Residual COD Research Articles

Effects of LED lights and cytokinin on the phytotreatment of simulated swine wastewater by Azolla spp.: Pollutant removal and biomass valorization

Phytoremediation is an eco-friendly and affordable option for tackling wastewater pollutants. The study focused on how light-emitting diodes (LED) light exposure, measured by intensity and duration (photoperiod), along with cytokinin, impacts Azolla microphylla's simulated swine wastewater treatment performance and biomass production. Under optimal treatment conditions, high removals of COD (89.2 % to 90.8 %), N-NH4+ (72.6 % to 91.2 %), N-NO3- (84.4 % to 88.6 %), Cu (75.4 % to 86.4 %), sulfamethoxazole (77.0 % to 79.0 %), P-PO43- (54.1 % to 59.9 %) and DOC (67.4 % to 71.3 %) while Zn presented a more moderate reduction (2.0 % to 9.7 %). Biomass productivity reached up to 34.8 t ha-1 yr-1. Protein production accounted for 23 % to 27 % of dry weight, while lipids ranged from 20 % to 34 % of dry biomass. Carbohydrate content varied from 8 % to 28 % of fresh weight. Higher light intensities, with both high or low values of photoperiods, and low concentrations of cytokinin were identified as optimal conditions for removal of almost all pollutants. However, pollutant removal was impacted differently by LED light and cytokinin concentration. In treatment conditions with the shortest photoperiods (8 h), the lowest residual Cu and Zn concentrations, whereas with longer photoperiods (24 h), the lowest residual concentrations of N-NH4+ and P-PO43- concentrations were recorded. On the other hand, SMX was the only parameter in which cytokinin had a clear influence on its removal, with the lowest residual concentration observed under 8-hour photoperiods combined with the lowest tested cytokinin concentrations (0.3 mg L-1). For residual COD and N-NO3-, no discernible pattern was evident for any of the analyzed factors. Therefore, the study demonstrates the potential for treating simulated swine wastewater using Azolla microphylla, aligned with its ability to produce biomass rich in high-value compounds.

Treatment of hydrocarbon marine pollution with cloud point extraction

AbstractThe release of hydrocarbons (HC) into the marine environment has serious consequences, both economically and ecologically. This work presents an efficient process to remove HC pollution from seawater: cloud point extraction (CPE), considered to be a reliable, inexpensive, and environmentally friendly method, using the readily biodegradable nonionic surfactants Lutensol ON30 and Tergitol 15‐S‐7. A real salt water sample with a high chemical oxygen demand (COD = 1700 mg O2/L) was thus treated. First, the phase diagrams of the binary systems (water–surfactant), and the pseudo‐binary systems (water–surfactant–HC), were determined. Second, after a 24 h settling time, considered as optimal, the extraction results, that is, residual soluble COD, residual percentage of surfactant in the dilute phase and volume fraction of coacervate at equilibrium, were expressed in terms of temperature and initial surfactant concentration. For each parameter, the results obtained were modeled using the response surface methodology and represented on three‐dimensional diagrams. They show that the COD can be reduced to 10 and 15 mg O2/L, using Lutensol ON30 and Tergitol 15‐S‐7, respectively, under seawater temperature conditions. Finally, it was shown that the surfactant can be recycled. The present work demonstrates that CPE can reduce the HC content of seawater on a laboratory scale.

Treatment of pharmaceutical wastewater by a sequential KMnO4/CoFe2O4-mediated catalytic ozonation process

