Chemical Oxygen Demand Reduction Research Articles

Application of combined hydrodynamic cavitation and Fenton reagent for COD reduction of cellulosic fiber industry effluents

The present work demonstrates the implementation of combined approach of hydrodynamic cavitation reactor and Fenton oxidation process for the treatment of three cellulosic fiber (CF) industry effluent streams using pilot scale reactor with operation at 500 L developed at an industrial site. In order to assess the techno-economic viability of the combined hydrodynamic cavitation (HC) and Fenton oxidation process, various sets of experimental runs were carried out. Effect of type of treatment approach, one step and stepwise addition of oxidants, number of cavitation passes, and finally the type of effluent varying in terms of initial chemical oxygen demand (COD) on the efficacy of treatment were studied. Based on the results, HC + Fenton oxidation scheme was demonstrated to be a viable option for the treatment of CF industry effluent streams. HC + Fenton treatment rapidly reduced COD, achieving almost 90 % reduction in just 10 min, highlighting its efficiency in industrial wastewater treatment. The treatment achieved substantial reduction in residual COD levels with actual value as up to 1000 mg/L COD in effluent-I, up to 150 mg/L COD in effluent-II, and up to 100 mg/L COD in effluent-III. The study also explored the operating cost expenditure (Opex) of the proposed system required to demonstrate it at a commercial level, including the cost of chemicals and electricity. The COD reduction cost evaluated were INR 140–230/kg COD depending on the effluent. The main highlight of the article is the practical demonstration at the manufacturing unit including the operating cost calculations.

Microalgae as A Bioremediation Agent for Palm Oil Mill Effluent: Production of Biomass and High Added Value Compounds

Palm oil mill effluent (POME) is high strength wastewater obtained from palm fruit processing, which contains high chemical oxygen demand (COD), biological oxygen demand (BOD), and other contaminants. The pollutant load in POME can serve as a source of nutrients for microalgae growth. As a result, the goal of this work was to utilize Spirulina sp. and Nannochloropsis oculata to reduce the nutritional content of POME while producing biomass rich in high-value chemicals. The cultivation was conducted in a batch reactor using various POME fractions (0-20%) under 5,000 lux light intensity and continuous aeration at a temperature of 22-28°C and a salinity of 30 ppt for 14 consecutive-days. The results demonstrate that Spirulina sp. produced the most biomass at 15% POME, accounting for 4.67±0.95 g/L with 0.57±0.11 1/day of growth rate and 3.33% of COD reduction efficiency. Meanwhile, Nannochloropsis oculata thrived in 20% POME, producing 4.43±0.36 g/L biomass, 1.18±0.31 1/day growth rate, and 14.43% COD reduction efficiency. In the proximate analysis. Spirulina sp. and Nannochlorpsis oculata provided 0.87%; 1.11% lipid and 1.03%; 0.86% protein, respectively.

Effects of leachate concentration, carbon dioxide and aeration flow rate on chlorophyll and carotenoid productivity and bioremediation potential of the microalga Chlorella minutissima

The use of microalgae cultures to process effluents from industries, leachates, and tanneries, among others, quantified by the reduction of metallic materials in the medium and the reduction of chemical oxygen demand (COD), helps reduce the environmental impact caused by human development. In addition, with the growth of the culture, it is possible to produce a significant amount of chlorophyll, a carotenoid of high value in the cosmetics and food industries that are used as a natural pigment. In this context, this work presents a study conducted to verify the bioremediation and chlorophyll production potential of the cultivation of the microalgae Chlorella minutíssima, using the Taguchi method. The microalgae Chlorella minutissima has given good results in the bioremediation of leachate, as a mean reduction of 33% in COD was obtained, as well as a 92% reduction in the toxic components. In addition, statistical analysis revealed that the four process factors were significant factors for chlorophyll a, chlorophyll b and carotenoid productivity (p < 0.05). Finally, it was observed that the maximum chlorophyll a (111.9 ± 0.8 mg‧L−1‧d−1), chlorophyll b (66.1 ± 1.7 mg‧L−1‧d−1), and carotenoid (31.9 ± 0.03 mg‧L−1‧d−1) values obtained occurred in Experiment 8, which is closer to the ideal conditions identified by statistical analysis, revealing the effectiveness of the use of the Taguchi method for the design of experiments.

