Solids Removal Efficiency Research Articles

Purification Effect and Microbial Community Analysis of Aquaculture Wastewater Using High-Efficiency and Stable Biochemical System

An adaptable, low-cost, and easy-to-operate biological treatment system for pollutant abatement in aquaculture water at the field pond scale needs to be developed. In this study, the pollutant removal capacity of a stable bioreactor for aquaculture wastewater was assessed, and the related mechanism was elucidated via an analysis of the microbial community’s characteristics and functions. The average removal efficiencies of chemical oxygen demand, suspended solids, total nitrogen, and total phosphorus were 40%, 86.22%, 38.62%, and 53.74%, respectively. The effluent quality meets the Requirement for Water Discharge from Freshwater Aquaculture Pond, SC/T9101-2007. The results indicate that the fillers under anaerobic conditions could attract Denitratisoma and unclassified_Rhodocyclaceae, promoting the denitrification reaction. This aligns with the characteristic that total nitrogen in aquaculture sewage mainly exists in the form of nitrate nitrogen. An anaerobic atmosphere helps degrade organic contaminants at liquid interfaces and remove nitrogen in the solid phase. The fillers under anaerobic conditions could attract Bacteroidota and promote the production of polysaccharides to form biofilms, which may be associated with phosphorus removal. The results indicate that the anaerobic stage can promote the formation of biofilm on the fillers to remove pollutants, thus achieving higher aquaculture sewage treatment efficiency.

Prolonged stirring pelleting coagulation for the enhanced treatment of fresh leachate: Removal performance and floc characteristics

Conventional coagulation (CC) is a widely adopted method for the pre-treatment of fresh leachate for enhancing subsequent advanced treatment processes. However, the formation of fluffy flocs in the CC process often results in limited separation and removal efficiency. In this study, a continuous alkali dosing prolonged stirring pelleting coagulation (C-PPC) process was proposed for the pre-treatment of fresh leachate. The C-PPC process consisted of three stages: prolonged stirring, reaction, and pelleting, achieving higher suspended solid (SS), turbidity, and organic removal efficiency compared with both CC and PPC processes. At a prolonged stirring intensity of 1500 r/min (G = 4241 s−1) and a final pH of 12, with polyaluminum chloride (PAC) and polyacrylamide (PAM) dosages of 2000 mg/L and 25 mg/L, impressive removal efficiency of 93.7 % SS, 99.7 % turbidity, and 35.7 % organic were obtained. In the prolonged stirring stage, the primary particle size decreased from 16.848 μm to 6.755 μm due to intensive stirring for 30 min, facilitating the compact floc formation. In the subsequent reaction stage, PAC was dosed once while NaOH was continuously dosed to achieve a final pH of 12 within 10 min. The floc size initially decreased due to fragmentation and small metal crystal generation. Subsequently, the generated small metal crystals served as the nuclei for organic matter adsorption and were entrapped by generated flocs, resulting in a significant increase in floc size with higher sphericity. Furthermore, compact pellets were formed during the pelleting stage after the addition of PAM. Floc restructuring also occurred during the pelleting stage, leading to a decreased pore volume of mesopores, achieving final floc densification and superior separation performance.

Development and evaluation of paddy straw and wheat chaff filter socks for sediment control in surface runoff

ABSTRACT Agricultural waste, often burned after harvest, poses significant environmental risks. This study explores the innovative use of these byproducts as biofilters for stormwater management. The study evaluated paddy straw and wheat chaff filter socks for removing suspended solids from canal water and stormwater runoff. Different sock sizes (15, 22.5, and 30 cm diameter) and densities were tested, each with a fixed length of 120 cm. They achieved up to 65% removal efficiency for suspended solids and turbidity while minimally impacting other water quality parameters. The filter sock’s life varied with inlet total suspended solids, lasting 44–56 hours for loads under 300 ppm and less than 14 hours for loads over 700 ppm. The study suggests using filter socks with a 30 cm diameter and medium to high density for optimal performance in reducing suspended solids. These filter socks offer a sustainable and eco-friendly solution for stormwater management, promoting resource conservation.

