Search

Safeguarding the drinking water quality remains a challenge from the production site to the tap. Alternatively to chemical disinfection, biostable drinking water could serve as a more sustainable approach to produce microbially safe drinking water and to maintain the microbial quality in the drinking water distribution system (DWDS). In this study, the potential of hydrogen-oxidizing bacteria (HOB) to produce biostable drinking water was examined in a continuous trickling filter supplied with hydrogen gas. A biofilm was naturally enriched for 5 months and the bacterial regrowth, invasion potential, and nutrient composition of the water were determined. Treatment improved the biostability significantly, and it is hypothesized that nutrient limitation, especially phosphorous, was a driving force. As a result, the regrowth and invasion potential were lowered, as shown with specific biostability bioassays. Overall, this study demonstrates the proof-of-concept of HOB for producing biostable drinking water through nutrient limitation. [ABSTRACT FROM AUTHOR]

Effluent reuse is a rapidly growing field of research where assessing the quality of effluent is one of the focus areas. This research examines the viability of using wastewater in agriculture by testing an integrated Upflow Anaerobic Sludge Blanket (UASB) reactor with a trickling filter (TF) system during the dry season. Compliance monitoring was conducted for 30 days from May 11 to June 9 of 2021. Samples were collected, handled, and analyzed following standard wastewater analysis procedures for biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), volatile suspended solids (VSS), cations, anions, heavy metals, E. coli, and helminth egg. The UASB-TF system in Kality wastewater treatment performed well in removing COD, BOD5, and TSS with average removal rates of 80.5%, 82.9%, and 80.9%, respectively, compared well with similar treatment configurations. The effluent quality satisfied the national inland discharge limit with a residual concentration of 125.1 mg/L for COD, 61.7 mg/L for BOD5 and 85.8 mg/L for TSS. On the other hand, high concentrations of chromium, nitrate-nitrogen, and helminth egg count restricted effluent reuse for agricultural purposes due to high health risks and environmental contamination. We found out that discharging industrial sewage into the domestic sewer network could inhibit microbial growth and affect the biological treatment processes. Furthermore, adopting integrated treatment systems in developing countries might face operational challenges and monitoring nitrate, helminth egg, and heavy metals would help provide timely operational feedback. An appropriate tertiary treatment unit—constructed wetlands or polishing ponds—is therefore needed to be introduced to ensure effluent reuse for agricultural purposes. [ABSTRACT FROM AUTHOR]

Phosphorus (P) discharge from anthropogenic sources, notably sewage effluent and agricultural runoff, significantly contributes to eutrophication in aquatic environments. Stringent regulations have heightened the need for effective P removal technologies in wastewater treatment processes. This paper provides a comprehensive review of current P removal methods, focusing on both biological and chemical approaches. Biological treatments discussed include enhanced biological P removal in activated sludge systems, biological trickling filters, biofilm reactors, and constructed wetlands. The efficiency of microbial absorption and novel biotechnological integrations, such as the use of microalgae and fungi, are also examined. Chemical treatments reviewed encompass the application of metal salts, advanced oxidation processes such as chlorination, ozonation, and the Fenton reaction, as well as emerging techniques including the Electro-Fenton process and photocatalysis. Analytical methods for P, including spectrophotometric techniques and fractionation analyses, are evaluated to understand the dynamics of P in wastewater. This review critically assesses the strengths and limitations of each method, aiming to identify the most effective and sustainable solutions for P management in wastewater treatment. The integration of innovative strategies and advanced technologies is emphasized as crucial for optimizing P removal and ensuring compliance with environmental regulations. [ABSTRACT FROM AUTHOR]

In this study, we evaluated the utilization rate of organic substrates contained in sanitary landfill leachates (SLLs) by fixed and suspended biomass reactors. Five bioreactors were designed, constructed, and tested for chemical oxygen demand (COD) removal. We applied three levels of organic loading in the influent for each bioreactor, including (1) a rotating biological contactor (RBC) (12, 20, and 25 g COD/m2/day); (2) a trickling filter (TF) (2.67, 5.33, and 8 kg COD/m3/day); (3) an upflow anaerobic sludge blanket (UASB) (13.31, 15.98, and 18.65 kg COD/m3/day); (4) an upflow anaerobic filter in two separated stages (UAF-2SS) (3.71, 2.76, and 1.8 kg COD/m3/day); and (5) an upflow anaerobic filter in three separated stages (UAF-3SS) (2.25, 3.45, and 4.44 kg COD/m3/day). Two equations for predicting the substrate utilization rate (SUR) of organic compounds by microorganisms were calibrated and validated, modeled under a nonsteady state condition. We modified Monod's equation to obtain the significant organic SUR and COD removal efficiency by the biomasses. These kinetic parameters were performed by the microorganisms fixing controlled experimental conditions for pH (8–9) and temperature for the UAFs (20°C, 27°C, and 34°C) and the remaining reactors (18°C– 20°C). The SUR and COD removal efficiency results were as follows: for UASB, −400 to −800 mg/L/h , 70% to 85%; for UAF-3SS, −100 to −300 mg/L/h , 85% to 95%; for UAF-2SS, −100 to −200 mg/L/h , 70% to 85%; and for RBC and TF, −50 to −250 mg/L/h , 70% to 80%. The results were mainly influenced by the structural arrangement of the organic compounds being biodegraded and the geometric configurations of the bioreactors in multiple separated stages, allowing the influence of the solubility of the recalcitrant substances, which varied from 7 to 14:1 COD dilition, to obtain subinhibitory levels for the microbial metabolism and achieve a high COD removal efficiency. Practical Applications: Two of the five bioreactors evaluated in this study, the upflow anaerobic filter in two separated stages and the upflow anaerobic filter in three separated stages, are proposed and designed as innovative reactors for treating groundwater from tropical aquifers contaminated with hydrocarbons. Additionally, UAFs were configured in a coupled bioreactor arrangement (i.e., a sequencing batch reactor followed by UAFs) to restore water quality by removing organic compounds in tropical rivers. By comparing the five bioreactors, the capacity for the chemical oxygen demand removal was significant related to the organic substrate utilization rate (SUR) for treating sanitary landfill leachates with low recalcitrance levels (i.e., rapidly biodegradable). Rapidly biodegradable SLLs can be associated with La Cortada-SLL percolated from the cells/trenches excavated for the disposal of municipal solid waste (MSW) (i.e., Pamplona Municipality, Colombia) due to the contents of a high fraction of putrescible wastes (67%) and a high biochemical oxygen demand/chemical oxygen demand ratio (62%). This level ratio produced a suitable SUR obtained from the microbial metabolism starting with the upflow anaerobic sludge blanket reactor (−400 to −1,200 mg/L/h) followed by the remaining bioreactors (−150 to −350 mg/L/h). Upflow anaerobic filters in multiple separated stages reactors constitute a feasible technical option for overcoming medium to high recalcitrance levels in SLLs obtained from cells/trenches excavated storing around 25% components fraction (e.g., metals, plastics, rubber, leather, textiles). [ABSTRACT FROM AUTHOR]

Sulfide is a toxic and hazardous substance in the agricultural environment, which can cause damage to humans and livestock when exposed to large amounts of air. In this study, we performed one-factor optimization of the culture conditions and culture fractions of the Cellulosimicrobium sp. strain L1 and combined it with a biological trickling filter cell for the degradation of hydrogen sulfide for 24 consecutive days. The degradation effect of strain L1 and the biological trickling filter (BTF) on hydrogen sulfide was investigated, and the changes in intermediate products in the degradation process were briefly analyzed. The results showed that strain L1 had the highest conversion efficiency when incubated with 3 g/L sucrose as the carbon source and 1 g/L NH4Cl as the nitrogen source at a temperature of 35 °C, an initial pH of 5, and a NaCl concentration of 1%. The concentration of thiosulfate increased and then decreased during the degradation process, and the concentration of sulfate increased continuously. When strain L1 was applied to the biological trickling filter, it could degrade 359.53 mg/m3 of H2S. This study provides a deeper understanding of sulfide degradation in biological trickling filters and helps promote the development of desulfurization technology and the treatment of malodorous gasses produced by the accumulation of large quantities of livestock manure. [ABSTRACT FROM AUTHOR]

