Chemical Oxygen Demand Reduction Research Articles

Bridging energy and microbes: How the anodic potential of microbial electrolysis cell improves anaerobic digestion

Enhanced methane production is typically attributed to cathodic electron transfer in microbial electrolysis cell coupled anaerobic digestion (MEC-AD). This study shifts focus to the overlooked anodic reactions, illuminating their integral role in methane production during MEC-AD. Experimentation at controlled anodic potentials established 0.6 V as optimal; this parameter yielded an 87 % increase in methane and a 53 % reduction in chemical oxygen demand. The anode enriched for electroactive bacteria, notably Pseudomonas, facilitating the oxidation of propionic and butyric acids into acetic acid, thus providing sufficient substrate for methanogens. The modulation of the NADH/NAD+ ratio by the anodic potential proved central to converting carbohydrates and volatile fatty acids into acetic acid. Selective potentials enriched microbes proficient in anaerobic digestion, corroborated by bioinformatics analyses indicating enzymatic upregulation in key pathways. This investigation provides actionable insights into optimizing MEC-AD systems, advancing bioenergy recovery technologies.

N/NiO-ornated graphitic fiber-engrained micro-carbon beads: Innovative packed bed type capacitive electrodes for microbial fuel cells

Nitrogen-doped nickel oxide-catalyzed carbon nanofiber-decorated micro-activated carbon beads (NiO-N-CNF/ACB) were synthesized through suspension polymerization and employed as capacitive fixed-packed bed electrodes in microbial fuel cell (MFC-) for wastewater treatment and byproduct electricity generation. The capacitive electrode was meticulously designed to manifest enhanced characteristics crucial for MFC applications. The large specific surface area of NiO-N-CNF/ACB offers advantages in terms of catalytic sites and stored charge produced by electrogenic bacteria to form an electrochemical double-layer on the electrode, thereby enhancing power generation. The incorporation of NiO, coupled with graphitic contents, biocompatibility, and the formation of three-dimensional structures, contributes to the excellent performance of the NiO-N-CNF/ACB electrodes. The NiO-N-CNF/ACB electrodes-based MFC operated in batch mode demonstrated an open-circuit potential of 0.8 V, an impressive maximum power density of 2900 mW/m3, and a noteworthy 74 % reduction in chemical oxygen demand. Additionally, the synthesized NiO-N-CNF/ACB exhibited a remarkable specific capacitance 754 F/g and a cumulative total charge of 255 C/g, surpassing the corresponding values for plain NiO-ACB and ACB. This study positions NiO-N-CNF/ACB as a promising capacitive packed bed electrode material, offering enhanced power generation, efficient wastewater treatment, and superior biofilm formation, thereby advancing the potential for sustainable and efficient MFC systems.

Treatment of aircraft maintenance wastewater by coupling low-temperature evaporation with Fe–C micro-electrolysis-configured ozonation

ABSTRACT A novel approach combining low-temperature evaporation with Fe–C micro-electrolytic ozone oxidation has been devised for treating substantial volumes of high-concentration organic cleaning wastewater generated during aircraft maintenance activities. The findings from experiments demonstrate impressive average removal rates for various contaminants, including chemical oxygen demand (93.1%), oil concentration (94.0%), suspended solids (98.9%), turbidity (98.8%), chroma (93.8%), total nitrogen (93.7%), and total phosphorus (99.2%). Within this integrated system, the synergistic effects between ozone oxidation, catalytic fillers, and electrochemical processes significantly enhance pollutant removal efficiency. The chemical oxygen demand reduction rates of the cleaning wastewater derived from engine maintenance, mechanical and electrical maintenance, aircraft accessory maintenance, and mixed wastewater exceed 98%. The optimal reaction times for four types of wastewater are 150, 120, 90, and 120 min, respectively. The time can be adjusted according to the different treatment objects in actual operation projects. Moreover, the average concentration efficiency achieved surpasses 92% while meeting all effluent quality standards set forth by municipal sewage networks, and it has reduced the disposal cost of the enterprise by about 80%. This technology provides enterprises with an effective way to reduce energy consumption and expenses.

