Journal of Environmental Sciences - Volume 16, issue 3

Authors: WANG, Lian-feng | CAI, Zu-cong | YAN, Hong

Article Type: Research Article

Abstract: A laboratory incubation experiment was conducted to investigate nitrous oxide (N_2 O) emission and reduction in a paddy soil (Stagnic Anthrosol) response to the pretreatment of water regime. The paddy soil was maintained under either air-dried (sample D) or submerged (sample F) conditions for 110 d before the soil was adjusted into soil moisture of 20%, 40%, 60%, 80% and 100% water holding capacity (WHC) respectively, and then incubated with or without 10%(v/v) acetylene for …138 h at 25°C. At lower soil water content (⩽ 60% WHC), N_2 O emission from the sample F was 2.29 times higher than that from the sample D (P < 0.01). While, N_2 O emission from the sample F was only 29 and 14 percent of that from the sample D at the soil moisture of 80% and 100% WHC, respectively (P < 0.01). The maximal N_2 O emissions observed at soil moisture of 80% WHC were about 24 and 186 times higher than the minima obtained at the soil moisture of 20% WHC for the sample F and D, respectively. But at the soil moisture of 80% and 100% WHC, N_2 O emission from the sample F with acetylene(F+ACE) was comparable to that of the sample D with acetylene (D+ACE). The results showed that the F sample produced N_2 O ability in denitrification was similar to the sample D, however, the sample F was in the better reduction of N_2 O to N_2 than the sample D even after the soil moisture was adjusted into the same level of 80% or 100% WHC. Therefore, the pretreatment of water regime influenced the strength and product composition of denitrification and N_2 O emission from the paddy soil. Show more

Keywords: denitrification, nitrous oxide reduction, acetylene, product composition, paddy soil

Citation: Journal of Environmental Sciences, vol. 16, no. 3, pp. 353-357, 2004

Authors: LIU, Hong | LIU, Hui-juan | QU, Jiu-hui

Article Type: Research Article

Abstract: A survey concerning the concentration of the nutrients in the Three Gorges Reservoir Area was carried out. This paper presents the parameters (NO_3^- -N, NO_2^- -N, Kjeldahl-N, non-ionic ammonia, P-PO_4 and TP) determined at 16 sampling sites from 1997 to 1999. The dominant soluble nitrogen form was NO_3^- -N followed by Kjeldahl-N, NO_2^- -N and non-ionic ammonia. Mean values of NO_3^- -N, NO_2^- -N …Kjeldahl-N and non-ionic ammonia ranged from 0.50 to 2.37 mg/L, 0.022 to 0.084 mg/L, 0.33 to 0.99 mg/L and 0.007 to 0.092 mg/L respectively. Mean values of P-PO_4 at most sampling sites were higher than 0.1 mg/L for subject to eutrophication. The major factors influencing the concentrations of N and P might be agricultural runoff, municipal and industrial effluents. In addition, 6 kinds of soil were sampled at the area where would inundated after the dam completed. Two approaches were adopted to simulate the N and P release from the inundated soils. The results showed that the soils would release nitrogen and phosphorus to the overlying water when the soils were inundated. The characteristics of soil affected the equilibrium concentrations of N and P between the soil and the overlying water. Show more

Keywords: The Three Gorges Reservoir Area, nitrogen, phosphorus, inundated soil

Citation: Journal of Environmental Sciences, vol. 16, no. 3, pp. 358-363, 2004

Authors: FENG, Shao-hong | ZHANG, Shu-juan | YU, Han-qing | LI, Qian-rong

Article Type: Research Article

Abstract: The degradation of nitrobenzene (NB) by γ-ray irradiation was studied. The influences of dose rate and initial NB concentration were investigated in details. At a dose rate of 55 Gy/min, the degradation kinetics was pseudo-first-order at NB concentrations from 0.2 mmol/L to 4.0 mmol/L. At an initial NB concentration of 0.8 mmol/L, the degradation of NB at various dose rates also followed pseudo-first-order kinetics. Dissolved oxygen was found to have a positive effect on NB …degradation. The degradation products were identified as nitrophenol, nitrosobenzene, and hydroquinone, and so on. Based on the product analysis, possible degradation pathways of nitrobenzene were proposed. Show more

