Organic Wastewater Treatment Research Articles

Research progress of MOF-based membrane reactor coupled with AOP technology for organic wastewater treatment.

MOF-based catalytic membrane reactor (MCMR), which can simultaneously achieve membrane separation and chemical catalytic degradation in an integrated system, is a cutting-edge technology for effective treatment of organic pollutants in water. The coupling of MCMR and advanced oxidation process (AOP) not only significantly improves the pollutant removal efficiency but also inhibits the membrane pollution through self-cleaning effect, thus improving the stability of MCMR. This paper reviews different MCMR systems combined with photocatalysis, Fenton oxidation, and persulfate activation, elucidates the reaction mechanism, discusses key issues to improve system effectiveness, and suggests future challenges and research directions.

Adsorption and Degradation of Organics in Wastewater on Municipal Sludge.

Adsorption and degradation of organic compounds on sludge were investigated by comparing activated and inactivated sludge at various dosages, pH values, and temperatures. The organic compounds in wastewater were identified and evaluated through fluorescence spectra. The results show that optimum adsorption occurred as the activated and inactivated sludge concentration was 4000 mg/L at a pH of 7.99 and a temperature of 30 °C. The fluorescence scanning spectrum indicated that activated sludge could remove protein-like organic matter, fulvic acid-like organic matter, and humic acid-like organic matter by 22.1, 9.4, and 41.2%, respectively, via adsorption only or by 25.9, 9.8, and 74.3%, respectively, via adsorption and degradation. Under optimum conditions, by using the good adsorption performance of sludge combined with other sewage treatment technologies, the treatment of high-content organic wastewater can be achieved.

Enhancing the anoxic/oxic process for treating hypersaline amide wastewater using a synthetic bacterial agent to regulate core bacterial interactions

Targeted enhancement of biological salt-tolerance, biodegradation performances, and functional microbial interactions by introducing new bacterial agent is crucial for constructing saline wastewater treatment bioreactor. Herein, we demonstrated the efficient removal of acetoacetanilide (AAA, an amide compound) simulated and real wastewater, microbial responses upon hypersaline (1–5 % salinity) stress using a halotolerant synthetic bacterial agent enhanced anoxic/oxic process. The results indicated that the bacterial agent significantly enhanced the removal efficiency (90.15 %) of AAA (1 % salinity, 1500 mg/L) with a hydraulic retention time of 49.40 h. Notably, the bacterial agent led to fivefold increase of NH3-N compared to the control group, remarkably facilitating the ammonification of AAA (5 % salinity) wastewater. Furthermore, it promoted positive interactions among oxic sludge communities and expanded the niche width of core bacteria. This study highlights the enhanced performance of bacterial agent by regulating the core bacterial interactions, presenting a sustainable bioaugmentation approach for hypersaline organic wastewater treatment.

A pilot scale of electrochemical integrated treatment technology and equipment driven by solar energy for decentralized domestic sewage treatment

Based on the natural air diffusion electrode (NADE) cathode, a solar-driven electrochemical integrated sewage treatment technology and equipment in a pilot scale was developed to treat dispersed rural wastewater. The non-aeration NADE had efficient and stable H2O2 production performance, maintaining the H2O2 output between 1474 and 1535 mg h−1 within 50 h with the current efficiency of 77.4%–80.6%. This electrochemical integrated wastewater treatment system was coupled with technologies such as dual-cathode electro-Fenton, peroxi-coagulation and photoelectro-Fenton, which effectively improved the conversion and utilization efficiency of H2O2. It integrated Fenton-like oxidation, electro-oxidation and UV/H2O2, as well as Fe(OH)3-dominated flocculation, which could effectively remove various pollutants in wastewater. The integrated sewage treatment equipment (500 L d−1) realized the effective treatment of a rural decentralized domestic sewage, achieving simultaneous removal of chemical oxygen demand (COD), NH3–N, total phosphorus (TP) and bacteria. Driven by solar energy, its application feasibility, superiority and stability have been proved, providing theoretical and technical support for the efficient and low-consumption treatment of dispersed organic wastewater.