Aquaponics is a promising solution for addressing food security concerns. Nonetheless, an effective water-purification system is necessary to achieve high and stable yields of fish and vegetables. This study aimed to evaluate the nitrification and oxygen transfer performance of a laboratory-scale down-flow hanging sponge (DHS) reactor with a Brassica oleracea aquaponics system to treat water in an Oreochromis niloticus closed-aquaculture system. The DHS reactor showed a higher oxygen transfer coefficient (KLa) than the conventional aerator and provided an adequate dissolved oxygen (DO) concentration of approximately 5.5 mg/L essential for O. niloticus growth throughout the experimental period. The evaluated DHS-based aquaponic system maintained high water quality in an aquaculture tank, with a survival rate of 97%. The O. niloticusgrew at a low feed conversion ratio of 1.5–2.1 and a low feeding rate of 0.5% at high stocking densities of 17.5–22.2 kg-fish-weight/m3. 16S rRNA gene sequencing indicated that the DHS sponge carrier effectively retained nitrifying bacteria such as Nitrosomonas and Nitrospira. This study demonstrated that the DHS reactor provided a high DO concentration and that a simultaneous DHS reactor with a hydroponic tank provided a low-cost aquaponic system that could be applied for food production in the aquaculture industry. [ABSTRACT FROM AUTHOR]

The study aimed to isolate heterotrophic nitrification–aerobic denitrification strains (HNAD) and improve the denitrification efficiency of these strains. Two HNAD were selected as the research objects. The nitrification, denitrification, and simultaneous nitrification–denitrification performance of NO-5 and NH-3, as well as the synergistic simultaneous nitrification–denitrification performance of the two strains were studied. Then, the synergistic denitrification conditions of the two strains were optimized through an orthogonal experiment. The results showed that the denitrification efficiencies of NO-5 and NH-3 were 38.19% and 32.78%, and their nitrification efficiencies were 78.64% and 82.16%, respectively. Both NO-5 and NH-3 also exhibited simultaneous nitrification–denitrification. The total nitrogen(TN) removal rate of NH-3 was 74.32%, which was higher than that of NO-5 (64.60%). When the two strains co-operate exhibiting simultaneous nitrification–aerobic denitrification, the maximum TN removal rate was 91.93%. Compared with simultaneous nitrification–aerobic denitrification, the synergistic denitrification performance of the two strains was better. The optimum conditions improved through the orthogonal experiment were as follows: carbon source composition (sodium succinate:sodium citrate) was 1:1, nitrogen source composition (NO3−-N:NH4+-N) was 2:3, strain composition (NO-5:NH-3) was 3:2, inoculation ratio was 1:100, salt concentration was 0.3%, and C: N was 20:1. Under the optimal conditions, the synergistic denitrification efficiency of the two strains was 95.45%, which was 4.18% higher than that without optimization. Finally, two strains of bacteria were applied to the biofilter experiment, and the results showed that the membrane formation of the mixed high-efficiency bacteria only took 8 days, with shorter start-up time, good stability, and strong resistance to load impact, which has good engineering application significance. [ABSTRACT FROM AUTHOR]

This paper characterizes the composition of extracellular polymeric substances (EPSs) in different types of activated sludge (AS) processes and analyzes the biosorption of soluble organics when waste AS (WAS) is mixed with raw wastewater for primary carbon diversion. The fraction of AS organics identified as EPSs was 26% in a membrane bioreactor (MBR), 54% in conventional AS (CAS), and 51% in a trickling filter/solids contact (TF/SC) process. EPSs were found to be approximately 15% carbohydrates, 40% proteins, 40% humics, and 5% uronics in CAS and MBR AS. Biosorption was not correlated to the organic portion (VSS) of the WAS; however, statistically significant correlations were found for the total amount of EPSs (for TF/SC and CAS) and the protein fraction (for TF/SC and MBR) in the VSS. EPSs from different types of AS biosorbed the same amount of soluble organics, removing 1.43 ± 0.15 (n = 16) mg of soluble chemical oxygen demand (sCOD), and 1.20 ± 0.18 (n = 16) mg of truly soluble COD (ffCOD), per mg of cation exchange resin (CER) total extracted EPSs. Utilizing multiple extraction methods in series (CER–base–sulfide) increased EPS extraction yields by nearly 100% relative to CER alone and indicated different EPS fractionization for CAS (a smaller fraction of carbohydrates and a larger fraction of humics). [ABSTRACT FROM AUTHOR]

Heavy metals (HMs) in wastewater could pose a significant challenge to biological treatment systems such as in an Up-flow Anaerobic Sludge Blanket Reactor (UASBr) as well as Trickling Filter (TF) performances. These HMs are associated with retention and accumulation of solid precipitates, limitting solid-liquid separation, disrupting biochemical processes, which ultimately brings environmental risks, such as soil contamination and public health issues, dominantly due to the inhibited activities of degrading microorganisms. A cross-sectional study was applied to investigate the levels of HMs in sewage using composite and grab sampling taken from Kaliti Wastewater Treatment Plant and the samples were analyzed using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The HMs concentrations in mean±(SD) were, Ag ranges from below detection level (BDL) to 63.5 (13.5) mg/kg; Ba 60 (4.47) μg/l to 1291(58.5) mg/kg; Al, BDL to 2358.5(662.5) mg/kg; Cd 0 μg/l to 0.35(0.15) mg/kg; Cr 0 μg/l to 10.5(0.7) mg/kg; Cu 0 μg/l to 23.9(1.2) mg/kg; Zn 5.45 (12.3) to 165(5.4) mg/kg, and Mn 165 (49.5) μg/l to 92.5(3.8) mg/kg. Results indicated that Kaliti Wastewater Treatment Plant was effective in removing pollutants and thereby meeting local and international discharge limits. The plant was also found to be effective in removing Al, Cd, Cu, and Cr, but not in removing Ba and Zn. However, a real time data collection and monitoring of seasonal physicochemical parameters and HM levels in the wastewater treatment plant is suggested useful.

In the United Kingdom, trickling filters remain the most widespread secondary biological treatment process for municipal sewage treatment in terms of number of installations. Ongoing improvement in environmental quality of surface waters requires many of these sites to meet stringent effluent standards. Since publication of the original model for nitrification on mineral media trickling filters by Pearce and Williams in 1999 and the model for nitrification on plastic media filters by Pearce and Edwards in 2010, they have attracted widespread use. Since publication, the models have undergone some refinement and benefitted from an increased application range. Furthermore, recent publications by Pearce and Yang have delivered widely based models for predicting average and seasonal humus tank effluent suspended solids and variability at a resolution of daily 95th percentile performance. This paper presents recent developments of the nitrification models and consolidates the suite of models now available for trickling filter design, evaluation and operation. [ABSTRACT FROM AUTHOR]

Organic pollutants in the air have serious consequences on both human health and the environment. Among the various methods for removing organic pollution gas, biotrickling filters (BTFs) are becoming more and more popular due to their cost-effective advantages. BTF can effectively degrade organic pollutants without producing secondary pollutants. In the current research on the removal of organic pollutants by BTF, improving the performance of BTF has always been a research hotspot. Researchers have conducted studies from different aspects to improve the removal performance of BTF for organic pollutants. Including research on the performance of BTF using different packing materials, research on the removal of various mixed pollutant gases by BTF, research on microbial communities in BTF, and other studies that can improve the performance of BTF. Moreover, computational fluid dynamics (CFD) was introduced to study the microscopic process of BTF removal of organic pollutants. CFD is a simulation tool widely used in aerospace, automotive, and industrial production. In the study of BTF removal of organic pollutants, CFD can simulate the fluid movement, mass transfer process, and biodegradation process in BTF in a visual way. This review will summarize the development of BTFs from four aspects: packing materials, mixed gases, micro-organisms, and CFD, in order to provide a reference and direction for the future optimization of BTFs. [ABSTRACT FROM AUTHOR]