Leveraging microbial synergy: Predicting the optimal consortium to enhance the performance of microbial fuel cell using Subspace-kNN

Microbial Fuel Cells (MFCs) are a sophisticated and advanced system that uses exoelectrogenic microorganisms to generate bioenergy. Predicting performance outcomes under experimental settings is challenging due to the intricate interactions that occur in mixed-species bioelectrochemical reactors like MFCs. One of the key factors that limit the MFC's performance is the presence of a microbial consortium. Traditionally, multiple microbial consortia are implemented in MFCs to determine the best consortium. This approach is laborious, inefficient, and wasteful of time and resources. The increase in the availability of soft computational techniques has allowed for the development of alternative strategies like artificial intelligence (AI) despite the fact that a direct correlation between microbial strain, microbial consortium, and MFC performance has yet to be established. In this work, a novel generic AI model based on subspace k-Nearest Neighbour (SS-kNN) is developed to identify and forecast the best microbial consortium from the constituent microbes. The SS-kNN model is trained with thirty-five different microbial consortia sharing different effluent properties. Chemical oxygen demand (COD) reduction, voltage generation, exopolysaccharide (EPS) production, and standard deviation (SD) of voltage generation are used as input features to train the SS-kNN model. The proposed SS-kNN model offers an accuracy of 100% during training period and 85.71% when it is tested with the data obtained from existing literature. The implementation of selected consortium (as predicted by SS-kNN model) improves the COD reduction capability of MFC by 15.67% than that of its constituent microbes which is experimentally verified. In addition, to prevent the effects of climate change and mitigate water pollution, the implementation of MFC technology ensures clean and green electricity. Consequently, achieving sustainable development goals (SDG) 6, 7, and 13.

ZnO nanostructures grown from spent batteries: Ambient catalytic aspects and novel mechanistic insights

The present work includes a facile and economic microwave assisted hydrothermal synthesis of Zinc Oxide (ZnO), Diethylene Triamine Pentaacetic Acid (DTPA) stabilized Zinc Oxide (ZD) and DTPA stabilized Silver doped Zinc Oxide (ZAD) nanostructures using Zn from spent alkaline batteries. The synthesised nanostructures were well characterised using electronic, vibrational and X-Ray spectroscopic techniques as well as thermal and microscopic techniques revealing the successful stabilisation of DTPA in ZD and doping of Ag in ZAD. The Fourier Transform Infrared Spectroscopy (FTIR) spectra showed peaks characteristic to the presence of ZnO in the fingerprint region and those to the presence of DTPA. The X-Ray Diffraction Spectroscopy (XRD) pattern of ZnO, ZD and ZAD indicated the hexagonal wurtzite structure of ZnO and face centred cubic metallic Ag in ZAD. The Transmission Electron Microscopy (TEM) images revealed rod shaped morphology for ZnO and spherical morphologies for ZD and ZAD. The nanostructures proved to be efficient catalysts to achieve 100 % degradation of Malachite Green, Crystal Violet and Reactive Blue-21 and their binary mixtures under ambient conditions in presence of Hydrogen peroxide (H2O2). ZAD exhibited relatively rapid degradation with rate constants 0.754 min−1, 0.187 min−1 and 0.0150 min−1 for MG, CV, and RB-21 respectively as well as 99 % reduction in Chemical Oxygen Demand (COD) value of the dye solutions. Scavenging studies and Electron Paramagnetic Resonance (EPR) studies using different spin trapping agents revealed the involvement of singlet oxygen species, hydroxyl radicals (OH.) and superoxide radicals (O2.-) in the degradation process. This work aligns with Sustainable Development Goals 6, 12 and 13.