Heterostructure CoFe2O4/kaolinite composite for efficient degradation of tetracycline hydrochloride through synergetic photo-Fenton reaction

Compared with single photocatalytic reaction and single Fenton reaction, visible light assisted Fenton (photo-Fenton) reaction has higher degradation efficiency for environmental pollutants and great potential in the treatment of organic wastewater. Herein, a CoFe2O4/kaolinite (CFO/K) composite photocatalyst was synthesized by a simple sol-gel method, using kaolinite as a carrier. Such a composite was used to degrade tetracycline hydrochloride (TCH) through synergetic photo-Fenton reaction. Compared with pure CoFe2O4 (CFO), CFO/K containing 40 wt% of kaolinite (CFO/K-40%) had larger specific surface area, abundant surface active sites, and higher photogenic electron hole pairs separation efficiency. Hence, it exhibited a higher photocatalytic degradation efficiency than CFO, and the degradation efficiency was up to 84.82% within 30 min. After three cycles, the photocatalytic degradation efficiency could remain at 76.58%, exhibiting good catalyst stability. During the TCH degradation process, hydroxyl radical and superoxide radical were the dominant active species. In addition, the CFO/K-40% composite exhibited a good degradation performance for different organic pollutants. This study suggested that the CFO/K composite material, as an efficient photocatalyst, has promising applications in the field of kaolinite-based photocatalysts for the treatment of organic wastewater.

Study on the Degradation of Methylene Blue by Cu-Doped SnSe.

Treatment of organic wastewater is still a difficult problem to solve. In this paper, Cu-doped SnSe powder was synthesized by a convenient and efficient hydrothermal method. Meanwhile, the degradation effect of different doping concentrations of SnSe on methylene blue was investigated. It was found that at low doping concentrations, the degradation effect on methylene blue was not obvious because Cu was dissolved in the lattice of the SnSe matrix at low concentrations. As the doping concentration increased, SnSe changed from a layered structure to a nanocluster structure with reduced particle size, and a mixed phase of SnSe and Cu2SnSe4 appeared. In fact, the degradation effect on methylene blue was significantly enhanced, and we found that the catalytic degradation effect on methylene blue was best at a doping concentration of 10 wt.%.

Nitrogen-doped bimetallic MOFs derivatives for efficient ionizing radiation catalytic degradation of chloramphenicol

Electron beam (EB) irradiation has received increased attention in sewage disposal due to the high efficiency, no additional chemicals and wastes produced. However, it’s still limited by relatively high processing costs. In this work, we report a novel nitrogen-doped Fe/Ni bimetallic metal organic frameworks (MOFs) derivative for efficient ionizing radiation catalytic degradation of chloramphenicol (CAP). Compared with the single EB irradiation, the radiation-catalytic process allows a 2.8-fold increment in degradation rate constant and a 21.2-fold enhancement in the TOC removal rate. The EPR experimental results confirmed that the optimized composite catalyst significantly enhances the generation of hydroxyl radicals. Intriguingly, the synergistic effect of Fe/Ni element in the valence state were observed in the radiation-catalytic process, in which the generation of Fe2+ promoted the production of hydroxyl radical. The adsorption experiments reveal that most of the high removal effect origins from complete degradation rather than the adsorption effect. These key indicators of irradiation degradation are all the highest compared to the reported literature. In addition, the catalyst also has excellent cycle stability under irradiation. The high-performance ionizing radiation catalytic degradation in synergy with bimetallic MOFs derivatives provides a facile and general strategy for efficient EB irradiation treatment of organic wastewater.

Mn-SR as an ozone catalyst for coal to ethylene glycol organic wastewater treatment: Activity evaluation and reaction mechanism

