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Water is an absolute necessity for life and water scarcity is a major problem all over the world. Reusing household wastewater for non-potable water applications is one of the solutions to tackle this problem. Many developing countries lack the technological resources to construct and operate costly wastewater treatment plants. They need cost-effective wastewater treatment options so that both economic aspects and human needs can be met easily. Centralized sewage treatment systems are unable to achieve future demands for sustainable wastewater management in developing countries due to the growing population and needs. The present work examines the effectiveness of treating urban wastewater with microbial-earthworm eco filters (MEEs) (reactor 2) and the filter unit without earthworms (reactor 1). Results of the use of the vermi-biofiltration wastewater treatment unit comprising the biological filtration treatment unit, Eisenia fetida earthworm species, live soil organisms, and natural stones to treat household wastewater are reported herein. The biological oxygen demand (BOD), total dissolved solids (TDS), chemical oxygen demand (COD), and total organic carbon (TOC) were monitored for seven weeks. These parameters exhibited a decreasing trend in both the filtration units. A 75 % reduction in TOC for reactor 2 shows the effectiveness of the proposed system for the utilization of wastewater from urban households. Reactor 2 also showed a reduction in BOD, COD, and TDS approximately in the range of 85, 90, and 30 % respectively. This technique seems to be useful for developing a low-cost and useful household purification system in water-scarce areas using harmless bio-organisms.

Biological filtration is a complex process consisting of two consecutive stages. The nutrient transport stage, which is influenced by various fluid mechanical and surface-physical factors, represents a precondition for the biochemical process taking place within the biofilm. Biological water filtration is based on the catalyzed decomposition of contaminant molecules with the help of enzymes. This article, in addition to describing the conditions and mode of action typical within this second stage, also aims to explore the practical implications of the established results, including the controllability of biological reactors. [ABSTRACT FROM AUTHOR]

Nitrate filters are widely used in various sectors of the national economy for the purpose of stable degradation of nitrates without complex technological changes and control, as well as for obtaining, for practical use, water free from impurities of various polluting substances. The relevance of the stated research topic is determined by the wide use of filters in various areas of water conditioning in order to improve the quality of consumed water, as well as the need to develop methods for qualitative measurements of the optimal time parameters for the water residence in the denitrification filter when using it. The purpose of this research work is the practical development of methods for measuring the optimal time for the water residence in a denitrification filter, in order to find optimal opportunities for eliminating harmful and polluting substances from water used for domestic and industrial needs. The methodology of this research involves the use of a combination of methods for the systematic study of practical application issues of denitrification filters in water purification systems, using the method of qualitative analysis of water conditioning problems that are important with reference to the need to obtain high-quality water in volumes sufficient to meet the current domestic and industrial needs. The results of this research work are of great importance from the point of view of studying the problematic issues of determining the optimal time parameters for the water residence in modern filters, in order to achieve optimal indicators of the cleaning quality. The results and conclusions of this research are of considerable practical value for water filter designers, solving practical problems of creating high-quality denitrification filters, as well as for ordinary users, for whom the issues of water purification for its further practical application are of great importance

Full‐scale sampling at 16 facilities illustrated that NDMA precursor concentrations, measured by adding chloramine under Uniform Formation Conditions (NDMAUFC), increased across biofiltration at 7 of 16 facilities (by 3–48 ng/L or 12%–296%) but stayed the same or decreased (by up to 5 ng/L or 24%) at the other nine facilities. Increases in NDMAUFC concentrations were attributed to both particulate and soluble precursors. Only two facilities had an increase in NDMAUFC greater than 10 ng/L. However, NDMAUFC concentrations in the biofilter effluent from five facilities exceeded 10 ng/L during one or more sampling events. For these facilities, testing at multiple scales showed that mitigation steps could include pretreatment with ozone (which resulted in overall lower NDMAUFC), increased free chlorine contact time prior to ammonia addition, and/or optimized biofilter design and operation. [ABSTRACT FROM AUTHOR]

Alameda County Water District has observed increased biofilter effluent manganese concentrations during winter operations. To investigate manganese removal across surface water biofilters during cold‐water conditions, trends were analyzed between water temperature and manganese removal across multiple testing scales, multiple biofilter influent water qualities, and both anthracite and GAC media. During acclimation of new biofilters, 100% removal of manganese was observed sooner across both anthracite and GAC biofilters brought online at 20°C compared to 12°C. Acclimation at 12°C required 18 extra days for the GAC biofilters and 48 additional days for the anthracite biofilters. For fully acclimated biofilters, a decrease in manganese removal across both GAC and anthracite biofilters at temperatures below 15°C was observed. However, greater and more consistent manganese removal was observed across GAC compared to anthracite biofilters. Performance differences between locations also suggest that operational and water quality conditions also likely affect manganese removal. [ABSTRACT FROM AUTHOR]

Abstract Background Malaria vector control approaches that rely on mosquito releases such as the sterile insect technique (SIT) and suppression or replacement strategies relying on genetically modified mosquitoes (GMM) depend on effective mass production of Anopheles mosquitoes. Anophelines typically require relatively clean larval rearing water, and water management techniques that minimise toxic ammonia are key to achieving optimal rearing conditions in small and large rearing facilities. Zeolites are extensively used in closed-system fish aquaculture to improve water quality and reduce water consumption, thanks to their selective adsorption of ammonia and toxic heavy metals. The many advantages of zeolites include low cost, abundance in many parts of the world and environmental friendliness. However, so far, their potential benefit for mosquito rearing has not been evaluated. Methods This study evaluated the independent effects of zeolite and daily water changes (to simulate a continuous flow system) on the rearing of An. coluzzii under two feed regimes (powder and slurry feed) and larval densities (200 and 400 larvae per tray). The duration of larval development, adult emergence success and phenotypic quality (body size) were recorded to assess the impact of water treatments on mosquito numbers, phenotypic quality and identification of optimal feeding regimes and larval density for the use of zeolite. Results Overall, mosquito emergence, duration of development and adult phenotypic quality were significantly better in treatments with daily water changes. In treatments without daily water changes, zeolite significantly improved water quality at the lower larval rearing density, resulting in higher mosquito emergence and shorter development time. At the lower larval rearing density, the adult phenotypic quality did not significantly differ between zeolite treatment without water changes and those with daily changes. Conclusions These results suggest that treating rearing water with zeolite can improve mosquito production in smaller facilities. Zeolite could also offer cost-effective and environmentally friendly solutions for water recycling management systems in larger production facilities. Further studies are needed to optimise and assess the costs and benefits of such applications to Anopheles gambiae (s.l.) mosquito-rearing programmes. Graphic abstract