Environmental pollution is an issue of particular concern, specifically when industrial waste products are not subjected to appropriate treatment. Among various industries in the agri-food sector, the brewing industry holds a significant position in this context, given that beer stands as the predominant choice of consumers. Brewery waste generates significant quantities of organic substances, along with ammonium nitrogen and phosphorus. Among the various methods for their treatment, adsorption has received substantial attention due to its cost-effectiveness and operational simplicity. The present study investigates the adsorption capacity of two materials, zeolite and palygorskite, for the removal of ammonium nitrogen and brewery waste, using columns and batches. Simultaneously, desorption and regeneration experiments were conducted, and the effect of pH on their effectiveness was also examined. To understand the adsorption mechanisms, isotherm and kinetic models have been estimated. The results of the experiments have demonstrated a marked adsorption efficiency of the adsorbent materials, surpassing 90%. In comparison, zeolite has exhibited a better adsorption capacity in the removal of ammonium nitrogen, while palygorskite has shown greater aptitude for phosphorus removal. The purpose of these experiments was to investigate the adsorption capacity of these two materials as a potential medium for brewery wastewater treatment (e.g., as part of adsorption filter, trickling filters, and constructed wetlands). [ABSTRACT FROM AUTHOR]

Wastewater treatment plants are designed, operated, and maintained in light of environmental legislation, which mainly determines the removal of certain pollutants. This article proposes to comparatively assess the environmental and economic impacts of wastewater treatment technological routes commonly used in Brazil. For this purpose, life cycle assessment and costing were applied to four wastewater treatment processes at two different scales. The results show the positive contribution of up-flow anaerobic sludge blanket reactors in the flowcharts of the wastewater treatment plants to reduce the generation of environmental and economic impacts by 3.15% to 84.53% and 25.03% to 38.68%, respectively. It can be concluded that the technological route that obtained the best environmental and economic performance is the upflow anaerobic sludge blanket reactor followed by a trickling filter. In contrast, the one that achieved the worst performance was activated sludge. [ABSTRACT FROM AUTHOR]

Microbial flora plays an important role in microorganism-enhanced technology. The pollutant degradation ability and viable counts of these agents are crucial to guarantee their practical application. In this study, an efficient pollutant-degrading microbial flora was screened, its medium components and culture conditions were optimized, and its effect was verified in zeolite trickling filter towers. After a 24 h culture under the optimal conditions, the viable count reached 4.76 × 109 cfu/mL, with the degradation rates of ammonia nitrogen (NH4+-N), nitrate nitrogen (NO3−-N), total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD) increased to 93.5%, 100%, 68.3%, 32.6%, and 85%, respectively. After optimizing the feeding strategy, the concentration of viable bacteria reached 5.80 × 109 cfu/mL. In the application effect verification experiment, the degradation rates of NH4+-N, TN, TP, and COD in the experimental group reached 96.69%, 75.18%, 73.82%, and 90.83%, respectively, showing a significant improvement compared to the results of the control group. The main components in the control group were Dokdonella, Brevundimonas, Alishewanella, Rhodobacter, Pseudoxanthomonas, and Thauera, whereas those in the experimental group were Dokdonella, Proteocatella, Rhodobacter, Dechlomonas, and Nitrospira. Proteocatella, Dechlomonas, and Nitrosra, which were unique to the experimental group, are common bacteria used for nitrogen and phosphorus removal. This explains the difference in the sewage treatment capacity between the two groups. This study provides an alternative sewage treatment microbial flora with a reasonable production cost and high degradation efficiency for NH4+-N, TN, TP, and COD. Keypoints: A mixed-bacteria group with a high degradation rate of NH4+-N, TN, TP, and COD was screened. The viable cell concentration and pollutant degradation efficiency of the screened microbial flora was increased significantly by optimizing its cultivation conditions. Increased pollutant degradation efficiency was verified in a zeolite trickling filter tower and explained by the microbial composition of the screened microbial flora. [ABSTRACT FROM AUTHOR]

The global effects of MP (MP) pollution on the environment are concerning, and they are exacerbated by the multiple sources of pollution in aquatic environments such as urban runoff, waste mismanagement, industrial pollution, and so on. South pacific islands host a large diversity of aquatic flora and fauna and given its ecological significance it is necessary to identify the sources of MP pollution in the region. To date, very little attention has been given to identify whether effluents from wastewater treatment plants (WWTP) are acting as a significant source of MP in the South Pacific region and its countries. Therefore, the present study analyzed and compared the treatment methods and fate of MPs in the country's two main WWTPs: 1) the Kinoya WWTP (simple secondary clarifier and trickling filter) and 2) Natabua WWTP (secondary pond treatment system). Sampling locations were based on the different treatment stages, and samples were collected from each stage of treatment before effluents were released into the ocean. Kinoya WWTP had an average of 3.45 ± 0.3 particles/L in the inlet stage and released an average of 0.3 ± 0.26 particles/L of MP through the outlet with 91% removal efficiency (RE) with an output equivalent of 4500 particles per day. The initial stage of treatment from the anaerobic pond outlet at Natabua had an average of 2.9 ± 1.05 particles/L, and the maturation outlet had an average of 0.53 ± 0.42 particles/L, a removal efficiency of 81% and thus an output equivalent of 4558 particles/L of MP. Polymer analysis under FTIR confirmed that cellophane or semi-synthetic cellulose and polypropylene were common polymers in the final effluent in Kinoya WWTP, and Natabua plant has cellophane or semi-synthetic cellulose, polypropylene and polyethylene were observed as common polymers. Although there are numerous study that have compared wastewater treatment processes, this is the first study in Fiji that investigates the efficiency of the two methods of water treatment process in the context of microplastic pollution and emphasizes the effectiveness of the treatment stages in determining the concentration of MP released into the ocean. [ABSTRACT FROM AUTHOR]

This study increases the mass transfer of hydrophobic contaminants in a microbial fuel cell-based trickling filter (MFC/TF) by adding non-aqueous phase liquid. The removal efficiency, mineralization efficiency and elimination capacity of styrene are respectively increased by 1.56 times, 1.86 times and 1.52 times, the power density is increased by 2.6 times and the internal resistance is reduced by approximately 22% after adding 10% silicone oil to the MFC/TF. This is mainly attributed to a decrease in the internal resistance after adding silicone oil, which increases electron transfer on the surface of the auxiliary anode packing and increases the number of electricity-producing bacteria. Adding 10% silicone oil to the MFC/TF increases the number of degrading bacteria and electricity-generating bacteria in the MFC/TF by 2.3–2.5 times. The performance of the MFC/TF using 10% silicone oil is significantly increased because there is increased mass transfer of styrene in the MFC/TF and increased power generation. [Display omitted] [ABSTRACT FROM AUTHOR]

Two variants (preliminary stage and main stage) of the experiment aiming to verify the possibility of using waste materials and composites for septic tank effluent (STE) treatment were investigated. The hydraulic load of filters during main stage was about two times lower than during preliminary stage. The aim of this study was to examine the mechanical and biological treatment efficiencies of four waste materials: polyethylene Raschel mesh (PERM), wood-polymer composite (WPC), cut plastic straws (CPS) and polyethylene (PE). Considering that the used STE was hardly biodegradable, the removal efficiencies of the used materials were relatively high. During main stage for PERM the removal efficiencies of chemical oxygen demand (COD), ammonium nitrogen (NNH4), total phosphorus (Ptot) and total suspended solids (TSS) were 84.6%, 92.8%, 24.5% and 83.6%, respectively. For CPS, efficiencies for COD, NNH4, Ptot and TSS were 58.8%, 40.2%, 43.1% and 84.7%, respectively. For WPC, efficiencies for COD, NNH4, Ptot and TSS were 60.2%, 51.8%, 44.1% and 85.2%, respectively. For PE, efficiencies for COD, NNH4, Ptot and TSS were 46.9%, 30.0%, 43.7% and 85.3%, respectively. The technology used in this study was relatively simple. For maximum effectiveness in wastewater reuse (e.g., for irrigation), mechanical pre-treatment should be performed. [ABSTRACT FROM AUTHOR]