Large amounts of soda residue waste from the production of sodium carbonate industries cause serious pollution to environment. In this study, a novel Mn-SR non-homogeneous ozone catalyst was prepared by mixed calcination method using soda residue as the main component for organics degradation of coal to ethylene glycol wastewater. Firstly, under the optimal Mn-SR preparation process (95% n-SR (msoda residue: mkaolin = 8:1), 5% MnO2, calcination temperature: 500 °C, calcination time: 4 h) and the optimal operating conditions (pH: 8, water temperature: 40 °C, catalyst dosage: 320 g/L, O3 dosage: 20 g/L) for the reaction of 60 min, the COD removal rate reaches to 77.1%, which is 63.9% higher than only ozonation COD removal efficiency under the same conditions. Kinetic study shows that water temperature is the most important factor affecting COD degradation rate in the reaction system. Through the adsorption performance, ozone utilization, free radical quenching experiments and three-dimensional fluorescence tests, the catalytic performance of Mn-SR catalysts for ozonation was investigated. The results showed that Ca and Mg in Mn-SR play a major role in organics degradation, while MnO2 plays a complementary role in the degradation of high COD concentrations. It was confirmed that hydroxyl radicals (·OH) are the main reactive radicals in the Mn-SR catalytic ozonation system, which plays an important role in the degradation of organics in wastewater. Meanwhile, after Mn-SR was reused and regenerated for five times, the COD removal rates was still higher than 67.0%, and Mn-SR recovery rates were more than 94.7%, which showed a good stability.

Quorum sensing in different subcommunities becomes the key factor affecting the humification of the aerobic composting system with sauerkraut fermentation wastewater

Aerobic composting is an effective and harmless method to treat Sauerkraut fermentation wastewater (SFW). Given the limited understanding of the effect of quorum sensing (QS) on humification in subcommunities under acidic environments, a large-scale analysis was conducted to identify features that impact the response of QS to humification in different subcommunities. The results showed that the addition of SFW directly affected humification in subcommunities A and C, and the abundances of functional genes related to carbon fixation and carbon degradation were significantly increased at 7 and 15 d, respectively. In addition, subcommunity B indirectly affected humus production but regulated carbon metabolic pathways such as glycolysis/gluconeogenesis and pentose phosphate by QS with subcommunities B. These findings provide a novel perspective for analysing the regulation of humification in aerobic composting and suggest that composting has potential applications in organic wastewater treatment.

Degradation of levofloxacin from antibiotic wastewater by pulse electrochemical oxidation with BDD electrode

Antibiotic-containing wastewater is a typical biochemical refractory organic wastewater and general treatment methods cannot effectively and quickly degrade the antibiotic molecules. In this study, a novel boron-doped diamond (BDD) pulse electrochemical oxidation (PEO) technology was proposed for the efficient removal of levofloxacin (LFXN) from wastewater. The effects of current density (j), initial pH (pH0), frequency (f), electrolyte types and initial concentration (c0(LFXN)) on the degradation of LFXN were systematically investigated. The degradation kinetics under four different processes have also been studied. The possible degradation mechanism of LFXN was proposed by Density functional theory calculation and analysis of degradation intermediates. The results showed that under the optimal parameters, the COD removal efficiency (η(COD)) was 94.4% and the energy consumption (EEC) was 81.43 kWh·m−3 at t = 120 min. The degradation of LFXN at pH = 2.8/c(H2O2) followed pseudo-first-order kinetics. The apparent rate constant was 1.33 × 10−2 min−1, which was much higher than other processes. The degradation rate of LFXN was as follows: pH = 2.8/c(H2O2) > pH = 2.8 > pH = 7/c(H2O2) > pH = 7. Ten aromatic intermediates were formed during the degradation of LFXN, which were further degraded to F−, NH4+, NO3−, CO2 and H2O. This study provides a promising approach for efficiently treating LFXN antibiotic wastewater by pulsed electrochemical oxidation with a BDD electrode without adding H2O2.

Comparison of organic wastewater treatment using anaerobic reactors fixed bed type in Germany and Indonesia

Waste that has a high organic matter content can be treated biologically under anaerobic conditions or using bacteria that can live in an environment without oxygen. One method of wastewater treatment that can reduce high organic content is the Fixed Bed type anaerobic reactor system. The purpose of this research is to compare the treatment of organic wastewater using a Fixed Bed type anaerobic reactor that has been implemented in Germany with that implemented in Indonesia. The method used is a literature study by comparing case studies between the two countries, so the methodology used is a systematic literature review. Based on the results of the discussion, it is known that the organic waste that is processed using an anaerobic reactor carried out in Germany has several differences starting from the sub-stages of the process, and operations to the materials used such as the use of pumps, installation storage tanks, sewage filtration, use of stainless steel and heat exchangers. These differences if applied in Indonesia can cost relatively a lot so they are not suitable for application in Indonesia. Based on the literature study, it was concluded that the anaerobic wastewater treatment solution using a fixed bed type in Indonesia can be a good opportunity and can be imitated by other countries because it has simple equipment, but the reactor efficiency and the resulting percentage of methane production are relatively high. although the required HRT is long, anaerobic catalysts can be used as a solution.

