Organic Removal Efficiency Research Articles

Comparative Study of Modified and Conventional Bioballs for Organics Removal from Sewage Treatment

One of the challenges researchers have to deal with is achieving a high surface area for the biofilm plastic media used in wastewater treatment. This study evaluates bioball biofilm reactors using two different bioball configurations (modified and conventional bioballs). It evaluates the performance of each configuration based on the biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total suspended solid (TSS) while monitoring the pH, temperature, and DO during a 36-day operation time. The lab-scale rector consists of a 1m3 feeding tank, a 100 L aeration tank, and a settling tank with a two-hour retention time and operated using real domestic wastewater. The removal efficiency for all parameters shows that the modified bioball reactor shows better organic matter removal efficiency (7% better BOD removal, 6% better COD, and 4% better TSS removal). In summary, the modified bioball reactor has promising potential to facilitate the construction of compact treatment plants or modernize poor-performing treatment plants.

Mix-Charged Nanofiltration Membrane for Efficient Organic Removal from High-Salinity Wastewater: The Role of Charge Spatial Distribution.

The efficient removal of organic contaminants from high-salinity wastewater is crucial for resource recovery and achieving zero discharge. Nanofiltration (NF) membranes are effective in separating organic compounds and monovalent salts, but they typically exhibit an excessive rejection of divalent salts. Modifying the charge characteristics of NF membranes can improve salt permeation; however, the role of charge spatial distribution in governing salt transport behavior is not fully understood. In this study, we developed a mix-charged NF membrane with a horizontal charge distribution by employing interfacial polymerization combined with a polyester template etching and solvent-induced polyamine intercalation strategy. The ratio of positive to negative charge domains in the membrane can be precisely controlled by adjusting the aqueous monomer ratio and polyamine modifier type. X-ray photoelectron spectroscopy (XPS) depth profiling and separation layer thickness analysis confirmed the complete penetration of polyamines into the separation layer, providing direct evidence of the formation of horizontally distributed charge domains. This unique charge distribution results in a high charge density and a near-electroneutral surface, which facilitates the permeation of the divalent salts. The size-dependent "plug-in" modification and covalent cross-linking further reduce pore size, enhancing rejection of small organic molecules. Additionally, the membrane demonstrated exceptional antifouling performance against both negatively and positively charged pollutants, attributed to its unique charge distribution and smooth surface. Molecular dynamics (MD) simulations further revealed that weak electrostatic interactions and a tightly bound hydration layer contribute to the membrane's superior antifouling properties. This work provides valuable insights into the design of NF membranes with tailored microstructures and charge distributions for improved water treatment performance.

Algal organic matter (AOM) characterization and removal efficiency using various seawater desalination pretreatment techniques

Algal organic matter (AOM) characterization and removal efficiency using various seawater desalination pretreatment techniques

Evaluating the performance and stability of microalgal-bacterial granular sludge in municipal wastewater treatment plants.

The microalgal-bacterial granular sludge (MBGS) process shows potential for carbon-neutral wastewater treatment, yet its application in wastewater treatment plants remains underexplored. This study attempted to use a continuous-flow raceway reactor to treat real municipal wastewater using the MBGS process. The results showed that the removal efficiencies of organics peaked on the fifth day, while declining trends were observed for nitrogen and phosphorus removal. Microbial community and functional gene analyses indicated that the removal of organics, nitrogen, and phosphorus might be heavily influenced by Proteobacteria, suggesting that fluctuations in their abundance significantly impacted the performance of MBGS. Bacteroidota and Actinobacteria played a vital role in cellulose decomposition via the cbhA gene. Moreover, energy shortages caused by light attenuation due to wastewater turbidity and environmental fluctuations disrupted the microbial balance, shifting metabolic activity towards carbon pathways. Key challenges for the broader application of the MBGS process include managing wastewater turbidity and ensuring process stability. These findings highlight the need for pretreatment measures and robust operational strategies to mitigate environmental fluctuations and maintain system performance.

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

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

Effect of Promising Sustainable Nano-Reinforcements on Polysulfone/Polyvinylpyrrolidone-Based Membranes: Enhancing Mechanical Properties and Water Filtration Performance.

