Wastewater Discharge Standards Research Articles

Physicochemical characterization of wastewater from the Niamey National Hospital (NNH) (Niger) and assessment of its impact on the environment

The Niamey National Hospital (NNH) is among the reference hospital in the Niamey region (Niger) to after the quality of care it offers to the population. However, these activities have a negative impact on the quality of the water of the river constituting one of the main sources of water supply for the population of Niamey and gardening activities. This study aims to determine the physicochemical quality of wastewater from the NNH activated sludge treatment plant and its impact on the environment. To carry out this study, twenty (20) wastewater samples were taken at the outlet of the NNH treatment station. The sampling lasted five (5) weeks to take into count fluctuations. The results obtained indicate that the average values of physicochemical parameters such as: the pH (6,91), temperature (27.825°C), conductivity (574.80 µS/cm) and certain heavy metals of this hospital are compliance with national and international standards for wastewater discharge. However, it was noted that the average values ​​obtained at the HNN for copper (1.982 mg/L); zinc (1.077 mg/L); in phosphorus (18.065 mg/L); DCO (808 mgO2/L) and DBO5 (442.5 mgO2/L) do not comply with national and international wastewater discharge standards. These abnormal levels must be treated before being released into the river.

Lanthanum(III) − 2,5 − Pyrazinedicarboxylate framework as an antibacterial adsorbent for highly efficient and selective capture of Pb(II) and Cd(II) from wastewater

Removing heavy metal ions and microorganisms from wastewater remains a persistent challenge in wastewater treatment. The development of a novel metal–organic framework (MOF), synthesized from 2,5-pyrazine-dicarboxylic acid and lanthanide (La(III), Ce(III), Pr(III)), targeting the concurrent remediation of heavy metal and bacterial pollutants in wastewater. La-PzDC demonstrated remarkable efficacy in removing Pb(II) and Cd(II), achieving maximum adsorption capacities of 697.72 mg g−1 and 398.26 mg g−1, respectively. La-PzDC achieved rapid adsorption equilibria—within 10 min for Pb(II) and 20 min for Cd(II), and conformed to the pseudo-second-order kinetics and Langmuir isotherm models. La-PzDC captured Pb(II) and Cd(II) from actual wastewater, and its residual levels met the relevant wastewater discharge standards. La-PzDC also exhibited excellent reusability and selectivity for Pb(II) and Cd(II). The adsorption mechanism through spectroscopic analysis and density functional theory (DFT) calculations, pinpointing coordination with oxygen and nitrogen-containing groups as a key factor. Significantly, La-PzDC achieves nearly 99 % bacterial elimination against E. coli and S. aureus. The above results indicated that La-PzDC has high selectivity, rapid removal capacity and excellent antibacterial activity, offering a new strategy for the dual challenge of heavy metal and bacterial contamination in wastewater treatment.

Assessment of the suitability of adsorption water treatment as a concentration process for resource recovery and wastewater treatment

Electroplating plants dispose of the diluted plating solution (DPS) as plating wastewater due to its reduced plating efficiency. Solid waste produced by various industries is discarded in landfills, leading to the generation of landfill leachate (LL). Employing suitable wastewater treatments is crucial for either recovering valuable resources from wastewater or ensuring that its discharge aligns with wastewater discharge standards. In this study, we examined the feasibility of an adsorption water treatment (AWT) process for recovering valuable resources from DPS and efficiently treating LL. The AWT process using DPS and LL demonstrated that the influence of feed quality (composition and concentration) on water treatment capacity was insignificant, with a water recovery of up to 50 %. In addition, the AWT process demonstrated its ability to efficiently concentrate DPS without the need for pre-treatment, resulting in a notable 12.1 % increase in the plating efficiency of the DPS. This made it reusable for electroplating, and it was realized with a low specific energy consumption (SEC) of 1.63 kWh/m3 by utilizing waste heat in electroplating plants. Furthermore, the freshwater produced by the AWT process, including simple pre- and post-treatments, met 26 water quality parameters of the landfill leachate discharge standard.