This study uses several years of effluent quality data from 43 sites where online monitoring has been operational for many years resulting in the accumulation of high‐resolution data sets. The data show a highly repeatable, seasonal dependence of effluent turbidity on temperature. This has been modelled with simple techniques producing a generic model that is neither data hungry nor requires site calibration. Viscosity‐based mechanisms are proposed and discussed. These mechanisms differ from conventional assumptions of suspended solids peaks being solely flow related and or ascribed to 'spring sloughing'. The proposal is that the organic loading of the filter and the physical temperature effects on settlement velocity are both as influential as hydraulic loading in determining effluent suspended solids concentration. Application of the models enables improved design for new/upgraded units and more accurate capacity assessment of trickling filters and humus tanks enabling improved operational risk management of compliance failure. [ABSTRACT FROM AUTHOR]

The current study focuses on a comprehensive review of the pilot scale production of biohydrogen and various factors affecting the design experiments. Biohydrogen is a clean energy carrier that can be used as a potential alternative to fossil fuels. Biohydrogen as a fuel has several advantageous attributes, including; carbon-neutral or carbon-zero nature, easy renewability, eco-efficient productivity (via biological routes), eco-friendly conversion, and the highest energy content among all existing fuels. Pilot-scale production of biohydrogen is limited because it requires a better understanding of the possible interactions involved in the process. In this review, biohydrogen production on various types of reactors such as stirred tank reactors, packed bed reactors, fluidized bed reactors, trickling filter reactors, etc., have been discussed. However, biohydrogen production has been mostly studied on small scale, the most challenging issue concerning large-scale production of biohydrogen is its relatively high cost over fuels from fossil owing to high feedstock and manufacturing costs. Therefore, cost-effective and eco-friendly biohydrogen production technologies should be necessarily developed and continuously improved to make this biofuel more competitive over its counterpart. In comparison with fossil fuels, biohydrogen has a high energy yield and is highly renewable. It can fulfill the future demand as a transport fuel. • Biohydrogen production performances of various reactor configurations. • The pros and cons of each reactor technology for biohydrogen production. • Challenges and perspectives concerning biohydrogen production. • Emerging trends and future scopes of the biohydrogen process. • Socio-economic aspects toward sustainable development. [ABSTRACT FROM AUTHOR]

The microbial community in biofilm is safeguarded from the action of toxic chemicals, antimicrobial compounds, and harsh/stressful environmental circumstances. Therefore, biofilm-based technology has nowadays become a successful alternative for treating industrial wastewater as compared to suspended growth-based technologies. In biofilm reactors, microbial cells are attached to static or free-moving materials to form a biofilm which facilitates the process of liquid and solid separation in biofilm-mediated operations. This paper aims to review the state-of-the-art of recent research on bacterial biofilm in industrial wastewater treatment including biofilm fundamentals, possible applications and problems, and factors to regulate biofilm formation. We discussed in detail the treatment efficiencies of fluidized bed biofilm reactor (FBBR), trickling filter reactor (TFR), rotating biological contactor (RBC), membrane biofilm reactor (MBfR), and moving bed biofilm reactor (MBBR) for different types of industrial wastewater treatment. Besides, biofilms have many applications in food and agriculture, biofuel and bioenergy production, power generation, and plastic degradation. Furthermore, key factors for regulating biofilm formation were also emphasized. In conclusion, industrial applications make evident that biofilm-based treatment technology is impactful for pollutant removal. Future research to address and improve the limitations of biofilm-based technology in wastewater treatment is also discussed. [ABSTRACT FROM AUTHOR]

This work aimed to assess the technical and energetic feasibility of a passively aerated laboratory‐scale trickling filter, configured as a two‐stage system, to produce urban wastewater (UWW) reusable in agriculture. The trickling filter was fed continuously with high‐strength UWW at four hydraulic retention times (HRTs), that is, 10, 5, 2 and 1 day, corresponding to organic loading rates (OLRs) of 0.1, 0.2, 0.5 and 0.9 kg COD/m3/d, respectively. The results revealed a good performance in organic load removal and nitrification at the four HRTs. The trickling filter showed high organic pollutant removal efficiencies of up to 93%, 94% and 98% for chemical oxygen demand (COD), BOD5 and total suspended solid (TSS), respectively, as well as high ammonia nitrogen removal above 96% at the shortest HRT of 1 day. All physicochemical parameters were significantly lower than the allowable limits set out in ISO 16075 for category C (non‐food crop irrigation) irrigation water. The reuse of treated UWW in irrigation led to germination indexes and growth parameters of triticale (Triticosecale Wittm.) almost equal to those obtained using tap water. Energy use was found to be about 0.2754 kWh/m3 of treated wastewater, making it competitive with trickling filter plants reported in the literature. The simplicity and energy efficiency of the developed trickling filter system, combined with its capacity for almost full nitrification, make it appealing for sewage treatment in small communities in developing countries. [ABSTRACT FROM AUTHOR]

Nano‐sized particles in wastewater are generally considered colloids, but their production and size distribution are not well understood. Organic nano‐sized particles are more abundant than engineered nanomaterials in wastewater, where they may cause membrane fouling, harbor pathogens, and transport contaminants to the environment. To our knowledge, this study is the first to examine the seasonal behavior, removal, and the quantity and size of suspended particles (both unfiltered and filtered through a 450 nm filter) at multiple points within different processes along two water resource recovery facilities (WRRFs, formerly wastewater treatment plants). In Southern California where wastewater is often reused or reclaimed, a better understanding of nano‐sized particles generation and removal may help reduce cost. We found that both types of the biological secondary treatments investigated (conventional activated sludge process and trickling filter) were more efficient in removing suspended particles larger than 450 nm than they were smaller ones. However, the results show that current treatment processes are not designed to remove nano‐sized particles efficiently. We also investigated the factors that correlate with their occurrence and found that there was a significant and direct correlation between influent dissolved chemical oxygen demand (COD) and the abundance of suspended particles both larger and smaller than 450 nm, suggesting that the suspended particles increased with dissolved COD in the WRRFs and thus were biogenically generated during the wastewater treatment. Although no conclusive seasonal correlations were found, dissolved COD management may control nano‐sized particle production. Practitioner Points: Conventional secondary treatments (activated sludge and trickling filter) could efficiently remove particles but not as efficiently for nano‐sized particles (40.1–52.7% removal).At one facility, particles of all sizes were found to correlate with dissolved carbon and EPS, meaning they were biogenic.Monitoring dissolved carbon or EPS precursors may help control membrane fouling post‐secondary treatment, and this warrants more studies. [ABSTRACT FROM AUTHOR]

The efficiency of photosynthesis in strawberry plants is measured to maintain the quality and quantity of strawberries produced. The latest method used to measure the photosynthetic status of plants is chlorophyll fluorescence imaging (CFI), which has the advantage of obtaining plant spatiotemporal data non-destructively. This study developed a CFI system to measure the maximum quantum efficiency of photochemistry (Fv/Fm). The main components of this system include a chamber for plants to adapt to dark environments, blue LED light sources to excite the chlorophyll in plants, and a monochrome camera with a lens filter attached to capture the emission spectra. In this study, 120 pots of strawberry plants were cultivated for 15 days and divided into four treatment groups: control, drought stress, heat stress, and a combination of drought and heat stress, resulting in Fv/Fm values of 0.802 ± 0.0036, 0.780 ± 0.0026, 0.768 ± 0.0023, and 0.749 ± 0.0099, respectively. A strong correlation was found between the developed system and a chlorophyll meter (r = 0.75). These results prove that the developed CFI system can accurately capture the spatial and temporal dynamics resulting from the response of strawberry plants to abiotic stresses. [ABSTRACT FROM AUTHOR]