In this study, polysulfone/polyvinylpyrrolidone (PSf/PVP, 20 wt%/5 wt%)-based ultrafiltration (UF) membranes reinforced with different ratios (0.5 and 1 wt%) of cellulose nanocrystals (CNCs) and cellulose nanofibres (CNFs) were prepared by the phase inversion method. The effect of CNC, CNF, and CNC-CNF reinforcement on the morphology, roughness, crystallinity, porosity, average pore size, mechanical properties, and filtration performance of PSf/PVP-based membrane was investigated. Distilled water and surface water (lake water) fluxes of the membranes were determined at 3 bar using a dead-end filtration system. The distilled water flux of the fouled-hydraulic cleaned membranes was determined, and scanning electron microscopy (SEM) images of the fouled-cleaned membranes were examined. The flux recovery ratio (FRR) and fouling parameters were calculated to examine the fouling behaviour of the membranes. The mechanical properties of the membranes were modelled by the Mori-Tanaka, finite element, Voigt-Reuss, self-consistent scheme, and Halpin-Tsai methods using Digimat and/or analytically. In addition, the von Mises equivalent stress distributions of the nanocomposites were presented. Among the investigated membranes, PSf/PVP/CNC-0.5 had the highest distilled water flux (475.5 ± 17.77 L/m2.h), PSf/PVP/CNF-1 exhibited the stiffest behaviour with an elasticity modulus of 70.63 ± 3.15 MPa, and PSf/PVP/CNC-1 had the best organic matter removal efficiency. The finite element was the most successful modelling method for estimating the mechanical properties of nanocellulose-reinforced flat sheet membranes.

Comparative analysis of hospital laboratory wastewater treatment techniques in Syrian Arab Republic

Background: Hospital wastewater poses a significant threat to human health due to the presence of difficult-to-degrade organic compounds, active pharmaceutical ingredients and multiple inorganic substances that can pollute water resources and ecosystems. Aim: To compare the effectiveness of different techniques for removing organic load from hospital laboratory wastewater in Aleppo, Syria. Methods: We treated wastewater samples from hospital laboratories at Aleppo University Hospital, Syria, using several techniques, including biological treatment with the rotating biological contactor, adsorption with Syrian natural clay, coagulation with aluminium sulphate, advanced oxidation with ultrasound, and a combined treatment using natural clay and ultrasound. We assessed the organic load removal efficiency for each technique under different conditions. Results: The most effective technique was the combination of natural clay and ultrasound. Applying natural clay at a concentration of 1 g/L of wastewater along with ultrasound at 40 kHz for 30 minutes achieved chemical oxygen demand and biochemical oxygen demand values suitable for irrigation, in accordance with the Syrian standard. The chemical oxygen demand value decreased to 212 mg/L with 94% removal rate, and the biochemical oxygen demand value decreased to 82 mg/L with 87% removal rate. Conclusion: Based on our findings, techniques that combine different methods of hospital wastewater treatment, such as combining adsorption with advanced methods like ultrasound, are more effective than those that use single methods. Such techniques should be promoted.

Predicting organic matter and nutrient removal efficiency in a constructed wetland using data mining

Vertical and horizontal flow constructed wetlands (VF and HF CWs) are most widely used in the treatment of domestic sewage, storm runoff and selected industrial wastewaters. Current research focuses on the search for new applications, alternative substrates and developing mathematical and statistical methods to model the process of removing pollutants in CWs. This is important from a scientific and practical point of view. The performance of VF CWs with two types of substrate (gravel and Certyd - a waste material) was investigated over a two-year period. The following parameters were analyzed: biological oxygen demand (BOD5), chemical oxygen demand (COD), ammonia nitrogen (N-NH4), total nitrogen (N-Total), total phosphorus (P-Total) and dissolved oxygen (DO). At the same time, both the temperature of the inlet sewage and the air temperature were monitored. A support vector machine with a Gaussian kernel function was used to model the treatment efficiency. To select the model parameters, a 10-fold cross-validation was applied. The models applied were characterized by a very good fit. The expected average efficiency of organic removal was 88.3% (BOD5) and 80.8% (COD) in the bed filled with Certyd, and 83.8% (BOD5) and 76.9% (COD) in the bed with a classic filling. The predicted average efficiency of N-NH4 and N-Total removal in CWs filled with Certyd and gravel were 80.4 and 74.2%, and 59.6% and 57.0% respectively.