Advanced wastewater treatment with microalgae-indigenous bacterial interactions

Microalgal-indigenous bacterial wastewater treatment (MBWT) emerges as a promising approach for the concurrent removal of nitrogen (N) and phosphorus (P). Despite its potential, the prevalent use of MBWT in batch systems limits its broader application. Furthermore, the success of MBWT critically depends on the stable self-adaptation and synergistic interactions between microalgae and indigenous bacteria, yet the underlying biological mechanisms are not fully understood. Here we explore the viability and microbial dynamics of a continuous flow microalgae-indigenous bacteria advanced wastewater treatment system (CFMBAWTS) in processing actual secondary effluent, with a focus on varying hydraulic retention times (HRTs). The research highlights a stable, mutually beneficial relationship between indigenous bacteria and microalgae. Microalgae and indigenous bacteria can create an optimal environment for each other by providing essential cofactors (like iron, vitamins, and indole-3-acetic acid), oxygen, dissolved organic matter, and tryptophan. This collaboration leads to effective microbial growth, enhanced N and P removal, and energy generation. The study also uncovers crucial metabolic pathways, functional genes, and patterns of microbial succession. Significantly, the effluent NH4+-N and P levels complied with the Chinese national Class-II, Class-V, Class-IA, and Class-IB wastewater discharge standards when the HRT was reduced from 15 to 6 h. Optimal results, including the highest rates of CO2 fixation (1.23 g L−1), total energy yield (32.35 kJ L−1), and the maximal lipid (33.91%) and carbohydrate (41.91%) content, were observed at an HRT of 15 h. Overall, this study not only confirms the feasibility of CFMBAWTS but also lays a crucial foundation for enhancing our understanding of this technology and propelling its practical application in wastewater treatment plants.

Insights into dynamic evolution of combined scaling-biofouling in reverse osmosis

Although extensive research has focused on individual membrane fouling, there is still a lack of studies regarding combined scaling-biofouling, which is more commonly encountered in practical membrane desalination processes due to the coexistence of inorganic scalants and microorganisms. To our best knowledge, it is the first study that elaborated the dynamic evolution of combined scaling-biofouling in the reverse osmosis (RO) cross-flow filtration process, compared with gypsum scaling and biofouling alone. The results indicated that scaling ions (35 mM CaCl2 + 20 mM Na2SO4) stimulated protein secretion but inhibited that of polysaccharide and total organic carbon (TOC). The gradually formed scaling layer evidently enhanced the hydrophilicity of the fouled membrane, and consequently improved the repulsion of membranes against microbes and the secreted extracellular polymeric substances (EPS), proved by the augmented energy barrier for microbial adhesion through XDLVO interfacial energy analysis, and resulted in the slower flux decline at the later stage of combined scaling-biofouling. In the other perspective, microorganisms and EPS diminished the (020), (021) and (041) facets of gypsum crystals, decreased the crystallinity and size of gypsum crystals, and thus prolonged the formation of inorganic scaling. It was suggested that scaling ions should be effectively controlled through pretreatment as they contributed to more rapid flux decline, as the cleaning efficiency of Ca2+ ions decreased from 84.8 % to 57 % after they combined with EPS, and thus chiefly contributed to reversible membrane fouling resistance. This study fills in the knowledge gap on interactions between gypsum scaling and biofouling during the formation of combined scaling-biofouling in RO filtration, which had significant environmental effects under the strict industrial wastewater discharge standards and zero liquid discharge (ZLD) requirements.

Mxene-based ceramic nanofiltration membranes for selective separation of primary contaminants in semiconductor wastewater