The discharge of emerging pollutants, such as beta-blockers (BB), has been recognized as one of the major threats to the environment due to the ecotoxicity associated with these emerging pollutants. The BB are prescribed to treat high blood pressure and cardiovascular diseases; however, even at lower concentration, these pollutants can pose eco-toxic impacts towards aquatic organisms. Additionally, owing to their recalcitrant nature, BB are not effectively removed through conventional technologies, such as activated sludge process, trickling filter and moving bed bioreactor; thus, it is essential to understand the degradation mechanism of BB in established as well as embryonic technologies, like adsorption, electro-oxidation, Fenton process, ultraviolet-based advance oxidation process, ozonation, membrane systems, wetlands and algal treatment. In this regard, this review articulates the recalcitrant nature of BB and their associated removal technologies. Moreover, the major advantages and limitations of these BB removal technologies along with the recent advancements with regard to the application of innovative materials and strategies have also been elucidated. Therefore, the present review intends to aid the researchers in improving the BB removal efficiency of these technologies, thus alleviating the problem of the release of BB into the environment. [ABSTRACT FROM AUTHOR]

Industrial production processes produce large amounts of toluene, endangering human health and air quality. The hydrophobicity of toluene limits the removal performance in biotrickling filters (BTFs). To improve the removal efficiency of toluene in BTFs, β-cyclodextrin (β-CD) coupled with atomization was employed in this study. The results showed that β-CD and atomization significantly enhanced the biodegradation of toluene and the maximum elimination capacity reached 90.9 g/(m3·h). At the optimized conditions that β-CD additional of 12.5 g/L and an atomizer with power of 19.8 W, the removal efficiency of toluene was up to 92.6 % (inlet concentration, 0.7 g/m3), which was 17 % higher than that of the control. The use of β-CD combined with atomization increased the extracellular protein and polysaccharide contents. The biofilm surface hydrophobicity of the experimental group reached 79 % which was 1.34 times that of the control. The abundance of toluene degrading bacteria, Pseudomonas sp. and Mycobacterium sp., significantly increased under β-CD with atomization. The addition of β-CD with atomization increased mass transfer, the relative hydrophobicity of biofilm, and the functional microbes so as to enhance treatment of toluene. This study may provide guidelines for the design and technological development of hydrophobic toluene control in industrial waste gas. [Display omitted] [ABSTRACT FROM AUTHOR]

Developing countries demand a sewage treatment plant with low-cost processes that are viable in warm climates. The UASB (upflow anaerobic sludge blanket) associated with the trickling filter (TF) would meet this requirement. However, there is still a need for studies aimed at the use of new support media. Based on this, the use of expanded polystyrene (EPS) as a support media in TF was evaluated in this study. As a result, the TF filled with EPS presented a final effluent with quality similar to reactors filled with crushed stone or patented materials. The density of EPS (6.56 ± 0.30 kg m−3), the void ratio (61.7 ± 2.1%), and the mean surface area (201.9 ± 14.9 m2 m−3) once again demonstrate that EPS has characteristics similar to other alternative or patented materials. Therefore, we found that EPS can be another alternative material to be used in sewage treatment, and also that one could give an appropriate destination to a portion of this material, which is currently still discarded in landfills. [ABSTRACT FROM AUTHOR]

The present study reports a detailed life cycle assessment and cost–benefit analysis of a commercially viable Internal-Stack-Trickling Bio-Electrochemical Reactor (IS-TrickBER). IS-TrickBER used wastewater as a feedstock and converted that wastewater through electrochemical methods into low-grade fertilizer and produced electricity. IS-TrickBER was observed for its performance in terms of power output and wastewater treatment. IS-TrickBER exhibited up to 4.2 Wh net energy yield while treating 84.84L wastewater per day along with 92.17% COD removal and 38.23% Columbic efficiency during the operational run with real municipal wastewater. Based on daily net energy yield, up to 1457.6Wh yearly net energy yield can be expected. A comprehensive start-to-end life cycle assessment study associated with the manufacturing, and operational phases of IS-TrickBER was also conducted to ascertain its impact on the environment. The environmental impact through air emissions during the manufacturing stage can be minimized by changing the plastic balls used as packing material in the reactor. A detailed cost–benefit analysis was also conducted to understand its economic viability. Cost–benefit analysis of IS-TrickBER, based on net energy yield, shows that IS-TrickBER could compensate its installation cost within a few years. IS-TrickBER performed well in eliminating the chemical load of wastewater and simultaneous electricity generation. Due to its scalability, compactness, and low maintenance, IS-TrickBER can be a suitable candidate in real-time wastewater treatment. [ABSTRACT FROM AUTHOR]

The effects of rhamnolipid chelating La (III) or Nd (III) on m-dichlorobenzene removal and biofilm growth were investigated. The rhamnolipid chelating La (III) or Nd (III) significantly increased the average m-dichlorobenzene elimination capacity by 24% and 29%, respectively, on day 70–130, and the average wet weights of biomass ranged from 11 kg/m3 to 15 kg/m3 in BTFs on day 100–180 at an inlet load of at 47–98 gm3/h and an EBRT of 60s-90s. Microbial community functional genes about biofilm growth and m-dichlorobenzene removal were also increased. In addition, the rhamnolipid chelating La (III) or Nd (III) can improve the membrane permeability, extracellular polymeric substance (EPS) production, catechol 2,3 dioxygenase (C23O) enzyme, and chlorobenzene dioxygenase activity. These results demonstrate that rhamnolipid chelating La (III) or Nd (III) have the potential to improve the performance of BTFs treating hydrophobic and highly toxic VOCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • The downflow hanging sponge reactor was operated with a short HRT. • HRT of 0.5 h was effective for high organic removal and nitrification efficiency. • Comammox bacteria are capable of enhancing nitrification in high-rate DHS reactors. A down-flow hanging sponge (DHS) reactor is a trickling filter system used for wastewater treatment, which employs sponges to retain biomass. This study assessed the process performance of a compact DHS combined with a sedimentation tank with seven phases at varying hydraulic retention times (HRT) over 500 days. The BOD of the DHS effluent was maintained at 4.0 ± 0.5 mg·L-1 for the shortest HRT 0.3 ± 0.1 h. The nitrification efficiency was considerably impacted by the reduced HRT, with NH 4 +-N and NO 3 –-N concentrations of 9.0 ± 1.2 mgN·L-1 and 2.2 ± 0.5 mgN·L-1, respectively. Nevertheless, the effluent complied with effluent discharge standards throughout the trial period. The number of comammox 16S rRNA gene copies ranged from 5.58 to 13.2 × 107 copies·mL−1, indicating that sponges biomass retained carrier can provide favorable conditions for comammox growth and could contribute to nitrification in the high-rate DHS reactor. [ABSTRACT FROM AUTHOR]

