Progress of Electrocatalytic Technology in Treating Organic Chemical Wastewater

In recent years,extensive research has been conducted on the preparation of high catalytic performance electrodes and the development of electrocatalytic water treatment processes.This article introduces the basic principles of electrochemical water treatment,the preparation of electrode materials,and the research progress of electrocatalytic technology for degrading organic chemical wastewater.It analyzes the problems faced by electrocatalytic degradation of organic chemical wastewater and looks forward to the development trend of electrocatalytic technology in the field of organic chemical wastewater treatment.

Petro-chemical wastewater treatment by biological process

In order to study the feasibility of treating petro chemical wastewater by the combination of anaerobic and aerobic biological process, a research of treating wastewater in UASB reactor and aeration basin has been conducted. The test results shows that under moderate temperature, with 5\^2 kgCOD/(m\+3·d) volumetric load of COD Cr in the UASB reactor and 24h of HRT, 85% removal rate of BOD 5 and 83% of COD \{Cr\} and 1\^34 m\+3/(m\+3·d) volumetric gas production rate can be obtained respectively. The aerobic bio degradability can be increased by 20%—30% after the petro chemical wastewater has been treated by anaerobic process. As Ns=0\^45 kgCOD/(kgMLSS·d), HRT=4h in the aeration tank, 94% removal rate of BOD 5, 93% of COD \{Cr\}, 98\^8% total removal rate of COD \{Cr\} and 99% removal rate of BOD 5 can be reached.

Utilizing 3D DOSY NMR in the characterization of organic compounds in coal chemical wastewater

Coal chemical wastewater(CCW)with the features of high toxicity and poor biodegradability is a big issue in environmental remediation,posing a great threat to aquatic ecosystems and to human beings.Such complex molecular mixtures are notoriously difficult to characterize without initial physical separation.Herein,we present the 3D diffusion ordered spectroscopy(DOSY)analysis for CCW using DOSY-COSY and DOSY-HSQC methods,the advantages of this strategy have been demonstrated in the analysis of mixtures of aliphatic oxygenates and aromatic compounds,before being implemented on a genuine CCW sample in this study.The results showed that 3D DOSY is a robust and reliable tool for providing superior resolution and virtual separation of complex pollutants,and can be used as a general approach for structural elucidation.

Troubleshooting and Optimization of High-Strength Inhibitory Chemical Wastewater Treatment Process

Wastewaters from the chemical industry are usually of high-strength and may contain minor inhibitory and recalcitrant organics that are at times not readily identifiable. This paper describes the experience of a biological waste water treatment plant （WWTP） processing a COD concentration of 43000 mg·L^-1 wastewater from an oxochemical manufacturing plant. Stage improvements of the plant process by dilution of the inhibitory influent using other chemical wastewater streams resulting in a synergistic process effect, and removal of inhibitory organics by phase separation via acidification, effectively achieved process optimization producing a high quality effluent. In particular, the COD removal efficiency of granular sludge based anaerobic reactors increased from 56% to 90%. The final effluent COD decreased from 250mg·L^-1 to 50mg·L^-1, consistently meeting the COD concentration of 100 mg·L^-1 regulatory discharge limit. The success of the process enhancements supports the hypothesis that long-chain quaternary carboxylic acids act as substrate inhibitors in the biological process.

Overview of enhancing biological treatment of coal chemical wastewater:New strategies and future directions

Coal chemical wastewater(CCW)is a type of refractory industrial wastewater,and its treatment has become the main bottleneck restricting the sustainable development of novel coal chemical industry.Biological treatment is considered as an economical,effective and environmentally friendly technology for CCW treatment.However,conventional biological process is difficult to achieve the efficient removal of refractory organics because of CCW with the characteristics of composition complexity and high toxicity.Therefore,seeking the novel enhancement strategy appears to be a favorable solution for enhancing biological treatment efficiency of CCW.This review focuses on presenting a comprehensive picture about the exogenous enhancement strategies for CCW biological treatment.The performance and potential application of exogenous enhancement strategies,including co-metabolic substrate enhancement,biofilm filler enhancement,adsorption material enhancement and conductive mediator enhancement,were expounded.Meanwhile,the enhancing mechanisms of different strategies were comprehensively discussed from a biological perspective.Furthermore,the prospects of enhancement strategies based on the engineering performance,economic cost and environmental impact(3E)evaluation were introduced.And novel enhancement strategy based on“low carbon emissions”,“resource recycling”and“water environment security”in the context of carbon neutrality was proposed.Taken together,this review provides technical reference and new direction to facilitate the regulation and optimization of typical industrial wastewater biological treatment.