Potential of Eco-enzyme Averrhoa bilimbi L. Fruit as an Innovation in Tempeh Wastewater Treatment in Plaju District, South Sumatra

Tempeh home industries have been established in residential areas, one of which is in the assisted village of PT Pertamina Internasional RU III Plaju Factory, Palembang, South Sumatra. Eco-enzyme is one of the methods for processing and reducing pollutant organic matter in liquid waste. This study aims to determine the eco-enzyme characteristics of Averrhoa bilimbi L. fruit and exploit its potential to reduce chemical oxygen demand (COD), total suspended solid (TSS), and total dissolved solid (TDS) in tempeh wastewater. Eco-enzymes are characterized by measuring pH, COD, TSS, TDS, and most probable number (MPN). The reduction in COD, TSS and TDS of tempeh wastewater was observed using a simple bioreactor which was treated with the addition of 10% eco-enzyme (three replicates) and without the addition of eco-enzyme (control). The characterization results showed that the eco-enzyme of A. bilimbi L. fruit had a pH of 1.84, COD of 85.33 mg/L, TSS of 440 mg/L, TDS of 15,800 mg/L, protein concentration of 0.459 U/mg, and MPN value of 0.03 CFU/100 mL. The COD value of tempeh liquid waste can be reduced from the initial COD of 256 to 154.67 mg/L. The TSS value of tempeh wastewater decreased by 60% from the initial value of 4,000 mg/L. It takes 18 days to reduce the TSS content below the quality standard. The TDS value of tempeh liquid waste can be reduced by 70% from the initial TDS of 7,333.33 to 1,666.67 mg/L.

Phenolic compounds, chemical oxygen demand and total carbon organic removal from olive mill wastewater by activated persulfate oxidation using full factorial design

Abstract This study investigated phenolic compounds (PC), chemical oxygen demand (COD) and total carbon organic total (TOC) removal from olive mill wastewater OMW via activated persulfate oxidation. Persulfate (PS, S 2 O 8 2 − ${\mathrm{S}}_{2}{\mathrm{O}}_{8}^{2-}$ ) was activated by thermal and transition metal to form sulfate radical ( S O 4 · − $\mathrm{S}{\mathrm{O}}_{4}^{{\cdot}-}$ ). A mathematical model was developed, and the process variables, namely oxidant dose (0.05 and 0.1 g L−1), type of catalyst (Fe2+, Cu2+), time of treatment (5 and 20 min) and temperature (25 and 45 °C) and their interaction were examined using a full factorial design methodology 24. The results indicated that activation methods are efficient for reduction of PC and COD in OMW. Under conditions maximizing responses, there was a considerable increase in PC, COD and TOC removal (44.73 %, 62.39 % and 95.13 % respectively). The correlation coefficient values of the polynomial model were found to be 90 % (CP removal) and 86 % (COD removal). The predicted values obtained using the response functions agreed well with the experimental data.

Insights into anode substrate optimization in bioelectrochemical systems for efficient cathodic lanthanum recovery during wastewater treatment

Wastewater containing lanthanum (La) is a significant global environmental concern, prompting the development of various treatment technologies. Existing methods are often costly, generate secondary waste streams, and prioritize removal over recovery. This study investigated La recovery in bioelectrochemical systems (BESs) using diverse substrates (acetate, lactate, methanol, and glucose) with anaerobic sludge as the inoculum. The results showed that acetate-fueled BESs achieved the highest power density (439.29 mW/m2), a chemical oxygen demand (COD) reduction efficiency of 96.52 ± 1.56 %, and a coulombic efficiency of 35.18 ± 1.86 %. Acetate and lactate-fed biofilms achieved high La recovery rates (98.96 ± 1.64 % and 98.24 ± 2.16 %, respectively) by the 36th hour. After 48 h, La was undetectable in these systems, surpassing the environmental guidelines. In contrast, methanol and glucose-fed systems yielded lower recoveries (80 ± 0.04 % and 32.8 ± 1.4 %, respectively) after 48 h, with final La concentrations remaining above the guideline levels. Acetate also enhanced the production of extracellular polymeric substances (EPS). Microbial community analysis revealed that Desulfovibrio and Geobacter predominated in acetate-fed microbial fuel cells (MFCs), while Klebsiella and Simplicispira were dominant in glucose and methanol-fed MFCs, respectively. Recovered La deposits, identified as La2O3 and La(OH)3, on the cathodic surfaces were confirmed via SEM-EDX, XRD, and XPS analyses. This study demonstrates the potential of BESs for efficient La recovery from wastewater.