Pharmaceutical compounds, which are of utmost concern, have found their way into natural water bodies, causing numerous problems for both human health and ecosystems. In this study, an integrated system including potassium permanganate (PM) pre-oxidation, followed by a heterogeneous catalytic ozonation process (HCOP) using CoFe2O4 magnetic nanoparticles (CF MNPs), and an activated sludge-based biological treatment (BT) was employed for the first time to treat pharmaceutical wastewater (PWW). In this regard, the effluent from PM pre-oxidation process was used as a batch for the HCOP, and the effluent was used as a batch for the BT process. The results showed that PM pre-treatment of PWW (PM dose = 1264 mg/L and pH = 8.0) reduced the COD content of the PWW from 900 ± 50 to 443 ± 10 mg/L within 120 min of reaction time. The application of HCOP for further treatment of PWW dramatically enhanced COD and TOC removal compared with the single ozonation process (SOP). Under optimum conditions (pH = 10, O3 = 4.0 mg/L, and CF MNPs = 1000 mg/L), HCOP successfully reduced the COD and TOC contents of PWW by 37 % and 46.1 %, respectively, after 120 min of treatment. The consecutive combination of PM pre-treatment followed by HCOP exhibited good potential and reduced COD by over 69 %, resulting in a residual COD of less than 280 mg/L. A biodegradability ratio of over 81 % and residual COD of 54 mg/L for the PWW treated by the PM/HCOP/BT integrated system indicated that biodegradability was enhanced, and a high fraction of refractory organic compounds was effectively removed. In conclusion, the PM/HCOP/BT integrated system is an efficient, synergistic, and easy-to-operate technique for enhancing the biodegradability of PWW.

Experimental support for a sustainable treatment strategy of acrylic fiber dyeing wastewater

AbstractThe study intended to devise a sustainable treatment scheme for acrylic fiber dyeing process effluents, which significantly differ from other textile plant wastewaters. The necessary experimental support was generated from a set of tests conducted on the wastewater of a plant operation, focused solely on acrylic fiber dyeing. Related experiments involved effluent characterization, biological treatability, and chemical settling/oxidation performed on raw and bio‐treated effluent, as pre‐treatment and/or polishing steps. A total COD level of 910 mg/L with a 70% soluble ratio, low total N and P contents below 10 mg/L, a detergent content of 50 mg/L and a dark/black color of 1150 Pt‐Co unit defined the average properties of the raw plant effluent. Experimental support indicated that activated sludge operation at a sludge age level above 25 d, remained insufficient as it could only provide an effluent with a soluble COD level above 150 mg/L, a biomass escape in the range of 40 to 100 mg/L and with an intense dark color. A similar experimental template, including chemical settling, chemical oxidation by NaOCl and combination of the two processes, was tested as pre‐treatment and a polishing step after biological treatment. Pre‐treatment, although with some benefit to remove toxic and inhibitory compounds, proved to be highly costly, due to excessive chemical usage and sludge generation for a sustainable, cost‐effective approach. The sequence of chemical oxidation and settling steps implemented as a polishing stage was quite effective as it secured complete color removal, a major source of concern for the selected wastewater and also, it reduced COD down to 60 mg/L, a level significantly below the residual COD threshold for biological treatment. This approach, although case‐specific for this study, provided a scientific and general perspective for similar work.

Electrocoagulation Technique for Treating Swine Slaughterhouse Wastewater from Batch to Semicontinuous Operation Mode

In this study, industrial swine slaughterhouse wastewater was treated by electrocoagulation process using batch and semicontinuous operation systems. Electrochemical technique was carried out in batch operation mode during 2.5 h applying different current densities in sulfate and chloride media. After finding the best operating parameters in batch mode (lab-scale), the process was transferred to a semicontinuous pre-pilot scale process using a filter-press FM01-LC type electrochemical reactor fitted with flat plate aluminum electrodes. In this stage, distinct current densities and mean linear flow rates were assessed.Total organic carbon, chemical oxygen demand, total phosphorus, total nitrogen, and potassium among other parameters were analyzed during both treatments. The industrial swine slaughterhouse wastewater contained TOC 333 mg L–1, COD 1765 mg L–1, TP 13.55 mg L–1, TN 327 mg L–1, K 45 mg L–1, turbidity 102 NTU, color –absorbance 0.90 A.U. at 415 nm–, conductivity 1.9 mS cm–1, and pH 6.9. The highest TOC removal efficiency (72.7%), in semicontinuous process, was found at j = 25 mA cm-2 and ur = 0.64 cm s-1 with an energy consumption of 19.80 kW h m-3. Residual COD and TP concentrations met the international standard limits. Moreover, complete discoloration and disinfection were achieved. EDXRF, SEM, EDAX, XRD, and FTIR analyzes indicate pollutants were removed by adsorption on aluminum/iron hydroxides/oxyhydroxides.