Aquaponics is a technique where a recirculating aquaculture system (RAS) and hydroponics are integrated to grow plants and fish in a closed system. We investigated if the growth of rainbow trout (Oncorhynchus mykiss) and baby spinach (Spinacia oleracea) would be affected in a coupled aquaponic system compared to the growth of the fish in RAS or plants in a hydroponic system, all systems as three replicates. We also investigated the possible effects of plants on the onset of nitrification in biofilters and on the concentration of off-flavor-causing agents geosmin (GSM) and 2-methylisoborneol (MIB) in rainbow trout flesh and spinach. For the fish grown in aquaponics, the weight gain and specific growth rates were higher, and the feed conversion ratio was lower than those grown in RAS. In spinach, there were no significant differences in growth between aquaponic and hydroponic treatments. The concentration of GSM was significantly higher in the roots and MIB in the shoots of spinach grown in aquaponics than in hydroponics. In fish, the concentrations of MIB did not differ, but the concentrations of GSM were lower in aquaponics than in RAS. The onset of nitrification was faster in the aquaponic system than in RAS. In conclusion, spinach grew equally well in aquaponics and hydroponic systems. However, the aquaponic system was better than RAS in terms of onset of nitrification, fish growth, and lower concentrations of GSM in fish flesh. [ABSTRACT FROM AUTHOR]

Background: Malaria vector control approaches that rely on mosquito releases such as the sterile insect technique (SIT) and suppression or replacement strategies relying on genetically modified mosquitoes (GMM) depend on effective mass production of Anopheles mosquitoes. Anophelines typically require relatively clean larval rearing water, and water management techniques that minimise toxic ammonia are key to achieving optimal rearing conditions in small and large rearing facilities. Zeolites are extensively used in closed-system fish aquaculture to improve water quality and reduce water consumption, thanks to their selective adsorption of ammonia and toxic heavy metals. The many advantages of zeolites include low cost, abundance in many parts of the world and environmental friendliness. However, so far, their potential benefit for mosquito rearing has not been evaluated. Methods: This study evaluated the independent effects of zeolite and daily water changes (to simulate a continuous flow system) on the rearing of An. coluzzii under two feed regimes (powder and slurry feed) and larval densities (200 and 400 larvae per tray). The duration of larval development, adult emergence success and phenotypic quality (body size) were recorded to assess the impact of water treatments on mosquito numbers, phenotypic quality and identification of optimal feeding regimes and larval density for the use of zeolite. Results: Overall, mosquito emergence, duration of development and adult phenotypic quality were significantly better in treatments with daily water changes. In treatments without daily water changes, zeolite significantly improved water quality at the lower larval rearing density, resulting in higher mosquito emergence and shorter development time. At the lower larval rearing density, the adult phenotypic quality did not significantly differ between zeolite treatment without water changes and those with daily changes. Conclusions: These results suggest that treating rearing water with zeolite can improve mosquito production in smaller facilities. Zeolite could also offer cost-effective and environmentally friendly solutions for water recycling management systems in larger production facilities. Further studies are needed to optimise and assess the costs and benefits of such applications to Anopheles gambiae (s.l.) mosquito-rearing programmes. [ABSTRACT FROM AUTHOR]

The City of Denton, Texas, upgraded the Lake Lewisville Water Treatment Plant (WTP) to add ozone and convert the existing chlorinated anthracite/sand filters to granular activated carbon (GAC) biofilters. Biofilter contaminant removal, operational performance, and biomass were monitored following startup on two filters, one brought online in winter and one brought online in summer, to understand seasonal impacts. In addition, the city also monitored anthracite biofilters following a winter shutdown at another WTP. Key conclusions include (1) acclimation (i.e., the time required to achieve steady‐state biomass, total organic carbon [TOC] removal, or total manganese removal, considered individually) was two to three times longer for filters brought online in the winter versus the summer, (2) no acclimation period was observed for turbidity or total iron removal, and (3) the relationship between TOC removal and water temperature was more significant for the WTP with anthracite than GAC biofilters. [ABSTRACT FROM AUTHOR]

2D nanomaterials have long been considered for development of high permeability membranes. However, current processes have yet to yield a viable membrane for practical use due to the lack of scalability and substantial performance improvements over existing membranes. Herein, an ultrathin graphene oxide (GO) membrane with a permeability of 1562 mL h−1 mmHg−1 m−2, two orders of magnitude higher than the existing nanofiltration membranes, and a tight molecular weight cut‐off is presented. To build such a membrane, a new process involving self‐assembly and optimization of GO nanoplatelet physicochemical properties is developed. The process produces a highly organized mosaic of nanoplatelets enabling ultra‐high permeability and selectivity. An adjustable molecular interlinker between the layers enables absolute nanometer‐scale size cut‐offs. These characteristics promise significant improvements to many nanoparticle and biological separation applications. In this work, the performance of the membrane in blood dialysis scenarios is evaluated. Urea and cytochrome‐c sieving coefficients of 0.5 and 0.4 are achieved while retaining 99% of albumin. Hemolysis, complement activation, and coagulation studies exhibit a performance on par or superior to the existing dialysis membrane materials. [ABSTRACT FROM AUTHOR]

This work aims to develop a suitable aquaculture system to solve issues pertaining to water quality in recirculating aquaculture systems (RAS) thereby improving fish growth performance and their feed conversion ratio (FCR). It is known that the efficiency of nutrient decomposition depends on the amount and species of bacteria present in the filter, and these can in turn be regulated by the pH. Our study shows that the significant increase in pH from 7.45 to 7.51 and 7.47 is achieved after the water was filtered through sawdust and wood wool respectively. At the same time, nitrite concentrations were found to have significantly decreased from 0.06 ppm in the control to 0.01 ppm in the sawdust treatment. Changes in the physical–chemical properties of treated water affect the biological properties of the organisms. It was found that the average final body weight for fish in the wood wool treatment 30.96 g and fish in the sawdust treatment 31.44 g was significantly higher compared to that for the fish in the control treatment 28.42 g. The use of sponge, wood wool or sawdust resulted in significantly lower FCR and therefore better fish productivity in RAS. At the same time, the red blood cell count, plasma urea, plasma creatinine, plasma albumin, and GOT and GPT were significantly higher in fish in the plastic, sponge, wood wool or sawdust treatment compared to the control treatment. In summary, this study demonstrates the benefits of using sponge, wood, wool and sawdust as biofilter media for aquaculture. [ABSTRACT FROM AUTHOR]

