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BACKGROUND Coal gasification wastewater ( CGW) is the most important wastewater of the coal chemical industry and if disposed of without adequate treatment can cause serious environmental pollution. Membrane bioreactors ( MBRs) have been widely used for high strength wastewater treatment; however, conventional MBRs potentially fail when the BOD/ COD of the biologically pretreated CGW ( BPCGW) is low. In the present study, strategies were employed to enhance MBR performance. RESULTS A long-term bio-augmented submerged membrane bioreactor ( BSMBR) has been developed for treatment of BPCGW. With the optimal methanol dosage of 30%, hydraulic retention time ( HRT) of 24 h, granular activated carbon ( GAC) dosage of 5 g L−1 and NaHCO3 dosage ratio of 3:1 (amount NaHCO3 to NH4+-N ratio, mol:mol), the concentrations of COD, total phenols and NH4+-N reached 39, 23 and 11 mg L−1 with removal efficiencies of 74%, 40% and 46%, respectively. HRT of 24 h and GAC dosage of 5 g L−1 facilitated membrane fouling mitigation while the co-metabolism process with methanol speeded up membrane fouling. High NaHCO3 dosage ratio (≥2:1) promoted nitritation-type nitrification. CONCLUSION This study suggests that it is technically feasible to treat BPCGW by BSMBR, which can provide an environmentally acceptable way to further engineering application in coal chemical industries. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The response surface methodology coupled with central composite design was applied to optimize the operational parameters of electro-Fenton (EF) as advanced treatment of biologically pretreated coal gasification wastewater. The integration of TOC, COD, and total phenols removal was selected as the response for model establishment and optimization. A quadratic model with high significance was developed to predict the treatment performance and optimize process parameters. The optimal parameters were determined as pH 3.83, 1.44 mmol L−1of Fe2+concentration, and 16.28 mA cm−2of current density, with the predicted optimal integration removal efficiency of 73.29%. TOC decay in the EF under optimal condition followed pseudo-first-order kinetic reaction with the apparent rate constant of 0.0103 min−1. The mass transfer constant was determined to be 4.29 × 10−5 m s−1at the optimal current density. The results demonstrated that EF could serve as a technically feasible and cost-effective method with potential applications for the advanced treatment of biologically stabilized coal gasification wastewater. [ABSTRACT FROM PUBLISHER]

The study aims to: (1) investigate the adsorption of powdered activated carbon (PAC) and granular activated carbon (GAC) for phenol, indole, and their mixtures, respectively, and (2) determine the bioregeneration efficiency and reusability of PAC loaded with phenol, indole, and their mixtures. The results showed that phenol was easier to be adsorbed than indole. The adsorption using PAC was obviously better than GAC. The considerably higher bioregeneration efficiency of the phenol-loaded PAC as compared to that of indole-loaded PAC was probably due to the recalcitrant nature of indole. PAC exhibited much higher adsorption capacity for indole, especially in the presence of low concentration of phenol. Besides, phenol improved the biodegradation of indole and therefore enhanced the reusability of indole-loaded PAC. Therefore, powdered activated carbon technology (PACT) was appropriate for the treatment of similar wastewater. Within the PACT system, PAC preferentially adsorbed the recalcitrant indole while the relatively easily degradable phenol was utilized by the biomass. Besides, phenol enhanced the degradation of indole and the reusability of PAC, which resulted in a stable and efficient performance. [ABSTRACT FROM PUBLISHER]