Ceramic membranes, known for their exceptional chemical stability, have found practical applications in the treatment of semiconductor wastewater. In this study, we have developed an innovative ceramic nanofiltration membrane featuring a nanochannel network created by two-dimensional (2D) nanomaterials, enabling high-performance separation and permeation. This accomplishment is realized through precise control of the size and thickness of MXene nanomaterials, which can be tailored using various coating conditions. The repeated stacking of MXene nanosheets onto the ceramic membrane substrate resulted in the formation of additional nanochannels and surface chemistry modifications, leading to significant enhancements in pollutant removal. These MXene-coated ceramic nanofiltration (NF) membranes significantly improved the removal efficiency of representative organic contaminants in semiconductor wastewater when compared to the pristine ceramic membrane. It enhanced the removal efficiencies by 4.2 times for dissolved silica, 3.7 times for dimethyl sulfoxide (DMSO), and 2.5 times for isopropyl alcohol (IPA). Furthermore, the MXene ceramic NF membrane exhibited exceptional fluoride removal capability, achieving approximately 99.1% removal, in addition to organic solvents. These findings not only help meet regulatory standards for wastewater discharge but also provide valuable insights into the transport behaviors of contaminants and their separation mechanisms. This innovative approach brings us one step closer to efficient and sustainable solutions for semiconductor wastewater treatment.

Research on Legal Risk Identification, Causes and Remedies for Prevention and Control in China’s Aquaculture Industry

Aquatic products fulfill the protein needs of people and play an important role in food safety. And aquaculture is prized for its high productivity, sustainability and environmental friendliness. Considering the importance of aquaculture, the legal risks exposed during the aquaculture process deserve attention in order to prevent them from hindering the development of the aquaculture industry. Through online research, literature analysis and practical communication, it is shown that the current legal risks with commonalities include land use violations, lack of legal documents, failure to meet tailing water criteria, unquarantined fry and misuse of prohibited agricultural pharmaceuticals through online research, literature analysis and practical communication. By analyzing the reasons for the formation of legal risks and combining the experiences in sustainable development of three major aquaculture countries, which are Korea, Norway and Chile, this paper provides targeted preventive remedies and suggestions for aquaculture operators, administrative parties, legislators and other parties on legal risks. It includes promoting the improvement of the rule of law in multiple aspects, clarifying the positioning of the aquatic breeding certificates, improving and propagating the standards for wastewater discharge, increasing the self-sufficiency rate of aquatic fry and fingerlings, as well as making use of the synergy of soft law and hard law.

A Comparative Analysis of Rural Domestic Wastewater Discharge Standards in the Yangtze River Delta Region, China

With the deepening of comprehensive improvement of rural living environments in China, various regions have issued rural domestic wastewater discharge standards based on their economic foundations, management levels, and characteristics of rural wastewater discharge. The Yangtze River Delta region, in particular, has been at the forefront of exploring these standards nationwide. By analyzing the local standards for rural domestic wastewater discharge in Shanghai, Jiangsu, Zhejiang, and Anhui provinces within the Yangtze River Delta region, along with the "Discharge standard of pollutants for municipal wastewater treatment plant" and the "Standard for irrigation water quality", it was found that the standards in each region primarily consider the classification based on the water environmental grade of the receiving water body. The pollutant concentration control requirements are generally consistent with the pollutant concentration limits for urban wastewater treatment plant discharge, but the total nitrogen and total phosphorus limits are more lenient than those for urban wastewater treatment plants. This paper can guide the transformation of rural domestic wastewater discharge from high standards to resource utilization, and provide references for the selection of wastewater treatment technologies, models, and governance strategies in the Yangtze River Delta region.

Efficiency and effectiveness of systems for the treatment of domestic wastewater based on subsurface flow constructed wetlands in Jarabacoa, Dominican Republic

Constructed wetlands (CW) are well known nature-based systems for water treatment. This study evaluated the efficiency and effectiveness of seven domestic wastewater treatment systems based on horizontal flow CWs in Jarabacoa, the Dominican Republic. The results showed that the CWs were efficient in reducing the degree of contamination of wastewater to levels below the Dominican wastewater discharge standards for parameters such as the 5-day biochemical oxygen demand (BOD5) and chemical oxygen demand, but not for the removal of phosphorus and fecal coliforms. In addition, a horizontal flow subsurface wetland in the peri-urban area El Dorado was evaluated in terms of the performance of wastewater treatment in tropical climatic conditions. The concentrations of heavy metals, such as zinc, copper, chromium, and iron, were found to decrease in the effluent of the wetland, and the concentrations for nickel and manganese tended to increase. The levels of heavy metals in the effluent were lower than the limit values of the Dominican wastewater discharge standards. The construction cost of these facilities was around 200 USD per population equivalent, similar to the cost in other countries in the same region. This study suggested some solutions to the improved performance of CWs: selection of a microbial flora that guarantees the reduction of nitrates and nitrites to molecular nitrogen, use of endemic plants that bioaccumulate heavy metals, combination of constructed wetlands with filtration on activated carbon, and inclusion of water purification processes that allow to evaluate the reuse of treated water.

