for plants receiving livestock wastewater was 1-4 times that of the controls, much more than that in N contents (0.04-1.30 times). N nutrient removal efficiencies were 84.3% (65.6% by soil and 18.7% by plant) and 95.5% (32.2% by soil and 63.4% by plant), respectively by Kandelia candel and B. gymnorrhiza pot-cultivation systems under freshwater condition. Under saline water condition, N nutrient removal efficiencies by K. candel and B. gymnorrhiza pot-cultivation systems were 92.7% (80.7% by soil and 12.0% by plant) and 98.0% (67.6% by soil and 30.3% by plant), respectively. P nutrient removal efficiencies by K. candel and B. gymnorrhiza systems under freshwater condition were 79.2% (76.6% by soil and 2.6% by plant) and 91.8% (88.2% by soil and 3.6% by plant), respectively. The corresponding values were 88.0% (84.2% by soil and 3.8% by plant) and 97.8% (95.9% by soil and 1.9% by plant) under saline water condition.     

The enrichment and removal of arsenic (III) from water samples using HFSLM

At specific concentrations oxyanions such as arsenic pose a major threat to human beings and to the environment because of their ability to biomagnify. The World Health Organization has set the drinking water standard at 10 μg l⁻¹ for arsenic. It is in this regard that novel and cheaper methods to detect oxyanions and remove them from the environment are developed. In this work, we have developed sample preparation methods involving solid phase and liquid membrane for the extraction and enrichment of these oxyanions in aqueous environments. Various parameters which govern their optimal extraction and enrichment have been optimised. The manipulation of the liquid membrane extraction process was utilised to selectively extract arsenic (III) which is more toxic as compared to arsenic (V). The liquid membrane consisted of a combination of two organic solvents, and n-undecane and di-n-hexyl ether were used in a combination at various ratios of the two liquid membranes. The means of detection was by graphite furnace atomic absorption spectroscopy (GFAAS) as well as inductively coupled plasma optical emission spectroscopy (ICP-OES). The applicability of the method was tested in real wastewater samples where it was able to remove at least 50% of As (III) with enrichment factors of up to 20.     

珠江三角洲湖库水体嗅味物质分布及其去除

采用固相微萃取-气质联用技术对珠江三角洲9个城市共48个湖库水体中的土臭素（GSM）、2-甲基异茨醇（MIB）和2,3,6-三氯苯甲醚（TCA）等5种嗅味物质进行检测,并探讨污水处理厂和自来水厂处理工艺中嗅味物质的浓度变化规律,同时研究强化混凝沉淀工艺对嗅味物质的去除效果.结果表明：珠江三角洲湖库水体中嗅味问题最严重的是广州、佛山、肇庆、东莞、惠州和深圳6个城市,各市湖库的嗅味物质平均浓度为70.93~116.61 ng/L;中山、珠海与江门3个城市的嗅味问题不明显,各市湖库的嗅味物质平均浓度为22.78~58.82 ng/L;珠江三角洲的湖库中浓度最高的嗅味物质是MIB、TCA和GSM,这3种嗅味物质占了嗅味物质总浓度的80.18%~100.00%;污水处理厂和自来水厂中的处理工艺对嗅味物质均有一定的去除效果,嗅味物质的去除主要发生在混凝沉淀阶段;污水处理厂对MIB、TCA和GSM的平均去除率分别为53.55%、57.40%和72.90%;自来水厂对MIB、TCA和GSM的平均去除率分别为64.14%、69.63%和36.86%;强化混凝沉淀实验中,当嗅味物质初始浓度为200 ng/L时,Al₂O₃投加量为13.75 mg/L可使得混凝沉淀工艺对嗅味物质的去除效果最佳且保证铝盐不超标,嗅味物质浓度增大时Al₂O₃投加量也需增大;反应体系的pH值处于5~8时,混凝沉淀工艺对嗅味物质的去除效果最佳;混凝搅拌速率越快,嗅味物质的去除率越高且越快达到稳定.     