Key Takeaways: Houston's Northeast Water Purification Plant expansion project is required to comply with subsidence district rules for conversion from groundwater to surface water supply. Innovative solutions for the expanded plant include two coagulation recipes to treat water from Lake Houston; treatment with chlorine dioxide, ozone, and biological filtration; and enhanced residuals treatment. A progressive design–build approach—used for the largest project of this kind presently underway in North America—maximized stakeholder involvement. [ABSTRACT FROM AUTHOR]

This study was conducted to determine the biological filtration capabilities of some culinary herbs co‐cultured with lemon fin barb hybrid in a nutrient film technique (NFT) recirculating aquaponic system. Lemon fin barb hybrid (Hypsibarbus wetmorei ♂ × Barbonymus gonionotus ♀) fingerlings were stocked in twelve 2‐tonne fibreglass tanks at 25 fish per tank and co‐cultured with Chinese celery (Apium graveolens var. secalinum Alef.), coriander (Coriandrum sativum) and peppermint (Mentha × piperita) for seven weeks. The impacts of the waste generated by the fish on the water quality, the filtration capability of the herbs and the ability of fish and herbs to retain nutrients (NPK) were also estimated. All the herbs showed water purifying potentials to varying degrees as significantly lower levels of nitrogenous compounds (NH3‐N, NO3‐N, NO2‐N) were observed after the herbal filtration. The plant growth seemed to be affected by their ability to absorb nutrients and consequently purify the culture medium. Interestingly, the lemon fin barb hybrid also showed significant differences in terms of weight gain, but the nutrient retention among fish treatments was not statistically different. The plants absorbed less phosphorus and potassium than the fish. After computing for the total system percentage of NPK recovered, nitrogen was the most retained nutrient. The peppermint showed superiority in terms of gross biomass and water purifying potential compared to the Chinese celery and coriander. [ABSTRACT FROM AUTHOR]

In order to improve the quality of the environment as well as its purification capacity, to reduce environmental costs and achieve clean and efficient management of malodorous gas pollution, on the basis of fully understanding the theory of biotechnology, this paper presents the research of biotechnology to control the pollution of malodorous pollutants. In this research, the biofiltration method was used to control the odour gas ammonia produced in waste composting, which can effectively purify gases, with a high ammonia removal rate. One week after the ammonia removal experiment, the removal rate was detected to be around 79.3 %. Twenty-four days after the experiment, the removal rate stabilized at around 98 %. Through the test of pH value of nutrient solution, it was found that the change in pH value corresponded to the increase in removal rate. There are many advantages of applying biotechnology to filter malodorous polluted gases, such as low energy consumption, high degree of purification, good environmental compatibility, simple operation and maintenance, and no secondary pollution. Therefore, it has good application prospects.

Incorporation of a carbon-based nutrient enhancement strategy for drinking water biofiltration is an attractive option, especially for source waters which contain recalcitrant organics. This study compared biofilters that were operated in parallel and individually enhanced with amino acids (including alanine, phenylalanine, and tryptophan), inulin, and sucrose to increase biomass concentration and promote biodegradation of dissolved organic carbon (DOC) in the source water, including disinfection by-product (DBP) precursors. Biomass activity was characterized by measuring adenosine tri-phosphate (ATP), dissolved oxygen (DO) consumption, and through the use of laccase and esterase enzyme assays. Performance was evaluated in terms of headloss, turbidity, pH, DOC, UV 254 , and DBP formation potential (DBP FP). The introduction of carbon-based nutrients significantly increased biomass activity, where ATP values peaked at 976 ng/g of filter media, 853 ng/g, and 513 ng/g for amino acids, inulin, and sucrose-spiked biofilters, respectively, while a non-spiked control only reached 104 ng/g. DO utilization by the enhanced biofilters was significantly higher than the control, with a strong correlation between ATP and DO uptake observed for all filters (R 2 > 0.74). Laccase and esterase enzyme activities of enhanced biofilters were also elevated (p > 0.05), suggesting greater biodegradation potential. Operational parameters such as headloss development and turbidity control were not impaired by carbon supplementation strategies or an increase in biomass concentration and activity. However, the enhancement strategy did not provide improvement in terms of source water carbon removal (DOC and UV 254) or DBP FP when treated filters were compared to a control. Unlabelled Image [ABSTRACT FROM AUTHOR]

Recirculating aquaculture systems (RASs) are intensive aquaculture facilities models that depend on diverse water treatment equipment to maintain good water quality and produce safe and healthy high‐quality aquatic products. This article combines the main farming‐mode of water purification recirculating processes with recent cultivation‐mode scientific research and the current development of the recirculating aquaculture industry. Harmful substances are present in aquaculture wastewater due to large quantities of residual particulate matter such as residual feed, faeces and small suspended solid particles, as well as ammonia, nitrite, bacteria and carbon dioxide (CO2), in the water. These harmful substances seriously affect the quality of aquatic products, so water treatment equipment is needed to remove these substances, add oxygen (O2) to the water and adjust the temperature of the water to ensure a high‐quality environment for fish survival. This article reviews the equipment for physical filtration (e.g. solid–liquid separation equipment, microscreen drum filter and foam fractionator) that could remove suspended solids during the water treatment of RASs and the equipment for biological filtration (e.g. fluidized sand biofilter (FSB), moving‐bed biofilm reactor (MBBR) and rotating biological contactor (RBC)) that could remove ammonia nitrogen, nitrite and other hazardous substances from wastewater, as well as equipment for water disinfection and sterilization, O2 addition, CO2 removal and temperature control. Comprehensive analysis and discussion of water treatment efficiency are provided for reference to create efficient high‐end recirculation aquaculture models and increase the precision and intelligence degree of recirculating water treatment technologies in the future. [ABSTRACT FROM AUTHOR]

Abstract Biological drinking water treatment technologies offer a cost-effective and sustainable approach to mitigate microcystin (MC) toxins from harmful algal blooms. To effectively engineer these systems, an improved predictive understanding of the bacteria degrading these toxins is required. This study reports an initial comparison of several unstructured kinetic models to describe MC microbial metabolism by isolated degrading populations. Experimental data was acquired from the literature describing both MC removal and cell growth kinetics when MC was utilized as the primary carbon and energy source. A novel model-data calibration approach melding global single-objective, multi-objective, and Bayesian optimization in addition to a fully Bayesian approach to model selection and hypothesis testing were applied to identify and compare parameter and predictive uncertainties associated with each model structure. The results indicated that models incorporating mechanisms of enzyme-MC saturation, affinity, and cooperative binding interactions of a theoretical single, rate limiting reaction accurately and reliably predicted MC degradation and bacterial growth kinetics. Diverse growth characteristics were observed among MC degraders, including moderate to high maximum specific growth rates, very low to substantial affinities for MC, high yield of new biomass, and varying degrees of cooperative enzyme-MC binding. Model predictions suggest that low specific growth rates and MC removal rates of degraders are expected in practice, as MC concentrations in the environment are well below saturating levels for optimal growth. Overall, this study represents an initial step towards the development of a practical and comprehensive kinetic model to describe MC biodegradation in the environment. Graphical abstract Image 1 Highlights • Unstructured kinetic models were applied to predict microcystin (MC) biodegradation. • Moser and Heijnen models reliably predicted MC removal kinetics across experiments. • Diverse growth characteristics were observed when comparing MC degrading bacteria. • Model predictions suggest MC removal kinetics are suboptimal in the environment. [ABSTRACT FROM AUTHOR]