Microalgae Cultivation Using Municipal Wastewater and Anaerobic Membrane Effluent: Lipid Production and Nutrient Removal

Microalgae cultivation using wastewater is a combined process for pollutant removal and lipid production that has been widely studied in recent years. In this study, the effects of anaerobic membrane effluent (AME) and municipal wastewater (MW) ratios on microalgae growth and pollutant removal processes were investigated, and the lipid production properties were also explored. Results show that microalgae can grow in all AME/WW ratios, and a 40% AME content is the optimal condition for microalgal biomass accumulation (52.9 mg/L·d) and lipid production (0.378 g/L). Higher AME addition would inhibit microalgae growth. In addition, high ammonia (approximately 97%) and phosphate (around 90%) removal efficiencies can be achieved in all AME/WW ratio conditions, while the total nitrogen removal efficiencies decreased with the addition of AME. Total nitrogen and phosphate are the limiting factors in treating water to meet the requirements of the integrated wastewater discharge standard. This study provided a new method for anaerobic digestion and municipal wastewater treatment and also realized green energy production based on the sustainable development principles.

Simultaneous Mixotrophic Nitrate Removal and Phosphorus Removal in a Sponge-Iron Denitrifying Filter

Due to stricter municipal wastewater discharge standards, there is an increased need for further treatment of nitrate in the secondary effluent of wastewater treatment plants. This is achieved through denitrification by the addition of external carbon sources, which leads to increased costs in wastewater treatment. The aim of this study was to examine the possibility of simultaneous removal of nitrate and phosphorus from simulated secondary effluent by employing a sponge-iron-based denitrifying filter at room temperature. The results indicate that at hydraulic retention times of over 2 h, more than 60% of the nitrate was reduced to ammonia and nitrite via iron-based abiotic nitrate reduction. However, sponge iron easily scaled after two months of operation. Therefore, a little glucose was added to the influent, resulting in a final COD/N ratio of 1:1. Mixotrophic nitrate reduction was observed, and the rust of sponge iron was successfully dissolved. Batch test results demonstrate that biological nitrate denitrification accounted for 70.0% of the total nitrate reduction. Additionally, high-efficiency phosphorus removal through the chemical reaction of released iron and phosphorus was achieved throughout the entire experiment, with removal efficiencies of more than 90% at hydraulic retention times of over 2 h. Moreover, high-throughput sequencing data show that the species diversity obviously increased after adding organic carbon, suggesting the coexistence of heterotrophic and autotrophic denitrifiers. Hence, the sponge-iron denitrifying filter has considerable prospects in the field of secondary effluent treatment and is likely to be the future direction of zero-valent iron application in sewage treatment.

Assessment of the impacts of selected physicochemical and bacteriological parameters of wastewater (hospital effluents) from the University teaching hospital of Butare on the surrounding environment

Physicochemical and bacteriological properties are used to assess the quality of wastewater before discharge into the surrounding environment. This presented study was carried out to determine the contamination of effluents from the University Teaching Hospital of Butare. The results showed that the mean values such as 185 ± 7.07 mg/L, 1816 ± 2.83 mg/L, 335 ± 4.24 mg/L, 150.66 ± 2 mg/L, 269 ± 13 mg/L, and 4.19 ± 0.41 mg/L for EC, TDS, TSS, BOD, COD, and phosphates in the treated effluents, exceeded the permissible limits of WHO standards for wastewater discharge in the surrounding environment. In the case of heavy metals, a higher concentration of cadmium (0.29 ± 0.04 mg/L) was observed out of the allowed limit of WHO standard, whereas those for manganese (0.02 ± 0.01 mg/L) and zinc (0.16 ± 0.04 mg/L) were within the stipulated limit. Lead, iron, and chromium were not detected in CHUB treated effluents. Although CHUB treatment plant showed higher treatment efficiency, including 99.2%, 99.9%, and 92.9%, the recorded mean values showed higher abundance (7 × 106 Cfu/100 mL of TC, 6 × 105 Cfu/100 mL, and 5 × 107 Cfu/100 mL) of TC, FC, and E.coli in treated CHUB effluents. The proper treatment of CHUB effluent should be ensured before it is discharged into the environment.

