Journal of Environmental Sciences - Volume 18, issue 4

Authors: ZHAO, Qing-liang | LIU, Xue-yan | QI, Xu-dong | LIU, Zhi-gang

Article Type: Research Article

Abstract: Landfill leachate recirculation treatment process is a promising and economic way in northeast China due to the distinct season variation. In order to study the impact of recirculation on leachate production and its quality, two simulated sanitary landfill reactors, one with leachate recirculation and the other without, were placed outdoor in Harbin. The two-year experimental results indicated that leachate production was reduced by 86% with leachate recirculation and less or no facility for leachate treatment required. …Recirculation could improve the leachate quality dramatically with lower COD, SS, NH^4_+ -N and higher pH level. Recirculation also could enhance waste degradation and stabilization and improve the efficiency of landfill. This study confirmed that leachate recirculation was a very feasible way for on-site landfill leachate treatment in cold areas. Show more

Keywords: cold area, sanitary landfill, leachate, recirculation, solid waste

Citation: Journal of Environmental Sciences, vol. 18, no. 4, pp. 625-628, 2006

Authors: ZHANG, Jin | SUN, Yu-xin | HUANG, Zhi-feng | LIU, Xing-qin | MENG, Guang-yao

Article Type: Research Article

Abstract: The oily wastewater generated from pretreatment unit of electrocoating industry contains oils, phosphate, organic solvents, and surfactants. In order to improve the removal efficiencies of phosphate and oils, to mitigate the membrane fouling, coagulation for ceramic membrane microfiltration of oily wastewater was performed. The results of filtration tests show that the membrane fouling decreased and the permeate flux and quality increased with coagulation as pretreatment. At the coagulant Ca (OH)_2 …dosage of 900 mg/L, the removal efficiency of phosphate was increased from 46.4% without coagulation to 99.6%; the removal of COD and oils were 97.0% and 99.8%, respectively. And the permeate flux was about 70% greater than that when Ca(OH)_2 was not used. The permeate obtained from coagulation and microfiltration can be reused as make-up water, and the recommended operation conditions for pilot and industrial application are transmembrane pressure of 0.10 MPa and cross-flow velocity of 5 m/s. The comparison results show that 0.2μm ZrO_2 microfilter with coagulation could be used to perform the filtration rather than conventional ultrafilter, with very substantial gain in flux and removal efficiency of phosphate. Show more

Keywords: ceramic membrane, crossflow microfiltration, coagulation, phosphate removal, fouling mitigation, phosphate-containing oily wastewater

Citation: Journal of Environmental Sciences, vol. 18, no. 4, pp. 629-633, 2006

Authors: WANG, Jian-ling | WANG, Bao-zhen | WANG, Lin | ZHANG, Jin-song | HUANG, Wen-zhang

Article Type: Research Article

Abstract: The concentration of suspended solids of effluent often varies in a wide range, therefore the dose of ultraviolet light (UV) in disinfection process needs to be adjusted to meet the disinfection criterion at a high frequency, and the desired disinfection effect is difficult to be ensured. The particles size and particle-associated fecal coliform (F.C.) contribution, and their influence on UV disinfection were investigated when ClO_2 and UV combined disinfection process was used. The …results showed that suspended solids content had a major impact on UV disinfection efficiency, especially the large particle size fraction. Particles (D>10μm) associated F.C. were difficult to be disinfected and were the main part of the tailings of F.C. inactivation curve. Pre-ClO_2 oxidation could reduce the number of particles in effluent, and make large particles decrease to small ones. Therefore, the influence of particles on UV disinfection could be reduced after pre-ClO_2 oxidation, and the resistance ability to particle loadings of combined process was enhanced. Moreover, the combined process has a lot of advantages, such as low toxicity, low operational/maintenance costs; it is also convenient to be established in the existing wastewater plant or the new planned one. Show more

Keywords: effluent disinfection, bio-toxicity, UV disinfection, ClO_2/UV combined disinfection

Citation: Journal of Environmental Sciences, vol. 18, no. 4, pp. 634-638, 2006

Authors: LI, Xin-gang | WANG, Tao | SUN, Jin-sheng | HUANG, Xin | KONG, Xiao-song