APPLICATION OF FENTON'S HETEROGENEOUS SYSTEM FOR THE TREATMENT OF ORGANIC-CONTAINING WASTEWATER

With the growth of the Earth's population, the problem of the shortage of clean water is becoming global. And for the survival of humanity, it is necessary to significantly reduce the amount of harmful wastewater that pollutes the environment. Wastewater polluted with organic substances, usually produced by the production of dyes and the food industry, causes great damage to the environment.
 The expediency of catalytic oxidation for the treatment of organic-containing effluents has been theoretically substantiated. As a catalyst, it is proposed to use new nanostructured composites of the «core-shell» type based on transition metal oxides (CoFe2O4/SiO2/CuO) for the Fenton system. The oxidizing agent in this system is H2O2, which is used in «green technologies».
 It was investigated that the degree of destruction of the dye methylene blue (MB) depends on the composition of the catalyst, the ratio of the concentrations of the catalyst and dye, and the presence of a preliminary stage of dye adsorption.
 The investigated catalyst was tested on simulated dairy wastewater (SDW). The research was carried out in a barbotage-type apparatus (Schott filter). For the system «dairy wastewater – CoFe2O4/SiO2/CuO – О2– Н2О2», the degree of dairy wastewater treatment is 63 %, and residual COD value is 39,52 mgO2/dm3. It was established that in the process of purification by the CoFe2O4/SiO2/CuO catalyst, active oxidizing compounds are formed, which significantly intensify the process.
 Thus, there are reasons to assert that the prospect of developing a highly efficient catalytic oxidation technology in the Fenton system for the treatment of wastewater containing organic pollutants. And the results obtained and the conclusions drawn about the technological feasibility of using CoFe2O4/SiO2/CuO as a catalyst can find practical application for the implementation of technological schemes closed behind water and in other wastewater treatment technologies, in particular food production.

Enhancing industrial swine slaughterhouse wastewater treatment: Optimization of electrocoagulation technique and operating mode

In this study, industrial swine slaughterhouse effluents were treated by an electrocoagulation process (EC) with aluminum and iron electrodes. Batch and semicontinuous operation were performed. EC tests were carried out in batch operating mode for 2.5 h using fixed current densities (j = 10, 20, and 30 mA cm−2) in sulfate and chloride media. At the laboratory scale, higher TOC removal efficiencies were observed using aluminum electrodes at 20 mA cm−2 without the addition of a supporting electrolyte (82.7%). However, the EC process with Fe electrodes consumed 43.6% less energy.After the best operating parameters were found at the laboratory scale, the process was tested as a semicontinuous prepilot process using a filter-press FM01-LC-type electrochemical reactor equipped with flat plate aluminum electrodes. In this stage, current densities and mean linear flow rates were assessed. The highest TOC removal efficiency of 72.7% (i.e., residual TOC concentration of 85.18 mg L−1) in the semicontinuous process was achieved by the application of j = 25 mA cm−2 and ur = 0.64 cm s−1 with an energy consumption of 19.80 kW h m−3. The residual COD and TP concentrations met the international standard limits. Moreover, complete decoloration and disinfection were accomplished. EDXRF, SEM, EDAX, XRD, and FTIR analyses indicated that pollutants were removed by adsorption on aluminum/iron hydroxides/oxyhydroxides.