Evaluation of combined efficiency of conventional coagulation-flocculation process with advanced oxidation process (sulfate-hydroxyl radical) in leachate treatment

This study evaluated a novel municipal solid waste leachate (MSWL) treatment system called the Batch flow leachate treatment system (BFLTS). This process uses a combination of coagulation/flocculation (C-F), advanced oxidation (sulfate-hydroxyl radical), and extended aeration of activated sludge (EAAS) to treat MSWL. The results indicated that the primary treatment phase using coagulation/flocculation with 0.8 g L<sup>-1</sup> FeCl<sub>3</sub> at pH 6 achieved 67% turbidity and 63% chemical oxygen demand (COD) reduction. The secondary treatment phase with the presence of both K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> and H<sub>2</sub>O<sub>2</sub> peroxides was more efficient than single peroxide processes. While PS-based or H<sub>2</sub>O<sub>2</sub>-based single peroxide processes are less effective (UV-PS 65.7%, UV-H<sub>2</sub>O<sub>2</sub> 43.2%, Heat-PS 58.6%, Heat-H<sub>2</sub>O<sub>2</sub> 34.5%, and Heat-PS/H<sub>2</sub>O<sub>2</sub> 74.8%). The UV-PS/H<sub>2</sub>O<sub>2</sub> system achieved the highest COD removal rate of 89.4%. In the third treatment phase, the efficient removal of COD and Biochemical oxygen demand (BOD) under optimal operating conditions was 87.3% and 94.7% respectively. Overall, the BFLTS treatment system has demonstrated high efficiency in removing COD, BOD, TSS, Turbidity, TKN, and Heavy metals by 99%, 98%, 97%, 89%, 86%, and 98%, respectively. This hybrid process has potential for reducing organic load in MSWL and can be used for various leachates.

Facile synthesis of NiAl-LDH/Ag/g-C3N4 ternary composite for photocatalytic degradation of methylene blue

The use of organic dyes has surged across industries like textiles, plastics, and construction. Contaminated water with these dyes is released into the environment, endangering both humans and ecosystems. In this research, we synthesized ternary composites of NiAl-LDH/Ag/g-C3N4 using hydrothermal methods. We conducted a comprehensive examination of the prepared catalysts, employing various analytical techniques to assess their structural, optical, morphological, and surface chemical properties. The surface area analysis confirmed a mean pore volume of 0.245 cm³/g, a favorable surface area of 36.4 cm2/g, and a pore diameter of 2.68 nm. The creation of strong interfacial contact between NiAL LDH, Ag, and g-C3N4 caused the charges to be separated for a long time. The degradation of methylene blue (MB) dye under the influence of solar light was used to test the photocatalytic performance of the as-prepared catalyst. A set of reusability experiments was carried out over four cycles using the photocatalyst, and the characterization findings demonstrated that the preservation of crystalline planes plays a pivotal role in achieving its high efficiency. Notably, a remarkable 99.1% reduction in chemical oxygen demand (% COD) was achieved for MB. Additionally, scavenger studies were undertaken to identify the primary reactive species involved in the process. The maximum degradation efficiency of 99.60%, with the highest R2 value of 0.9921 was achieved for the photocatalytic degradation of MB respectively in 160 min. These results indicated that the new z-scheme ternary photocatalyst can be used as an efficient, green, effective, and recyclable for the photocatalytic degradation of organic pollutants.