Wastewater treatment process using immobilized microalgae.

Microalgae biomass products are gaining popularity due to their diverse applications in various sectors. However, the costs associated with media ingredients and cell harvesting pose challenges to the scale-up of microalgae cultivation. This study evaluated the growth and nutrient removal efficiency (RE) of immobilized microalgae Tetradesmus obliquus in sodium alginate beads cultivated in swine manure-based wastewater compared to free cells. The main findings of this research include (i) immobilized cells outperformed free cells, showing approximately 2.3 times higher biomass production, especially at 10% effluent concentration; (ii) enhanced organic carbon removal was observed, with a significant 62% reduction in chemical oxygen demand (383.46-144.84 mg L-1) within 48 h for immobilized cells compared to 6% in free culture; (iii) both immobilized and free cells exhibited efficient removal of total nitrogen and total phosphorus, with high REs exceeding 99% for phosphorus. In addition, microscopic analysis confirmed successful cell dispersion within the alginate beads, ensuring efficient light and substrate transfer. Overall, the results highlight the potential of immobilization techniques and alternative media, such as biodigested swine manure, to enhance microalgal growth and nutrient RE, offering promising prospects for sustainable wastewater treatment processes.

Application of algal-mycelial pellets in the treatment of the mariculture wastewater

Hypersaline mariculture wastewater necessitates treatment prior to its discharge into marine environments. Algal-mycelial pellets (AMPs), known for their cost-effectiveness, energy efficiency and sustainability, have not been previously explored for their flocculation and pollutant removal capabilities in hyperhaline conditions. This work employed an orthogonal test design to investigate the effects of nine factors at three levels on the treatment efficiency of mariculture wastewater using Chlorella sp. TNBR1 and Aspergillus niger AMPs. The comprehensive optimal conditions for achieving the highest flocculation efficiency and pollutant removal are determined to be a temperature of 30 °C, light intensity of 6000 lux, a 12:0 light-dark cycle, an initial pH of 6, a microalgal density of 11.25 × 106 cell/mL, microalgal growth phase at the early logarithmic stage, a fungal spore density of 9.00 × 105 spore/mL and a fungal pellet phase of 60 h. Under such conditions, the treatment of nonsterile actual mariculture wastewater with Chlorella sp. TNBR1 and Aspergillus niger AMPs results in a 93.35 %±7.20 % reduction in chemical oxygen demand (COD), 92.83 %±7.29 % reduction in total nitrogen (TN), 100 % removal of total phosphorus (TP), and a flocculation efficiency of 69.21 %±5.36 %. These findings confirm that AMPs are a viable solution for effectively treating COD, TN and TP in real hypersaline mariculture wastewater, while also facilitating the flocculation and harvesting of microalgae.

Treatment of the Textile Wastewater using Malaysian Ganoderma lucidum Mycelial Pellets

Purification of textile wastewater using biomass and in particular different fungi is gaining exponential interest to minimize the impacts of current physical-chemical and biological wastewater treatment by-products. This study investigates the potential of Malaysian Ganoderma lucidum mycelium pellets (GLMP) for the decontamination of wastewater samples received from a commercial textile manufacturer. All studies were performed under ambient temperature (26-35 ℃) and unsterilized conditions using a simple bioreactor design (stirred batch bioreactor) for a more practical assimilation of the current available wastewater treatment process system. The optimal conditions of adsorption by GLMP were determined by variation effects of adsorbent concentration (0, 8.75, 12.5 and 25 g/L), pH (unadjusted 7.10 – 8.22, 4 and 6), and wastewater dilution factor (1:0, 1:4, and 2:3, v/v). This method was proved to be effective in both decolorization and chemical oxygen demand (COD) reduction, simultaneously. The most significant percentage of decolorization observed was 77.24% in a 72 h treatment, whereas COD reductions were 78.32% in a 36 h treatment. The present study fits both Langmuir and Freundlich adsorption isotherms as the values of R2 both model were close to 1, indicating the favorable adsorption of dyes towards Malaysian GLMP.