Biotoxicity dynamic change and key toxic organics identification of coal chemical wastewater along a novel full-scale treatment process

It is particularly important to comprehensively assess the biotoxicity variation of industrial wastewater along the treatment process for ensuring the water environment security.However,intensive studies on the biotoxicity reduction of industrial wastewater are still limited.In this study,the toxic organics removal and biotoxicity reduction of coal chemical wastewater(CCW)along a novel full-scale treatment process based on the pretreatment process-anaerobic process-biological enhanced(BE)process-anoxic/oxic(A/O)process-advanced treatment process was evaluated.This process performed great removal efficiency of COD,total phenol,NH_(4)^(+)-N and total nitrogen.And the biotoxicity variation along the treatment units was analyzed from the perspective of acute biotoxicity,genotixicity and oxidative damage.The results indicated that the effluent of pretreatment process presented relatively high acute biotoxicity to Tetrahymena thermophila.But the acute biotoxicity was significantly reduced in BE-A/O process.And the genotoxicity and oxidative damage to Tetrahymena thermophila were significantly decreased after advanced treatment.The polar organics in CCW were identified as the main biotoxicity contributors.Phenols were positively correlated with acute biotoxicity,while the nitrogenous heterocyclic compounds and polycyclic aromatic hydrocarbons were positively correlated with genotoxicity.Although the biotoxicity was effectively reduced in the novel full-scale treatment process,the effluent still performed potential biotoxicity,which need to be further explored in order to reduce environmental risk.

Advances Treatment Technologies in Chemical Industry Wastewater

The main treatment methods of chemical wastewater were reviewed.Physical,chemical,and biochemical treatment technologies effective for removing those pollutants were presented with their applicability,effectiveness and advantages.The problems facing the wastewater treatment in the petroleum chemical industry and coal chemical industry were introduced.In the end,the new progress and trend of the processes were overviewed.

Synthesis and evaluation of cationic flocculant P(DAC-PAPTAC-AM) for flocculation of coal chemical wastewater

In this study,a high-efficiency cationic flocculant,P(DAC-MAPTAC-AM),was successfully prepared using UV-induced polymerization technology.The monomer Acrylamide(AM):Acryloxyethyl Trimethyl ammonium chloride(DAC):methacrylamido propyl trimethyl ammonium chloride(MAPTAC)ratio,monomer concentration,photoinitiator concentration,urea content,and cationic monomer DAC:MAPTAC ratio,light time,and power of highpressure mercury lamp were studied.The characteristic groups,characteristic diffraction peaks,and characteristic proton peaks of P(DAC-MAPTAC-AM)were confirmed by fourier transform infrared spectroscopy(FTIR),X-Ray diffraction(XRD),1H nuclear magnetic resonance spectrometer(1H NMR),and scanning electron microscopy(SEM).The effects of dosage,pH value,and velocity gradient(G)value on the removal efficiencies of turbidity,COD,ammonia nitrogen,and total phenol by poly aluminum ferric chloride(PAFC),P(DACMAPTAC-AM),and PAFC/P(DAC-MAPTAC-AM)in the flocculation treatment of coal chemical wastewater were investigated.Results showed that the optimal conditions for the flocculation of coal chemical wastewater using P(DAC-MAPTAC-AM)alone are as follows:dosage of 8-12 mg/L,G value of 100-250 s^-1,and pH value of 4-8.The optimal dosage of PAFC is 90-150 mg/L with a pH of 2-12.The optimal dosage for PAFC/P(DAC-MAPTAC-AM)is as follows:PAFC dosage of 90-150 mg/L,P(DAC-MAPTAC-AM)dosage of 8-12 mg/L,and pH range of 2-6.When P(DAC-MAPTAC-AM)was used alone,the optimal removal efficiencies of turbidity,COD,ammonia nitrogen,and total phenol were 81.0%,35.0%,75.0%,and 80.3%,respectively.PAFC has good tolerance to wastewater pH and good pH buffering.Thus,the flocculation treatment of coal chemical wastewater using the PAFC/P(DAC-MAPTAC-AM)compound also exhibits excellent resistance and buffering capacity.