In recirculating aquaculture systems (RAS), maintaining water quality in aquaculture tanks is a paramount factor for effective fish production. A down-flow hanging sponge (DHS) reactor, a trickling filter system used for water treatment of RAS that employs sponges to retain biomass, has high nitrification activity. However, nitrification in seawater RAS requires a long start-up time owing to the high salinity stress. Therefore, this study aimed to evaluate the nitrification characteristics and changes in the microbial community during the conversion of freshwater to seawater in a DHSreactor fed with ammonia-based artificial seawater. The total ammonia nitrogen concentration reached 1.0 mg-N·L−1 (initial concentration 10 mg-N·L−1) within 11 days of operation, and nitrate production was observed. The 16 S rRNA gene sequence of the DHS-retained sludge indicated that the detection rate of the ammonia-oxidizing archaeon Candidatus Nitrosocosmicus decreased from 23.9 % to 14.0 % and 25.8–17.6 % in the upper and lower parts of the DHS reactor, respectively, after the introduction of seawater. In contrast, the nitrite-oxidizing bacteria Nitrospira spp. increased from 0.1 % to 9.5 % and from 0.5 % to 10.5 %, respectively. The ammonia oxidation rates of 0.12 ± 0.064 and 0.051 ± 0.0043 mg-N·g-MLVSS−1·h−1 on the 37th day in the upper and bottom layers, respectively. Thus, nitrification in the DHS reactor performed well, even under high-salinity conditions with short operational days. This finding makes the transition from freshwater to saltwater fish in the RAS system simple and economical, and has the potential for early start-up of the RAS. [Display omitted] • DHS reactors can carry out efficient nitrification with NH 4 CL addition. • TAN decreased from 10.0 to 1.0 mg-N·L−1 in the RAS within 11 days of operation. • The conversion of NO 2 −-N to NO 3 −-N was observed on the 21st day of operation. • Microbial community structure shifts during freshwater to seawater transition. [ABSTRACT FROM AUTHOR]

It is expected that, by 2050, the rapid rise in population and simultaneous urbanization shall deplete clean water supplies. Domestic wastewater (DWW) contains inorganic and organic components that can be harmful to aquatic organisms. Traditional remediation approaches (physical, chemical and biological) can be used on-site or off-site to purify polluted domestic water (activated sludge, built-wetlands, stabilization ponds, trickling filters and membrane bioreactors), and each has its own advantages and limitations. Biosorption through microorganisms, bacteria (microbe-mediated remediation), fungi (mycoremediation) and algae (phycoremediation) has shown promising results in removing toxic chemicals and nutrients. The type of waste and its concentration, heterogeneity level and percentage of clean-up required; and the feasibility of the clean-up technique and its efficiency, practicability, operational difficulties, environmental impact and treatment costs are all factors that are to be considered when choosing a technique for domestic wastewater treatment (DWWT). This review focuses on the roles of conventional methods in DWWT, including their merits, demerits and future prospects. It promotes the concept of "reduce, reuse and recycle" of DWWT and also highlights the problem of emerging contaminants in WWT regimes. We provide insights into the different membrane filtration procedures and water purification techniques and the synergism of conventional and non-conventional WWT strategies for human and environment health security. [ABSTRACT FROM AUTHOR]

Copyright of Environmental Science & Technology (10036504) is the property of Editorial Board of Environmental Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Continuous biohydrogen production by dark fermentation valorizes organic effluents like winery vinasse (WV), being an economical alternative to fossil fuels, to produce clean and renewable hydrogen. Trickling bed reactors (TBR) operated with low hydraulic retention time (HRT) favor hydrogen production. However, its large-scale application has still been limited in the literature due to possible operational risks and costs. To maximize the hydrogen production rate (HPR) rapidly, an innovative on-line feedback control was evaluated using WV in a TBR. Based on continuous HPR measurements, the strategy alternates the operation between a high HRT of 5.5 h and a low HRT of 3 h (an organic shock load) by detecting either a peaking phenomenon during the transient or the steady state after it. Use of the controller increased the mean HPR to 177.5 ± 12.3 mL H 2 ⋅ L reac − 1 ⋅ h − 1 from 93.9 ± 9.9 mL H 2 ⋅ L reac − 1 ⋅ h − 1 under a usual fixed HRT operation, and only 91.5 h were needed to automatically find the optimal mean HRT at 3.76 ± 0.15 h. Bacterial community and metabolite analysis helped explain the increase in hydrogen yield (1.1 ± 0.4 mmol H 2 gCOD added − 1) by a cross-feeding interaction between lactic acid and hydrogen-producing bacteria. [Display omitted] • Trickling filter bioreactor produces hydrogen from treatment of winery vinasses. • Feedback control with temporary shock loads maximizes biohydrogen production. • Optimal hydrogen production is reached quickly and can be sustained. • Hydrogen yield depends on cross-feeding interaction involving lactic acid bacteria. • HPR reached 177.5 mL/L/h, 64% higher than without feedback control. [ABSTRACT FROM AUTHOR]

The research aims to study the purification performance of a local and natural material as an input or as a biological filter for treating urban domestic wastewater. For this purpose, pozzolan was used as the biofiltration support that was provided from Beni Saf located in the North-West of Algeria. Tests were carried out with a specially modified pilot unit (TE900) for wastewater treatment over a period of four months. To assess the efficiency of the treatment, two main parameters have been focused on - the height of the sprinkler filter (40 cm and 80 cm) and the flow rate (10, 16, and 25 dm3·h-1). Physicochemical and bacteriological analyses were carried out on raw wastewater and treated water. The obtained results show that the Beni Saf pozzolan-filled trickling filter eliminates a large fraction of the studied pollutants. The purification yields obtained are fairly encouraging; 98% for turbidity, 88% for suspended solids (SS), 94% for chemical oxygen demand (COD), and 98% for biological oxygen demand (BOD5). As for bacterial indicators, the formation of biofilms has significantly reduced bacterial activity with a percentage of over 80%. It can be concluded that the reduction of pollutant parameters clearly indicates the effectiveness of the treatment by this ecological process. Therefore, the use of local and natural materials for wastewater treatment can be a promising alternative based on sustainable environmental technologies and development. [ABSTRACT FROM AUTHOR]

Biological methanation is the production of CH4 from CO2 and H2. While this approach to carbon capture utilization have been widely researched in the recent years, there is a gap in the technology. The gap is towards the flexibility in biomethanation, utilizing biological trickling filters (BTF). With the current intermittent energy system, electricity is not a given surplus energy which will interfere with a continuous operation of biomethanation and will result in periods of operational downtime. This study investigated the effect of temperature and H2 supply during downtimes, to optimize the time needed to regain initial performance. Short (6 h), medium (24 h) and long (72 h) downtimes were investigated with combinations of three different temperatures and three different flow rates. The results from these 27 experiments showed that with the optimized parameters, it would take 60 min to reach 98.4% CH4 in the product gas for a short downtime, whereas longer downtimes needed 180 min to reach 91.0% CH4. With these results, the flexibility of biomethanation in BTFs have been proven feasible. This study shows that biomethanation in BTFs can be integrated into any intermittent energy system and thereby is a feasible Power-2-X technology. [ABSTRACT FROM AUTHOR]

The existence of risk factors of wastewaters to high organic materials, phenol compound, chlorinated compound and other complex providing a discharge of receptive waters could be serious hazards created for life in the water. In this study activated sludge/trickling filter (AS/TF) two-step integrated with upflow suspended growth denitrification (USGD) processes operation evaluated for inert chemical matter removal to conventional treatment. From the wastewater activated sludge system of Isfahan with trickling filter used to sequentially. The media from polypropylene, 240 m2/m3 specific area, 1.8 m diameter and 6 m height applied to TF tank instal. Half industrial pilot part of this two-step system operated from 90 days with flow minimum equivalent to 3.6 m3/h until reached steady state. From AS/TF effluent used to feed four reactors in batch condition and lab scale. These reactors along with two reactors to glucose substrate and equivalent COD with other reactors performance from 504 h in the aerobic condition and room temperature (23–26°C). Each of which of soluble inert materials,total soluble COD, degradable suspended materials, degradable COD, refractory suspended materials and degradable soluble materials parameters calculated for single activated sludge (SAS), AS/TF and USGD effluent that mg/l reached for SAS 32, 180, 86, 234, 220 and 148 respectively. These parameters calculated for a two-step system 16, 180, 195,359,111 and 164 and the USGD process as 8, 180, 201, 373, 105 and 172 respectively. The calculations showed when AS integrated to TF in compare with when one applies single is capable inert COD removed two times and for USGD removed four times. [ABSTRACT FROM AUTHOR]