Wastewater treatment using a microalgae consortium mainly composed of chlorella, in Mexico

The bioremediation capacity of microalgae found in the wastewater channels in Irrigation District 03 (DR03) in Mexico was studied. The study evaluated the effect of pH, aeration, light intensity, and water source on the productivity, culture time, and composition of the microalgal biomass, predominantly made up of Chlorella vulgaris spp. Parameters such as Chemical Oxygen Demand (COD), total solids (TS), and turbidity were monitored to assess the efficiency and bioremediation capacity of the microbial consortium. The yield production of microalgal biomass was measured to evaluate the amount produced per unit volume of treated water. Two culture conditions were assessed: uncontrolled and controlled conditions of aeration and lighting. Under controlled culture conditions, a productivity of 0.031 g L−1 d−1 biomass with 17% lipidic fraction and 37.65% ash content was observed, along with a reduction in COD and turbidity by 57 and 85%, respectively. A biomass productivity of 0.024 g L−1 d−1 was obtained.

Treatment of real carwash wastewater using high-efficiency and energy-saving electrocoagulation technique

This study focused on the treatment of actual wastewater from a car wash facility using electrocoagulation. The primary objective was to decrease chemical oxygen demand (COD) and eliminate turbidity by employing various electrodes such as Stainless Steel (SS) 304, Galvanized Iron (GI), and aluminum foil (α-Al) in a batch configuration. Several factors including contact time, current density, initial pH, and electrode material were examined to optimize process efficiency. The sludge generated during electrocoagulation was analyzed using Scanning Electron Microscopy/Energy-Dispersive X-ray Spectrometry (SEM-EDS). The results indicated that COD removal efficiency initially decreased between 30 and 60 min before improving. The data for COD, turbidity, and total phosphate reduction aligned well with the pseudo-first-order kinetic model, with R2 values of 0.275, 0.898, and 0.522, respectively. Minor variations were observed in pH, Total Dissolved Solids (TDS), Electrical Conductivity (EC), and alkalinity, while the temperature increased from 12 to 18.6 °C. Optimal removal efficiency for turbidity, total phosphate, and COD was achieved at pH = 6. The study demonstrated that higher current density resulted in enhanced COD reduction and turbidity removal. Chloride levels decreased with increasing applied current. The α-Al electrode exhibited superior performance compared to SS 304 and GI electrodes, with notable pH fluctuations during the process. UV–visible absorption spectra indicated differences in treated wastewater patterns based on the electrode utilized. SEM analysis revealed distinct characteristics of sludge produced by different electrodes. Energy and electrode consumption varied among the electrodes, with SS 304 displaying the lowest values.

COD, color, and turbidity reduction from surface water using natural coagulants: Investigation and optimization

Several researchers have established the performance of natural coagulants in treating water via coagulation and flocculation process. This study is aimed at investigating the use of Linseed-based natural coagulant for treating surface water, especially in rural areas where most people cannot afford the high cost of chemically coagulant-treated water. The influence of various experimental parameters such as coagulant dosage, pH, and stirring time on the percentage of color, chemical oxygen demand (COD), and turbidity removal has been studied. The experimental results showed that the use of Linseed has shown high removal of color (97.76 %), turbidity (96.58 %), and COD (90 %) at pH values of 3.03 using a 1.75 g/L coagulant dosage and a stirring time of 37.37 minutes. Upon the numerical optimization of the parameters investigated, the removal of color, turbidity, and COD were found to be 94.0 %, 95.5 %, and 86.35 %, respectively, at pH of 7.0, coagulant dosage of 2.5 g, and stirring time of 40 minutes. The findings showed that Linseed has excellent coagulating competence and is very effective in the removal of impurities from surface water.