Development of data-driven models for the optimal design of multilayer sand filters for on-site treatment of greywater

Greywater, with limited content of pathogens, makes up more than half of the produced wastewater in urban areas. Given the high cost of wastewater management and treatment, it causes sense to collect greywater separately at the source and employ an on-site treatment system to increase opportunities for on-site water reuse. For this purpose, this paper aims to propose a multilayer granular filter as an inexpensive and simple on-site treatment method for greywater reuse. Furthermore, as determining the optimal structure of multilayer filters is a serious challenge, a simulation-optimization model is developed for determining the best filter configuration. An Artificial Neural Network (ANN) is trained based on experimental results to simulate the filter performance with different combinations of layers and the Genetic Algorithm (GA) is used to find the optimal thickness of different layers based on ANN simulation results. The proposed filter in this paper for greywater treatment consists of silica sand (in three different gradings) and activated carbon (with fixed grading) and treatment measures for evaluation of filter performance are considered as Chemical Oxygen Demand (COD) and Electrical Conductivity (EC). Due to difficulties in collecting, transferring, and storing the real greywater, synthetic greywater was used in this study. 49 experiments with different combinations of filter media thicknesses were performed and the performance of the filter was analyzed. Generally, three-layer filters perform better in COD and EC reduction, however, the average COD and EC elimination equals 36.3% and 15.1%, respectively, which indicates more efficiency of filter in COD reduction in comparison with EC. Based on the optimization-simulation model and experimental results, a filter consisting of 33 cm of fine sand, 20 cm of activated carbon, and 7 cm of medium sand results in the maximum efficiency and can reduce the COD and EC of greywater by 72% and 30%, simultaneously. According to the optimization outputs, the ideal filter can treat greywater up to having EC of 1000 μS/cm and COD of 321 mg/L, which is generally suitable for irrigation purposes.

Absorbent mixtures optimisation for COD and Ammonia Nitrogen reduction in stabilised leachate

This paper describes the optimisation of mixed media for Chemical Oxygen Demand (COD) and Ammonia Nitrogen (NH3-N) removal from stabilised leachate by feldspar (FE), zeolite (ZE), activated carbon (AC), and cockle shells (CS) mixtures using D-optimal mixture design. Linear equations characterised the optimal mixture. The optimum mitigation of COD and NH3-N in landfill leachate was favourable at 12.5 mg/L, 9.72 mg/L, 6 mg/L, and 11.79 mg/L of adsorbent mixed dosage for FE, ZE, AC, and CS, respectively, with the desirability value of 0.886. The predicted R-squared values for NH3-N (0.9839) and COD (0.8972) were in close agreement with the adjusted R-squared values of 0.9940 and 0.9900 for COD and NH3-N, respectively, which validates the obtained regression models. The Lack of Fit F-values of 0.6015 (COD) and 0.4565 (NH3-N) are insignificant, indicating that the models accurately predict the removal. The Fourier transform infrared spectroscopy (FTIR) revealed that the predominant hydroxyl group consisted of –OH at spectra 3306.18 and 3338.74. The study also revealed that the D-optimal mixture design has extremely high application potential as it produces a good mixture design based on the remediation of contaminants from stabilised leachate.

Efektivitas Instalasi Pengolahan Air Limbah Berdasarkan Parameter COD, BOD, TSS, pH (Studi Kasus Industri Tahu di Dusun Janten Ngestiharjo Kasihan Bantul)

The liquid waste generated from tofu production process contains high Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), Total Suspended Solid (TSS) as well as low pH levels or acidity. Therefore, the tofu waste needs to be treated before being discharged into the environment to prevent negative impacts on the surrounding environment. Thus, this study aimed to test the effectiveness of the tofu wastewater treatment plant by monitoring the parameters of COD, BOD, TSS and pH using the closed reflux titrimetry, gravimetri and pH meter methods. The sampling was carried out with triple sampling (triplo) at each testing point, which were the equalization tank, anaerobic baffle reactor tank, anaerobic filter tank, and final settling tank. The sample testing was conducted at the "Balai Laboratorium Kesehatan dan Kalibrasi Yogyakarta". The results of the testing were used to determine the reduction in COD and the increase in pH between the wastewater treatment plant tanks, and then the effluent of the wastewater treatment plant was compared with the wastewater quality standards. The results of this study indicate that the average reduction of COD in the effluent is 94%, BOD is 93%, and TSS is 87%. Based on these findings, it can be concluded that the effluent from the wastewater treatment plant is not yet effective in meeting the wastewater quality standards. However, it is worth noting that the pH parameter meets the wastewater quality standards, with an increase of +1.38 compared to the influent pH level. Therefore, in terms of this parameter, the wastewater treatment plant can be considered effective in raising the pH.