Novel cationic and amphoteric starch-modified coagulants for efficient treatment of relatively high turbidity and large organic matter source waters: Performance, predictive modeling and mechanism analysis

Finding alternative solutions of water source containing short-term relative high turbidity and large organic content is a pressing need in view of the inherent limitations of traditional inorganic coagulants. Requirement of significant dosage increase for conventional iron and aluminum salt coagulants can create several challenges including dose adjustment, suboptimal performance and high concentration of residual metal ions. In this study, acrylamide monomer (AM) and methacryloyloxyethyltrimethylammonium chloride (DMC) were grafted onto starch and carboxymethyl starch to obtain novel cationic and amphoteric starch-modified coagulants. Concurrently, the obtained coagulants were comprehensively evaluated under varying simulated water quality conditions to analyze their turbidity and organic matter removal efficiencies. Polymerized aluminium chloride (PACl) was used as the reference coagulant to evaluate the roles of polymer charge density, total charge, and molecular chain length in the coagulation mechanism for further illustration of their efficacy. In comparison to the traditional coagulant PACl, the modified coagulant was found to be more effective in enhancing flocculation and aggregation behavior, lowering of energy barriers, and enhancing adsorption energy by using the Density Functional Theory (DFT) calculations and Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory based investigation of the mechanism. Moreover, these behaviors were mainly attributed to significant exchange of charge density between coagulant and the pollutants. Additionally, in order to facilitate accurate and efficient treatment of water having diverse qualities, quadratic polynomial equation based mathematical model was constructed for quantitative analysis and model prediction. Findings of this study point towards an effective and precise approach to coagulation technology and thereby enabling sustainable and efficient purification of turbid source water containing large organic matter.

Degradation of the Antibiotic Sulfamethoxazole by Ozonation: A Comprehensive Review

ABSTRACTSulfamethoxazole (SMX) is an antibiotic widely used for the treatment of several diseases, especially respiratory and urinary. Due to its widespread use, its presence in the environment has been on the rise. This study discusses the degradation of the antibiotic SMX through the ozonation process. SMX is preferentially degraded by the direct action of O3 on the molecule, starting by breaking the double bonds in the aromatic ring. Through ozonation it is possible to obtain complete SMX degradation within 10 min, but the mineralization of the solution is not achieved, reaching total organic carbon removal efficiencies of 5%–60%, depending on the reaction time. Factors such as the presence of organic matter (OM) and the pH of the solution interfere with the degradation of SMX. The OM acts as a radical scavenger, decreasing the efficiency of degradation, while the pH interferes with the decomposition of O3 into radicals and the dissolution of the oxidant in the medium, in addition to influencing the state of ionization of the SMX making it more or less prone to reactions. In general, most other remediation processes are carried out on a laboratory scale. To increase the level of these processes to a full scale, more pilot‐scale studies are needed. In addition, it is necessary to focus on the practice of reusing materials, avoiding the generation of secondary pollution, and increasing the useful life of the material. The review also discusses the reaction mechanisms, intermediate compounds formed, mineralization of the solution, and factors that influence the process, which can help in making decisions for future studies to be carried out in the area. Prospects in the research area revolve around using metal–organic frameworks as molecular imprinting technology to modify heterogeneous catalysts, integration of external energy, bimetallic systems, and evaluation of deactivation mechanisms.

Acclimatation of Microbial Biomass to Effluents From a Swine Slaughterhouse in Batch Reactors

Objective: To evaluate the acclimatization of microbial biomass in sequential reactors to optimize the treatment of wastewater from pig slaughterhouses. Theoretical framework: The meat industry generates highly contaminated wastewater. Biological treatments, such as aerobic and anaerobic systems, are more efficient and sustainable than physicochemical ones. Materials and methods: Industrial effluents were collected in a pig slaughterhouse and then characterized. The microbial biomass was collected from the same slaughterhouse and was subjected to an acclimatization process in a sequential batch reactor. Results and discussion: The results showed that the wastewater from the pig slaughterhouse had high levels of BOD, COD and suspended solids, exceeding the limits established by local regulations. During the acclimatization process, the microbial biomass demonstrated a gradual improvement in its COD removal capacity, reaching efficiencies greater than 70%. The positive correlation observed between volumetric organic load and organic matter removal efficiency indicates that acclimated biomass has a greater capacity to treat effluents with high levels of organic load. Research implications: Biomass acclimatization is essential to improve the efficiency of biological treatment in slaughterhouse effluents, reducing its environmental impact and the need for costly treatments. Value/originality: This study proposes a more sustainable and efficient solution for the treatment of slaughterhouse wastewater, highlighting the importance of biomass acclimatization.