Abstract The combination of biological growth and particle loading can adversely affect hydraulic performance in drinking water biofilters. In this study, upstream oxidant addition was used to distribute biologically-derived filter clogging in granular activated carbon (GAC) biofilters. Oxidant penetration was assessed during pilot-scale operation and backwashing of dual media (GAC/sand) and multimedia (GAC/anthracite/sand) biofilters. Influent chlorine (HOCl), monochloramine (NH 2 Cl), and hydrogen peroxide (H 2 O 2) residuals were optimized to react with the GAC surface in the upper portion of the filter media bed (depth < 0.5 m) to attenuate biomass development. As the oxidant residual was quenched by surface-mediated reaction with the filter media, biomass growth was promoted deeper in the filter bed (depth > 0.5 m). The oxidant-induced effects on biomass and hydraulic performance were monitored through measurements of adenosine triphosphate (ATP) and head loss accumulation at different media depths. Addition of oxidants (e.g., 0.6 mg Cl 2 /L HOCl) could decrease terminal head loss by 20% in dual media filters and 40% in multimedia filters. These hydraulic benefits were achieved without significantly affecting removal of assimilable organic carbon (AOC), total organic carbon (TOC), turbidity, and particle counts. Oxidant type, residual concentration, media type, media age, and media depth influenced the passage of oxidant residuals and distribution of filter biomass. When oxidants were added during backwashing, oxidant residual was quenched through the bed depth from a combination of reactions with GAC media and biofilm degradation. This attenuation of residual oxidant may prevent the oxidant residual from penetrating the entire bed depth, potentially compromising backwashing objectives. Graphical abstract Image 1 Highlights • Select upstream oxidants may limit biomass concentrations at the filter surface. • Oxidants may induce better distribution of biologically-derived fouling mechanisms. • More distributed fouling of the biofilter improves hydraulic performance. • Oxidant concentration, type, and media bed characteristics affect oxidant penetration. [ABSTRACT FROM AUTHOR]

Abstract The objective of this pilot-scale study was to investigate the effectiveness of incorporating ozone (O 3) and advanced oxidation (hydrogen peroxide/ozone: H 2 O 2 /O 3) in combination with biofiltration for taste and odour control, organic carbon removal, and disinfection byproduct (DBP) precursor reduction. Implementation of O 3 and H 2 O 2 /O 3 with and without biofiltration was investigated at pilot-scale in terms of geosmin, 2-methylisoborneol (MIB), and DBP precursor removal efficiency. Two media types (granular activated carbon and anthracite) were compared in conjunction with investigating the impact of pre-oxidation with O 3 (2 mg/L) and varying H 2 O 2 /O 3 mass ratios (0.1, 0.2, 0.35, and 0.5 mg/mg). When O 3 preceded biologically active carbon (BAC) or biologically active anthracite, geosmin removals of 80% and 81%, respectively, were observed at 10 °C; this increased to 89% and 90%, respectively, at 16 °C. Optimal MIB removal (67%) was achieved with 0.1 H 2 O 2 /O 3 (mg/mg) in combination with BAC at 16 °C. In general, geosmin proved to be more amenable to biodegradation than MIB. BAC without pre-oxidation removed 87% geosmin and 85% MIB, at 22 °C. MIB removals decreased to 60% and 46%, respectively at 16 °C and 10 °C. The application of 0.2 H 2 O 2 /O 3 (mg/mg) prior to BAC provided treatment which effectively removed geosmin and MIB. However, in terms of DBP precursor reduction, there was no beneficial impact of H 2 O 2 addition on trihalomethane or haloacetic acid formation potentials. Highlights • BAC alone may serve as a suitable treatment technology for T&O control at warmer temperatures. • Biologically activated anthracite outperformed non-biological anthracite in removing both geosmin & MIB. • O 3 efficiency and BAC biodegradation rates significantly decreased in cold water conditions. • H 2 O 2 /O 3 advanced oxidation improved MIB removal in cold water conditions. • Biopolymers were observed to preferentially react with $OH rather than O 3. [ABSTRACT FROM AUTHOR]

Ammonia is a metabolic waste product excreted by aquatic organisms that causes toxicity when it accumulates. Aquaria and aquaculture systems therefore use biological filters that promote the growth of nitrifiers to convert ammonia to nitrate. Ammonia-oxidizing bacteria (AOB) have been isolated from aquarium biofilters and are available as commercial supplements, but recent evidence suggests that ammonia-oxidizing archaea (AOA) are abundant ammonia-oxidizers in aquarium biofilters. In this study, we report the cultivation and closed genome sequence of novel AOA representative Candidatus Nitrosotenius aquariensis, which was enriched from a freshwater aquarium biofilter. Ca. N. aquariensis oxidizes ammonia stoichiometrically to nitrite with a concomitant increase in thaumarchaeotal cells and a generation time of 34.9 hours. Ca. N. aquariensis has an optimal growth temperature of 33°C, tolerates up to 3 mM NH4Cl, and grows optimally at 0.05% salinity. Transmission electron microscopy revealed that Ca. N. aquariensis cells are rod-shaped, with a diameter of -0.4 µm and lengths ranging from 0.6-3.6 µm. In addition, these cells possess S-layers and multiple proteinaceous appendages. Phylogenetically, Ca. N. aquariensis belongs to group I.1a Thaumarchaeota, clustering with sequences from freshwater aquarium biofilters, aquaculture systems, and wastewater treatment plants. The complete 1.70 Mbp genome encodes for genes involved in ammonia oxidation, bicarbonate assimilation, flagella synthesis, chemotaxis, S-layer production, defense, and protein glycosylation. Incubations with differential inhibitors indicate that Ca. N. aquariensis-like AOA contribute to ammonia oxidation within the isolation source biofilter. [ABSTRACT FROM AUTHOR]