Experimental investigation and theoretical modeling on scale behaviors of high salinity wastewater in zero liquid discharge process of coal chemical industry

Zero liquid discharge(ZLD)treatment and reuse equipment of high salinity wastewater in coal-chemical industry often occur in various types of blockage problems because of high salt content,affecting the long-term stability of the device.In this study,the effects of solution temperature,steel,reaction time and wall roughness on fouling were investigated.The changes in the contents of fouling and fouling substances were qualitatively and quantitatively analyzed by XRD and EDS respectively,and the formation of scale was observed by SEM.The results show that with temperature increasing,Q235 steel is the most difficult to scale.Scaling rate of all salt scales reaches a maximum after 12 h,and the fouling rate decreases significantly from 12 to 48 h.It gradually stabilizes at 48 to 96 h.With the roughness increasing,the thickness of fouling layer increases,and a linear relationship is presented for 1 to 10 h.By comparing actual and simulated wastewater scaling rates,the relationship between actual and simulated wastewater scaling rates is y=ax-0.494.The composition of the scale was analyzed,calcium carbonate is the main product and increases with fouling time.Based on the above-mentioned results combining literatures,the hybrid prediction model with calcium carbonate as the main product is put forward.It is discussed microscopically that calcium carbonate is converted from aragonite and vaterite in a thermodynamically metastable state to calcite in a thermodynamically stable state.

A Review of Chemical Industry Wastewater Treatment

With the development of China＇ s industry, the domestic industrial parks greatly emerge and thus give rise to the diversity of pollutants in chemical wastewater. In this paper, the main sources of China＇ s chemical industry wastewater, main pollutants types and the wastewater characteristics of the chemical industry＇ s different branches are introduced, the related technologies and methods mainly applied to chemical industry wastewater treatment at home and abroad are analyzed and the application of different chemical wastewater treatment process is explained, and also all sorts of treatment technologies, methods, and processes are reviewed, and finally the study achievements and problems of all technol^ogies are concluded.

Advanced Treatment of Biologically Treated Chemical Comprehensive Wastewater by Nano-TiO2 Photocatalytic Oxidation

Nano-TiO2 photocatalytic oxidation was used to perform the advanced treatment of biologically treated chemical comprehensive wastewater. The effects of reaction time,nano-TiO2 dosage and initial p H of the wastewater on the removal rate of COD were tested. The GC/MS and EEM techniques were used to qualitatively analyze organic compounds in the wastewater before and after treatment. The result showed that after the biologically treated chemical comprehensive wastewater was treated by nano-TiO2 photocatalytic oxidation under the conditions of reaction time 3 h,nano-TiO2 dosage 8 g/L,and pH 8. 0,the effluent COD was 61. 9 mg/L and its removal rate was 63. 8%. Additionally,the species of organic pollutants reduced from 12 to 6. Meanwhile,the content of humic-like and fulvic-like substances dropped dramatically.

Evaluation and Optimization of Electrode Configuration of Multi-Channel Corona Discharge Plasma for Dye-Containing Wastewater Treatment

A discharge plasma reactor with a point-to-plane structure was widely studied experimentally in wastewater treatment.In order to improve the utilization efficiency of active species and the energy efficiency of this kind of discharge plasma reactor during wastewater treatment,the electrode configuration of the point-to-plane corona discharge reactor was studied by evaluating the effects of discharge spacing and adjacent point distance on discharge power and discharge energy density,and then dye-containing wastewater decoloration experiments were conducted on the basis of the optimum electrode configuration.The experimental results of the discharge characteristics showed that high discharge power and discharge energy density were achieved when the ratio of discharge spacing to adjacent point distance（d/s） was 0.5.Reactive Brilliant Blue（RBB） wastewater treatment experiments presented that the highest RBB decoloration efficiency was observed at d/s of 0.5,which was consistent with the result obtained in the discharge characteristics experiments.In addition,the biodegradability of RBB wastewater was enhanced greatly after discharge plasma treatment under the optimum electrode configuration.RBB degradation processes were analyzed by GC-MS and IC,and the possible mechanism for RBB decoloration was also discussed.