Biopolymeric Composite Columns for Improving Water Quality in a Freshwater Stream Receiving Wastewater Treatment Plant Effluents

Inefficiently treated wastewater, which contains a high concentration of pollutants, is hazardous when it is mixed with the clean water of rivers and lakes. Nitrate in particular is a major global problem that leads to eutrophication and poses a threat to both aquatic ecosystems and human health. To address this issue, this work assessed the efficiency of polymeric cryogel (PC) and biopolymer (EPS)-blended composites (EPS@PC) in removing nitrates. Tests were also conducted to quantify the decrease in phosphate, chloride ions, and chemical oxygen demand (COD) in real water samples taken from the Ankara stream, which receives effluents from both urban (UWTP) and industrial (IWTP) wastewater treatment plants. Five different columns with varying adsorptive properties were prepared, some of which were combined with iron. The EPS-@PC-C5 column demonstrated the highest adsorption ratio for nitrate removal compared to the other tested columns. The EPS@PC-C5 achieved a high removal efficiency of 126.38 mg nitrate/g and showed COD reduction ranging from 60.2 to 94.1%. The removal ratio of chloride concentration varied between 56.0 and 75.7%, while the removal of phosphates ranged from 87 to 99%. Columns composed of EPS (EPS@PC) with both negatively and positively charged ligands are dependable and suitable options for water remediation.Graphical

Developing a novel continuous-flow cascade photocatalytic system for effective sulfamethoxazole elimination from hospital wastewater

In this study, we introduce a novel continuous-flow cascade photocatalytic system specifically designed to efficiently remove sulfamethoxazole (SMX) from hospital wastewater, addressing the critical need for sustainable pharmaceutical wastewater treatment. The system utilizes a carbon sponge-based TiO2 photocatalyst synthesized via a hydrothermal process under mild conditions. The system’s design incorporates multiple stages in a cascade configuration, meticulously optimized to enhance photocatalytic efficacy, thereby significantly improving the rate of SMX elimination while minimizing energy consumption. The study encompasses comprehensive characterization of the photocatalyst, including matching its absorption spectrum to the emission spectrum of the light source, as well as fine-tuning key operational parameters such as catalyst quantity, flow rates, and cascade configuration. Real-world application tests confirm the system’s efficiency, achieving approximately 80 % SMX removal efficiency alongside a notable reduction in Chemical Oxygen Demand (COD) levels. Furthermore, the system’s energy efficiency, as reflected by an Electrical Energy per Order (EEO) value of 7.53 kWh/m3, highlights its potential for scalable and sustainable wastewater treatment solutions. This study not only contributes significantly to the field of environmental catalysis but also represents a significant advancement in sustainable environmental management, offering a promising solution to the urgent challenge of pharmaceutical pollution in water sources.

Green marvel: Harnessing spinach leaves' power for enhanced photodegradation of various effluents with biogenic ZnO nanoparticles

This study investigates the use of ZnO NPs (Zinc oxide nanoparticles) derived from spinach leaf extracts in a sustainable photocatalytic technology to enhance the decomposition of hazardous effluents from refineries and paper mills. The biosynthesized ZnO NPs were characterized through X-ray diffraction (XRD), UV-Vis spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The XRD analysis reveals that ZnO NPs possess a hexagonal wurtzite structure, exhibiting a preferred arrangement of (101) planes. The synthesized ZnO NPs have a spherical shape, as seen in the SEM images. TEM analysis detected the size of the ZnO NPs to be between 35 and 40 nm. The results indicate that ZnO NPs produced via biosynthesis have photocatalytic activity in efficiently decomposing the organic chemicals found in gasoline refining effluent when exposed to light. At a pH of 8, the ZnO NPs exhibited the highest rate of degradation for toluene (84.26 %) and xylene (90.36 %) after being exposed to simulated sunlight for 240 min. In the context of the photocatalytic treatment of paper mill effluents, it has been shown that the subsequent cycles resulted in a reduction in chemical oxygen demand (COD) levels of 81.24 %, 74.14 %, 68.92 %, 60.24 %, and 53.82 %, respectively.