A MODEL FOR SELECTION OF DECENTRALIZED SANITARY SEWER SYSTEMS FOR SMALL MUNICIPALITIES

The precariousness of sanitation services in small Brazilian municipalities is exacerbated by technical and financial limitations. In these places treatment technologies need to be simple, sustainable, economically viable, and socially accessible. This work aims to propose a selection model for decentralized sewage treatment technologies for small municipalities. The PROMETHEE II multi-criteria method was used to rank the technologies with aid decision-making agents to prioritize technical, environmental, economic, and social criteria based on the characteristics of the sewer basins. After validating the method in the sewage catchment areas of four municipalities in Paraíba, the results showed that the constructed wetlands technology occupied the best position in 88.9% of the sewer basins. This technology stands out for its high organic matter and suspended solids removal efficiency, in addition to not generating sludge and performing well in terms of social criteria (odor production and vectors). The septic tank and septic tank + anaerobic filter alternatives ranked lower in the basins studied. The robustness of the method and the assignment of preferences to criteria for sewer basins with different classifications indicate that the model is replicable for small municipalities. Thus, the study contributes to the optimization of decision-making for sewage treatment systems, allowing the better use of resources, the reduction of vulnerabilities, and promotion of municipal development.

Evaluating the Separation Performance and Efficiency of MF Membranes in Industrial Textile Wastewater Treatment

The rapid growth of the population and industrial development have led to a significant increase in wastewater generation across various sectors. The textile industry stands out as a major contributor to economic growth but also a substantial source of environmental pollution. The typical effluents discharged from textile industries are a complex mixture of dyes, metals, and other pollutants. The presence of high levels of pollutants may overwhelm traditional treatment methods. Therefore, it is necessary to use more advanced techniques such as membrane filtration to treat the wastewater. Membrane technology has recently become famous for wastewater treatment due to its flexibility, high efficiency in removing contaminants, and low energy usage. There are several membrane filtration methods which are extensively used in water treatment procedures, including microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO). In this study, the membrane process investigated the effect of feed pressure using a commercial MF flat sheet membrane on the performance of treatment. The pressure of the feed varies from 2 to 10 bar, with a stepwise increment of 2 bar. The water flux was measured using a cross-flow filtration system, and performance was assessed by calculating the water flux and removal efficiencies for total suspended solids (TSS) and turbidity. The results show that the MF membrane has a high removal efficiency of total suspended solids and turbidity. The removal efficiency of TSS ranged from 87.1% to 96.2%, while the removal efficiency of turbidity ranged from 91.2% to 93.7%.

Solid-state anaerobic digestion of sweet corn waste: The effect of mixing and recirculation interval

The mixing and sludge recirculation interval is one of the key successes of the solid-state anaerobic digestion process, a promising technology for converting high-solid agro-industrial wastes to renewable energy. This study employed a pilot-scale completely stirred tank reactor to examine biogas production from sweet corn waste, including corn cobs, husks, and seeds. The reactor was operated as solid-state anaerobic digestion at an ambient temperature. The mixing and recirculating intervals were set to non-mixing and mixing for 10 minutes every 3, 6, and 12 hours. The initial total solid of the feedstock was 25%, while the hydraulic retention time was 30 days. The results showed that during the mixing and recirculation every three hours, the highest chemical oxygen demand, total solid, and volatile solid (VS) removal efficiencies were 85.42%, 62.92%, and 64.59%, respectively. The ratio between volatile fatty acid and alkalinity ranged between 0.20 and 0.30 without any sign of system failure. The highest specific methane yield of 766 L/kg VSadded was obtained in the experiment with mixing and recirculating intervals every 3 hours. It was found that the modified Gompertz model could effectively fit the methane yields with an R2 of 0.9667. The modeled methane production potential and the maximum methane production rate were 867.40 NL/kg VSadded and 132.01 NL/kg VSadded-d, respectively. Additionally, the levelized cost of the biogas produced from the solid-state anaerobic digestion of the sweet corn waste was calculated to be 0.61 USD/kg. The findings of this study can serve as a guide for the design and operation of the SS-AD system, which aims to transform various types of lignocellulosic waste into environmentally friendly energy.