Keywords: degradation, irradiation, nitrobenzene(NB), kinetics

Citation: Journal of Environmental Sciences, vol. 16, no. 3, pp. 364-366, 2004

Authors: XIA, Shi-bin | LIU, Jun-xin

Article Type: Research Article

Abstract: The oxidation ditch process is economic and efficient for wastewater treatment, but its application is limited in case where land is costly due to its large land area required. An innovative integrated oxidation ditch with vertical circle (IODVC) system was developed to treat domestic and industrial wastewater aiming to save land area. The new system consists of a single-channel divided into two ditches (the top one and the bottom one by a plate), a Kesner type …brush, and an innovative integral clarifier. Different from the horizontal circle of the conventional oxidation ditch, the flow of IODVC system recycles from the top zone to the bottom zone in the vertical circle as the brush is running, and then the IODVC saved land area required by about 50% compared with a conventional oxidation ditch with an intrachannel clarifier. The innovative integral clarifier is effective for separation of liquid and solids, and is preferably positioned at the opposite end of the brush in the ditch. It does not affect the hydrodynamic characteristics of the mixed liquor in the ditch, and the sludge can automatically return to the down ditch without any pump. In this study, experiments of domestic and dye wastewater treatment were carried out in bench scale and in full scale, respectively. Results clearly showed that the IODVC efficiently removed pollutants in the wastewaters, i.e., the average of COD removals for domestic and dye wastewater treatment were 95% and 90%, respectively, and that the IODVC process may provide a cost effective way for full scale dye wastewater treatment. Show more

Keywords: integrated oxidation ditch, vertical circle, domestic wastewater, dye wastewater treatment

Citation: Journal of Environmental Sciences, vol. 16, no. 3, pp. 367-370, 2004

Authors: CANG, Long | WANG, Yu-jun | ZHOU, Dong-mei | DONG, Yuan-hua

Article Type: Research Article

Abstract: The heavy metals pollution in poultry and livestock feeds and manures under intensive farming in Jiangsu Province was investigated. 97 feed and manure samples were sampled from 31 farming plants in 10 major cities of Jiangsu. 14 metals, including Zn, Cu, Pb, Cd, Cr, Ni, Mo, Mn, Ba, Co, Sr, Ti, As and Hg, were analyzed after samples acid digestion. The results showed that the most feed samples contained high concentration of metals exceeding National Hygienical …Standard for Feeds. Meanwhile, it was found that Cu, Zn, Pb, Cd and Cr concentrations in animal manures were also high, for example, Cu concentration in a manure sample reached to as much as 1726.3 mg/kg. Heavy metals loading quantities in soil per year were then calculated when metals contaminated organic fertilizers were applied, and its effects on soil environmental quality were further evaluated. Show more

Keywords: heavy metal, intensive farming, feed, manure, Jiangsu Province

Citation: Journal of Environmental Sciences, vol. 16, no. 3, pp. 371-374, 2004

Authors: LI, Yun-cang | ZOU, Lin-da | Hu, Eric

Article Type: Research Article

Abstract: Photocatalytic oxidation (PCO) process is an effective way to deal with organic pollutants in wastewater which could be difficult to be degraded by conventional biological treatment methods. Normally the TiO_2 powder in nanometre size range was directly used as photocatalyst for dye degradation in wastewater. However the titanium dioxide powder was arduous to be recovered from the solution after treatment. In this application, a new form of TiO_2 (i.e. pillar pellets …ranging from 2.5 to 5.3 mm long and with a diameter of 3.7 mm) was used and investigated for photocatalytic degradation of textile dye effluent. A test system was built with a flat plate reactor (FPR) and UV light source(blacklight and solar simulator as light source respectively) for investigating the effectiveness of the new form of TiO_2 . It was found that the photocatalytic process under this configuration could efficiently remove colours from textile dyeing effluent. Comparing with the TiO_2 powder, the pellet was very easy to recovered from the treated solution and can be reused in multiple times without the significant change on the photocatalytic property. The results also showed that to achieve the same photocatalytic performance, the FPR area by pellets was about 91% smaller than required by TiO_2 powder. At least TiO_2 pellet could be used as an alternative form of photocatalyst in applications for textile effluent treatment process, also other wastewater treatment processes. Show more