This research estimates the efficiency of domestic wastewater treatment in the removal of organic pollutants and nitrogen compounds with a two-stage treatment sequence (an activated sludge reactor in the first stage, and a trickling filter in the second stage), and with the application of floating carriers in the activated sludge reactor. The materials "Polyvom", "Polystyrene" and "Bioballs" were adopted as floating carriers with previously determined filling ratios in the reactor volume of 10%, 20% and 20%, respectively. After the first stage of the study, it was found that the most effective treatment was achieved using the "Polyvom" material. Therefore, only this floating carrier was considered in the second and third stages of the study. Within the stages of the research, lab-scale benches operated under different operation modes of the treatment sequence. At the end of the study, it was possible to achieve the following levels of purification: BOD5 (2.1 mg/L), NH4 (0.4 mg/L), NO2 (1.0 mg/L), and NO3 (25 mg/L). The mean values of the concentrations of BOD, NH4, and NO3 met the requirements, but the concentration of NO2 exceeded the requirements (1.0 mg/L vs. 0.08 mg/L). These results were achieved under a hydraulic retention time in the activated sludge reactor of 8 h, and the MLSS for the free-floating and immobilized activated sludge was 0.2 and 0.9 g/L, respectively. [ABSTRACT FROM AUTHOR]

Biofilters (BFs) and biotrickling filters (BTFs) are two types of bioreactors used for treatment of volatile organic compounds (VOCs). Both BFs and BTFs use packing materials in which various microorganisms are immobilised. The water phase in BFs is stationary and used to maintain the humidity of packing materials, while BTFs have a mobile liquid phase. Optimisation of irrigation of packing materials is crucial for effective performance of BFs and BTFs. A literature review is presented on the influence of water content of packing materials on the biofiltration efficiency of various pollutants. Different configurations of BFs and BTFs and their influence on moisture distribution in packing materials were discussed. The review also presents various packing materials and their irrigation control strategies applied in recent biofiltration studies. The sources of this review included recent research articles from scientific journals and several review articles discussing BFs and BTFs. [ABSTRACT FROM AUTHOR]

Down-flow hanging sponge (DHS) reactor that is sponge-based trickling filter was considered to be an alternative aerobic treatment system for low strength sewage treatment under tropical conditions. This study aims to determine the process performance of the DHS reactor combined with a pre-treatment sedimentation tank (SED) system installed at the municipality sewage treatment plant in Khon Kaen, Thailand over, 1,600 days. The DHS reactor was operated with three operational periods: low (0.2 kgBODm3 per day), high (0.5–1.3 kgBODm3 per day), and super rates (1.7–2.2. kgBODm3 per day). The results showed effective reductions in biochemical oxygen demand (BOD) and suspended solids by more than 74% and 78%, respectively, during the entire experimental period. Moreover, the final effluent met the Thailand discharge standard with an external short hydraulic retention time of 0.2 h. In addition, the combined system facilitates simultaneous nitrification and denitrification and effectively removed up to 43% of total nitrogen. The self-degradation of the organic compounds occurs owing to the retained sludge in the DHS reactor; this leads to undisputed clogging in sponge media. Therefore, the combined SED-DHS system could be an appropriate sewage treatment system for tropical conditions. [ABSTRACT FROM AUTHOR]

Optimization of operational parameters of wastewater treatment system using the modeling technique may lead to enhance the system's operational and treatment efficiency. The present research was carried out to investigate the treatment efficiency of conventional trickling filter (CTF) and cascade cum trickling filter (CCTF) for treatment of domestic wastewater. Both the systems (CTF and CCTF) were operated for a period of four months under temperature range of 21–48 °C. The maize cob (MC) and date palm fibre (DPF) were used as biofilm support media. Biological oxygen demand (BOD) reaction kinetic model was developed and evaluated for optimization of BOD removing efficiency of CTF and CCTF. The removing efficiency of CTF and CCTF has increased with increasing operational time from 12 to 48 h. The CCTF showed 3–25% higher efficiency in removing organic matter, nutrients and sulphates compared to CTF regardless the supporting media. Similarly, MC showed 3–8% higher removal efficiency of the tested parameters compared to the DPF as supporting media in both CTF and CCTF systems. The BOD reaction kinetic model estimated the optimal volumetric design BOD loading rates (Bvd) of 1.5–2.1 kg BOD/m3 day for designing efficient trickling filter systems. The CCTF with MC media was found efficient than other reactors due to highest BOD removal efficiency (91.8%) and good capacity to treat high BOD load (2.1 kg/m3.day). Hence, the CCTF system has higher potential for efficient removal of organic and inorganic contaminants from the wastewater in developing countries. [ABSTRACT FROM AUTHOR]

Treatment wetland has become a reference in wastewater treatment, particularly for the treatment of domestic or agricultural effluent in rural areas. The AZOE process developed by the company SCIRPE is an optimised system of water treatment based on a conventional two-stage treatment wetlands with vertical hydraulic flow. A trickling filter has been added at the head of the system and filtration stages have been partially saturated to promote anoxic conditions. This study presents the monitoring of a complete pilot-scale AZOE system receiving real and continuous effluents. Effluents from two periods of the year are studied: autumn and spring when the organic load is higher. The performance of each treatment unit, as well as the total treatment unit is presented in this study. The main results show that i) the trickling filter consumes about half of the carbon load whatever the season but that nitrification is lower when the incoming organic load is higher ii) the first stage of filtration contributes a lot to denitrification thanks to the anoxic zones iii) the contribution of the second stage is lower but can increase in case of higher incoming load highlighting a safety role of the treatment. The continuous ammonium and nitrate data at the outlet of the first and second stages show a very characteristic dynamic of this system during the feeding period: a well-defined nitrate peak at the outlet of the first stage which is found on the second stage. The lack of carbon is pointed out as the most limiting factor to denitrification on the second stage. [Display omitted] • TF performance variability strongly influences first stage nitrogen removal • First stage achieves most of the denitrification • A peak of nitrates concentration is observed at first stage outlet shortly after feeding • Second stage guarantees high COD and TKN removal rates • Organic carbon availability in second stage is the main limitation to denitrification [ABSTRACT FROM AUTHOR]

[Display omitted] • Two validated models to reveal role of comammox bacteria in granular PN/A system. • AOB-based PN/A achieved > 80 % TN removal at higher DO with 1.7 %∼2.8 % N 2 O production. • Comammox bacteria-based PN/A removed > 80 % TN in a wider range of DO and NH 4 +. • Comammox bacteria-based PN/A produced negligible N 2 O but was more sensitive to DO. In this study, two bioprocess models were first constructed with the newly-discovered comammox process described as one-step and two-step nitrification and evaluated against relevant experimental data. The validated models were then applied to reveal the potential effect of comammox bacteria on the granular bioreactor particularly suitable for undertaking partial nitritation/anammox (PN/A) under different operating conditions of bulk dissolved oxygen (DO) and influent NH 4 +. The results showed although comammox bacteria-based PN/A could achieve > 80.0 % total nitrogen (TN) removal over a relatively wider range of bulk DO and influent NH 4 + (i.e., 0.25–0.40 g‐O 2 /m3 and 470–870 g‐N/m3, respectively) without significant nitrous oxide (N 2 O) production (< 0.1 %), the bulk DO should be finely controlled based on the influent NH 4 + to avoid the undesired full nitrification by comammox bacteria. Comparatively, conventional ammonium‐oxidizing bacteria (AOB)-based PN/A not only required higher bulk DO to achieve > 80.0 % TN removal but also suffered from 1.7 %∼2.8 % N 2 O production. [ABSTRACT FROM AUTHOR]