Hydrothermal Carbonization of Sewage Sludge: New Improvements in Phosphatic Fertilizer Production and Process Water Treatment Using Freeze Concentration

In recent years, promising developments in the hydrothermal carbonization (HTC) of sewage sludge, as well as the potential to reclaim phosphorus and nitrogen, have emerged. In this study, the HTC of digested sewage sludge (DSS) was investigated for the downstream production of heavy metal (HM)-free fertilizer and the use of freeze concentration (FC) as a novel technology for process water treatment. To obtain clean fertilizer, phosphatic acid extracts were first treated with ion-exchange resins to remove dissolved HM, as well as phosphorus precipitating agents (i.e., aluminum and iron). Over 98% of the aluminum (Al) and 97% of the iron (Fe) could be removed in a single treatment step. The purified extract was then used for the precipitation of HM-free struvite crystals, with P-recovery rates exceeding 89%. Process water (PW) makes up the largest share of the two main HTC-products (i.e., hydrochar and PW) and is very rich in organic compounds. Compared to evaporation or membrane separation, FC is a promising technology for concentrating solutes from PW. Separation experiments resulted in the recovery of over 90% of the dissolved compounds in the concentrate. In our study, the concentrate was later utilized as an ammonium source for struvite precipitation, and the subsequent aerobic digestion of the remaining ice water resulted in an 85% reduction in chemical oxygen demand (COD) in 15 days.

Sustainable methane energy from bagasse treated via bokashi technology: comparative between neural network and mathematical modeling

Bagasse is the major leftover material from the sugarcane industry, and it has significant untapped energy. Biogas production from bagasse is employed as eco-friendly energy but its intricate composition makes it resistant to degradation. This study endeavors to explore the impact of bokashi technology, a technique that applies effective microorganisms on the potential methane production from bagasse. According to findings, bagasse had the ability to produce biogas but applying bokashi technology to bagasse led to getting more methane production. The methane production from treated bagasse for one month via bokashi bran was 243.80 LCH4/kgVS compared to 106.84 LCH4/kgVS only from fresh bagasse which is often attributed to improved fibrous carbohydrates degradation by the pre-treatment process. The reduction of total solids and chemical oxygen demand were more with treated bagasse. Two-dimensional mathematical modeling (TDMM) and artificial neural network (ANN) were utilized to forecast the production of methane through the anaerobic co-digestion process. The main advantage of ANN model is its ability to be constructed and trained for any experiment, regardless of the availability of a pre-existing study or understanding of the underlying phenomena. On the other hand, existence of a mathematical model that accurately describes the behavior of the current experiment is a fundamental requirement for constructing the TDMM model. The TDMM model remains stable in each run, as it relies on the established mathematical equations. On the other hand, ANN model may exhibit variations in each run due to the random initialization of weights.Graphical abstract

Microbial-earthworm ecofilters (MEES) for urban wastewater treatment

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

The impact of concentration on the biotreatment of hair relaxers using Hydrocarbonoclastic Pseudomonas and Mucor Species from Ezu River, Awka, Nigeria

