Journal of Environmental Sciences - Volume 18, issue 1

Authors: LI, Xiang-kun | HUANG, Rong-xin | BAO, Lin-lin | SHAO, Chun-hong | ZHANG, Jie

Article Type: Research Article

Abstract: The ability of simultaneous biological phosphorus and nitrogen removal was investigated in a lab-scale continuous-flow two-sludge system. Alternating anaerobic and anoxic conditions were combined with contact oxidation stage for treating raw municipal wastewater. Long-term experiments showed that the contradiction of competing for the organic substrate between denitrifying bacteria and PAOs (phosphorus accumulating organisms) in traditional phosphorus and nitrogen removal system has been resolved. The system can adapt to low influent COD/TN ratio …(C/N). Furthermore the SRT (sludge retention time) of nitrifying sludge and denitrifying phosphorus removal sludge can be controlled at optimal conditions respectively. The removal efficiency of COD, TP, TN, and NH_4 -N was 81.78%, 92.51%, 75.75%, and 84.47% respectively. It was also found that the appropriate influent C/N should be controlled at the range of 3.8–6, while the optimal C/N to the system ranged between 4–5, and the BFR (bypass sludge flow rate) should be controlled at 0.35 around. Show more

Keywords: continue-flow two-sludge system, denitriflcation phosphorus removal, nitrification, contact oxidation

Citation: Journal of Environmental Sciences, vol. 18, no. 1, pp. 52-57, 2006

Authors: LU, Gang | ZHENG, Ping | JIN, Ren-cun | QAISAR, Mahmood

Article Type: Research Article

Abstract: Shortcut nitrification for ammonium-rich wastewater is energy-saving and cost-effective procedure that has become one of the hotspots in the field of biological denitrogenation. An orthogonal experiment was performed to study the combined effects of operational parameters on the performance of internal-loop airlift bioreactor for shortcut nitrification. The optimum operational parameters for the shortcut nitrification were found as temperature 35°C, pH 8.0, dissolved oxygen concentration 1.0 mg/L, ammonium concentration 4 mmol/L and HRT …16 h, which have different influence on the performance of shortcut nitrification reactor. The pH, temperature and dissolved oxygen concentration have significant bearing on the process. The results showed that the shortcut nitrification reactor could be successfully started up within 42 d, and the reactor performance is steady with minimum NO_2^- /NO_x^- of 85.2%, maximum 93.4% and average value of 91.4% in effluent. Based on the analysis of experimental data, a new control strategy named "priority + combination" for shortcut nitrification was suggested. Through this strategy, the startup and operation of shortcut nitrification for ammonium-rich sludge digester liquids were optimized. The control strategy works well to keep the reactor operation in steady state and in achieving high-efficiency for shortcut nitrification. Show more

Keywords: internal-loop airlift bioreactor, shortcut nitrification, orthogonal experiment, control strategy, sludge digester liquids

Citation: Journal of Environmental Sciences, vol. 18, no. 1, pp. 58-61, 2006

Authors: LIU, Yan-chen | FAN, Long | SHI, Han-chang | WANG, Zhi-qiang

Article Type: Research Article

Abstract: With the development of activated sludge model, the simulation software for the design and operation of wastewater treatment plant (WWTP) was produced and has been widely used. The dynamic change of the quality and flow of influent are major factors causing the unstable operation of wastewater treatment process. As a basic model, ASM1 model was used for the simulation of activated sludge process, and double exponential model was selected for the simulation of secondary sedimentation tank. …The influences of influent change to the aeration tank and secondary sedimentation tank were investigated, and the relationship among influent change, the quality of effluent and the level of sludge blanket in secondary sedimentation tank was established. On the basis of the simulation results, the operation of the WWTP could be adjusted under the dynamic change of the influent. Furthermore, the controlling strategy combined the feed-forward on the influent flow and the feedback on the level of sludge blanket in the secondary sedimentation tank was studied. Show more

Keywords: modeling, dynamic simulation, static simulation, controlling strategy, influent

Citation: Journal of Environmental Sciences, vol. 18, no. 1, pp. 62-68, 2006

Authors: QIN, Min | XIE, Pin-hua | LIU, Wen-qing | LI, Ang | DOU, Ke | FANG, Wu | LIU, Jian-guo | ZHANG, Wei-jun

