Journal of Environmental Sciences - Volume 14, issue 4

Authors: Lin, Jian-zhong | Wang, Ye-long | Wang, Wei-xiong | Yu, Zhao-sheng

Article Type: Research Article

Abstract: The sedimentation of cylindrical pollutant particleswhich fall through a fluid is investigated. Differing from previous research work, particle oscillation and effect of particle on thefluid are considered, and the torque exerted on a particle whenviscous fluid flow around a particle is got through experiment andincluded in the numerical simulation. The computational results showed that the sedimentation velocities of particle increase slowly with the increase of particle aspect ratio . For disk-like particle, …when the motion direction of particle is parallel to axis of particle, particle falls more slowly than the case ofperpendicular to axis of particle; while for rod-like particle, itis inverse. For sedimentation of a crowd of high-frequency oscillating cylindrical particles with arbitrary initialorientation, both vertical velocity and horizontal velocityoscillate dramatically, the degree of oscillation of the former is stronger than the later. A crowd of particles fall more quicklythan an isolated particle. Particles tend to strongly align in thedirection of gravity. The computational results agreed well withthe experimental ones and helpful for controlling of pollutant particles. Show more

Keywords: cylindrical pollutant particles, sedimentation, orientation, velocity, numerical simulation

Citation: Journal of Environmental Sciences, vol. 14, no. 4, pp. 433-438, 2002

Authors: Zhou, Dong-mei | Hao, Xiu-zhen | Tu, Cong | Chen, Huai-man | Si, You-bin

Article Type: Research Article

Abstract: Speciation of heavy metals in soil subsamples experimentally loaded with Pb, Cd, Cu and Zn in orthogonal design was investigated by sequential extraction, and operationally defined as water-soluble and exchangeable(SE), weakly specific adsorbed(WSA), Fe and Mn oxides-bound(OX) and organic-bound(ORG).The results show that speciation of heavy metals in the soil subsamples depended on their kinds. About 90% of Cd and 75% of Zn existed in soil subsamples in the SE fraction. Lead and Cu existed in soil …subsamples as SE, WSA and OX fractions simultaneously,although SE was still the major fraction. Organic-bound heavy metals were not clearly apparent in all the soil subsamples. Theconcentration of some heavy metal speciation in soil subsamples showed good correlation with ionic impulsion of soil, especially for the SE fraction. Continuous saturation of soil subsamples with0.20 mol/L NH_4Cl, which is the first step for determination of the negative surface charge of soil by the ion retention method, resulted in desorption of certain heavy metals from the soil. It was found that the percentage desorption of heavy metals from soil sub samples depended greatly on pH, the composition and originalheavy metal content of the soil subsamples. However, most of theheavy metals in the soil subsamples were still retained aftermultiple saturation. Compared with the parent soil, the negative surface charge of soil subsamples loaded with heavy metals did notshow differ significantly from that of the parent one bystatistical analysis. Heavy metals existed in the soil subsamplesmainly as exchangeable and precipitated simultaneously. Show more

Keywords: soil, heavy metals, speciation, soil surface charge

Citation: Journal of Environmental Sciences, vol. 14, no. 4, pp. 439-444, 2002

Authors: Lee, Tao Ho | Ike, Michihiko | Fujita, Masanori

Article Type: Research Article

Abstract: A laboratory sequential anaerobic-aerobic bioreactor system,which consisted of an anaerobic fixed film reactor and two aerobic chemostats, was set up to degrade tetrachloroethylene (PCE) without accumulating highly toxic degradation intermediates. A soil (ca. 150 mg/liter) of PCE stoichiometrically intocis-1,2-dichloroethylene (cis-DCE), was attached to ceramic media in the anaerobic fixed film reactor. A phenol degrading strain, Alcaligenes sp. R5, which can efficiently degrade cis-DCE byco-metabolic oxidation, was used as inoculum for the aerobicchemostats …consisted of a transformation reactor and a growth reactor. The anaerobic fixed film bioreactor showed more than 99 %of PCE transformation into cis-DCE in the range of influent PCE48h. On the other hand, efficient degradation of the resultant cis-DCE by strain R5 in the following aerobic system could not beachieved due to oxygen limitation. However, 54% of the maximum (H_2O_2) was supplemented to the transformation reactor as an additional oxygen source. Further studies are needed to achieve more efficient co-metabolic degradation of cis-DCE in the aerobic reactor. Show more