A novel experimental and machine learning model to remove COD in a batch reactor equipped with microalgae

By using microorganisms and the microalgae Chlorella vulgaris in conjunction with sequencing batch reactors (SBRs), the performance of a wastewater treatment facility was studied. For this purpose, the effect of pH, temperature, {mathrm{COD}}_{mathrm{inlet}}, and air flowrate on COD removal rate and residual was investigated. A single-factorial optimization method is utilized to optimize the amount of COD removal, and the best result is obtained with a pH of 8, {mathrm{COD}}_{mathrm{inlet}}=600, mathrm{mg}/mathrm{l}, and an airflow rate of 55 l/min. Under optimal conditions, the amount of residual COD in the effluent reached 36 mathrm{mg}/mathrm{l}, showing an augmentation in the efficiency of the desired system. Moreover, empirical correlations are proposed for double-factorial optimization of residual COD and COD removal. Also, a multilayer perceptron artificial neural network is proposed to model the process and predict the residual COD concentration. The useful technique of hyperparameter tuning is utilized to obtain the best result for the predictions. All the effective parameters, including the number of hidden layers, neurons, epochs, and batch size, are adjusted. Data from the experiments agreed well with the artificial neural network modeling results. For this modeling, the values of the correlation coefficient ({R}^{2}) and mean absolute error (MAE) were obtained as 0.98 and 2%, respectively.

Treatment of catalyst wastewater through an environmentally friendly electrodeposition-precipitation-electrooxidation coupling process: Recovery of copper and silicate, and removal of COD

An environmentally friendly coupling process of electrodeposition—chemical precipitation—electrooxidation was explored to recover copper and silicate, and remove COD, showing a promising effect in treating catalyst wastewater. The feasibility and the key influencing factors of the process were investigated. The results showed that more than 99.8% of copper and 89.7% of silicate were recovered through the electrodeposition process and precipitation process, and 96.4% of COD was removed in the electrooxidation process. The purification of recovered copper was higher than 99.12% and the residual COD was lower than 500 mg/L. A higher initial pH value (>12.9) or the addition of a certain amount of NaCl is essential in avoiding the fouling of the anode in the electrodeposition process. In the chemical precipitation process, CaCl2 was selected as the precipitator, and the dosage of Ca: Si molar ratios of 1:1 was feasible for silicate removal. After processing, the content of copper and COD met the discharge standard.

Transformation from biofiltration unit to hybrid constructed wetland-microbial fuel cell: Improvement of wastewater treatment performance and energy recovery

This study aimed to compare the performance of biofiltration, constructed wetland, and constructed wetland microbial fuel cell (CW-MFC). The transformation from a biofiltration unit to a hybrid CW-MFC was demonstrated with the advantages of improvement of wastewater treatment while generating electricity simultaneously. The introduction of plants to the upper region of the bioreactor enhanced the DO level by 0.8 mg/L, ammonium removal by 5 %, and COD removal by 1 %. The integration of electrodes and external circuits stimulated the degradation rate of organic matter in the anodic region (1 % without aeration and 3 % with aeration) and produced 5.13 mW/m3 of maximum power density. Artificial aeration improved the nitrification efficiency by 38 % and further removed the residual COD to an efficiency of 99 %. The maximum power density was also increased by 3.2 times (16.71 mW/m3) with the aid of aeration. In treating higher organic loading wastewater (3M), the maximum power density showed a significant increment to 78.01 mW/m3 (4.6-fold) and the COD removal efficiency was 98 %. The ohmic overpotential dominated the proportion of total loss (67-91 %), which could be ascribed to the low ionic conductivity. The reduction in activation and concentration loss contributed to the lower internal resistance with the additional aeration and higher organic loading. Overall, the transformation from biofiltration to a hybrid CW-MFC system is worthwhile since the systems quite resemble while CW-MFC could improve the wastewater treatment as well as recover energy from the treated wastewater.