CuCoFe-LDHs activated sodium percarbonate (SPC) for the degradation of ciprofloxacin

Sodium percarbonate (SPC) is widely used in Fenton-like technology for the organic wastewater treatment because of its low costs and convenient transportation. However, low utilization efficiency of hydrogen peroxide limits its application. In this work, a catalyst (CuCoFe-LDHs) was designed to activate SPC for degrading ciprofloxacin (CIP) effectively in heterogeneous Fenton system with higher H2O2 utilization rate (62 %) and higher stability (degradation rate of CIP decreased 5.6 % after five cycles). Since SPC was dissolved in water, H2O2 and CO32- were generated, and CO32- was transferred to HCO3- subsequently along with the variation of pH value. Plenty of •OH and •O2- was generated, and most of •OH was directly reacted with CIP. However, •O2-, was prone to react with HCO3- to form •CO3-, and then for degrading CIP. Compare with CuMgFe-LDHs catalyst, the electrochemical impedance spectroscopy (EIS) showed that CuCoFe-LDHs with stronger electron transfer ability. Therefore, the Co atom could facilitate the generation of specific free radical via enhancing electron transfer rate for the degradation of CIP in CuCoFe-LDHs. In summary, this study provides a cheap, recyclable, efficient and environmentally friendly wastewater treatment method for the degradation of refractory organic pollutants.

Construction and demolition waste as a high-efficiency advanced process for organic pollutant degradation in Fenton-like reaction to approach circular economy

The Fenton-like reaction is a promising organic wastewater treatment reaction among advanced oxidation processes (AOP), which has emerged to replace the conventional Fenton reaction. Recycled construction and demolition waste (CDW), which is porous and rich in iron, manganese, and magnesium, can be reused as a Fenton-like catalyst. This study proposes an AOP wastewater treatment strategy using recycled porous CDW mixed with hydrogen peroxide (H2O2) to decompose methylene blue (MB) wastewater. According to the apparent first-order rate (Kapp) of 10 ppm MB adsorption, CDW-3, having the highest specific surface area, also has the highest Kapp of 0.23 min−1 g−1. The optimized conditions recommended by the Taguchi method include a 0.3 g mL−1 CDW-3 concentration, a 0.254 g mL−1 H2O2 concentration, and 10 ppm MB, resulting in an about 2.01 min−1Kapp value. In addition, MB concentration is observed as the most influential factor for Kapp, which decreases with increasing MB concentration and is about 0.62 min−1 at 1000 ppm MB. Repeating the Fenton-like reaction five times at 100 p.m. MB using the same CDW-3, the Kapp is about 0.64 min−1, which is 86% of the initial run. The synergistic effect index (ξ) is defined to quantify the level of interaction between CDW and H2O2, which produces free radicals during the Fenton-like process. The ξ of CDW-3 is about 2.16. Overall, it is demonstrated that CDW is a promising catalyst for Fenton-like reactions, and the synergistic effect index (ξ) can be used as a reference index to evaluate the catalytic generation of free radicals between the catalyst and H2O2.

Overall evaluation of a multi-stage reverse electrodialysis reactor series system for organic wastewater treatment and power generation

A multi-stage reverse electrodialysis reactor (REDR) series system for organic wastewater treatment and power generation is proposed in this paper. An energy evaluation method is developed for the first time by analyzing the electrical energy and oxidative degradation energy conversion efficiencies of the system. The influences of the current and feed solution velocity on the overall performances of the system are investigated by experiments. Results demonstrate that a high current can enhance the gross output power but reduce the net output power and total energy conversion efficiency. A peak value of the total COD removal can be obtained at an appropriate current. A low feed solution velocity can improve the performance of the system except for the lower net output power. Although the electrical energy conversion efficiency reduces as the serial number of REDR increases, the oxidative degradation energy conversion efficiency increases significantly, which results in the total energy conversion efficiency enhancement. Under the given experimental conditions, the maximal values of the net output power, total COD removal and total energy conversion efficiency are 1.05 W, 450.98 mg·L−1, and 11.41%, respectively.