Keywords: anaerobic-aerobic bioreactor, co-oxidation, reductive dechlorination, tetrachloroethylene

Citation: Journal of Environmental Sciences, vol. 14, no. 4, pp. 445-450, 2002

Authors: Shi, Yao | Li, Wei

Article Type: Research Article

Abstract: A novel system has been proposed for the capture and separation of CO_2 from flue gas. In this method, a resin isemployed to regenerate the amine capturing CO_2 from flue gas atroom temperatures. The feasibility for the resin to regenerateamines such as MEA, MAE, TEA, and ammonia has been demonstrated. It was also discovered that the resin could be regenerated by hotwater.

Keywords: separation, CO2, flue gas, amine

Citation: Journal of Environmental Sciences, vol. 14, no. 4, pp. 451-456, 2002

Authors: Li, Ai-min | Zhang, Quan-xing | Chen, Jin-long | Fei, Zheng-hao | Long, Chao

Article Type: Research Article

Abstract: Adsorption equilibrium isotherms of phenolic compounds,phenol, p-cresol, p-chlorophenol and p-nitrophenol, from aqueous solutions by Amberlite XAD-4 polymeric adsorbent and its acetylized derivative MX-4 within temperature range of 283-323K were obtained and fitted to the Freundlich isotherms. The capacities ofequilibrium adsorption for all four phenolic compounds from theiraqueous solutions increased around 20% on the acetylized resin,which may be contributed to the specific surface area and thepartial polarity on the network. Estimations of the …isosteric enthalpy, free energy , and entropy for the adsorption process are reported. Show more

Keywords: macroporous polymeric adsorbent, phenolic compound, adsorption thermodynamic, temperature effect

Citation: Journal of Environmental Sciences, vol. 14, no. 4, pp. 457-463, 2002

Authors: Soltan, M.E.

Article Type: Research Article

Abstract: Environmental chemical study were carried out on theFatimid cemetery marsh at Aswan city(24°1'N and 32°9'E), Egypt.Marsh contents(warter, soil, sediment, metal and nonmetal-bearing salts, and emergent weed) were analysed to known the source of marsh water, speciation of the different elements between the marsh contents, and the toleration of emergent weed(Phargmitesaustralies) for different metals and their bioaccumulation coefficients. Thus, metals(Ca, Mg, Na, K, Ni, Fe, Mn, Cu, Zn, Cd and Pb) and nonmetals(CO, …HCO, Cl-, SO, PO, NO, SiO_2, organic matter and pH value) were determined in the samples. According to the chemical analysis, and applying the base exchange equation (water type) and calculate the hydrochemical parameters for marsh water samples, we can indicate that the marsh water is ground water with Na-SO_4 type and deep meteoric genesis. Topsoil of marsh dry land characterized by CaCl as dominant salt,while NaCl is a dominant salt in subsoil. The elevated pH values of marshc ontents minimized the metal solubilities in different samples.Phragmites australies showed a strong ability to accumulate Mn (Fe in the aerial part in opposite to Co, Ni and Cd. Show more

Keywords: marsh, water, soil, sediment, emergent, weed, Egypt

Citation: Journal of Environmental Sciences, vol. 14, no. 4, pp. 464-473, 2002

Authors: Li, Xiao-ming | Zeng, Guang-ming | Liu, Jing-jin | Chen, Jian | Lun, Shi-yi

Article Type: Research Article

Abstract: The high strength easily biodegradable pollutants(represented by COD_E) are strong inhibitors of terephthalic acid(TA) anaerobic biodegradation. At the same time, TA can inhibit easily biodegradable pollutants removal under anaerobic conditions to a limited extent. This mutual inhibition could happen and cause a low removal efficiency of both TA and CODE, when the effluent from TA workshops containing TA and easily biodegradable pollutants are treated by a single anaerobic reactor system. Based upon the treatment kinetics analysis …of both TA degradation and COD_E removal, a two-stage up-flow anaerobic sludge blanket and up-flow fixed film reactor(UASB-UAFF) system for dealing with this kind of wastewater was developed and run successfully at laboratory scale. An UASB reactor with the methanogenic consortium as the first stage removes the easily biodegradable pollutants(COD_E). An UAFF reactor as the second stage is mainly in charge of TA degradation. At a COD_E loading of 15.3 g/(L·d) and a TA loading of 1.4 g/(L·d), HRT 18.5h, the COD_E and TA removal rate of the system reached 89.2% and 71.6%, respectively. Show more