Photocatalytic treatment as a polishing step for the degradation of bio‐recalcitrant fractions of winery wastewater under solar, UVA‐LED, and blacklight irradiation

AbstractBACKGROUNDThis study investigates, for the first time, the most beneficial conditions for photocatalytic oxidation under ultraviolet (UV) irradiation provided by either a solar simulator, UVA light‐emitting diode (UVA‐LED), or UVA blacklight lamp (UVA‐BL) as a post‐treatment step for the degradation of the residual COD and color in winery wastewater (WiWW) after biological treatment.RESULTSThe effect of WiWW dilution (0, 50%), TiO2 concentration (0–1000 mg/L), catalyst type (TiO2, ZnO), pH (3, 6, 8.4), H2O2 addition (0–1000 mg/L), and treatment time on process efficiency was evaluated. At the best‐assayed conditions (1000 mg/L TiO2, 1000 mg/L H2O2), COD removal percentages in the range of 94–97% were obtained and color was removed by 99% within 180 min of treatment under all irradiation sources. The process was enhanced when the WiWW was subjected to 50% dilution and its pH was adjusted to 6. Among the three irradiation sources, UVA‐BL led to a marginally higher photocatalytic performance than solar and UVA‐LED, both of which achieved similar removal efficiencies. Regarding energy efficiency, UVA‐LED was found to be up to 1.7 times more energy efficient than UVA‐BL/TiO2. Finally, in most cases, the phytotoxicity of secondary effluent was eliminated during solar photocatalytic treatment.CONCLUSIONAlteration of basic operating parameters significantly improved process efficiency. In all cases, LED‐driven photocatalysis combined high removal performance and energy efficiency, proving to be an appropriate and sustainable alternative to solar photocatalysis for 24 h operation or for supplementary application during the harvest, when the majority of WiWW is generated. © 2022 Society of Chemical Industry (SCI).

The impact of activation temperature and time on the characteristics and performance of agricultural waste-based activated carbons for removing dye and residual COD from wastewater

The release of colored compounds containing wastewaters into the environment and surface water resources is known as a serious threat to public health and aquatic ecosystems. Accordingly, in the present study, cost-effective and efficient activated carbons (ACs) were prepared employing agricultural wastes (walnut shell) over a two-stage physical activation under CO2 at various activation temperature (700–1000 °C) and time (30–120 min). The prepared ACs were characterized by various analyses of SEM, XRD, FTIR, BET, and also their adsorption performance was checked via the measure of methylene blue (MB) number in order to determine selected activated carbon. According to the reported results, the AC produced at the activation temperature and time of 900 °C and 60 min, respectively, indicated better physicochemical properties and more favorable performance compared to others. The selected AC had the highest BET surface area (SBET) of 903.9 m2/g and the greatest adsorption capacity of 307.4 mg/g as the MB number. Furthermore, the adsorption capacity as iodine number and pH of point of zero charge (pHPZC) were reported to be 1150 mg/g and 4.6, respectively, for the selected AC. In the following, the performance of the selected AC was further evaluated as adsorption of synthetic (MB) and natural dyes from biologically treated wastewaters under different conditions. Maximum absorption capacity of the MB was obtained to be 307.45 mg/g at optimum conditions (the adsorbent dosage of 1 g/L, adsorbate concentration of 400 mg/L, contact time of 3 h, and agitation speed of 150 rpm). Moreover, the selected AC demonstrated appreciable performance at adsorbent dosage of 1 g/L and the contact time of 240 min using three biologically treated wastewaters. The highest adsorption capacity of 395.7 mg/g was obtained by the biologically treated baker's yeast wastewater as the adsorbate. The selected AC revealed the highest conformity with the Langmuir isotherm model (R2 = 0.9999) and the Pseudo-second-order kinetic model (R2 = 0.9994).

Photo-fermentative hydrogen production from cheese whey: Engineering of a mixed culture process in a semi-continuous, tubular photo-bioreactor