Assessing Environmental Impacts of Wastewater Treatment Alternatives for Small‐Scale Communities

The effluents of wastewater treatment plants in small sized communities of less than 2000 population equivalent (PE), which are discharged into sensitive receiving water environments, must receive “appropriate treatment” according to the EU Urban Wastewater Treatment Directive. Appropriate treatment depends on the quality objectives of the receiving waters as well as the relevant provisions of the member states. In this study, wastewater treatment options, such as vegetated land treatment (VLT), constructed wetlands (CW), and activated sludge treatment (AST), by which effluents are discharged to sensitive and less sensitive areas are evaluated by the life cycle assessment (LCA) approach. For this purpose, data related to energy usage, land requirement, raw material consumption, and released emissions from the life phases were collected with an inventory study and the environmental impacts were assessed by using SimaPro 7.1 LCA software. The results obtained from the assessments were compared with each other, which indicated that for small‐scale communities VLT and CW are the most environmentally friendly wastewater treatment option.     

Anwendung von biologischen Testverfahren an Abwässern der Textilindustrie

Testing Effluents of the Textile Refining Industry with Biological Methods The environmental problems caused by the manufacture of finished textiles involve a long chain of individual processes. This “textile chain” includes very diverse enterprises of varied size and structure. The textile refiners occupy a key position in the “textile chain”. On the one hand, this is due to their use of an obscurely large number of chemicals which can end up in the wastewater as well as in the textile products. On the other hand, this key role of the textile refining industry is based on their central position between the preproduction stage and the consumers. This study dealt with the textile refining industry's wastewater. As measured by volume and contents of its wastewater, this industry can be counted among the major industrial plants which discharge into municipal wastewater treatment plants. German wastewater legislation includes the provision that substances which are toxic, persistent, capable of accumulating, carcinogenic, fetotoxic or mutagenic be kept out of natural waters as well as technically possible (Wasserhaushaltsgesetz WHG). Several biotest methods for examining the effect of the substances contained in the wastewater were incorporated into the appendix of the German wastewater regulation (Rahmenabwasser-Verwaltungsvorschrift based on § 7a WHG). The aim of this study was to show, with the aid of biotest methods, how strongly the wastewater of textile refining companies is polluted as compared to other known industrial branches and to what degree the pollution of these wastewaters is eliminated by the treatment in wastewater treatment plants. Finally, we experimented to find out which biotest methods were suited for the examination of these wastewaters. The study's results show that the ecotoxicity of the textile refining industry's wastewater was only extraordinary high in isolated cases as compared to other examined branches of industry. The textile wastewaters exhibit values of G_L = 3 to G_L = 96 in the luminescent bacteria test, G_D = 1 to G_D = 192 (with one exception of G_D > 30000) in the daphnia test and G_F < = 2 to G_F = 32 in the fish test. It turned out though, that a large number of the samples from the textile refining companies (27%) reacted mutagenically in the Ames test in their native state. Consecutive tests for chromosomal aberrations (V79 hamster cell test) also showed mutagenic potential in five out of nine native samples. The employed testing methods with fish, daphnia and luminescent bacteria demonstrate a higher sensitivity of the luminescent bacteria and/or the daphnia as opposed to the fish in most cases. As the fish test is controversial anyway on the grounds of animal protection, a replacement of the fish test by these other tests should be aimed at: on account of the different end points of the luminescent bacteria and the daphnia test, a combination of these tests appears most sensible.     

Using selected pharmaceutical compounds as indicators for surface water and groundwater interaction in the hyporheic zone of a low permeability riverbank

This study investigates the applicability of selected pharmaceutical compounds (e.g. sulfamethoxazole, carbamazepine, ibuprofen) as anthropogenic indicators for the interaction of surface water and groundwater in the hyporheic zone of an alluvial stream. Differences in transport behaviour and the resulting distribution of the pharmaceuticals in the riverine groundwater were evaluated. The investigated field site in the Grand Duchy of Luxembourg, Europe is represented by low permeable sediments and confined aquifer conditions. Water samples from single‐screen and multilevel observation wells installed in the riverbank at the field site were taken and analysed for selected pharmaceuticals and major ions for a period of 6 months. Surface water and groundwater levels were recorded to detect effluent and influent aquifer conditions. Nearly all pharmaceuticals that were detected in the stream were also found in the riverine groundwater. However, concentrations were significantly lower in groundwater than in surface water. A classification into mobile and sorbing/degradable pharmaceuticals based on their transport relevant properties was made and verified by the field data. Gradients with depth for some of these pharmaceuticals were documented and a more detailed understanding of the system stream/riverbank was obtained. It was demonstrated that the selected pharmaceutical compounds can be used as anthropogenic indicators at the investigated field site. However, not all compounds seem to be suitable indicators as their transport behaviour is not fully understood. Copyright © 2012 John Wiley & Sons, Ltd.     