Rapid degradation of organic pollutants by enhanced persulfate activation using CeO2-MnFe2O4 nanostructures: A polymetallic synergistic effect

Persulfate-based advanced oxidation processes (AOPs) have attracted considerable attention in the treatment of organic wastewater with high performance and long lifetime. The construction of efficient, environmentally-friend, and stable nanocatalysts has been recognized as a promising approach to activate persulfate. Herein, magnetic CeO2-MnFe2O4 nanomaterials fabricated via a simple sol-gel method were used for the first time to enhanced activate persulfate (PS) for the removal of the organic pollutant enrofloxacin (ENR). It was demonstrated that 97.2% of ENR (10 mg L−1) was efficiently degraded. 63.3% of TOC decreased within 35 min under a neutral solution (pH 6.81) in the PS+CeO2-0.2MnFe2O4 system using a catalyst dosage of 0.25 g L−1 and 0.18 mM PS. The magnetic CeO2-MnFe2O4 nanostructures maintained excellent recovery as well as recyclability ENR removal efficiency was 90% after recycling five times. EPR and quenching tests indicated that sulfate radicals (SO4•−) and hydroxyl radicals (•OH) significantly contributed to ENR removal. XPS analysis showed that the synergistic redox cycles of Ce3+/Ce4+, Mn2+/Mn3+, and Fe2+/Fe3+ are essential to activate PS for ENR degradation. DFT calculations also revealed that PS molecules preferred to adsorb to and dissociate on CeO2-MnFe2O4 surfaces rather than just CeO2 and MnFe2O4 surfaces. CeO2 plays a dual role in the charge transfer from CeO2-MnFe2O4 to PS molecules, i.e., both electron storage and donor. This work also provides a new interpretation to explain the activation mechanism of PS. The developed CeO2-MnFe2O4 nanostructures with rapid removal efficiency, high degradation efficiency and good recyclability may provide potential guidance for the design of polymetallic oxide nanocatalysts in PS-based AOPs.

Kinetic modeling and cost analysis of coupled ultrasonic processes for the treatment of dairy wastewater

Sonolysis with bubble cavitation is an effective tool for the degradation of complex, recalcitrant organic compounds. Thermal and cavitation effects are additive to the breaking of complex bonds in organic contaminants by hydroxyl radicals. Strong oxidants such as persulfate (PS) and hydrogen peroxide (H2O2), with their high redox potentials (2.01 and 1.8 V, respectively), are coupled with ultrasound energy for the degradation of contaminants. PS and H2O2 generate SO4̇ and ȮH radicals, respectively with higher redox potentials (2.6 and 2.8 V, respectively). Consequently, the radicals are even more active at breaking the strong covalent bonds of the contaminants. Coupled methods in different combinations of coagulation-flocculation, chemical oxidation, and sonication are investigated for the treatment of organic content dairy wastewater. The doses of PS and H2O2 are optimized at 0.75 g/L and 25.5 g/L, respectively. The kinetic study reveals that pseudo-second-order kinetic fits experimental data with a R2 value of 0.99. The oxidation by PS and H2O2, along with ultrasound application, facilitates the removal of COD up to 84.3 % at an economically feasible treatment cost of $5.635 per kg of COD removal. Coupled process is found able to qualify dairy wastewater as dischargeable at a feasible cost of treatment.

Progress in the Preparation of Metal Oxide Electrodes for the Electrochemical Treatment of Organic Wastewater: A Short Review

The direct discharge of untreated organic wastewater poses significant threats to the environment and to human health. To address these threats, electrocatalytic oxidation technology has emerged as a key solution for organic wastewater treatment. Building on research conducted over the past three years, this review highlights the considerable advantages of electrocatalytic oxidation technology in the context of organic wastewater treatment, with a particular emphasis on the application of metal oxide electrodes. The review also provides a summary of the primary methods used in the preparation of such electrodes. Subsequently, the applications of both single-metal-oxide electrodes and metal oxide composite electrodes in organic wastewater treatment are summarized. Finally, we discuss the future development of metal oxide electrodes.