This work approaches the engineering of photo fermentative hydrogen production from cheese whey, for the scale-up of photo-bioreactors. Firstly, a brief review has been performed to identify the optimal reactor configuration as well as the main literature lacks. Results of the review analysis suggest that tubular photobioreactors are effective for the photo fermentation process. On the other hand, one of the main drawbacks to the scale-up of the proposed systems is the wide use of pure cultures, which requires aseptic environments and carefully controlled conditions. Based on the critical evaluation of the state of the art, a semi-continuous tubular photobioreactor, performing mixed culture hydrogen production from cheese whey, under unsterile conditions, was started up. Due to the lack of studies in this field, the case study was developed to provide a methodology for the reactor start-up, which represents the most critical phase of its operation. Preliminary tests were performed to choose the optimal operating conditions. To assess the effectiveness of cheese whey, results were compared to those obtained from a glucose based synthetic substrate, under steady state conditions. Experimental outcomes showed that the optimal Hydraulic Retention Time was 2 days and the most appropriate recirculation/pumping system consisted of an intermittent peristaltic pump. The semi-continuous feeding of cheese whey resulted in 87 mL/L d of hydrogen, which was similar to the productivity obtained under glucose feeding. The characterization of the residual organic content further indicated the possible accumulation of polyhydroxyalcanohates, which was estimated to constitute about the 40% of the total residual COD. These results further addressed the identification of key points to be better investigated to promote the effective photo fermentation scale-up for cheese whey valorization, such as the enhancement of the illumination conditions as well as the search for strategies to improve the uniform exposure of microbial cells to light.

TERI Advanced Oxidation Technology (TADOX®) to treat industrial wastewater with integration at pre- and post-biological stage: case studies from India

Abstract The current problem with industrial wastewater treatment is that we rely heavily on biological treatment systems without realising that these have severe limitations in terms of shock load-bearing capacities, ineffectiveness against removal of toxicity and recalcitrant and dissolved organics. However, biological systems have their own benefits as well. Therefore, it is essential to support them with integration of advanced oxidation nanotechnology (AON) interventions, which are expected to address these challenges. In this pursuit, The Energy and Resources Institute (TERI) has developed an AON-based wastewater treatment technology called TERI Advanced Oxidation Technology (TADOX®). This paper presents two sections of three case studies each, to showcase how TADOX® technology intervention at pre-biological and post-biological treatment helps in achieving adequate treatment. In the first section, TADOX® has been implemented at pre-biological stage for three highly polluting streams from (i) phenolic wastewater from a 2,4-dichlorophenoxyacetic acid (2,4 D) plant from a Gujarat pesticide manufacturing company, (ii) phenolic wastewater from an anisole plant of a Gujarat chemical industry, and (iii) hydrocarbon-rich effluent from the Jharkand oil and gas sector. Pre-biological integration is expected to support biological treatment by reduction in COD, toxicity, microbial growth hindering compounds and increase in biodegradability (BOD to COD ratio). The second section in the paper explores the implementation potential of TADOX® to treat biologically treated streams from (i) Uttarakhand pharmaceutical, (ii) Uttar Pradesh tannery and (iii) Uttar Pradesh slaughterhouse. The post-biological integration is expected to remove residual COD, colour, BOD and odour leading to treated water meeting norms for safe surface discharge and water reuse. Presented studies from India may be useful and relevant to other developing countries as a possible approach to sustainably manage water resources, together meeting the challenges of economic growth, industrial development, and regulatory and environmental compliance.

Cost-effective Application of Fenton Oxidation Process to the Biologically Treated Leachate Containing Refractory Organics and Nitrite

This paper presents an economic application of Fenton oxidation process to biological treatment effluent containing high-strength nitrite and refractory organics. To cope with two major drawbacks in applying Fenton oxidation process to the nitrite-rich effluent simultaneously, i.e. expensive reagent and excessive sludge production, we examined two pretreatment methodologies prior to the application of Fenton process in the following way. First, residual nitrite in the biologically treated leachate (BTL) was removed with iron-catalyzed air oxidation (ICAO) as a cost-effective pretreatment. The time necessary for ICAO reaction is approx. 5 hr. Secondly, to reduce organic loads iron sludge was regenerated for an alternative coagulant. With the regenerated iron sludge, the dose of Fenton’s regent can be reduced by half to remove residual COD in the BTL.