Preparative isolation and characterization of heavy metal complexes from acid mine drainage and surface wastewater

A preparative method was developed to sample dissolved organic carbon (DOC) and heavy metals (Ni, Mn) from polluted surface waters. Main focus was set on the preparative production of freeze‐dried samples mainly composed of organic ligands from heavy metal complexes. First characterizations were done in the aqueous phase. Finally, freeze‐dried samples provide stable organic matter for multiple characterizations. Acid mine drainage of the former mining area of Ronneburg (Germany) hold elevated concentrations of heavy metals and low concentrations of DOC. Municipal wastewater, passing the spoil pile, held elevated concentrations of DOC and low concentrations of heavy metals. Dissolved components smaller than 0.45 μm and larger than 1 nm were concentrated by nanofiltration. Organic heavy metal complexes were isolated from this solution by size‐exclusion chromatography (SEC). Different size classes of molecules were collected from the column effluent, depending on their elution time, and were characterized by UV spectroscopy, ICP‐OES, and DOC measurements. All samples held organic heavy metal compounds with different retention times. The organic heavy metal complexes in acid mine drainage had higher retention times than complexes from municipal wastewater. Most interestingly, we found different affinities of heavy metals to different size classes of DOC. This affinity of the heavy metals differs with size and origin of the DOC.     

Water quality and spatio-temporal hot spots in an effluent-dominated urban river

In arid and semi-arid regions, many rivers experience extremely low flow conditions during seasonal dry periods. During these times, effluent from wastewater treatment plants can make up the majority of flow in the river. However, water quality in urban systems can also be strongly influenced by the natural or human-influenced flow regime and discharge from other anthropogenic sources such as industrial operations and runoff from impervious surfaces. In this study, we aimed to determine whether water quality was controlled primarily by wastewater discharge in an effluent-dominated river. Between May 2016–May 2019, we systematically measured water temperature, pH, dissolved oxygen, biochemical oxygen demand, and the concentrations of nitrate-N, ammonia-N, and orthophosphate in the South Platte River in the Denver metropolitan area, Colorado, USA. We found that, despite being an effluent-dominated river, wastewater treatment plant discharge was not the principal factor controlling water quality in many of the sampled areas. Non-point source pollution from impervious surfaces, delivered to the river through storm drains and minor tributary streams, also contributed to the high nutrient conditions in several locations. We also noted a strong seasonality in water quality, with higher concentrations of nutrients and higher biochemical oxygen demand in the winter months when wastewater effluent can make up more than 90% of the flow in the river. Thus, the interaction of discharge location and reduced seasonal flow produced spatio-temporal hot spots of diminished water quality. More stringent enforcement of water quality regulations may improve water quality in this system. However, a large portion of the pollution seems to be from non-point sources, which are very difficult to control.     

Oil refinery wastewater treatment using coupled electrocoagulation and fixed film biological processes

Oil refinery wastewater was treated using a coupled treatment process including electrocoagulation (EC) and a fixed film aerobic bioreactor. Different variables were tested to identify the best conditions using this procedure. After EC, the effluent was treated in an aerobic biofilter. EC was capable to remove over 88% of the overall chemical oxygen demand (COD) in the wastewater under the best working conditions (6.5 V, 0.1 M NaCl, 4 electrodes without initial pH adjustment) with total petroleum hydrocarbon (TPH) removal slightly higher than 80%. Aluminum release from the electrodes to the wastewater was found an important factor for the EC efficiency and closely related with several operational factors. Application of EC allowed to increase the biodegradability of the sample from 0.015, rated as non-biodegradable, up to 0.5 widely considered as biodegradable. The effluent was further treated using an aerobic biofilter inoculated with a bacterial consortium including gram positive and gram negative strains and tested for COD and TPH removal from the EC treated effluent during 30 days. Cell count showed the typical bacteria growth starting at day three and increasing up to a maximum after eight days. After day eight, cell growth showed a plateau which agreed with the highest decrease on contaminant concentration. Final TPHs concentration was found about 600 mgL⁻¹ after 30 days whereas COD concentration after biological treatment was as low as 933 mgL⁻¹. The coupled EC-aerobic biofilter was capable to remove up to 98% of the total TPH amount and over 95% of the COD load in the oil refinery wastewater.