Tequila Vinasse Treatment in Two Types of Vertical Downflow Treatment Wetlands (with Emergent Vegetation and Ligninolytic Fungi)

The aim of this study was to evaluate and compare the efficiency of two types of vertical downflow wetlands (VDFWs) (with the presence of ligninolytic fungus Trametes versicolor and planted with Iris sibirica) for the treatment of tequila vinasses (TVs) as a secondary treatment; control systems with only a filter medium were also included. The systems operated with a 7-day run/resting mode of operation. Various water quality parameters were analyzed in both the influent and the effluents, namely total suspended solids (TSS), chemical oxygen demand (COD), biological oxygen demand (BOD5), total organic carbon (TOC), pH, electrical conductivity (EC), true color and turbidity, total phosphorus (TP), total nitrogen (TN), etc. The two types of VDFWs as well as the control treatment were effective in reducing the different pollutants (p < 0.05); however, planted systems showed a tendency toward higher efficiencies. With an influent concentration of 49,000 mg L−1 and an organic loading rate of 4942 g COD m−2d−1, the COD reduction was around 40% in the planted systems, while in the other two, the reduction was 35%. Furthermore, TSS removals were 36, 20 and 16% in the VDFWs with vegetation, ligninolytic fungus and control systems, respectively. These results suggest that the fungus Trametes versicolor did not develop the desirable enzymatic expression for pollutant removal, probably as a result of the absence of aerobic conditions in the systems. Therefore, more research is needed to achieve a better fungal performance in VDFWs.

Ozonation for improved sludge reduction, cytotoxicity and estrogenicity control in anaerobic digestion

Anaerobic digestion (AD) is a common treatment for sludge reduction and stabilization. Simultaneously reductions in sludge chemical oxygen demand (COD), cytotoxicity, and estrogenicity are desired for safer handling and reuse. We investigated the impact, mechanism, and control strategy of ozonation (common sludge biodegradability method) on AD, methane production, and sludge cytotoxicity and estrogenicity modulations. Results revealed that ozone treatment could boost the methane production potential and rate by up to 36.5 and 69.2 %, respectively, but only after partial sludge digestion. Ozone modulated sludge cytotoxicity and estrogenicity, significantly improving this effect (maximum reductions of 28 and 23 %, respectively) by introducing anaerobically digested sludge to the ozonation module due to lowered volatile solids (VS) compared to raw sludge and less competition from the abundant biodegradable organics. Results support introducing ozone during AD for simultaneous COD reduction, and cytotoxicity and estrogenicity control.

Integration of coagulation–flocculation and photolysis processes for treating reverse osmosis concentrate (ROC) of pharmaceutical wastewater management

ABSTRACT This study provides novel insights into optimizing the integral treatment process, contributing to ROC treatment strategies. A comprehensive treatment approach for reverse osmosis concentrate (ROC) from pharmaceutical wastewater was investigated using an integral system consisting of a coagulation-flocculation and photolysis process. Ferric chloride (FC) and poly-aluminum chloride (PAC) are examined as coagulants within the range (0.1–1) gL−1, focusing on turbidity, chemical oxygen demand (COD), and total organic carbon (TOC) removal. The findings show that the optimal FeCl3 dosage is 0.4 gL−1, achieving significant turbidity reduction to 1 NTU. PAC at 0.2 gL−1 is optimal, reducing turbidity to 1 NTU and exhibiting non-linear behavior in COD and TOC removal, introducing them as a starting point to the post-treatment. Photolysis of treated samples at pH 7 yields COD reductions of 60.5% for PAC and 79.5% for FC, with respective TOC reductions of 79.5% and 75.23% over 360 min. At (pH 3.5) showed a significant reduction in the COD and TOC of treated ROC. The FC coagulant could decrease the COD from 261 to 5 mgL−1 (98% COD removal) and the TOC from 143.9 to 5 mgL−1 (74.8% TOC removal). The FAC coagulant could decrease the COD from 675 to 39 mgL−1 (93% COD removal) and the TOC from 186 to 13.1 mgL−1 (69.7% TOC removal). The conventional oxidant (H2O2) at optimal dosages enhanced COD and TOC removal at pH 7, with treated PAC and FeCl3 achieving 81.8% and 97.2% COD reduction and 89% and 98% TOC reduction at 360 minutes. These results were supported by the cost analysis in which this system was cost effective manner. This system can offer a solution for the efficient treatment of other types of industrial wastewater and open the door to new applications for water reuse on a broad scale, contributing to global water sustainability.