Treatment of cauliflower processing wastewater by nanofiltration and reverse osmosis in view of recycling

The vegetable industry is a large consumer of drinking water. This paper investigates the possibilities of Reverse Osmosis (RO) or tight Nanofiltration (NF) for the treatment of cauliflower blanching wastewater with a view to recycling within the production unit. Ultrafiltration at 100 000 g mol −1 molecular weight cut-off was necessary to decrease turbidity below 1 NTU as required before NF or RO. Three NF (DK, NF270 and SRD3) and one RO (ESPA4) membranes were tested at bench-scale in a crossflow filtration mode. Only RO allowed to reach the desired quality for a reuse purpose, with an acceptable residual COD content of 225 mg O 2 L −1 . The Solution-Diffusion model was validated for the transfer of glucose and fructose, for NF270, DK and ESPA4 membranes and their permeability coefficients calculated. • Ultrafiltration followed by reverse osmosis allows to consider recycling of cauliflower wastewater. • ESPA4 membrane at 19 bar leads to 70 L h −1 . m −2 permeate flux and 95% COD rejection. • Solution-diffusion model considering concentration polarization was successfully applied. • DK, NF270 and ESPA4 permeabilities for fructose and glucose were determined. • Nanofiltration with 150–300 g mol −1 molecular weight cut-off is not suitable, due to the transfer of small metabolites.

Catalytic ozonation of real textile wastewater by magnetic oxidized g-C3N4 modified with Al2O3 nanoparticles as a novel catalyst

• The graphitic carbon nitride was oxidized by a novel method. • The BET surface area increased from 57.31 to 115.41 m 2 /g after Al 2 O 3 immobilization. • Catalytic ozonation using O@g-C 3 N 4 /Al 2 O 3 nanocatalyst resulted in 75% COD removal. • Textile wastewater effluent resulted in meeting EPA discharge criteria. • BI enhanced from 0.27 to 0.74 after 60 min of catalytic ozonation. Textile wastewater has been known for its high resistance toward conventional wastewater treatment because of its low biodegradability index (BI). In this study, the catalytic ozonation of real textile wastewater has been carried out using a novel magnetic oxidized g-C 3 N 4 / Al 2 O 3 (O@g-C 3 N 4 / Al 2 O 3 ) nanocatalyst. The effect of Al 2 O 3 content on the catalytic activity of nanocatalyst was investigated, and the results marked that the nanocomposite with the equal mass ratio of Al 2 O 3 to magnetic oxidized g-C 3 N 4 had the best performance. The material characterization was investigated using Field-Emission Scanning Electron Microscopy (FESEM), Vibrating Sample Magnetometer (VSM), X-Ray Diffraction (XRD), Dynamic Light Scattering (DLS), Fourier Transform Infrared (FTIR), and Brunauer-Emmett-Teller (BET) analysis, respectively. The effect of pH, catalyst dosage, and oxygen flow rate were studied, and the maximum performance was achieved at a pH of 7.1, the oxygen flow rate of 1.5 L/min, and the catalyst dosage of 0.5 g/L. The ozonation kinetics plots of the single ozonation process (SOP) and catalytic ozonation process (COP) showed two different linear parts. The rate of COD removal was much greater in the first 5 min of ozonation because of oxidation of easily degradable compounds. Furthermore, the rate constant of COP after 5 min of ozonation was four times higher compared to that of SOP, indicating the greater potential of COP toward oxidation of recalcitrant compounds. However, the rate constant in the first 5 min of COP was only two times greater than that of SOP, which is a result of oxidation of easily degradable compounds. The COD and color removal of 77% and 99% and BI of 0.74 were attained in 60 min in the COP process. However, treated wastewater resulted in 127 mg/L residual COD of initial wastewater after catalytic ozonation meeting EPA standards discharge for textile and dyeing industry effluent. The results of regeneration experiments indicated that the COD removal decreased only about 8% after five regeneration cycles.