Fabrication of a novel robust gelatine-based poly-cationic flocculant with dual flocculation and bactericidal functions for manure wastewater treatment

Manure suspended solids and pathogens negatively contribute to many environmental aspects including water contamination, air pollution, greenhouse gas emissions (GHG), unpleasant odor and spread of pathogenic bacteria. Production of an environmentally friendly flocculant with dual function of sterilization and flocculation of the manure solids and particles is a challenge. Here, gelatin (Gel) was covalently modified with non-vinyl monomer, glycidyltrimethylammonium chloride (GMTA) to form poly-cationic Gel (GMTA@Gel) via a single step functionalization under mild conditions. The developed cationic Gel (GMTA@Gel) showed positive zeta potential (ZP) value > +50 mv in a wide pH range (3−10), excellent removal efficiency of total suspended solids (97 %) and E. coli (98 %) in dairy wastewater, and disinfection capability of microorganisms adsorbed on the Gel, which were confirmed by elemental analysis and cell rupture analysis. The developed Gel-based flocculant showed 95 % removal of both MSS and E. coli from real manure wastewater collected from manure ponds of dairy farms in Central Valley, California and reduced 97 % of volatile solids, which suggest its contribution in reducing GHG emissions. The developed GMTA@Gel flocculant has the advantages of environmental protection, excellent removal efficiencies for anionic contaminants and enhanced coagulation effect on suspended bacterial cells and particles which suggest GMTA@Gel to be applied on removal of suspended anionic suspensions (particles or cells) from various wastewater sources.

Process efficiency assessment of turbidity removal from tigris river using microfiltration membranes

The current study aims to use microfiltration membrane units instead of using traditional treatment methods (flocculation and coagulation) to enhance water treatment efficiency and lower operational and fixed costs. Specifically, it explores using a polypropylene membrane with a pore size of 1 µm and a ceramic membrane with a pore size of 0.5 µm to remove turbidity, total suspended solid TSS, and Escherichia coli bacteria from the Tigris River water within Baghdad. An experimental study compared the removal efficiency of real and simulated Tigris River water with different turbidity for polypropylene and ceramic membranes. Operational parameters such as initial turbidity concentration, temperature, flow rate, and membrane fouling were studied as a function of time. Also, two operating methods, dead-end, and crossflow, were discussed regarding the removal efficiency of suspended solids, turbidity, and Escherichia coli bacteria 65 %, 91 %, and 99 %, respectively, for the polypropylene membrane. And 75 %, 97 %, and 100 % for the ceramic membrane. The results of the current study indicate that ceramic membranes are the most susceptible to contamination by fouling, but at the same time, they are the most resistant and have the highest rate of removal efficiency than the polypropylene membrane. In addition, the crosse flow operation is better than the dead-end operation and is also considered a way to reduce the fouling that occurs in the membrane filtration. Microfiltration in general can achieve economic profit and minimal environmental impact, and ceramic microfiltration membranes in particular can achieve high-quality water.

Sustainable treatment of combined industrial wastewater: synergistic phytoremediation with Eichhornia crassipes, Pistia stratiotes, and Arundo donax in biofilm wetlands

This study investigates the treatment of combined wastewater from Hattar Industrial Estate using Biofilm Wetlands (BW) planted with monoculture species: Eichhornia crassipes (EAC), Pistia stratiotes (WL), and Arundo donax (GR). Each species showed distinct capabilities in organic degradation, metal uptake, and pH stabilization. BW2, planted with EAC, achieved the highest total solids (TS) and total suspended solids (TSS) removal efficiencies of 66% and 65%, respectively. GR effectively reduced initial COD concentrations from 232 mg/L to 58.67 mg/L, while EAC and WL reached reductions to 72.78 mg/L and 70.67 mg/L, respectively. Overall, the plant efficiency ranking was EAC > GR > WL. These findings underscore the potential of these plant species in synergistic BW systems, highlighting their role as natural solutions for remediating complex industrial effluents. This research contributes to advancing eco-friendly wastewater treatment approaches, suggesting promising applications for sustainable practices in industrial contexts. RESEARCH HIGHLIGHTS This research assessed the effectiveness of phytoremediation using Eichhornia crassipes, Pistia stratiotes, and Arundo donax for removing pollutants i.e. heavy metals (Cd, Pb, Ni, K, Ca, Mg, Na, Fe, Hg) nitrates, phosphates and sulfates from combined industrial wastewater of Hattar Industrial Estate Pakistan. It highlighted the potential of selected plant species’ as natural treatment systems, providing crucial insights into their efficiency. Findings contribute to understanding nature-based solutions for complex industrial effluents.