Comparison of Soil Nitrate and Phosphorus Concentrations Prior to and Five to Eleven Years after Recycled Water Irrigation

Increasing demand on water supplies in western US and more stringent wastewater discharge standards have made recycled water a common water source for irrigating urban green spaces. Studies are needed to evaluate nitrate-N leaching potential and phosphorus (P) movement along soil profile when recycled wastewater is used for irrigation. We collected and analyzed soil samples at the commencement and 5 and 11 years after recycled water irrigation on 2 golf courses, 5 metropolitan parks, and 1 school ground. Samples were taken at 0-20, 20-40, 40-60, 60-80, and 80-100 cm depths on golf courses and at 0-20 and 20-40 cm depths at other locations. Soil samples were tested for soil pH, soil nitrate, and AB-DTPA extracted P level. No increase in soil nitrate-N was observed over 5 and 11 years with recycled water irrigation, suggesting leaching of nitrogen to the groundwater was not a great concern. Soil P concentration at the surface soil depth was the highest 11 years after recycled water irrigation. Moreover, soil P increasing below the surface layer was observed on sites with sandy soil, suggesting long-term recycled water irrigation could impose some risk for P leaching on sandy soil.

Reductive roasting of arsenic-contaminated red mud for Fe resources recovery driven by johnbaumite-based arsenic thermostabilization strategy

Arsenic-contaminated red mud (As-RM) is a hazardous waste with limited recycling approaches. Generally, through reductive roasting and magnetic separation, RM could be transformed into Fe-rich concentrate for Fe resource recovery. However, due to the poor thermostabilization of As species, reductive roasting of As-RM would cause severe As volatilization pollution together with high As leaching risks from heated residue. Herein, a novel johnbaumite-based As thermostabilization strategy is developed for clean Fe resources recycling from As-RM. We found that in the presence of Ca(OH)2, the As species in As-RM could be immobilized as thermostable and insoluble johnbaumite (Ca5(AsO4)3OH) at 900 °C, effectively enhancing the As thermostability and insolubility. Introducing 1.5% Ca(OH)2 into As-RM suppressed the As volatilization ratio from 60.3% to 15.7% during reductive roasting. Meanwhile, the As leaching concentration of the reduced residue was reduced to < 100 µg/L, thus satisfying the Japanese wastewater discharge standard. A concentrate with approximately 67.5% total iron grade was obtained from As-RM through this clean reductive roasting and magnetic separation. Overall, the approach introduced in this work effectively reduces the As diffusion pollution deriving from As-RM thermal reduction, which could contribute to hazardous As-RM reutilization, clean Fe resources recovery, and As pollution mitigation.

Assessing the Effect of a Newly Implemented Basic Wastewater Discharge Standard on the Concentrations of Pharmaceutical and Personal Care Products in the Daqing River Basin, China

Wastewater discharge standards often play a crucial role in water environmental management. However, most of these standards only focus on conventional water pollutants such as chemical oxygen demand (COD), 5-day biochemical oxygen demand (BOD5), ammonia (NH3-N), total nitrogen (TN), and total phosphorus (TP). It is unclear if there is an impact on the removal of pharmaceuticals and personal care products (PPCPs). The Daqing River Basin is an important water system in China. In 2018, a new wastewater discharge standard for the Daqing River Basin (DB 13/2795–2018) was issued, which mainly limits the discharge of conventional water pollutants, including COD (20–40 mg L−1), BOD5 (4–10 mg L−1), NH3-N (1–2 mg L−1), TN (10–15 mg L−1), and TP (0.2–0.4 mg L−1). Herein, we evaluated the performance of the new wastewater discharge standard, especially the effect on the removal of PPCPs. We characterized the occurrence of PPCPs and the resulting ecological impact in the basin, and compared the occurrence of PPCPs before (2017) and after (2021) implementation of the standard. A total of 16 PPCPs were detected, of which diclofenac, carbamazepine, ibuprofen, and bezafibrate pose risks to crustaceans and fish in the basin. A positive impact from the implemented standard, on the removal of some PPCPs, was confirmed, especially for lincomycin and trimethoprim.