The evolving demands of drinking water treatment necessitate processes capable of removing a diverse suite of contaminants. Biofiltration can employ biotransformation and sorption to remove various classes of chemicals from water. Here, pilot-scale virgin anthracite-sand and previously used biological activated carbon (BAC)-sand dual media filters were operated for ∼250 days to assess removals of 0.4 mg/L ammonia as nitrogen, 50–140 μg/L manganese, and ∼100 ng/L each of trace organic compounds (TOrCs) spiked into pre-ozonated Colorado River water. Anthracite achieved complete nitrification within 200 days and started removing ibuprofen at 85 days. Limited manganese (10%) removal occurred. In contrast, BAC completely nitrified ammonia within 113 days, removed all manganese at 43 days, and exhibited steady state removal of most TOrCs by 140 days. However, during the first 140 days, removal of caffeine, DEET, gemfibrozil, naproxen, and trimethoprim decreased, suggesting a shift from sorption to biotransformation. Acetaminophen and sulfamethoxazole were removed at consistent levels, with complete removal of acetaminophen achieved throughout the study; ibuprofen removal increased with time. When subjected to elevated (1 μg/L) concentrations of TOrCs, BAC removed larger masses of chemicals; with a subsequent decrease and ultimate cease in the TOrCs spike, caffeine, DEET, gemfibrozil, and trimethoprim notably desorbed. By the end of operation, anthracite and BAC exhibited equivalent quantities of biomass measured as adenosine triphosphate, but BAC harbored greater microbial diversity (examined with 16S rRNA sequencing). Improved insight was gained regarding concurrent biotransformation, sorption, and desorption of multiple organic and inorganic contaminants in pilot-scale drinking water biofilters. [ABSTRACT FROM AUTHOR]

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Conventional wastewater treatment plants are ineffective in removing a broad range of micropollutants, resulting in the release of these compounds into the aquatic environment, including natural drinking water resources. Ozonation is a suitable treatment process for micropollutant removal, although, currently, little is known about the formation, behavior, and removal of transformation products (TP) formed during ozonation. We investigated the elimination of 30 selected micropollutants (pharmaceuticals, X-ray contrast media, industrial chemicals, and TP) by biological treatment coupled with ozonation and, subsequently, in parallel with two biological filters (BF) or granular activated carbon (GAC) filters. The selected micropollutants were removed to very different extents during the conventional biological wastewater treatment process. Ozonation (specific ozone consumption: 0.87 ± 0.29 g O3 g DOC −1 , hydraulic retention time: 17 ± 3 min) eliminated a large number of the investigated micropollutants. Although 11 micropollutants could still be detected after ozonation, most of these were eliminated in subsequent GAC filtration at bed volumes (BV) of approximately 25,000 m 3 m −3 . In contrast, no additional removal of micropollutants was achieved in the BF. Ozonation of the analgesic tramadol led to the formation of tramadol-N-oxide that is effectively eliminated by GAC filters, but not by BF. For the antiviral drug acyclovir, the formation of carboxy-acyclovir was observed during activated sludge treatment, with an average concentration of 3.4 ± 1.4 μg L −1 detected in effluent samples. Subsequent ozonation resulted in the complete elimination of carboxy-acyclovir and led to the formation of N-(4-carbamoyl-2-imino-5-oxo imidazolidin)-formamido-N-methoxyacetetic acid (COFA; average concentration: 2.6 ± 1.0 μg L −1 ). Neither the BF nor the GAC filters were able to remove COFA. These results highlight the importance of considering TP in the evaluation of advanced wastewater treatment processes. The results further indicate that post-treatment of ozonated wastewater with GAC filtration seems to be more suitable than BF, due to the sorption of formed TP to the activated carbon. [ABSTRACT FROM AUTHOR]

Disinfectant-enhanced backwash is frequently required to control the over-growth of biomass in biologically active carbon (BAC) filters for drinking water treatment. This study was conducted to investigate the impact of different backwashing strategies on the biodegradation and adsorption performance of BAC filters and attached biomass concentration in the filters. The biodegradation performance was evaluated using the three chloroacetic acids (CAAs) as indicator chemicals. Results showed that both free chlorine- and chloramines-enhanced backwashes could significantly increase the removal efficiency of attached biomass, but they also impaired the CAA degradation in BAC filters. The deterioration of CAA degradation could not be correlated with the removed attached biomass. Use of CAAs was a feasible approach to evaluate the biodegradation performance of BAC filters either during operation or after backwash. Chloramines-enhanced backwash is suggested to be employed to sustain the operation of BAC filters when excessive biomass growth takes place, due to its higher efficiency in removing attached biomass and lower adverse impact on BAC adsorption properties compared with free chlorine-enhanced backwash. However, the more pronounced adverse impact on organic matter degradation and the inconvenience of using chloraminated water must be considered. [ABSTRACT FROM AUTHOR]

Incomplete nitrification in biological filters during drinking water treatment is problematic, as it compromises drinking water quality. Nitrification problems can be caused by a lack of nutrients for the nitrifying microorganisms. Since copper is an important element in one of the essential enzymes in nitrification, we investigated the effect of copper dosing on nitrification in different biological rapid sand filters treating groundwater. A lab-scale column assay with filter material from a water works demonstrated that addition of a trace metal mixture, including copper, increased ammonium removal compared to a control without addition. Subsequently, another water works was investigated in full-scale, where copper influent concentrations were below 0.05 μg Cu L −1 and nitrification was incomplete. Copper dosing of less than 5 μg Cu L −1 to a full-scale filter stimulated ammonium removal within one day, and doubled the filter's removal from 0.22 to 0.46 g NH 4 -N m −3 filter material h −1 within 20 days. The location of ammonium and nitrite oxidation shifted upwards in the filter, with an almost 14-fold increase in ammonium removal rate in the filter's top 10 cm, within 57 days of dosing. To study the persistence of the stimulation, copper was dosed to another filter at the water works for 42 days. After dosing was stopped, nitrification remained complete for at least 238 days. Filter effluent concentrations of up to 1.3 μg Cu L −1 confirmed that copper fully penetrated the filters, and determination of copper content on filter media revealed a buildup of copper during dosing. The amount of copper stored on filter material gradually decreased after dosing stopped; however at a slower rate than it accumulated. Continuous detection of copper in the filter effluent confirmed a release of copper to the bulk phase. Overall, copper dosing to poorly performing biological rapid sand filters increased ammonium removal rates significantly, achieving effluent concentrations of below 0.01 mg NH 4 -N L −1 , and had a long-term effect on nitrification performance. [ABSTRACT FROM AUTHOR]