Efficiency of Backwashing in Removing Solids from Sand Media Filters for Drip Irrigation Systems

Sand media filters are especially recommended to prevent emitter clogging with loaded irrigation waters, but their performances rely on backwashing. Despite backwashing being a basic procedure needed to restore the initial filtration capacity, there is a lack of information about the solid removal efficiency along the media bed depth. An experimental filter with a 200 mm silica sand bed height was used to assess the effect of two operation velocities (30/45 and 60/75 (filtration/backwashing) m h−1) and two clogging particles (inorganic sand dust and organic from a reclaimed effluent) on the efficiency of backwashing for removing the total suspended solids retained in different media bed slices. The average solid removal backwashing efficiency was greater with organic particles (78%) than with inorganic ones (64%), reaching its maximum at a 5–15 mm bed depth. A higher operation velocity increased the solid removal efficiency by 16%, using organic particles, but no significant differences were observed with inorganic particles. The removal efficiencies across the media bed were more uniform with organic particles (63–89%) than with inorganic (40–85%), which makes it not advisable to reduce the media height when reclaimed effluents are used. This study may contribute to future improvements in sand media filter design and management.

Enhancement of Fermentation Performance in the Anaerobic Co-Digestion of Chicken Manure and Corn Straw under Biogas Slurry Reflux via Air Stripping of the Digestate

Ammonium inhibition is a key limiting factor for anaerobic digestion when using chicken manure as the main substrate, especially in a digestion system with biogas slurry reflux. Air stripping is usually used as a recycled biogas slurry treatment. In this study, we carried out the anaerobic co-digestion of chicken manure and corn straw. The fermentation performance was investigated with and without air stripping at different biogas slurry reflux ratios and with an increasing organic loading rate. The results show that air stripping enhanced biogas production, system stability, and volatile solid removal efficiency via the mitigation control of ammonium inhibition. The total ammonium nitrogen in the digesters with air stripping was 20.24–46.40% lower than in those without air stripping. The highest specific biogas production and volatile solid removal efficiency values were obtained in the digesters at an organic loading rate of 3.3 g volatile solid (VS)/(L·d) and a reflux ratio of 75% with air stripping, reaching 480.43 mL/gVSadd and 63.36%, respectively. Moreover, air stripping also improved the organic loading rate and reflux ratio. Stable operation was achieved at an organic loading rate of 5.3 gVS/(L·d) and a reflux ratio of 75%, with specific biogas production of 392.35 mL/gVSadd and a volatile solid removal efficiency of 50.33%. The fermentation performance deteriorated when the organic loading rate was increased to 8.0 gVS/(L·d) at a reflux ratio of 75%, even when air stripping was conducted, indicating that a slighter lower reflux ratio (50%) could be more feasible at a higher organic loading rate (8.0 gVS/(L·d). Additionally, the methanogen community structure varied according to the use of air stripping, with a shift in the methanogenic pathway from hydrogenotrophic to acetoclastic methanogens. Overall, our findings support the adoption of air stripping for ammonium mitigation in anaerobic digestion with biogas slurry reflux.

Vermifiltration as a green solution to promote digestate reuse in agriculture in small-scale farms

Digestates from low-tech digesters need to be post-treated to ensure their safe agricultural reuse. This study evaluated, for the first time, vermifiltration as a post-treatment for the digestate from a low-tech digester implemented in a small-scale farm, treating cattle manure and cheese whey under psychrophilic conditions. Vermifiltration performance was monitored in terms of solids, organic matter, nutrients, and pathogens removal efficiency. In addition, the growth of earthworms (Eisenia foetida) and their role in the process was evaluated. Finally, the vermicompost and the effluent of the vermifilter were characterized in order to assess their potential reuse in agriculture.Vermifilters showed high removal efficiency of chemical oxygen demand (55–90%), total solids (60–80%), ammonium nitrogen (83–97%), and phosphate-P (28–49%). Earthworms effectively grew and reproduced on digestate (i.e. earthworms number increased by 183%), enhancing the vermifiltration performance, while reducing clogging and odour-related issues. Both the vermicompost and effluent produced complied with legislation limits established for soil improvers and wastewater for fertigation, respectively. Indeed, there was an absence of pathogens and non-detectable heavy metals concentrations. Vermifiltration may be thus considered a suitable post-treatment option for the digestate from low-tech digesters, allowing for its safe agricultural reuse and boosting the circular bioeconomy in small-scale farms.