Study on the hydrolysis characteristics of polymeric aluminum chloride forced by fine bubbles and its key factors affecting the efficiency and capacity of forcing hydrolysis

Enhanced coagulation is an important way to remove natural organic matter and reduce disinfection by-products in traditional water treatment processes, in which the micromolecular organic matter that is difficult to be removed during conventional coagulation can be enhanced more conveniently by modulating the dominant Al species in the traditional metal salt coagulants (e.g., polymeric aluminum chloride, PACl). Based on the forcing hydrolysis characteristics of fine bubbles due to the adsorption of hydroxide ions on their surfaces, this study verified the adaptability of the forced PACl hydrolysis by fine bubbles under different operating conditions objectively and comprehensively. The morphological changes of PACl before and after forced hydrolysis by fine bubbles were characterized figuratively, and the evolution of the dominant Al species before and after forced hydrolysis by fine bubbles was reasonably elaborated. The experimental results showed that fine bubbles had the effect of forcing the hydrolysis of PACl with different degrees of alkalinity and modulating the dominant Al species. It was innovatively found that the mass transfer efficiency of the fine bubbles determined their efficiency in forcing PACl hydrolysis (Pearson's r = -0.9423) and the concentration of fine bubbles affected their capacity to force PACl hydrolysis (Pearson's r = 0.8189). At pH = 7 and an air flow rate of 20 mL/min, the DOC concentration of micromolecular organics and the DOC removal efficiency of total organics could be reduced by 0.54 mg/L and enhanced by 12.6 %, respectively, after forced PACl hydrolysis by fine bubbles. While deepening the mechanism of forced PACl hydrolysis by fine bubbles, the above results preliminarily verified the relevance and feasibility of modulating the dominant Al species through forced PACl hydrolysis by fine bubbles to improve the coagulation efficiency, which provided theoretical and data support for the construction of a fine bubble-enhanced coagulation process for drinking water treatment plants.

Comparative organic pollutants removal efficiency and life cycle assessment of pyrolysis and solvent elution for industrial waste salt recycling

Managing industrial waste salt plays a vital role in environmental protection and resource utilization, with a focus on effective removal of organic pollutants and comprehensive life cycle assessment. This study focuses on waste salt produced by the pharmaceutical, pesticide, fluorochemical, and dyeing industries, assessing the efficiency of pyrolysis and solvent elution techniques in removing organic pollutants. Additionally, a life cycle assessment (LCA) was conducted to assess the environmental impacts associated with the two technologies. The findings reveal that pyrolysis significantly enhances the removal of organic pollutants, offering an average improvement of 19.37% over the solvent elution method. This improvement is particularly notable in the treatment of waste salt from agricultural and textile industries, where removal rates exceed 90%. Moreover, ammonium-based waste salts produced by the dyeing industry, due to their lower thermal stability and reduced pyrolysis yield, are more suitable for solvent elution. The LCA indicates that pyrolysis results in less overall environmental risk compared to the solvent elution process. In terms of carbon emission potential, pyrolysis technology emits less carbon dioxide equivalent (CO2 eq.), with a total of 1144 kg CO2 eq. emitted when processing one ton of waste salt. The environmental impact of pyrolysis is primarily attributed to the energy consumption during the pyrolysis and evaporation stages. In contrast, the environmental impacts of solvent elution are mainly related to the use of toxic eluents and the high energy consumption of the subsequent distillation to recover the solvent.

Enhanced Organics Removal Using 3D/GAC/O3 for N-Containing Organic Pharmaceutical Wastewater: Accounting for Improved Biodegradability and Optimization of Operating Parameters by Response Surface Methodology

Pharmaceutical industry effluents often contain high concentrations of refractory organic solvents, chemical oxygen demand (COD), and total dissolved solids (TDSs). These wastewaters, including N-containing organic solvents known for their persistence and toxicity, pose significant environmental challenges. The study evaluated the efficacy of 3D/Granular Activated Carbon (GAC)/O3 treatment compared to linear process additions when treating real pharmaceutical wastewater, and revealed a 2.73-fold enhancement in COD mineralization. The process primarily involves the direct oxidation of monoprotic organic acids found in real pharmaceutical effluents, such as acetic and formic acid, crucially influencing mineralization rates. Optimal conditions determined via the response surface methodology were 125 g/L GAC, 30 mA/cm2, and 75 mg/L O3, achieving high total organic carbon (TOC) and COD removal efficiencies of 87.19 ± 0.19% and 89.67 ± 0.32%, respectively (R2 > 0.9), during verification runs. Current density emerged as the key parameter for organic abatement, aligning with the emphasis on direct oxidation at the anode surface. This integrated approach enhances biodegradability (BOD5/COD) and reduces acute toxicity associated with persistent N-containing solvents, demonstrating promising applications in pharmaceutical wastewater treatment.