Keywords: wastewater treatment, anaerobic system, inhibition , kinetics, terephthalic acid(TA)

Citation: Journal of Environmental Sciences, vol. 14, no. 4, pp. 474-481, 2002

Authors: Wen, Rui-mei | Liang, Jun-wu

Article Type: Research Article

Abstract: The purpose of this article is to examine the methods and equipment for abating waste gases and water produced during the manufacture of semiconductor materials and devices. Three separating methods and equipment are presented in this article to control three different groups of electronic wastes. The first group includes arsine and phosphine emitted during the processes of semiconductor materials manufacture. The abatement procedure for this group of pollutants consists of adding iodates, cupric and manganese salts …to a multiple shower tower (MST) structure. The second group includes pollutants containing arsenic, phosphorus,HF, HCl, NO_2, and SO_3 emitted during the manufacture of semiconductor materials and devices. The abatement procedure involves mixing oxidants and bases in an oval column with a separator in the middle. The third group consists of the ions of As, P and heavy metals contained in the waste water. The abatement procedure includes adding CaCO_3 and ferric salts in a flocculation-sedimentation compact device equipment. Test results showed that all waste gases and water after the abatement procedures presented in this article passed the discharge standardsset by the state Environmental Protection Administration of China. Show more

Keywords: waste gases, waste water, abatement, pollutant, semiconductor

Citation: Journal of Environmental Sciences, vol. 14, no. 4, pp. 482-488, 2002

Authors: Hao, Zheng-ping | Zhang, Shi-chao | Liu, Zhi-ming | Zhang, Hui-ping

Article Type: Research Article

Abstract: With in situ IR, two different CO adsorption bands were detected on various chemical state gold catalysts. One band is attributed to the linear CO on an oxidized gold catalyst(2100 cm ^-1),the other one is ascribed to the bridged CO on metallic gold (2085cm^-1). CO pulse reaction showed that Au/Fe_2O_3 catalyst had a room-temperature activity even in the presence of moisture. The produced CO_2 was detained and more easily desorbed from supported gold catalyst than support …oxide. TPD-IDT results indicated that the O_2^- superoxide ions are the possible active oxygen species. Show more

Keywords: supported gold catalyst, room-temperature CO oxidation, pulse reaction, TPD-ITD technique

Citation: Journal of Environmental Sciences, vol. 14, no. 4, pp. 489-494, 2002

Authors: Peng, Wang | Lau, W C Ivan | Fang, H P Herbert

Article Type: Research Article

Abstract: Nearly 97% of organic chemicals in Hong Kong leachate could be effectively removed by the UASB(upflow anaerobic sludge blanket) process followed by the Fenton coagulation. The COD of leachate was lowered from an average of 12900 mg/L to 1440 mg/L after the UASB treatment, and was further lowered to 394 mg/L after the Fenton coagulation. The remaining refractory residues could be further removed by ozonation with the addition of H_2O_2. The ozonation for the supernatant of …the Fenton coagulation was mosteffective at pH 7-8, with the addition of 300 mg/L of H_2O_2, and 30 min of reaction. The final effluent contained only 85 mg/L of COD and 10 mg/L of BOD_5. On the other hand, direct ozonation of UASB effluent lowered the COD to 905 mg/L and BOD_5 to 103 mg/L.Ozonation improved the biodegradability of the organic residues,and also converted part of organic-N in the leachate into NH_3-N and NO_3^--N. Show more

Keywords: biodegradability, Fenton coagulation, hydrogen-peroxide, leachate, ozonation, UASB

Citation: Journal of Environmental Sciences, vol. 14, no. 4, pp. 495-500, 2002