Treatment of Textile Wastewater from Spinning Mill Using Electrocoagulation-Flocculation Process

Textile spinning mills generate wastewater containing high levels of pollutants such as suspended solids, dyes, oils, and organic compounds. This study investigates the electrocoagulation-flocculation (ECF) process as a sustainable treatment method. ECF combines electrocoagulation, where an electric current induces pollutant coagulation, and flocculation, which aggregates these pollutants for removal. Extensive lab experiments were conducted, analyzing setup, procedures, and results. The study found that ECF significantly reduced pollutants, achieving high removal efficiencies for suspended solids, COD, color, and oil/grease. Economic analysis confirmed ECF's cost- effectiveness over conventional methods. A case study demonstrated successful implementation, highlighting operational efficiency and environmental compliance. The paper concludes with recommendations for future research and industrial applications. Key Words: Electrocoagulation, Textile Wastewater, Sustainable Wastewater Treatment, Spinning Mill, Pollutant Removal

Improved bioenergy recovery and desalination efficiency using innovative configuration of an upflow triple enclosed cuboid compartments -photosynthesis microbial desalination cell: Experimental and modeling study

Performance of an innovative configuration of enclosed cuboid compartments-photosynthesis microbial desalination cell (EC-PMDC) for synchronous sewage treatment, desalination of seawater, and renewable energy recovery. Bioanode and biocathode were inoculated with jumbled bacterial species and mixed microalgae, respectively. The results demonstrated that maximum removal efficiency of organic content as chemical oxygen demand (COD) from the sewage was up to 99 %, whereby the total dissolved solids (TDS) removal efficiency from seawater was 91 %, accompanied with maximum power generation of 975 mW/m3. Kinetic study of bacterial growth in the EC-PMDC demonstrated excellent agreement between experimental data and those predicted by Blackman, Monod, Moser, and Teissier models with coefficients of determination (R2) equal to 0.98, 0.97, 0.96, and 0.97, respectively. Significant harmonization was obtained between the experimental results of voltage, current density, and power density with those predicted by the adopted electrochemical model. For comparison purposes, a conventionally designed photosynthesis microbial desalination cell (SC-PMDC) consisted of triple sequential cuboid compartments was setup. It was fed with similar influents as for the EC-PMDC. Maximum efficiencies of COD and TDS removals were 99 % and 81 %, respectively accompanied with power recovery of 420 mW/m3 were observed in the SC- PMDC indicating the superiority of EC-PMDC design.

Pilot-scale evaluation of cascade anaerobic digestion of mixed municipal wastewater treatment sludges.

This work assessed the performance of a pilot-scale cascade anaerobic digestion (AD) system when treating mixed municipal wastewater treatment sludges. The cascade system was compared with a conventional continuous stirred tank reactor (CSTR) digester (control) in terms of process performance, stability, and digestate quality. The results showed that the cascade system achieved higher volatile solids removal (VSR) efficiencies (28-48%) than that of the reference (25-41%) when operated at the same solids residence time (SRT) in the range of 11-15 days. When the SRT of the cascade system was reduced to 8days the VSR (32-36%) was only slightly less than that of the reference digester that was operated at a 15-day SRT (39-43%). Specific hydrolysis rates in the first stage of the cascade system were 66-152% higher than those of the reference. Additionally, the cascade system exhibited relatively stable effluent concentrations of volatile fatty acids (VFAs: 100-120 mg/l), while the corresponding concentrations in the control effluent demonstrated greater fluctuations (100-160 mg/l). The cascade system's effluent pH and VFA/alkalinity ratios were consistently maintained within the optimal range. During a dynamic test when the feed total solids concentration was doubled, total VFA concentrations (85-120 mg/l) in the cascade system were noticeably less than those (100-170 mg/l) of the control, while the pH and VFA/alkalinity levels remained in a stable range. The cascade system achieved higher total solids (TS) content in the dewatered digestate (19.4-26.8%) than the control (17.4-22.1%), and E. coli log reductions (2.0-4.1 log MPN/g TS) were considerably higher (p < 0.05) than those in the control (1.3-2.9 log MPN/g TS). Overall, operating multiple CSTRs in cascade mode at typical SRTs and mixed sludge ratios enhanced the performance, stability digesters, and digestate quality of AD. PRACTITIONER POINTS: Enhanced digestion of mixed sludge digestion with cascade system. Increased hydrolysis rates in the cascade system compared to a reference CSTR. More stable conditions for methanogen growth at both steady and dynamic states. Improved dewaterability and E. coli reduction of digestate from the cascade system.