Influence of bisphenol A concentration on organic matter removal and nitrification in biological wastewater treatment

Microplastics and plastic additives have become ubiquitous in our environment, posing a major challenge to wastewater treatment processes. This study investigated the impact of Bisphenol A (BPA), a common plastic additive, on the efficiency of organic matter removal and nitrification in biological wastewater treatment. The obtained results indicated that a BPA concentration of 10 mg·L−1 in the influent affected the Chemical Oxygen Demand (COD) in the effluent. In comparison, concentrations of 1 or 5 mg·L−1 did not show such noticeable differences. Additionally, an increase in BPA load inhibited the nitrification process, resulting in a high concentration of nitrogen in its ammoniacal form in the effluent when the BPA concentration was increased to 10 mg·L−1. In fact, the microbial community analysis revealed a considerable reduction of Nitrosomonas in the reactor fed with wastewater containing 10 mg·L−1 of BPA. Despite compromising the nitrification process, this situation did not deprive the biomass of its ability to remove BPA from the system, as this component was not detected in the effluent once the microorganisms completed their adaptation process. 16 S rRNA gene sequencing showed that the predominant phyla across all samples were associated with Proteobacteria, Bacteroidota, Patescibacteria and Actinobacteriota, similar to previous studies.

Fabrication cellulose/epoxy sponge via surface embedding for efficient and continuously oil/water separation

Discharging oily waste into environment have caused sever water, soil and air pollution. Mechanical compressible polymeric sponges show great potential in oil/water separation through adsorbing/filtering. However, most of these developed sponges were intermittent/manually in oil/water separation and the fabrication always complex. Herein, we developed superwetting sponge by embedding a handful amount of cellulose at the surface of sponge skeleton and delivered excellent mechanical elasticity and robustness. The cellulose/epoxy sponge (embedding 0.33 w% cellulose) can be compressed to 60 % strain with 60 kPa stress and returned to its original shape after 50 times cyclic strain-stress tests. Increasing the embedding amount generated adverse effects on mechanical elasticity and porosity. The as-fabricated cellulose/epoxy sponge showed high separation efficiency (94–99 %) on various oil/water mixtures and showed stable cyclic separation efficiency (>94 %). The optimized cellulose/epoxy sponge was placed into designed separator to separate dispersed oils showing satisfactory total organic carbon removal efficiency (56.63 %) and the inject flow rate showed adverse effects on separation efficiency. Surface embedding is feasible for fabrication mechanical elastic and robust superwetting sponge. The sponge separator showed high separation efficiency of dispersed oil indicating the great of potential polymeric sponge in practical application.

A novel multifunctional photocatalytic membrane based on β-FeOOH for oily wastewater purification

In order to deal with the environmental pollution caused by complex oily wastewater, it is necessary to develop filtration membrane materials. However, significant challenges such as poor effect of emulsion separation, limited functionality, and susceptibility to membrane fouling require urgent resolution. Here, we successfully prepared a β-hydroxyl iron oxide/polydopamine-polyethylenimine/polyacrylonitrile (β-FeOOH/PDA-PEI/PAN) nanofiber membrane for treatment of complex wastewater by growing PDA-PEI on a blow-spinning PAN nanofiber membrane and decorating the membrane with β-FeOOH. The porous structure and the large number of hydrophilic groups greatly increase the hydrophilicity of the membrane and give the membrane high permeation fluxes (11531.26 L m−2 h−1) for surfactant-free kerosene-in-water emulsion. The loaded β-FeOOH nanorods increase the roughness of the membrane surface, which enhances the underwater superoleophobic ability of the membrane, and promotes the demulsification of the emulsion and makes it have high separation efficiency of 99.48 % for surfactant-stabilized kerosene-in-water emulsion. In addition, the β-FeOOH/PDA-PEI/PAN also exhibited high organic dye removal efficiency (99.38 %) due to the presence of β-FeOOH. The synergistic effect of low oil adhesion and photocatalysis enhances the antifouling and self-cleaning performances of the material. Significantly, the multifunctional membrane also shows exceptional oil/water separation ability and good stability. The presented synergistic strategy of β-FeOOH/PDA-PEI/PAN membrane materials represents a prospective candidate for the treatment of complex wastewater.