Deep separation of critical metals of Mo and Re from waste solution by stepwise precipitation flotation: Selective chelation underlying separation mechanism

Conventional selective precipitation method has disadvantage in the low-efficiency filtration of fine precipitated particles during the treatment of waste solutions. To overcome this shortcoming, a stepwise precipitation flotation process was proposed to deeply separate Mo and Re from Mo-Re mixing waste solution with low concentrations in this work. Chelating agents are critical for the selective separation of Mo and Re. Experimental results show that the rhenate can be firstly separated from mixing solution by the synergistic effect of cetyl trimethyl ammonium bromide (CTAB) and dodecyl trimethyl ammonium bromide (DTAB). In the weak alkaline solutions with pH range of 6–10, CTAB shows a stronger competitive adsorption capacity with rhenate than molybdate through electrostatic interactions and coordination reactions. Meanwhile, DTAB has a great inhibition effect on the chelation of molybdate by CTAB in this pH range, which can further enhance the selective chelation of rhenate by CTAB. After Re separation, molybdate can be further recovered by CTAB from the residual solution with pH range of 3–5. In this pH range, Mo mainly exists in the form of isopolymolybdates acid, and molybdate shows a stronger competitive adsorption ability with CTAB than DTAB. Molybdate reacts with CTAB to form precipitate, and the fine precipitated particles are readily separated via flotation. The turbidity of the residual liquid after flotation is less than 5 NTU, meeting the wastewater discharge standard. In the Re precipitation flotation procedure, the comprehensive efficiencies of Re and Mo are 96.6% and 0.14% under the main conditions of temperature of 25°C, n(CTAB)/n(Re) molar ratio of 2:1, n(DTAB)/n(CTAB) molar ratio of 2:1, and pH of 6. In the further Mo flotation separation, Mo comprehensive recovery of 97.9% is achieved by using CTAB and KH2PO4 as chelation agent and flocculant, respectively. The technological parameters of the conventional selective precipitation method and precipitation flotation method as well as the Mo and Re distributions in these two processes were compared in this study. Moreover, compared with the conventional selective precipitation method using inorganic precipitators, the precipitation flotation process shows a unique advantage in the easy purification of obtained products due to the utilization of organic agents.

Desalinating Real Shale Gas Wastewater by Membrane Distillation: Performance and Potentials

Shale gas wastewater is a hypersaline industrial effluent in demand of efficient treatment or resource recovery. Membrane distillation (MD) is a heat-driven desalination process of high potential to deal with such streams. However, its application is highly limited by the unsatisfactory hydrophobic membranes that involve a trade-off between vapor permeability and fouling/wetting resistance. Our previous studies highlighted the potential role of an intermediate coating layer of a carbon nanotube (CNT) for the superhydrophobic membrane with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FAS) grafted to address the trade-off issue against synthetic saline oily wastewater. The work herein investigated its application performance in the continuous concentration and water recovery of real shale gas wastewater, with a commercial PVDF membrane as the reference. The modified membrane recycled 48.2% of the total volume as high-quality water and rejected 99% of feed salinity, achieving a superior concentration rate and flux recovery rate compared to PVDF. The value of the COD, total nitrogen, and ammonia nitrogen in the permeate after the modified membrane was less than 50, 20, and 20 mg/L, meeting the local wastewater discharge standard. It was pointed out that the inorganic fouling for the MD membrane was more of a concern in dealing with a real stream, but the modified membrane exhibited excellent fouling resistance. The cost associated with the treatment was estimated at USD 2.2/m3 for a production capacity of 2000 m3/d. The proposed superhydrophobic membrane has proven to be a feasible alternative from both technical and economic standpoints, offering the potential to improve MD effluent water quality and mitigate membrane fouling.