Performance evaluation of integrating Vertical Garden Constructed Wetlands (VGCWs) with diverse plant species and modified media for treating septic tank effluent

Vertical Garden Constructed Wetland (VGCW) system has been used as a secondary treatment system to improve effluent quality of septic tanks and cesspools by enhancing nutrients, organic and solid removal according to the guidelines of effluent discharge. This study aimed to investigate the treatment performance of the VGCWs by integrating with diverse plant species and modified media used as secondary treatment for conventional or solar septic tanks. In the study, laboratory-scale VGCW utilizing soil as the media and planted with Water Pennywort were operated at hydraulic retention times (HRT) of 6, 12, and 24 h, while modified planted vertical garden constructed wetlands (mpVGCW) operated at an HRT of 36 h, was fed with effluent collected from a septic tank. The treatment performance of VGCWs treating effluent from the septic tank and operating at an HRT of 24 h was found to achieve the highest removal efficiencies for organic matter, nutrients, and solids (up to over 90%), compared to an HRT of 6 or 12 h. Moreover, the highest log reduction of E.coli of 2.8 was also observed at the 24 h HRT, in comparison to HRTs of 6 or 12 h. The Spider Ivy, Coleus, and Selaginella frosty could be planted in the mpVGCW system to enhance the overall treatment efficiencies with consistently showed high removal efficiencies for TCOD (91.37–93.39%), TKN (97.1–97.8%), and TP (87.18–88.58%). These results suggested the potential of the VGCWs as a secondary treatment system for polishing septic tank effluent and improving environmental quality.

A biotechnological approach for suspended solids removal in biogas slurry via microbially induced calcite precipitation (MICP)

This study investigated the application of the microbially induced calcite precipitation (MICP) technique for removing suspended solids from biogas slurry. A series of laboratory tests on suspended solids content and colority determination was conducted to evaluate the feasibility of this technique and the removal performance of suspended solids. Combined with tests on residual calcium ions concentration and micro scale, the effects of crucial factors (including urease activity and CaCl2-Urea content) and the mechanisms of suspended solids removal were explored. The results unequivocally demonstrated the effectiveness of the MICP technique in removing suspended solids, achieving optimum removal efficiencies of 91.67 ± 1.68% for suspended solids and 96.50% for colority. The introduction of additional urease-producing bacteria via centrifugation-extraction increased the urease activity of bacterial solution and further enhanced the degree of MICP reaction, but undesirably led to a slight reduction in the removal efficiencies of suspended solids and colority due to the presence of bacteria themselves as suspended solids. Appropriately increasing the CaCl2-Urea content could offer a more adequate material supply to prolong the duration of the MICP process, significantly enhancing the removal efficiency. Nevertheless, the high salinity environment associated with excessive CaCl2-Urea addition (2.0 mol/L) would impair bacteria survival and impede the MICP process, negatively affecting suspended solids removal. The SEM-EDS analysis indicated that in the MICP process, suspended solids were tightly encapsulated by calcium carbonate (mainly calcite) to form strong immobilization aiding their gravity-driven removal. Due to the richness of organic components, they could be considered for reuse as soil amendments and fertilizers. This research provides an innovative insight into the removal of suspended solids from biogas slurry using a biotechnological approach. The MICP technique holds promise for practical applications due to its effectiveness and workability.