Efficient desalination and synergistic toxic organics removal in RO concentrates with electrochemical advanced oxidation processes

A novel Ce-doped Ti4O7 (Ti/Ti4O7-Ce) electrode was fabricated and investigated in treatment of reverse osmosis (RO) concentrates with Electrochemical advanced oxidation processes (EAOPs). Characterization results showed that Ce was successfully incorporated into the Ti4O7, leading to an increase on the hydroxyl radical (•OH) generation and electrochemical stability compared with Ti/Ti4O7. Ti/Ti4O7-Ce electrodes achieved efficient desalination and oxidation of toxic organics, which was mainly attributed to the indirect oxidation induced by electro-generated •OH and change of electrochemical properties. The action of electric field had great effect on desalination process, and the anions in reverse osmosis concentrates (ROC) deposited on the cathode through this action by characterization and analysis. In the treatment, about 10.8–11.2 % of desalination efficiencies can be obtained, and the removal efficiency of toxic organics enhanced with the increase of Ce addition and current density. In the experiments, TOC removal efficiencies were 57 %, 66 % and 69 % under 10, 20 and 30 mA/cm2 in the 180 min treatment. Toxic chemicals, such as alkanes, haloalkanes, etc., were the main components in treatment, and the organic pollutants with medium molecular weight (MMW) (1400 g/mol) and low molecular weight (LMW) (40–230 g/mol) in ROC were removed. Although slight decreased durability was observed due to Ce leaching, Ti/Ti4O7-Ce electrode maintained stable desalination performance and total organic carbon (TOC) removal efficiency within 60 cycles. This study indicated that Ti/Ti4O7-Ce was a promising electrode for synergistic toxic organics removal and desalination in EAOPs.

The effect of Fenton sludge on anaerobic digestion of papermaking wastewater in an upflow anaerobic sludge blanket reactor

An upflow anaerobic sludge blanket (UASB) reactor was used to investigate the effect of adding Fenton sludge (FS) on the anaerobic digestion of actual papermaking wastewater. The results showed that a one-time addition of 10 g/L FS could sustainably promote the performance of UASB for more than 40 days. The organic matter removal efficiency increased by 15.56%, and the biogas production increased by 24.52%. The proportion of methane in biogas increased by 12.87%. Adding FS increased the capacitance values of sludge extracellular polymeric substances and the electron transfer system activity in reactor increased by 1.76 times. The dehydrogenase activity and coenzyme F420 of the sludge increased by 1.54 and 2.11 times, respectively. Adding FS enriched the iron-reducing bacteria (Thermodesulfobacteriota) and hydrolytic acid-producing bacteria (Chloroflexota and Synergistota), thereby promoting the hydrolysis and acidification process. Adding FS was beneficial to the enrichment of methanogen, especially Methanosaeta, significantly increasing the methane production.

Enhancing textile wastewater treatment for subsequent biological processes by integrating electrooxidation and electrocoagulation

ABSTRACT The presence of refractory contaminants in textile wastewater is one of the major concerns while handling them with the biological processes at common effluent treatment. Electro-oxidation (EO) as a standalone process is an insufficient treatment method for the abolition of inorganic contaminants (carbon and non-carbon). By incorporating electrocoagulation (EC) as an associated treatment method after EO, removal of such contaminants becomes easy, which not only makes the treated wastewater fit for biological remediation but also reduces load on biological units. The removal of non-carbonic impurities was assessed in terms of improvement in the chemical oxygen demand (COD) post EC. L25 orthogonal array of experiments was obtained using the Taguchi method. From the S/N ratio plot, the optimal process combination was obtained as, EO with current density = 25 mA/cm2, electrolysis time = 50 min followed by EC with current density = 18 mA/cm2, speed of rotation = 50 rpm and electrolysis time = 40 min. The enhancement in COD and total organic carbon removal efficiencies after EC were 65.11 and 63.57%, respectively, over EO. The biodegradability index also improved from an initial value of 0.098–0.737 post-hybrid treatment. Inorganic carbon reduced from a value of 36.37 mg/L after EO to 0.1 mg/L post EC.