Keywords: dyes degradation, photocatalytic reactions, TiO_2 catalystIntroduction

Citation: Journal of Environmental Sciences, vol. 16, no. 3, pp. 375-379, 2004

Authors: WANG, Shu-ying | GAO, Da-wen | PENG, Yong-zhen | WANG, Peng | YANG, Qing

Article Type: Research Article

Abstract: A novel treating technology for nitrogen removal from soybean wastewater was studied. The process for nitrogen removal was achieved by alternating aeration and mixing, combined with real-time control strategies. Results showed that the COD and total nitrogen removal rates are more than 90% and 92% at COD and total nitrogen loads of 1.0–1.2 kg COD/(kgMLSS ˙ d) and 0.20–0.27 kg TN/(kgMLSS ˙ d), respectively. In addition, it could improve sludge setting property. SVI value is less …than 70 g/ml during the whole cycles. The method not only may be adapted to treat soybean wastewater with high nitrogen, but also may be applied to treat other high nitrogen wastewater. Show more

Keywords: fuzzy control, nitrification, nitrite, ORP, pH, SBR

Citation: Journal of Environmental Sciences, vol. 16, no. 3, pp. 380-383, 2004

Authors: WANG, Yan-ming | YANG, Min | ZHANG, Yu | GAO, Meng-chun | ZHANG, Jing

Article Type: Research Article

Abstract: The biological removal of methanol from condensate of ammonia manufacturing processes for the purpose of reclamation using contact type reactor was studied. Methanol of 60 mg/L was removed completely under an HRT of 1.12 h. Optimal inorganic nutrient dose was determined on evaluating methanol removal performance and dehydrogenase activities (DHA) under different nutrition doses. The optimal inorganic nutrient dose only gave an increase of conductivity of ca. 10 μs/cm_2 in the effluent on …treating synthetic condensate containing methanol of 30 mg/L. The results demonstrated that biological removal of methanol was effective for the purpose of recovering the methanol-bearing condensate. Show more

Keywords: reclamation, condensate, methanol removal, biological contact reactorIntroduction

Citation: Journal of Environmental Sciences, vol. 16, no. 3, pp. 384-386, 2004

Authors: LIU, Min | REN, Nan-qi | CHEN, Ying | ZHU, Wen-fang | DING, Jie

Article Type: Research Article

Abstract: On the basis of continuous tests and batch tests, conversion regular patterns of acetate, propionate and butyrate in activated sludge at different heights of the UASB reactor were conducted. Results indicated that the conversion capacity of the microbial is decided by the substrate characteristic when sole VFA is used as the only substrate. But when mixed substrates are used,the conversion regulations would have changed accordingly. Relationships of different substrates vary according to their locations. In the …whole reactor, propionate's conversion is restrained by acetate and butyrate of high concentration. On the top and at the bottom of the reactor, conversion of acetate, but butyrate, is restrained by propionate. And in the midst, acetate's conversion is accelerated by propionate while that of butyrate is restrained. It is proved, based on the analysis of specific conversion rate, that the space distribution of the microbe is the main factor that affects substrates' conversion. The ethanol-type fermentation of the acidogenic-phase is the optimal acid-type fermentation for the two-phase anaerobic process. Show more

Keywords: conversion regular pattern, VFAs, specific conversion rate, UASB reactor

Citation: Journal of Environmental Sciences, vol. 16, no. 3, pp. 387-391, 2004

Authors: SONG, Hua | WU, Guang-xia | LIU, Kai

Article Type: Research Article

Abstract: The sensitivity of poly (arylsulfone)(PSf) for UV irradiation in different solvents (water and ethanol) was investigated. It is confirmed that acrylic acid (AA) and acrylamide (AAm) are grafted only onto the surface of the membrane instead of the interior by FTIR and scanning electron microscope (SEM). The membrane performance (ΔJ/J_0 and contact angle θ) after photografting was studied. In the range of conditions used, the grafting yield increases with irradiation time and monomer …concentration growing. After photografting and N-3-dimethyl-aminopropyl-N'-ethycarbodiimide hydrochloride (EDC) activation, PSf membrane was immobilized with hydrogen peroxide oxidoreductase, and showed a higher activity than the control membrane. Show more

Keywords: photografting, poly (arylsulfone) ultrafiltration membrane, immobilization

Citation: Journal of Environmental Sciences, vol. 16, no. 3, pp. 392-396, 2004