The NEWgeneratorTM non-sewered sanitation system: Long-term field testing at an informal settlement community in eThekwini municipality, South Africa

Globally, there is a dire need for a new class of advanced non-sewered sanitation systems (NSSS) to provide onsite wastewater treatment that is capable of meeting stringent discharge or reuse criteria. These systems need to be simple to operate and maintain, reliable, and resilient to unreliable electrical service. The NEWgenerator (NG) is a compact, automated, solar-powered wastewater treatment system comprised of three major treatment processes: anaerobic membrane bioreactor (AnMBR), nutrient capture system (NCS) with ion exchange and carbon sorption, and electrochlorination (EC). The NG system operated at an informal settlement community in South Africa over a 534 d period, treating high-strength blackwater (BW) and yellow water (YW) from a public toilet facility. Over three test stages (BW, BW + YW, BW) that included several periods of dormancy, the NG system was able to provide a high level of removal of total suspended solids (97.6 ± 3.1%), chemical oxygen demand (94.5 ± 5.0%), turbidity (96.3 ± 9.7%), color (92.0 ± 10.5%), total nitrogen (82.1 ± 24.0%), total phosphorus (43.0 ± 22.1%), E. coli (7.4 ± 1.5 LRV, not detected in effluent), and helminth ova (not detected in effluent). The treatment levels met most of the ISO 30500 NSSS standard for liquid effluent and local water reuse criteria. A series of maintenance events were successfully conducted onsite over the 534 d field trial: two membrane cleanings, two NCS regenerations, and granular activated carbon replacement. Desludging, a major pain point for onsite sanitation systems, was unnecessary during the field trial and thereby not performed. The AnMBR performed well, removing 94.5 ± 5.0% of the influent COD across all three stages. The high COD removal rate is attributed to the sub-micron separation provided by the ultrafiltration membrane. The NCS was highly efficient at removing total nitrogen, residual COD and color, but the regeneration process was lengthy and is a topic of ongoing research. The EC provided effective disinfection, but frequent prolonged run cycles due to power supply and water quality issues upstream limited the overall system hydraulic throughput. This extended field trial under actual ambient conditions successfully demonstrated the feasibility of using advanced NSSS to address the global water and sanitation crises.

Water recovery and on-site reuse of laundry wastewater by a facile and cost-effective system: Combined biological and advanced oxidation process

Combined biological and physicochemical process was selected for treatment of laundry wastewater. The results show that after microbial adaptation, almost 91% of COD was removed at food to microorganism (F/M) ratio of 0.12 gBOD/gMLSS·d. Dehydrogenase activity of the biomass showed an increasing trend and finally reached 3.8 μgTFgbiomass.d corresponding to the highest process performance. 16SrRNA fragment and phylogenetic analysis identified Pseudomonas pharmacofabricae and Bacillus spp. as the dominant bacteria. The effluent of the biological process was then injected into the UV/O3 process for complete removal of residual COD and detergent. Finally, microfiltration and ultrafiltration were used to remove any remaining suspended solids. The operating cost analysis showed that 0.65 €/m3 treated wastewater is required for treatment of the laundry wastewater. Accordingly, the suggested combination of the biological and physicochemical process could be a promising and highly efficient process for treatment and reuse of laundry wastewater.

Heterogeneous electro-Fenton catalysis with self-supporting CFP@MnO2-Fe3O4/C cathode for shale gas fracturing flowback wastewater

Self-supporting electrodes have triggered great interests in improving electro-Fenton (EF) system for degradation of refractory organic pollutants. In this work, a novel self-supporting carbon fiber paper (CFP) electrode modified by transition metals, e.g. Fe and Mn, was fabricated and employed as a heterogeneous EF cathode. The prepared electrode exhibited excellent degradation for a number of typical organic pollutants along with superior stability. Remarkably, a high removal efficiency was achieved in the EF treatment of shale gas fracturing flowback wastewater. Results indicated that 65.2% TOC and 74.8% COD were eliminated after 4 h degradation. The residual COD value of the real wastewater was 80 mg L−1, meeting the emission requirement of the integrated wastewater discharge standard (COD＜100 mg L−1) with a low specific energy consumption of 6.9kWhkg−1COD−1. This work demonstrates a competing alternative for efficient decontamination of real wastewater using an electro-Fenton strategy with a low-cost electrode.