Reusable flexible poly (vinyl alcohol)/chitosan-based polymer carbon dots composite film for acid blue 93 dye adsorption.

The design and synthesis of water-insoluble chitosan-based polymer carbon dots (P (CS-g-CA)CDs) are described. Then, a polyvinyl alcohol/chitosan-based polymer carbon dots (PVA/P (CS-g-CA)CDs) composite film was prepared by a simple casting method to be used in dye adsorption. The composite film was characterized using FTIR, XPS, transparency, contact angle, and mechanical properties tests, which showed the successful incorporation of P (CS-g-CA)CDs into the film and also revealed that hydrogen bonding improved the mechanical properties of the PVA film. Furthermore, the composite film displayed substantially enhanced hydrophobicity, making it suitable for use in water environments. In addition, the composite film exhibited stable adsorption of acid blue 93 (AB93) at pH 2-9, with an enhanced adsorption capacity of 433.24 mg/g. The adsorption obeyed the Langmuir law and with an efficiency of greater than 89% even after five cycles. Therefore, the PVA/P (CS-g-CA)CDs film is a promising material for the treatment of organic dye-polluted wastewater.

Synthesis of Ag-OMS Catalyst for Sunlight-Assisted Photodegradation of Crystal Violet Dye

The contamination of water with organic pollutants, such as dyes, has become a serious threat to the environment. Therefore, the development of a cost-effective, eco-friendly, proficient, and visible-light-driven catalyst for the treatment of organic dye-contaminated wastewater has been a burning issue recently. Photocatalysis is suggested as a potential treatment technique for the eradication of organic pollutants. The 1D tunnel-structured manganese oxide octahedral molecular sieve (OMS) is a suitable substance to be tested as a visible-light-driven photocatalyst for the degradation of organic contaminants. However, the fast recombination of photoinduced charges (h+/e−) limits its photocatalytic application. The development of heterojunctions between OMS and other metals, such as Ag, is a suitable technique for improving the photocatalytic performance of OMS. In this study, Ag-OMS with plasmon-enhanced photocatalytic activity is reported for the photodegradation of crystal violet dye. Manganese oxide OMS was prepared by an acidic precipitation method using potassium permanganate, manganese acetate, and nitric acid as precursor materials. Ag nanoparticles were deposited on OMS using leaf extracts of Calotropis gigantea. The deposition of Ag enhanced the photocatalytic performance of OMS from 68 to 95%. The effects of Ag contents, catalyst dosage, and concentration of crystal violet dye on catalytic performance were explored as well. Approximately 100, 95, and 75% photodegradation of 50, 100, and 150 mg/L crystal violet dye was observed in 90, 120, and 120 min in the presence of 10% Ag-OMS, respectively. Excellent photocatalytic performance, low dose utilization, and reusability proved that Ag-OMS might have practical environmental applications.

Biochar/layered double hydroxides composites as catalysts for treatment of organic wastewater by advanced oxidation processes: A review

Heterogeneous advanced oxidation process has been widely studied as an effective method for removing organic pollutants in wastewater, but the development of efficient catalysts is still challenging. This review summaries the present status of researches on biochar/layered double hydroxides composites (BLDHCs) as catalysts for treatment of organic wastewater. The synthesis methods of layered double hydroxides, the characterizations of BLDHCs, the impacts of process factors influencing catalytic performance, and research advances in various advanced oxidation processes are discussed in this work. The integration of layered double hydroxides and biochar provides synthetic effects for improving pollutant removal. The enhanced pollutant degradation in heterogeneous Fenton, sulfate radical-based, sono-assisted, and photo-assisted processes using BLDHCs have been verified. Pollutant degradation in heterogeneous advanced oxidation processes using BLDHCs is influenced by process factors such as catalyst dosage, oxidant addition, solution pH, reaction time, temperature, and co-existing substances. BLDHCs are promising catalysts due to the unique features including easy preparation, distinct structure, adjustable metal ions, and high stability. Currently, catalytic degradation of organic pollutants using BLDHCs is still in its infancy. More researches should be conducted on the controllable synthesis of BLDHCs, the in-depth understanding of catalytic mechanism, the improvement of catalytic performance, and large-scale application of treating real wastewater.