Coal gasification wastewater (CGW) is a refractory wastewater, whose anaerobic treatment has been a severe problem due to its toxicity and poor biodegradability. Using a two-stage anaerobic digestion as a control, the two-phase anaerobic digestion of real CGW was investigated. After 210 d of operation, the maximum removal efficiencies of COD and total phenols (TP) reached 50–60% and 55–60%, respectively, in the two-phase anaerobic digestion at total hydraulic retention time (HRT) of 48 h; the corresponding efficiencies were at low levels of 40–45% and 42–50%, respectively, in the two-stage anaerobic digestion. COD and TP removal efficiencies increased to 69.7 and 65.9%, when 50% of the effluent was recirculated to the hydrolytic acidogenic reactor. Phenol utilization rate and specific methanogenic activity (SMA) were decreased to 57.6 mg phenol/(gVSS d) and 394.3 mg COD-CH4/(gVSS d), respectively, as the HRT in the hydrolytic acidogenic reactor was reduced to 18 h. After the two-phase anaerobic digestion, the wastewater concentrations of the aerobic effluent COD could reach below 150 mg/l when compared to 237.2 mg/l if two-stage anaerobic digestion was done and 328.5 mg/l if sole aerobic pretreatment was done. The results suggested that the two-phase anaerobic digestion improved significantly both anaerobic and aerobic biodegradation of real CGW. [ABSTRACT FROM PUBLISHER]

Heterogeneous catalytic ozonation was applied to the treatment of coal chemical industry wastewater secondary effluent. Activated carbon-supported copper and manganese oxide were used as catalysts to assist ozone in degrading COD and NH3-N of secondary effluent. The results indicated that the presence of catalysts significantly elevated the removal efficiency of ozone on COD and NH3-N, as compared to the single ozone oxidation. The final effluent removal efficiency of COD and NH3-N were 60% - 72% and 30% - 35% respectively, the average concentration of COD and NH3-N was lower than 60 and 15 mg/L, and met Wastewater Discharge Standard (GB 18918-2002). The catalytic activity was restricted in acidic conditions and promoted in alkali conditions, however, catalysts improved degradation efficiency regardless of acid-base conditions as compared to the single ozone oxidation. The final effluent biodegradability was significantly improved, and no secondary pollution in the receiving water was produced. [ABSTRACT FROM AUTHOR]

Abstract: By the reflux to different sites, that is all reflux to denitrification stage (DN) or shunting circuit into settling bucket and DN at a certain proportions,the performance of pre-denitrification biological aerated filter in a pilot-scale was assessed, especially enhancing denitrificaion methods for low carbon-to-nitrogen domestic sewage. The results showed that in the condition of all reflux to DN,at the reflux ratio ranges from 100,130 to 150%, the average removal efficiency of TCOD enhanced with the value 58.5, 62.3 and 65.8% and that of NH4-N was 84.5, 87.5 and 94.7%, whereas the average removal efficiency of TN presented 37.1, 40.9 and 39.7%. In the test, the removal increase of total nitrogen had no unanimous increase with the reflux ratio increase. The TN average removal achieved 56.4% and 60.5% when the quantities of reflux were shunted circuit to settling bucket and DN by 1:1 and 2:1 at 130% of the return flow. Therefore, most of reflux passing by settling bucket for oxygen consumption was the better proposal of improving TN removal efficiency for low C/N wastewater. [Copyright &y& Elsevier]

Abstract: Hydrolysis acidification/pre-denitrification biological aerated filter was adopted in an domestic wastewater treatment plant. The effluent was accorded with A standard in the Integrated Wastewater Discharge Standard(GB18918-2002), in which the effluent phosphorus was demanded below 0.5mg/L. Through analysis on the process biological phosphorus removal, biological method can be found to total phosphorus 1.5mg/L. If you reach level to A emissions standards, phosphorus chemical experiment research, finally determined by strategy for the CN pool, point for adding potions FeCl3, dosing quantity for 35mg/L. [Copyright &y& Elsevier]

Abstract: A2O process with fluidized carriers was used to treat municipal wastewater. Put fluidized carriers sharing 40% volume into aerobic zone to enhance nitrifying capacity of the system. The average of NH 4 +-N removel rate was about 83.7%, and the tiptop could reach 95.16%. The average of TN removal rate was 60.3%, and the tiptop could reach 73.7%. The TN removal was beyond the bacteria assimilation. TN removal rate could be as high as 16.3% of the whole reactor. The system showed a significant phenomenon of simultaneous nitrification and denitrification. [Copyright &y& Elsevier]