The contamination of an aquatic environment by hydrocarbons and other noxious compounds due to human activities may cause toxicity to microorganisms and may stimulate microbial activity especially at low concentrations while their persistence can be detrimental to the entire ecosystem. It is crucial therefore, to assess the risks of these pollutants for environmental policy. Diesel was used as carbon source in mineral salts medium for the isolation of petroleum degrading microorganisms from Ezu River using vapor transfer technique. Plates were incubated at 37 0C and 28 0C for bacterial and fungal cultures, respectively. Of the 23 bacterial and 4 fungal isolates recovered, Mucor species and Pseudomonas aeruginosa were the best hydrocarbon utilizing isolates obtained. The isolates were assessed for their ability to utilize both lye-containing and lye-free hair relaxers at different concentrations (0.2 – 1% w/v) in mineral salts medium for 14 days. The optical density (OD660nm), the biochemical oxygen demand (BOD5), chemical oxygen demand (COD), and pH of the medium were monitored during incubation. The toxicity of the hair relaxers to Nitrobacter sp. was also assessed. Results showed that Pseudomonas aeruginosa utilized both lye-free(Lf) and lye-containing (Lc)hair relaxers at all concentrations as indicated by the high colony counts, reduction in BOD5 and COD during the incubation period. Mucor sp. grew better on higher concentrations Lc hair relaxer (1%> 0.8%> 0.6% w/v), but with minimal growth at lower concentrations of same relaxer (0.2%< 0.4%< 0.6% w/v). On the contrary, lye-free hair relaxer supported heavy growth of Mucor sp. at all concentrations tested. The growth of Nitrobacter sp. got inhibited by both types of hair relaxers between concentrations 0.6 and 1% w/v, with moderate growth at lower concentrations (0.2 – 0.4% w/v). The toxicity outcome of these hair relaxers to Nitrobacter species implies that the indiscriminate discharge of hair-relaxer-containing salon wastewater into the soil may affect the biogeochemical activities of the soil microbial communities. In addition, Pseudomonas aeruginosa and Mucor species recovered in this study can be used to attenuate sites contaminated by hair salon wastewater.

Effects of Different TiO2/CNT Coatings of PVDF Membranes on the Filtration of Oil-Contaminated Wastewaters.

Six different TiO2/CNT nanocomposite-coated polyvinylidene-fluoride (PVDF) microfilter membranes (including -OH or/and -COOH functionalized CNTs) were evaluated in terms of their performance in filtering oil-in-water emulsions. In the early stages of filtration, until reaching a volume reduction ratio (VRR) of ~1.5, the membranes coated with functionalized CNT-containing composites provided significantly higher fluxes than the non-functionalized ones, proving the beneficial effect of the surface modifications of the CNTs. Additionally, until the end of the filtration experiments (VRR = 5), notable flux enhancements were achieved with both TiO2 (~50%) and TiO2/CNT-coated membranes (up to ~300%), compared to the uncoated membrane. The irreversible filtration resistances of the membranes indicated that both the hydrophilicity and surface charge (zeta potential) played a crucial role in membrane fouling. However, a sharp and significant flux decrease (~90% flux reduction ratio) was observed for all membranes until reaching a VRR of 1.1-1.8, which could be attributed to the chemical composition of the oil. Gas chromatography measurements revealed a lack of hydrocarbon derivatives with polar molecular fractions (which can act as natural emulsifiers), resulting in significant coalescent ability (and less stable emulsion). Therefore, this led to a more compact cake layer formation on the surface of the membranes (compared to a previous study). It was also demonstrated that all membranes had excellent purification efficiency (97-99.8%) regarding the turbidity, but the effectiveness of the chemical oxygen demand reduction was slightly lower, ranging from 93.7% to 98%.

Comparative performance of sustainable anode materials in microbial fuel cells (MFCs) for electricity generation from wastewater