Global occurrence of organic micropollutants in surface and ground water: Highlighting the importance of wastewater sanitation to tackle organic micropollutants

The occurrence, fate and distribution of organic micropollutants (OMPs) in different water matrices is of increasing concern due to the negative effects towards flora, fauna and human health. This metadata study provides an updated picture of the global occurrence of OMPs in freshwater and wastewater in five geographical regions, and illustrates how socioeconomic factors are key elements that influence the concentration of these OMPs in the different water matrices. The study also aims to provide a collated database of OMPs removal efficiencies achieved by the different biological treatment technologies. Our findings demonstrated that OMPs like acetaminophen, ibuprofen, and triclosan are present globally in freshwater (> 500 ng/L) and wastewater (> 10, 000 ng/L), and at relatively higher concentrations than the other evaluated OMPs. Significant correlations between OMPs concentration in wastewater versus freshwater demonstrated wastewater to be a potential source of certain OMPs to the freshwater environment. This was further confirmed through correlation between OMPs concentration and socioeconomic factors like infrastructure index and governance index in both wastewater and freshwater. These results highlighted the importance of wastewater sanitation to control and reduce OMPs dissemination in the environment. Thus, various types of biological wastewater treatment processes including activated sludge processes, biofilm processes, wetland and lagoon, and membrane bioreactor were analyzed for their OMP’s removal efficiencies. Findings demonstrated that advanced processes like membrane bioreactors (MBR) may not always outperform other low-costs biotechnologies in the treatment of OMPs (e.g., bisphenol A removal by activated sludge with anoxic and oxic zone, AS-AAO was 93% versus MBR at 89%). But rather, the removal efficiency will depend on pollutant properties and certain operational parameters such as hydraulic retention time, treatment capacity, and removal efficiency of total suspended solids.

Actas Pink-2B dye removal in biochar nanocomposites augmented vertical flow constructed wetland (VF-CWs)

Industries generate hazardous dye wastewater, posing significant threats to public health and the environment. Removing dyes before discharge is crucial. The ongoing study primarily focused on synthesizing, applying, and understanding the mechanism of green nano-biochar composites. These composites, including zinc oxide/biochar, copper oxide/biochar, magnesium oxide/biochar, and manganese oxide/biochar, are designed to effectively remove Actas Pink-2B (Direct Red-31) in conjunction with constructed wetlands. Constructed wetland maintained pH 6.0–7.9. At the 10th week, the copper oxide/biochar treatment demonstrated the highest removal efficiency of total suspended solids (72%), dissolved oxygen (7.2 mg/L), and total dissolved solids (79.90%), followed by other biochar composites. The maximum removal efficiency for chemical oxygen demand (COD) and color was observed at a retention time of 60 days. The electrical conductivity also followed the same order, with a decrease observed up to the 8th week before becoming constant. A comprehensive statistical analysis was conducted, encompassing various techniques including variance analysis, regression analysis, correlation analysis, and principal component analysis. The rate of color and COD removal followed a second-order and first-order kinetics, respectively. A significant negative relationship was observed between dissolved oxygen and COD. The study indicates that employing biochar composites in constructed wetlands improves textile dye removal efficiency.

Enhancing kitchen waste anaerobic digestion by recycled aluminum industry waste: Alkali treatment and potential electron transfer mechanism

Kitchen waste has become a significant environmental concern worldwide. Red mud, an industrial solid waste characterized by its porous structure and high iron oxide content, exhibits potential as a conductive conduit in the direct interspecies electron transfer (DIET) pathway. In this study, red mud pretreatment of kitchen waste was conducted to enhance anaerobic digestion (AD). The effect and mechanism of enhancing kitchen waste AD by red mud pretreatment was studied for the first time. Results indicated that red mud pretreatment could accelerate the hydrolysis of organic compounds and alleviate the acid inhibition. Consequently, the methane production rate was increased from 260.7 mL/g VS to 402.3 mL/g VS, i.e., up to 54.3%. And volatile solids removal efficiency was increased from 53.9% to 73.1%, i.e., up to 35.6%. Furthermore, microbial community analysis revealed the enrichment of electrochemically active bacteria (Synergistaceae), acetogenic bacteria (Syntrophomonadaceae) and methanogens (Methanobacterium and Methanosarcina), which played essential roles in interspecies hydrogen transfer (IHT) and DIET. This study showed that red mud pretreatment has the potential to enhance kitchen waste AD which contributes to carbon mitigation. It also threw the potential new insights to the relative mechanism.