Article Type: Research Article

Abstract: Measurements of nitrous acid (HONO) and nitrogen dioxide (NO_2 ) in Beijing City have been performed by means of a developed differential optical absorption spectroscopy (DOAS) system based on photodiode array (PDA), during the autumn of 2004. HONO and NO_2 were simultaneously identified by their characteristic absorption bands in the spectral region between 337 nm and 372 nm with high sensibility and time resolution. The concentrations of HONO exhibit obviously …diurnal variation with a nocturnal maximum and a daytime minimum. The highest HONO value up to 11.8 μg/m^3 was observed during the night of 2/3 September. Possible sources of the observed HONO were discussed. Good correlation to NO_2 indicates that NO2 is a main source component. The measurement also shows direct emission of HONO is an important source in strongly polluted urban area. Show more

Keywords: atmospheric measurements, HONO, NO_2, DOAS, source

Citation: Journal of Environmental Sciences, vol. 18, no. 1, pp. 69-75, 2006

Authors: HU, Chun | LIN, Lan-yu | HU, Xue-xiang

Article Type: Research Article

Abstract: The morphology of supported metal nanoparticles on TiO_2 /silical gel (TSO) and photothermal synergism were investigated for destruction of ethylene. During photocatalytic deposition of metal nanopartilces, the effects of pH and light intensity on the morphology of coated platinum, palladium, gold on TiO_2 /silical gel were studied. Moreover, these catalysts were characterized by TEM, UV-Vis DRS. The pH of preparing solution have strong influence on dispersion, size and sites of …Pt, Pd and Au on TSO, which were controlled by the electrostatic binding of HPtCl_6^- , AuCl_4^- and TiOH_2^+ , Pd^{2+} and TiO^- respectively. Platinum, gold and palladium nanoparticles were uniformly highly dispersed on the titanol sites not silanol of TiO_2 /silical gel under pH=2, pH=9.9 respectively. For the photodegradation of ethylene, they show higher photothermal efficiency than those prepared with other pH conditions under UV illumination in a non-circulating photoreactor. The optimum weight loadings of Pt. Au, and Pd were 0.25 wt%, 0.5 wt%, 1 wt%, respectively. The synergistic effect enhanced ethylene removal and CO_2 production. These results verify that the best photothermal synergistic effect depends on the dispersion, size of noble metal nano-particles. FTIR analyses of the used Pt-, Pd-TSO catalysts indicated that no significant by-products were accumulated on the surface of the catalysts, leading to them longer lifetime. Show more

Keywords: photodeposition, TiO_2/silical gel, noble metal, dispersion, photothermal synergism

Citation: Journal of Environmental Sciences, vol. 18, no. 1, pp. 76-82, 2006

Authors: Indarto, Antonius | CHOI, Jae-wook | LEE, Hwaung | SONG, Hyung-keun

Article Type: Research Article

Abstract: Decomposition of chlorinated hydrocarbons, CCl_4 and CHCl_3 , in gliding plasma was examined. The effects of initial concentrations, total gas flow rates, and power consumption have been investigated. The conversion result was relatively high. It reached 80% for CCl_4 and 97% for CHCl_3 . Using atmospheric air as the carrier gas, the plasma reaction occurred at exothermic reaction and the main products were CO_2 , CO, and …Cl_2. Transformation into CCl<FORMULA>_4 was also detected for CHCl_3 decomposition reaction. The conversion of CCl_4 and CHCl_3 were increased with the increasing applied frequency and decreasing total gas flow rate. Show more

Keywords: plasma;gliding arc, CCl_4, CHCl_3, decomposition reaction

Citation: Journal of Environmental Sciences, vol. 18, no. 1, pp. 83-89, 2006

Article Type: Other

Citation: Journal of Environmental Sciences, vol. 18, no. 1, pp. 89-89, 2006

Authors: LU, Sen-lin | SHAO, Long-yi | WU, Ming-hong | JIAO, Zheng

Article Type: Research Article

Abstract: This work mainly focuses on the mineralogical study of particulate matter (PM_{10} ) in Beijing. Samples were collected on polycarbonate filter from April, 2002 to March, 2003 in Beijing urban area. Scanning electronic microscopy coupled with energy dispersive X-ray (SEM/EDX) was used to investigate individual mineral particles in Beijing PM_{10} . 1454 individual mineral particulates from 48 samples were analysed by SEM/EDX. The results revealed that mineral particulates were complex …and heterogeneous. 38 kinds of minerals in PM_{10} were identified. The clay minerals, of annual average percentage of 30.1%, were the main composition among the identified minerals, and illite/smectite was the main composition in clay minerals, reaching up to 35%. Annual average percentage of quartz, calcite, compound particulates, carbonates were 13.5%, 10.9%, 11.95%, 10.31%, respectively. Annual average percentage less than 10% were gypsum, feldspar, dolomite, and so on. Fluorite, apatite, halite, barite and chloridize zinc (ZnCl_{2} ) were firstly identified in Beijing PM_{10} . Sulfurization was found on surface of mineral particles, suggested extensive atmospheric reaction in air during summer. Show more