The effect of pH/PAC on the coagulation of anionic surfactant wastewater generated in the cosmetic production

The wastewater generated from the production of cosmetic raw materials contained a large number of anionic surfactants, which could hardly meet the wastewater discharge standards in China when biological technology was employed as a sole treatment strategy. Coagulation pretreatment was one of important operation units of wastewater treatment, and it could greatly reduce the burden of subsequent biological treatment and improve the efficiency of wastewater treatment. The pH value of the wastewater directly affected the hydrolysis intermediates of the coagulants, thereby influencing the performance of the flocculation reaction. In this study, the effects of adjusting the pH value of raw wastewater on the removal efficiencies of the pollutants, dissolved organic matter and sludge morphology were discussed. The changes of coagulation performance and group structure and thermal stability of flocculated sludge under the coupling action of pH/polyaluminum chloride (PAC) were studied. The results showed that only adjusting the pH of raw wastewater could promote removal efficiencies of chemical oxygen demand (COD) and linear alkylbenzene sulfonate sodium (LAS) and enhance the conductivity of actual cosmetic wastewater, but could not remove the aromatic proteins. The highest coagulation efficiency was achieved under PAC concentration of 2.6 g/L and the pH value of 6. The molecular weight distribution of organics after coagulation was mainly concentrated in the range of> 100 kDa and< 3 kDa, and medium molecular weight organics were mainly removed. It was expected to provide strategies for improving the coagulation performance of actual cosmetic wastewater.

Photo-assisted self-driven bioelectrochemical systems for simultaneous enhanced treatment of etching terminal wastewater and selective recovery of heavy metals

Practical application of photo-assisted bioelectrochemical systems (BESs) for actual etching terminal wastewater (ETW) treatment, requires its energy-saving and high treatment efficiency with simultaneous recovery of multiple heavy metals. Herein photo-assisted self-driven BESs composed of two serially connected microbial fuel cells (MFC) in-situ utilized for powering one microbial electrolysis cell (MEC), are continuously fed with actual ETW. Such BESs achieve enhanced recalcitrant organics mineralization (37.9–38.2%) with simultaneous Cu(II) recovery (68.2 ± 0.4%-69.1 ± 0.4%) in the cathodes of MFCs, along with those (recalcitrant organics mineralization: 29.9 ± 0.4%; Ni(II) recovery: 64.9 ± 0.0% on the cathode electrodes; Zn(II) recovery: 75.7 ± 1.4% at the cathodic bottoms) in the MECs without any external energy consumption, allowing the final effluent meeting the China national wastewater discharge standards. Active species of ·OH, O2·-, holes and H2O2 varying degrees contribute to recalcitrant organics mineralization in the MFC and MEC units. This study provides an alternative zero energy consumption approach for efficient mineralization of recalcitrant organics with simultaneous selective recovery and separation of multiple heavy metals in actual ETW, moving photo-assisted self-driven BESs closer to applicable complex wastewater treatment with simultaneous recovery of multiple value-added heavy metals.

Remediation of chromium-contaminated soil in semi-arid areas by combined chemical reduction and stabilization

ABSTRACT The indoor simulation remediation of chromium-contaminated soil in semi-arid areas with chemical reduction-stabilization method was conducted to study the effects of remediation agent types and dosage, water (mL)-soil (g) ratio and remediation time on reduction and stabilization efficiency of the chromium-contaminated soil. The results showed that FeSO4 was the most effective reduction agent for reduction of Cr(VI) in soil. The optimally combined chemical reduction-stabilization remediation conditions were 2.5 times theoretical reaction dosage FeSO4 and 8% of modified corn stover biochar (KBC), 50% of water-soil ratio, and 7 days remediation time. The total Cr and Cr(VI) leaching concentrations and Cr(VI) content in soil were reduced from 65.65 mg L-1, 61.98 mg L-1 and 1000.00 mg kg-1 without treatment to 0.114 mg L-1, 0.125 mg L-1 and 18.909 mg kg-1 after treatment, respectively. They were according with comprehensive wastewater discharge standards and construction land soil contamination risk control standards, respectively.