Microbial fuel cells (MFCs) are a promising technology to generate electricity from wastewater and reduce the organic content. Whilst there has been a significant enhancement in MFC efficiency arising from the introduction of novel materials and cell designs, challenges remain with respect to the performance, cost, and sustainability of anode materials. This paper reports the development of single chamber MFCs with a focus on novel, cost-effective, and recycled carbon-based anode materials, including Recycled Water Filter Block/Powder (RWFB/RWFP), Recycled Chopped Carbon Fibre (RCCF), Carbon Felt (CF) and Graphite Flexible powder (GFG). Anodes prepared from GFG were shown to provide high power density (342.8 mW/m2), followed by RCCF, CF, RWFP, RWFB and CF (77.6, 71.8, 59.0 and 57.9 mW/m2, respectively). Chemical Oxygen Demand (COD) reduction was measured initially and at day 30, with GFG anodes observed to remove 83% of the initial load, compared to RCCF, RWFB, RWFP and CF anodes, where COD reductions of 69%, 61%, 65% and 73% were observed, respectively. Electrochemical analysis and biofilm imaging confirmed recycled materials were colonised by microorganisms and performed to high standards. GFG offers significant promise as an anode material, with excellent performance supported by a reduction in capital cost of up to 90% in comparison to CF. The use of recycled carbon material as MFC anodes shows promise, but requires additional work to improve the stability and durability of systems to permit scale-up.

Intensified treatment of kitchen wastewater in a filter- press type electrochemical reactor

Commercial kitchen wastewater (KW), characterized by a high load of bio-refractory organics, can be effectively treated by electrochemical methods for non-potable applications. This work explores the electrochemical degradation of KW in a batch recirculation type flow reactor consisting of mixed metal oxides coated titanium mesh anode and stainless steel cathode. The effect of operating factors such as current density, supporting electrolyte concentration, initial pH, and recirculation flow rate on chemical oxygen demand (COD) reduction was examined by following one-factor-at-a-time method. The %COD reduction increased with an increase in electrolyte concentration and current density. The optimum current density and electrolyte concentration were found to be 2 A/dm2 and 2 g/L, respectively. The treatment was intensified by incorporating mechanical stirring and ultrasound irradiation in the reservoir. The results showed about 99 % COD reduction, and the kinetic model proposed predicted the experimental data satisfactorily.

Musico-bioremediation of seafood canning wastewater by Yarrowia lipolytica.

Due to the lack of water resources and the harmful effects of wastewater on environment and human health, treatment of wastewater becomes necessary. The present study explored the effect of musical sounds on the biological treatment of seafood canning wastewater by using Yarrowia lipolytica. Our results showed that low frequency (21Hz to 1356Hz) and high frequency (21 Hz to 16,214 Hz) musical sounds stimulated the growth of Y. lipolytica and increased the polluant removal efficiency. Such treatment decreased significantly the chemical oxygen demand (COD) and salinity as well as the color of this wastewater. Our study revealed that low frequency musical sounds are more effective in COD (87.5%) and salinity (44%) reduction as well as the decolorization (86.46%) of this effluent. Additionally, after 7 days of incubation significant yeast cell dry biomass (3.46 ± 0.22g/L) and single cell proteins (46.45 ± 0.7mg/g) were obtained under low frequency waves. Musico-bioremediation represents an innovative ecotechnological approach to wastewater treatment with low operating costs and significant environmental benefits.

The effect of social economy-water resources-water environment coupling system on water consumption and pollution emission based on input-output analysis in Changchun city, China

With the rapid development of social economy, water resources consumed excessively and water pollution emissions increased. However, few studies have considered the feedback of water resources and water environment on social economy. In this study, a social economy-water resources-water environment coupling system was constructed by multiple regression model and system dynamic model. Five scenarios were set to investigate the relationship among industrial restructuring, pollution treatment and water conservation in Changchun city, China. Based on input-output model, this study analyzed the effect of the coupling system on the economic efficiency of sectoral water consumption and pollution emission. The driving factors were identified and the contributions were quantified using structural decomposition analysis model. The results showed that pollution treatment and water conservation promoted economic development and increased Gross Domestic Product (GDP) by 36.76%. The comprehensive effect of industrial restructuring, pollution treatment and water conservation was better than single measures, which made the GDP increment (44.39%), Chemical Oxygen Demand (COD) reduction (34.11%), Ammonia Nitrogen (NH3–N) reduction (52.50%) and total water consumption increment (7.56%) largest. Meanwhile, the comprehensive effect improved the water consumption efficiency of agriculture and service industries, reduced indirect water consumption in industrial sectors, and improved the economic benefits of pollution emissions in all sectors. The industrial restructuring further increased the contribution of population to COD emissions and the contribution of emission intensity to NH3–N emissions. Under the condition of comprehensive effect, the final demand level was the main factor for the increase of COD and NH3–N, contributing 36998.80 t and 821.07 t, respectively. Therefore, the government should pay attention to saving water resources and protecting water environment while developing social economy. The study quantified the coupling relationship between social economy, water resources and water environment, and provided guidance for water resources management in sectors.