Keywords: inhalable particulate matter (PM_{10}), individual analysis, mineral composition

Citation: Journal of Environmental Sciences, vol. 18, no. 1, pp. 90-95, 2006

Authors: GENG, Chun-nu | ZHU, Yong-guan

Article Type: Research Article

Abstract: In the present study, arsenate (As(V)) and phosphate (P(V)) interactions were investigated in growth, uptake and RNA content in yeast (Saccharomyces cerevisiae). Yeast grew slowly with As(V) concentrations increasing in the medium. However, the maximal population density was almost the same among different As(V) treatments. It was in the late log phase that yeast growth was augmented by low As(V), which was maybe due to the fact that methionine metabolism was stressed by vitamin B_6 …deprivation, so As(V) treatments did not affect maximal population density. However, with P(V) concentrations increasing, the maximal population density increased. Therefore, the maximal population density was determined by P(V) concentrations in the medium but not by As(V) concentrations in the medium. Ycf1p (a tonoplast transpor) transports As(GS)_3 into the vacuole, but arsenic (As) remaining in the thalli was 1.27% with As(V) exposure for 60 h, from which it can be speculated that the percentage of As transported into vacuole should be lower than 1.27%. However, the percentage of As pumped out of cell was 71.49% with As(V) exposure for 68 h. Although two pathways (extrusion and sequestration) were involved in As detoxification in yeast, the extrusion pathway played a major role in As detoxification. RNA content was the highest in the early-log phase and was reduced by As(V). Show more

Keywords: yeast, maximal population density, arsenic essentiality, arsenic speciation

Citation: Journal of Environmental Sciences, vol. 18, no. 1, pp. 96-100, 2006

Authors: SONG, Ning-hui | YANG, Zhi-min | ZHOU, Li-xian | WU, Xin | YANG, Hong

Article Type: Research Article

Abstract: Response of two wheat cultivars (Triticum aestivum cv. YM 158 and NM 9) to the herbicide chlorotoluron and the effect of two forms of dissolved organic matter on the chlorotoluron toxicity to the plants were characterized. Treatment with chlorotoluron at 10–50μg/ml inhibited the seed germination and a dose-response was observed. The inhibition of seed germination was correlated to the depression of α-amylase activities. To identify whether chlorotoluron induced oxidative damage to wheat plants, the …malondlaldehyde (MDA) content and electrolyte leakage were measured. Results showed that both MDA content and electrolyte leakage in the chlorotoluron-treated roots significantly increased. Activities of several key enzymes were measured that operate in citric acid cycle and carbohydrate metabolic pathway. Inhibited activities of citrate synthase and NADP-isocitrate dehydrogenase were observed in the chlorotoluron-treated roots as compared to control plants. We also examined malate dehydrogenase and phosphoenolpyruvate carboxylase in wheat roots exposed to 30 μg/ml chlorotoluron. However, none of the enzymes showed significant changes in activities. Application of 160 μg/ml dissolved organic matter (DOM) extracted from non-treated sludge (NTS) and heat-expanded sludge (HES) in the medium with 30 μg/ml chlorotoluron induced an additive inhibition of seed germination and plant growth. The inhibition of growth due to the DOM treatment was associated with the depression of activities of α-amylase, citrate synthase and NADP-isocitrate dehydrogenase, as well as the increase in malondlaldehyde content and electrolyte leakage. These results suggested that the presence of DOM might enhance the uptake and accumulation of chlorotoluron, and thus resulted in greater toxicity in wheat plants. The two forms of DOM exhibited differences in regulation of chlorotoluron toxicity to the wheat plants. Treatments with DOM-NTS induced greater toxicity to plants as compared to those with DOM-HES. In addition to DOM affecting chlorotoluron-induced toxicity to wheat plants, the cultivars could have also contributed to differences. Generally, NM-9 showed a higher sensitivity to chlorotoluron than YM 158 either in the absence or in the presence of DOM. Show more

Keywords: dissolved organic matter, chlorotoluron, Triticum aestivum, toxicity

Citation: Journal of Environmental Sciences, vol. 18, no. 1, pp. 101-108, 2006