As preventive of possible environmental nuisances that can cause discharges water in nature, we undertook this study of the influence of salinity wastewater on the treatment efficiency of a biological filter consisting of dune sand. In this work, we designed six identical columns of filtration with sand from the same region of the N’Goussa city (located in the southeast of Algeria). The filters used are fed with wastewater at six different total salinity rates ranging from 0.065% to 0.265% corresponding to the electrical conductivity of 0.85 mS/cm to 3.5 mS/cm. This filtration efficiency was assessed by monitoring changes in the conductivity and the overall pH of the treated water and the chemical oxygen demand (COD). The results obtained showed that the change in the salinity of sewage water has a negative effect on the degradation of organic matter. Indeed, over the salt content is high, over the effectiveness of the biological treatment is reduced, suggesting in this type of case a prior desalination system and tests are under way in our laboratory. [ABSTRACT FROM AUTHOR]

The removal of biodegradable ozonation by-products was evaluated at pilot-scale using one conventional biofilter containing sand and anthracite and five fixed bed biofilm reactors (FBBRs) containing plastic media. Four of the FBBRs incorporated chemical or environmental optimization strategies (light restriction, chloramine, hydrogen peroxide, and nutrients) to either promote healthy biomass or minimize macrofauna proliferation. Conventional media biofiltration consistently removed assimilable organic carbon (AOC) by a maximum of 70% and was not susceptible to snail grazing. The control FBBR reduced AOC by a maximum of 60%, but dropped to zero following snail grazing on established biomass. Adenosine triphosphate (ATP) was used to quantify viable biomass attached to plastic media (tATP) and aqueous biomass in the column effluent (cATP). The control FBBR averaged 61 ng tATP/cm3of attached biomass compared to chloramine (7 ng tATP/cm3), hydrogen peroxide (21 ng tATP/cm3), dark conditions (45 ng tATP/cm3), and nutrients (61 ng tATP/cm3). Hydrogen peroxide (1.8 mg/L) and light restriction strategies precluded dark algae and chironomids, but allowed snail development. None of this biota was observed in the presence of chloramine (0.20 mg/L). While the conventional biofilter and control FBBR produced similar AOC removals, FBBRs were sensitive to hydraulic disruptions and susceptible to grazer organisms. [ABSTRACT FROM PUBLISHER]

Basatin Estuary is located in the north of the Persian Gulf and in the east of Boushehr province, which is opening into the Nayband Bay and is connected to the Gavbandi River. This estuary is considered as one of mangroves forests in the northern shores of the Persian Gulf because of its spectacular ecological condition. On the other hand, Basatin estuary is setting for enrichment of several kinds of pollutions during the recent years. Therefore, this research aimed at 1) highlighting the role of the mangrove forest in mitigation and reducing concentration of pollutions, 2) estimating the concentration of metallic and metalloid elements, in particular oil bonded and terrestrial bonded in surface and in the sediment columns of Basatin Estuary, and 3) identifying key horizons in the column sediments and their compatibility with the environment and man-made events. Therefore, a comprehensive sampling of the sedimentary faces and chemical analysis of wide range of elements (50 elements) were implemented. Totally 120 sediment samples were recorded and were analyzed using ICP-OES devices. In addition, statistical analysis was carried out to reveal relationships between similarity or dissimilarity elements. The results approved the research hypothesis, and e.g. showed that changing in the estuary mouth in 1991 has resulted in limitation of hydraulic circulation of tidal currents and caused a severe increase in sediment accumulation, followed by covering aerial roots by sediments and finally drying of mangrove trees. This process has a direct role in the enrichment of heavy metals in the environment. Furthermore, the uppermost layer of sediment column (0-25 cm) has experienced moderate to high degrees of pollution by petrochemical industries. This layer was significantly enriched by Zr, V, Ti, S, P, Ni, Mn, Li, Cr, Co, Ce, Cd, Bi, Ba, as elements. Finally, time correlation of key horizons and environmental events showed that the average rate of sedimentation in the estuary Basatin fluctuated between 1.8 and 2 cm per year.

Ammonia (NH 4 + -N) removal pathways were investigated in a potable water treatment biofilter that simultaneously removes manganese (Mn) and NH 4 + -N. The results indicated a significant loss of nitrogen in the biofilter. Both the completely autotrophic nitrogen removal over nitrite (CANON) process and nitrification were more likely to contribute to NH 4 + -N removal. Moreover, the model calculation results demonstrated that the CANON process contributed significantly to the removal of NH 4 + -N. For influent NH 4 + -N levels of 1.030 and 1.749 mg/L, the CANON process contribution was about 48.5% and 46.6%, respectively. The most important finding was that anaerobic ammonia oxidation (ANAMMOX) bacteria were detectable in the biofilter. It is interesting that the CANON process was effective even for such low NH 4 + -N concentrations. [ABSTRACT FROM AUTHOR]

Biofilters have gained in popularity for drinking water treatment for reasons that include reducing disinfectant demand, disinfection by-product formation, and regrowth in distribution systems. Adenosine triphosphate (ATP) detection is being used more frequently as an easy and rapid method to quantify viable biomass in biofilters; however, there is little information on the relationship of ATP levels to biofiltration parameters and performance. In this study, a comprehensive comparison of published ATP data was conducted, which found that concentrations at the top of active, acclimated biofilters typically were in the range of 102 to 103 ng ATP/cm3 media. The effect of various biofilter parameters (source water characteristics and quality, pretreatment, hydraulic loading rate, temperature, and sampling depth) on ATP levels is discussed and evaluated using published ATP data. The authors also assess the relationship between ATP and biofilter performance in terms of carbon removal and identify a need for further research in this area. [ABSTRACT FROM AUTHOR]

Abstract: Invertebrate colonization of granular activated carbon (GAC) filters in the waterworks is one of the most frequently occurring and least studied biological problems of water processing in China. A survey of invertebrate colonization of GAC filters was carried out weekly from October 2010 to December 2011 at a reservoir water treatment works in South China. Twenty-six kinds of invertebrates were observed. The abundance was as high as 5600ind.m−3 with a mean of 860ind.m−3. Large variations in abundance were observed among different seasons and before and after GAC filtration. The dominant organisms were rotifers and copepods. The average invertebrate abundance in the filtrate was 12–18.7 times of that in the pre-filtered water. Results showed that the GAC filters were colonized by invertebrates which may lead to a higher output of organisms in the filtrate than in the pre-filtered water. The invertebrate abundance in the GAC filters was statistically correlated with the water temperature. Seasonal patterns were observed. The invertebrate abundance grew faster in the spring and summer. Copepods were dominant in the summer while rotifers dominated in all other seasons of the year. There was a transition of small invertebrates (rotifers) gradually being substituted by larger invertebrates (copepods) from spring to summer. Control measures such as backwashing with chloric water, drying filter beds and soaking with saliferous water were implemented in the waterworks to reduce invertebrate abundances in the GAC filters. The results showed that soaking with saliferous water (99%, reduction in percent) was best but drying the filter beds (84%) was more economical. Soaking filter beds with 20g/L saliferous water for one day can be implemented in case of emergency. In order to keep invertebrate abundance in the acceptable range, some of these measures should be adopted. [Copyright &y& Elsevier]