Nanocomposites from spent coffee grounds and iron/zinc oxide: green synthesis, characterization, and application in textile wastewater treatment.

This study reports on a novel composite of bimetallic FeO/ZnO nanoparticles supported by spent coffee grounds (SCGs). The leaves of eucalyptus (Eucalyptus globulus Labill) and trumpet (Cuphea aequipetala Cav), with their high antioxidant content, serve as bio-reductant agents for the green synthesis of nanoparticles. It was characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Stable nanoparticles were produced with different diameters of 5-30 nm, and they were applied as catalysts in Fenton-like processes. Box-Behnken experimental design (BBD) was used to determine the optimal removal efficiency with three factors and was used in the degradation of textile dyes from wastewater. The nanocomposite displayed a high decolorization ratio (88%) of indigo carmine in the presence of H2O2 combined. This resulted in a reduction in chemical oxygen demand (COD) of 56% at 120 min of contact time at an initial pH of 3.0 and a 0.5 g/L of catalyst dose, a H2O2 concentration of 8.8 mM/L, an initial dye concentration of 100 mg/L, and a temperature of 25 °C.

Long-range hydrophobic force enhanced interfacial photocatalysis for the submerged surface anti-biofouling.

Developing anti-biofouling and anti-biofilm techniques is of great importance for protecting water-contact surfaces. In this study, we developed a novel double-layer system consisting of a bottom immobilized TiO2 nanoflower arrays (TNFs) unit and an upper superhydrophobic (SHB) coating along with the assistance of nanobubbles (NBs), which can significantly elevate the interfacial oxygen level by establishing the long-range hydrophobic force between NBs and SHB and effectively maximize the photocatalytic reaction brought by the bottom TNFs. The developed NBs-SHB/TNFs system demonstrated the highest bulk chemical oxygen demand (COD) reduction efficiency at approximately 80% and achieved significant E. coli and Chlorella sp. inhibition efficiencies of 5.38 and 1.99 logs. Meanwhile, the system showed a sevenfold higher resistance to biofilm formation when testing in a wastewater matrix using a wildly collected biofilm seeding solution. These findings provide insights for implementing nanobubble-integrated techniques for submerged surface protection.

Ammonium Recovery from Manure Wastewater and Simultaneous Electrosynthesis Using Ammonium-Ion Selective Redox Material

The environmental pressure due to greenhouse gas emissions and water contamination generated by livestock manure motivates the development of new approaches to reduce their environmental impacts and improve sustainability. Effective approaches to recover nutrients, especially ammonium, from manure wastewater to produce fertilizer are needed. Here we develop a new electrochemical strategy to achieve simultaneous ammonium recovery and electrochemical synthesis using potassium nickel hexacyanoferrate (KNiHCF) as the ammonium ion-selective redox material to mediate the processes. The KNiHCF electrode spontaneously uptakes ammonium (and K+) from manure wastewater with a nutrient (NH4 + and K+) selectivity of ~100% and effective reduction of chemical oxygen demand (COD). The subsequent electrochemical process achieves the co-production of NH4 +-rich fertilizers and value-added chemicals, such as H2 as a green fuel and H2O2 as a disinfectant, without expensive ion-exchange membranes. These results provide a new conceptual strategy and insights for distributed electrochemical resource recovery and on-demand electrochemical manufacturing that can improve agricultural sustainability.