Effect of a high strength chemical industry wastewater on microbial community dynamics and mesophilic methane generation

A high strength chemical industry wastewater was assessed for its impact on anaerobic microbial com- munity dynamics and consequently mesophilic methane generation. Cumulative methane production was 251 mL/g total chemical oxygen demand removed at standard temperature and pressure at the end of 30 days experimental period with a highest recorded methane percentage of 80.6% of total biogas volume. Volatile fatty acids （VFAs） analysis revealed that acetic acid was the major intermediate VFAs produced with propionic acid accumulating over the experimental period. Quantitative analysis of microbial communities in the test and control groups with quantitative real time polymerase chain reaction highlighted that in the test group, Eubacteria （96.3%） was dominant in comparison with methanogens （3.7%）. The latter were dominated by Methanomicrobiales and Methanobacteriales while in test groups increased over the experimental period, reaching a maximum on day 30. Denaturing gradient gel electrophoresis profile was performed, targeting the 16S rRNA gene of Eubacteria and Archaea, with the DNA samples extracted at 3 different time points from the test groups. A phylogenetic tree was constructed for the sequences using the neighborhood joining method. The analysis revealed that the presence of organisms resembling Syntrophomonadaceae could have contributed to increased production of acetic and propionic acid intermediates while decrease of organisms resembling Pelotomaculum sp. could have most likely contributed to accumulation of propionic acid. This study suggested that the degradation of organic components within the high strength industrial wastewater is closely linked with the activity of certain niche microbial communities within eubacteria and methanogens.

Effect of alkalinity on nitrite accumulation in treatment of coal chemical industry wastewater using moving bed biofilm reactor

Nitrogen removal via nitrite （the nitrite pathway） is more suitable for carbon-limited industrial wastewater. Partial nitrification to nitrite is the primary step to achieve nitrogen removal via nitrite. The effect of alkalinity on nitrite accumulation in a continuous process was investigated by progressively increasing the alkalinity dosage ratio （amount of alkalinity to ammonia ratio, mol/mol）. There is a close relationship among alkalinity, pH and the state of matter present in aqueous solution. When alkalinity was insufficient （compared to the theoretical alkalinity amount）, ammonia removal efficiency increased first and then decreased at each alkalinity dosage ratio, with an abrupt removal efficiency peak. Generally, ammonia removal efficiency rose with increasing alkalinity dosage ratio. Ammonia removal efficiency reached to 88% from 23% when alkalinity addition was sufficient. Nitrite accumulation could be achieved by inhibiting nitrite oxidizing bacteria （NOB） by free ammonia （FA） in the early period and free nitrous acid in the later period of nitrification when alkalinity was not adequate. Only FA worked to inhibit the activity of NOB when alkalinity addition was sufficient.

Capability of phenol-degrading biofilm

The degradation rate of phenol-degrading biofilm was studied.The biofilm of the biofilm was a kind of phenol-degrading bacteria.The bacteria was separated from coal chemical industry wastewater.The carbon source adopted four kinds of phenols,including phenol,methyl phenol,2-methyl phenol and resorcinol.Stenotrophomonas maltophilia K279a was gained.Twelve ratio of artificial phenol mixture was designed.The degradation rate of the twelve groups was all 99.9% in 16 h.The degradation rate from high to low was phenol,resorcinol,methyl phenol,2-methyl phenol.Phenol improved the degradation of the other phenols.The coal chemical wastewater contained 980 mg/L COD and 805 mg/L phenol.The degradation rate of COD and phenol was 70% and 77%,respectively.The domesticated biofilm (D) and the biofilm without domestication (WD) respectively used 45 h and 56 h.The results showed that the biofilm can be applied to the aerobic treatment process with high proportion of total phenol.

Hybrid peroxi-coagulation/ozonation process for highly efficient removal of organic contaminants

Aromatic compounds such as phenols presented widely in coal chemical industry wastewater(CCW)render the treatment facing great challenge due to their biorefractory characteristics and potential risks to the environment and human health.Ozone-based advanced oxidation processes show promising for these pollutants removal,but the mineralization via ozonation alone is unsatisfactory and not cost-effective.Herein,a hybrid peroxi-coagulation/ozonation process(denoted as PCO)was developed using sacrificial iron plate as an anode and carbon black modified carbon felt as cathode in the presence of ozonation.An enhanced phenol removal of∼100%within 20 min and phenol mineralization of∼80%within 60 min were achieved with a low energy consumption of 0.35 kWh/g TOC.In this novel process,synergistic effect between ozonation and peroxi-coagulation was observed,and beside O_(3) direct oxidation,peroxone played a dominant role for phenol removal.In the PCO process,the hydrolyzed Fe species enhanced the generation of reactive oxygen species(ROS),while•OH was dominantly responsible for pollutant degradation.This process also illustrated high resistance to high ionic strength and better performance for TOC removal in real wastewater when compared with ozonation and peroxi-coagulation process.Therefore,this process is more cost-effective,being very promising for CCW treatment.