This study aimed to investigate the removal of 24 semivolatile organic compounds in Yangtze River (China) source water treated by six biofilters using different backwashing methods. Health risks induced by the pollutants in the influent and effluent water were also assessed based on the chemical detections. Comparatively, the biofilter backwashed with both air (15 m/h, 3 min) and water (8 m/h, 5 min) was most efficient in removing semivolatile organic compounds and reducing health risk. PCR-denatured gradient gel electrophoresis showed that backwashing alterations posed considerable influences on microbial community structure in the six biofilters. About 72.4 % of di- n-butyl phthalate and 81.8 % of bis(2-ethylhexyl)phthalate (two main semivolatile organic compounds in the river water) were removed under the optimal backwashing conditions. However, in the effluent of each biofilter, non-carcinogenetic risks of 2,6-dinitrotoluene and bis[2-ethylhexyl]phthalate and carcinogenetic risks of dibenz[a,h]anthracene and benzo[a]pyrene did not reach safety levels, revealing that these pollutants in the source water deserve more public health concerns. This study might serve as a basis for biofiltration process optimization and also as a benchmark for the authorities to reduce the health risk induced by exposure to the hazardous pollutants. [ABSTRACT FROM AUTHOR]

Removal of dissolved organic and inorganic contaminants is an anticipated benefit of the biofiltration of drinking water; however, common biofiltration design and operational practices do not seek to enhance the biological activities associated with those removals. A pilot-scale study identified two enhancement strategies-nutrient and peroxide dosing-that improved both water quality and hydraulic performance of a biofilter. These strategies control the formation of extracellular polymeric substances (a potential foulant of biological filters) while maintaining or increasing microbial activity. Biofilter nutrient enhancement was found to decrease terminal head loss by ∼ 15% relative to a control filter with no nutrient enhancement. Nutrient enhancement also sustainably decreased breakthrough of 2-methylisoborneol (MIB), manganese (Mn), and dissolved organic carbon (DOC). Peroxide enhancement was performed to increase oxidative action of biofilter microorganisms and promote the oxidation of inactive biomass. Peroxide enhancement decreased terminal head loss up to ∼ 60% relative to the control filter, while maintaining MIB, Mn, and DOC treatment performance. This case study is an important step in moving the practice of biofiltration from a passive process to a purposefully operated biological system, i.e., engineered biofiltration [ABSTRACT FROM AUTHOR]

Wastewaters have the potential to proliferate excessive numbers of cyanobacteria due to high nutrient levels. This could translate to the production of metabolites, such as the saxitoxins, geosmin and 2-methylisoborneol (MIB), which can impair the quality of wastewater destined for re-use. Biological sand filtration was assessed for its ability to remove these metabolites from a wastewater. Results indicated that the sand filter was incapable of effectively removing the saxitoxins and in some instances, the effluent of the sand filter displayed greater toxicity than the influent. Conversely, the sand filter was able to effectively remove geosmin and MIB, with removal attributed to biodegradation. Granular activated carbon was employed as an alternative filter medium to remove the saxitoxins. Results showed similar removals to previous drinking water studies, where efficient removals were initially observed, followed by a decrease in the removal; a consequence of the presence of competing organics which reduced adsorption of the saxitoxins. [ABSTRACT FROM AUTHOR]

Abstract: The treatment of cyanobacterial metabolites can consume many resources for water authorities which can be problematic especially with the recent shift away from chemical- and energy-intensive processes towards carbon and climate neutrality. In recent times, there has been a renaissance in biological treatment, in particular, biological filtration processes, for cyanobacteria metabolite removal. This in part, is due to the advances in molecular microbiology which has assisted in further understanding the biodegradation processes of specific cyanobacteria metabolites. However, there is currently no concise portfolio which captures all the pertinent information for the biological treatment of a range of cyanobacterial metabolites. This review encapsulates all the relevant information to date in one document and provides insights into how biological treatment options can be implemented in treatment plants for optimum cyanobacterial metabolite removal. [Copyright &y& Elsevier]

Abstract: The effect of hydraulic retention time (HRT), solar radiation and seasonality on the removal efficiency of 18 emerging contaminants has been studied in a biological filtration pilot plant based on Daphnia sp. The pilot plant consisted of a homogenization tank and two lines, A and B, each with four 1m3 tanks. One of these lines was directly exposed to sunlight whereas the other line was covered. Our results suggest that biodegradation and photodegradation are the most important removal pathways, whereas sorption makes a minor contribution. The removal efficiency ranged from no detectable removal to more than 90%. The kinetics of the degradation process was fit to a first order kinetic, with half-lives from 0.6 to 42days, depending on the particular compound. However, a scaling effect comes into play as the pilot plant was found to be more efficient than a similar full-scale polishing pond. [Copyright &y& Elsevier]

Two of the fishing resources processing enterprises in Cuba had treatment plants with filtration ditches. Due to the losses that take place in those treatment plants with the discharge of polluted water without treatment or with a deficient one, a technical study of two treatment plants of that type was conduced in Sancti Spíritus and Santiago de Cuba enterprises respectively, to determine the efficiency of both systems and obtain waste water quality criteria. The following parameters were measured: temperature, pH, oxygen biochemical demand, total and volatile solids, total phosphorus, nitrite, nitrate, ammonium and fat, using the standard determination methods. The results showed that the ditch design installed in Santiago de Cuba enterprise can be taken as a model for the construction of similar systems due to its high efficiency. [ABSTRACT FROM AUTHOR]