Eight on-site greywater treatment facilities of four different types (A, B, C and D) were investigated. Three were commercially available package plants (A–C) and one was a conventional sand filter (D). The treatment unit of Type A consisted of a geotextile-fitted trickling filter and a sand filter bottom layer, the Type B consisted of packs of fibrous mineral wool filter materials, and the Type C consisted of a fine-meshed plastic filter. The treatment systems were assessed in terms of their removal efficiency for organic matter (e.g. BOD, COD, TOC), nutrients (nitrogen and phosphorus), surfactants, indicator bacteria (E. coli and enterococci) as well as microplastics. Systems A and D effectively reduced organic matter by >96% BOD, >94% COD and >90% TOC. Their effluent BOD was <29 mg/l. The BOD reduction in the treatment facilities of types B and C was in the range of 70–95%. Removal of anionic surfactants was >90% with effluent concentration <1 mg/l in all facilities. In general, the treatment systems were ineffective in removing E. coli and enterococci; the most efficient was the sand filter (type D), achieving 1.4–3.8 log 10 for E. coli and 2.3–3.3 log 10 for enterococci. Due to the high E. coli in the effluents, all the on-site systems were classified as Poor (score: 0–44) according to the water quality index (WQI) assessment. In two of the studied facilities, nine microplastic polymers were targeted (i.e. PVC, PS, PET, PE, PC, NG, PMMA, PP and PA6) and analyzed using the thermal extraction desorption gas chromatography-mass spectrometry (TED-GCMS) technique. PVC, PS, PET and PA6 were commonly detected in the influent and effluent. The effluent quality from type A and D systems was found to comply with the European Commission's guideline for the reuse of reclaimed water except for the indicator bacteria concentration. • The eight investigated on-site package-plants provided efficient BOD reduction (27–100%). • The removal of surfactants was >91%. • The effluent concentrations of P were relatively high (0.6–2.8 mg/l). • The removal of nutrients was less efficient, 3–68% for N, 10–56% for P. • Results indicate an effective retention of microplastics in systems that include sand filtration. [ABSTRACT FROM AUTHOR]

The down-flow hanging sponge (DHS) reactor, a type of trickling filter used as a sponge, is a promising treatment system for low-cost sewage treatment. However, the performance of dried sponges that have been non-operational for 8 months has not been evaluated. Accordingly, herein, the re-startup process performance of a DHS reactor treating low-strength domestic sewage in Thailand that had stopped operation for over eight months was investigated. The dried sponge carrier immediately retained water in the sponge biomass-retained carrier and absorbed organic compounds. High nitrification activity of the DHS reactor was observed after 13 d, which was the same as that of the pure sponge biomass-retained carrier start-up. The tracer test results showed that the restarted DHS reactor had a high hydraulic retention time (HRT)/theoretical HRT ratio of 134.2 % at the beginning of the operation from the water retention property of the sponge carrier. Microbial community analysis showed that nitrifying microorganisms were effectively recovered in the biomass-retained sponge carrier. These results demonstrate that the sponge carriers in the DHS reactor that were left into dry condition are available for reuse and has high potential for rapid re-startup. • Restart performance of the DHS reactor was evaluated. • The sponge carrier quickly absorbed water and organic compounds. • High nitrification activity in the DHS reactor was observed after 13 days. [ABSTRACT FROM AUTHOR]

Gilthead sea bream (Sparus aurata) was raised in six individual recirculating aquaculture systems (RAS) whose biofilters' performance was analyzed. Fish were fed with three different diets (a control diet, a fishmeal-based diet (FM), and a plant meal-based diet (VM)) and with three different feeding strategies (manual feeding to apparent satiation, automatic feeding with restricted ration, and auto-demand feeding). For every combination of diet and feeding strategy, the mean oxygen consumption, ammonia excretion, and ammonia removal rate were determined. Fish fed with the VM diet consumed the most oxygen (20.06 ± 1.80 gO2 consumed kg−1 day−1). There were significant differences in ammonia excretion depending on the protein content and protein efficiency of the diet, as well as depending on feeding strategy, which in turn affected ammonia removal rates. Fish fed by auto-demand feeders led to the highest mean ammonia removal rate (0.10 gN-TAN removed m−2 biofiltration area day−1), while not leading to peaks of high ammonia concentration in water, which preserve fish welfare and growth. [ABSTRACT FROM AUTHOR]

Contaminants of emerging concerns (CECs) persist in the environment and are present in the air, water, and soil. They include various industrial, chemical, pharmaceutical, and personal care products (PCPs) and metallic elements, pesticides, and endocrine disruptors. CECs can cause adverse ecological and health impacts by passing into plants and human foods via different routes. Recently, different treatment processes have been investigated for the remediation of CECs that are present in wastewater, and a current review emphasized different biological treatments for the removal of a wide range of CECs. Based on these studies, endocrine disrupting compounds (EDCs) can be removed by a membrane bioreactor (MBR) and pharmaceuticals and pesticides can be effectively removed by biological activated carbon (BAC). Microalgae-based treatment can remove some types of CECs, to some extent, and the activated sludge process (ASP) and trickling filters (TFs) can remove an average amount of CECs from wastewater. Due to the deficiencies of these treatment processes when removing CECs in wastewater, various hybrid treatment systems have been explored. This study will focus on the different conventional and novel biological treatment processes for the removal of different CECs. [ABSTRACT FROM AUTHOR]

To cope with water scarcity, Morocco needs to integrate the reuse of treated wastewater fully into its water management strategies. However, this option imposes several concerns about the appropriate wastewater treatment system (WWTS) whose performance is balanced by technical, environmental, financial, and societal sustainability. To deal with these challenges, the present study aims to assess the sustainability of five WWTS using the cardinal (CAR) and PROMETHEE methods. After hierarchizing the criteria and identifying the WWTS, two separate surveys were performed in order to rank criteria and alternatives by preference strength. The delivered rankings were converted, then, respectively into cardinal weights (criteria) and cardinal scores (alternatives). The PROMETHEE rankings showed that the membrane systems are the most sustainable followed by trickling filters, while the infiltration-percolation is the least sustainable WWTS. The activated sludge and lagoon systems were incomparable using PROMETHEE I partial ranking, and they were both ranked in the third position of sustainability. In contrast, PROMETHEE II complete ranking favored the activated sludge than lagoon systems due to its slightly high net outranking flow. The stability intervals indicated that the weights of all criteria could not affect the two first actions, which is mainly due to the high precision and robustness of the CAR method in eliciting weights. Finally, each criterion affected variably the sustainability of WWTS according to their characteristics, but overall, the process efficiency is the key factor (21.07% of weight) to reaching higher sustainability levels in addition to gaseous emissions (12.41% of weight), flexibility (8.32% of weight), and energy requirement (7.50% of weight). [ABSTRACT FROM AUTHOR]

The novel two-stage treatment system consisting of cascade cum trickling filter (CCTF) and multilayer adsorption (MLA) bioreactor was developed to enhance the contaminants removal such as chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP). The maize cob and date palm fiber were used as biofilm support media in trickling filter. The MLA bioreactor was operated using the composite adsorbent (refused crushed brick + rice husk + steel slags). The maximum adsorption uptake of composite adsorbent was observed as 0.6 mg/g for ammonium and 3.5 mg/g for phosphorus. Kinetic analysis showed that the composite adsorbent had a faster removal rate for phosphate than ammonium. The maximum desorption of ammonium and phosphate was found to be 14.6% and 6.5%, respectively. The performance of both cascade cum trickling filter and multilayer adsorption (CCTF-MLA) systems was also evaluated using the various COD-TN ratios and flow rates. The removal efficiencies of COD, TN and TP were found 93%, 87% and 86%, respectively, and their corresponding mean effluent concentrations were noted 18 mg/L, 5.5 mg/L and 2.3 mg/L. The developed CCTF-MLA system removed the 3log of the total count and total coliform and 2log of Escherichia coli and salmonella. So, the CCTF-MLA system could be efficient for wastewater treatment due to the steady removal rate of COD, TN and TP. [ABSTRACT FROM AUTHOR]