Article Type: Research Article

Abstract: Functional microorganisms to high concentration phenol containing Cr^{6+} and Pb^{2+} were cultured and biofilm was formed on polypropylene packings in bioelectro-reactor. It was found that the biodegradation capability of such biofilm to phenol changed with the applied voltage. Under the optimal electric field conditions (voltage of 3.0 V, electric field of strength 17.7 V/m and current density of 1.98 A/m^2 ), biodegradation efficiency of phenol aof concentration …of 1200 mg/L increased 33% compared to the instance without applying electric field. However, voltage had inverse effect on biodegradation, as microorganisms were killed under strong electric field. Voltage had little effect on heavy ions elimination. Higher absorption rate of Cr^{6+} and Pb^{2+} was observed when changing pH from acidic to neutral. The experiment results indicated that, after treatment, 10 L phenol of 2400 mg/L was biodegraded completely within 55 h and concentrations of Cr^{6+} and Pb^{2+} dropped to less than 1 mg/L within 12 h and 6 h, from initial values of 50 mg/L and 30 mg/L, respectively. Show more

Keywords: biofilm, biodegradation, phenol, heavy ions, electric field, reactor

Citation: Journal of Environmental Sciences, vol. 18, no. 4, pp. 639-643, 2006

Authors: WEI, Chao-hai | HU, Cheng-sheng | WU, Chao-fei | YAN, Bo

Article Type: Research Article

Abstract: The supercritical water gasification of phenolic wastewater without oxidant was performed to degrade pollutants and produce hydrogen-enriched gases. The simulated o-cresol wastewater was gasified at 440–650°C and 27.6 MPa in a continuous Inconel 625 reactor with the residence time of 0.42–1.25 min. The influence of the reaction temperature, residence time, pressure, catalyst, oxidant and the pollutant concentration on the gasification efficiency was investigated. Higher temperature and longer residence time enhanced the o-cresol …gasification. The TOC removal rate and hydrogen gasification rate were 90.6% and 194.6%, respectively, at the temperature of 650°C and the residence time of 0.83 min. The product gas was mainly composed of H_2 , CO_2 , CH_4 and CO, among which the total molar percentage of H_2 and CH_4 was higher than 50%. The gasification efficiency decreased with the pollutant concentration increasing. Both the catalyst and oxidant could accelerate the hydrocarbon gasification at a lower reaction temperature, in which the catalyst promoted H_2 production and the oxidant enhanced CO_2 generation. The intermediates of liquid effluents were analyzed and phenol was found to be the main composition. The results indicate that the supercritical gasification is a promising way for the treatment of hazardous organic wastewater. Show more

Keywords: supercritical water, gasification, o-cresol, hydrogen-enriched gas, wastewater treatment

Citation: Journal of Environmental Sciences, vol. 18, no. 4, pp. 644-649, 2006

Authors: LIU, Wen-jun | ZHANG, Yong-ji

Article Type: Research Article

Abstract: The effects of UV intensity and turbidity on selected microbial indicator inactivation were investigated. Results showed that UV disinfection was effective in killing all the selected microbial indicators, the resistance order of the microorganisms was as follows: MS-2 coliphage > Bacillus subtilis > E. coli > Staphylococcus aureus and Candida albicans. UV intensity had influence on the inactivation of all the microorganisms, high UV disinfection efficency was obtained with higher UV intensity. …Turbidity had impact on the bacteria inactivation rate, but there was no evidence that turbidity had any negative contribution to MS-2 coliphage. Under the same UV dosage, higher UV intensity could overcome the negative influence of turbidity on UV performance, enhanced microorganism inactivation effect in turbidity water. Show more

Keywords: UV disinfection, intensity, exposure time, microbial indicator

Citation: Journal of Environmental Sciences, vol. 18, no. 4, pp. 650-653, 2006

Authors: LI, Jun | ZHANG, Zhen-jia | LI, Zhi-rong | HUANG, Guang-yu | Abe, Naoki

Article Type: Research Article

Abstract: The distillery wastewater of Guangdong Jiujiang Distillery, which is characteristic of containing high organic matters and rich total nitrogen, was treated by a combination of methane fermentation and denitrification/nitrification processes. 80% of COD in the raw wastewater was removed by methane fermentation at the COD volumetric loading rate of 20 kg COD/(m^3 ·d) using the expanded granule sludge bed (EGSB) process. However, almost all the organic nitrogen in the raw wastewater …was converted into ammonia by ammonification there. Ammonia and volatile fatty acids (VFA) remaining in the anaerobically treated wastewater were simultaneously removed utilizing VFA as an electron donor by denitrification occurring in the other EGSB reactor and nitrification using PEG-immobilized nitrifying bacteria with recirculation process. An aerobic biological contact oxidization reactor was designed between denitrification/nitrification reactor for further COD removal. With the above treatment system, 18000–28000 mg/L of COD in raw wastewater was reduced to less than 100 mg/L. Also, ammonia in the effluent of the system was not detected and the system had a high removal rate for 900–1200 mg/L of TN in the raw wastewater, only leaving 400 mg/L of nitrate nitrogen. Show more