Abstract: Studies evaluating the impact of organic carbon on biological filters at the large scale for aquaculture production are lacking. Understanding the performance characteristics of different biofilters under actual production conditions will be the only means by which recirculating system designers may properly select and size biological filters for commercial production use. Previous studies have determined the impact of organic carbon on biofilter performance at the small lab scale often using artificial waste nutrients in the evaluation. Evaluations under actual production conditions using real wastewater produce vastly different results than previous lab scale studies using artificial nutrients. As such, this study is a preliminary step in evaluating the impact of organic carbon on three different commercially available biological filters at the large scale under actual recirculating aquaculture production conditions. The study was conducted at the North Carolina State University Fish Barn—a commercial scale research and demonstration recirculating aquaculture facility operated by the Biological and Agricultural Engineering department. The study was based on a 60m3 Tilapia system with average daily feed rates of 45kg using a 40% protein feed and an average biomass of 6750kg. The system was dosed with sucrose (C12H22O11) to increase the concentration of biodegradable organic carbon in the system. The effect of elevated organic carbon concentrations on total ammoniacal nitrogen (TAN) removal rates was evaluated and determined based on biofilter media volume. Variability increased substantially in the volumetric TAN removal rate (VTR) for all three filters. VTR for all three filter types was reduced by approximately 50% as compared to normal production conditions. The results demonstrate the importance of controlling the concentration of biologically available organic carbon in a recirculating aquaculture system. [ABSTRACT FROM AUTHOR]

Abstract: Six biofilters were used for advanced treatment of Yangtze River source water to investigate the effects of hydraulic loading rate (HLR) on pollutant removal and microbial community. HLR was found to exert significant influences on the removal efficiency of the conventional pollutants and 24 detectable semivolatile organic compounds (SVOCs). More than 85% of chemical oxygen demand and assimilable organic carbon was removed at the optimal HLR of 3.0mh−1. With the increase of HLR, SVOC removal showed a decreasing trend. Di-n-butyl phthalate and bis(2-ethylhexyl)phthalate, two main SVOCs in the source water, had the highest removals of 71.2% and 84.4%, respectively. Nearly 65% of 2,6-dinitrotoluene and 80% of isophorone were removed at the lowest HLR. Phylogenetic analysis showed that Escherichia coli, Shigella sp., E. fergusonii and Firmicutes bacteria predominated in the bioreactors. The dominance of E. coli in the low-HLR biofilters might contribute greatly to the high SVOC removal. [Copyright &y& Elsevier]

Abstract: Three different commercially available biological filters were evaluated in triplicate on a 60m3 tank-based Tilapia system under commercial warmwater growout conditions. The study was performed at the North Carolina State University Fish Barn—a commercial scale research and demonstration recirculating aquaculture facility operated by the department of Biological and Agricultural Engineering. Total ammoniacal nitrogen (TAN) removal rates were determined for the three types of biofilters for a range of concentrations ranging from 0.13 to 1.20g TAN m−3. TAN concentrations were varied by feed rates and ammonium chloride additions, and limited by fish feeding response. Maximum feed rates were 65kgfeedd−1 using a 40% protein diet at a maximum biomass of 5500kg. Average observed TAN removal rates (in g TAN m−3 of unexpanded media d−1 ±standard deviation) for the three filters were 267±123, 586±284, and 667±344 for the moving bed bioreactor, floating bead filter, and fluidized sand filter, respectively. These results are considerably lower than results previously published at the laboratory scale using artificial waste nutrients. This study highlights the need for future biofilter evaluations at the commercial scale using real aquaculture waste nutrients. [Copyright &y& Elsevier]

Base on the principle of developing a suitable aquaculture system that will fit the present climate and environmental challenges to enhance breeding and production in aquaculture. Against the backdrop of issues connected to water quality in recirculating aquaculture system which has negative impact on the fish comfort, feeding rate and blood biochemistry, this may later affect its growth performance and general wellbeing. Although, the rate of waste disintegration and the bacteria species present in the filter system determine the physicochemical parameters of the treated water, which further affect the biological characteristics of the fish. This study intends to reveal the effect of biological filtration media (wood coal, rice hulls and wheat hay) on water properties and its further effects on growth performance, plasma biochemistry, liver and gills histopathology of common carp in RAS. After the acclimation interval, 24 tanks were stocked with 8 fish average initial weight of 15.74 g. However, treatments were assigned to each tank at random sampling to make four treatments. The results showed a significant effect on Common carp growth and body biomass, for those with filter media compared to the control. Though, a better growth performance of Common carp culture in water exposed to wheat hay and rice hulls were recorded at significant level with lower FCR. Hence improvement in fish productivity was observed in the treatments compared to the control. Moreover, there are significant changes on cell counts, and plasma biochemistry parameters. In synopsis, the study reveals the benefits in using additional media such as wheat hay and rice hulls as a biological filter media to improve water quality and growth performance of common carp in aquaculture. The use of this new media should be encourage since the installation of this biological filter media is simple, affordable and can be retrofitted into existing systems, to increase water management and aquaculture productivity. • This study revealed the effect of biological filtration media on water quality and carp. • Additional filtration organic media has improved the water quality for better carp culture. • The blood parameters were within the normal range with media then the control. • A new biological filtration media significantly increased growth and body biomass of carp. • From the results obtained wheat hay was recommended. [ABSTRACT FROM AUTHOR]

The article discusses a study on the fate of saxitoxins in biologically active water treatment plant (WTP) filters. The saxitoxins, a group of potent alkaloid neurotoxins produced by cyanobacteria and dinoflagellates in freshwater and marine environments, block nerve cell sodium channels and can cause death if consumed in sufficient quantity. Findings revealed that decreases in the concentration of the less toxic variants coincided with increases in the concentrations of the more toxic variants through the filters containing anthracite sourced from two different WTPs. According to the study, organisms within the biofilm of the anthracite filters possessed the ability to biotransform the saxitoxins variants, which has important implications for the treatment of drinking water.

Nitrification was developed within a biological filter to simultaneously remove biodegradable organic matter (BOM) and residual ammonia added to control bromate formation during the ozonation of drinking water. Testing was performed at pilot-scale using three filters containing sand and anthracite filter media. BOM formed during ozonation (e.g., assimilable organic carbon (396–572μg/L), formaldehyde (11–20μg/L), and oxalate (83–145μg/L)) was up to 70% removed through biofiltration. Dechlorinated backwash water was required to develop the nitrifying bacteria needed to convert the residual ammonia (0.1–0.5mg/L NH3-N) to nitrite and then to nitrate. Chlorinated backwash water resulted in biofiltration without nitrification. Deep-bed filtration (empty-bed contact time (EBCT)=8.3min) did not enhance the development of nitrification when compared with shallow-bed filtration (EBCT=3.2min). Variable filtration rates between 4.8 and 14.6m/h (2 and 6gpm/sf) had minimal impact on BOM removal. However, conversion of ammonia to nitrite was reduced by 60% when increasing the filtration rate from 4.8 to 14.6m/h. The results provide drinking water utilities practicing ozonation with a cost-effective alternative to remove the residual ammonia added for bromate control. [Copyright &y& Elsevier]