Keywords: ammonia, COD, VFA, methane fermentation, denitrification, nitrification, distillery wastewater, immobilized nitrifying bacteria

Citation: Journal of Environmental Sciences, vol. 18, no. 4, pp. 654-659, 2006

Authors: REN, Guang-meng | SUN, De-zhi | CHUNG, Jong Shik

Article Type: Research Article

Abstract: An investigation on the process of ozone combined with hydrogen peroxide and ultraviolet radiation has been carried out in order to establish the kinetics for photochemical oxidation of polyacrylamide (PAM) in aqueous solution. Effects of operating parameters, including initial PAM concentration, dosages of ozone and hydrogen peroxide, UV radiation and pH value on the photochemical oxidation of PAM, have been studied. There was an increase in photochemical oxidation rate of PAM with increasing of dosages of …O_3 , H_2 O_2 and ultraviolet radiation. Upon increasing of the initial PAM concentration, the photochemical oxidation rate of PAM decreased. Slight effect of pH value on the photochemical oxidation rate of PAM was observed in the experiments. The kinetics equation for the photochemical oxidation of PAM by the system has been established. Show more

Keywords: photochemical oxidation, polyacrylamide, kinetics, ozone/hydrogen peroxide/ultraviolet radiation

Citation: Journal of Environmental Sciences, vol. 18, no. 4, pp. 660-664, 2006

Authors: CUI, Li-hua | LIU, Wen | ZHU, Xi-zhen | MA, Mei | HUANG, Xi-hua | XIA, Yan-yang

Article Type: Research Article

Abstract: The integrated wetland systems were constructed by combining horizontal-flow and vertical-flow bed, and their purification efficiencies for septic tank effluent were detected when the hydraulic retention time (HRT) was 1 d, 3 d, 5 d under different seasons. The results showed that the removal efficiencies of the organics, phosphorus were steady in the hybrid systems, but the removal efficiency of total nitrogen was not steady due to high total nitrogen concentration in the septic tank effluent. …The average removal rates of COD (chemical oxygen demand) were 89%, 87%, 83%, and 86% in summer, autumn, winter and spring, respectively, and it was up to 88%, 85%, 73%, and 74% for BOD_5 (5 d biochemical oxygen demand) removal rate in four seasons. The average removal rates of TP (total phosphorous) could reach up to 97%, 98%, 95%, 98% in four seasons, but the removal rate of TN (total nitrogen) was very low. The results of this study also indicated that the capability of purification was the worst in winter. Cultivating with plants could improve the treated effluent quality from the hybrid systems. The results of the operation of the horizontal-flow and vertical-flow cells (hybrid systems) showed that the removal efficiencies of the organics, TP and TN in horizontal-flow and vertical-flow cells were improved significantly with the extension of HRT under the same season. The removal rate of 3 d HRT was obviously higher than that of 1 d HRT, and the removal rate of 5 d HRT was better than that of 3 d HRT, but the removal efficiency was not very obvious with the increment of HRT. Therefore, 3 d HRT might be recommended in the actual operation of the hybrid systems for economic and technical reasons. Show more

Keywords: constructed wetlands, hybrid system, horizontal-flow, vertical-flow, removal efficiency, septic tank effluent

Citation: Journal of Environmental Sciences, vol. 18, no. 4, pp. 665-669, 2006

Authors: LIU, Ya-nan | XUE, Gang | YU, Shui-li | ZHAO, Fang-bo

Article Type: Research Article

Abstract: Three sequencing batch reactors supplied with different carbon sources were investigated. The system supplied with glucose gained the best enhanced biological phosphorus removal although all of the three reactors were seeded from the same sludge. With the measurement of poly-β-hydroxyalkanoate (PHA) concentration, phosphorus content in sludge and extracellular exopolymers (EPS) with scanning electron microscopy (SEM) combined with energy dispersive spectrometry (EDS), it was found that the biosorption effect of EPS played an …important role in phosphorus removal and that the amount of PHA at the end of anaerobic phase was not the only key factor to determine the following phosphorus removal efficiency. Show more

Keywords: biological phosphorus removal, extracellular exopolymers, biosorption

Citation: Journal of Environmental Sciences, vol. 18, no. 4, pp. 670-674, 2006