Effects of Ca(OH)2 assisted aluminum sulfate coagulation on the removal of humic acid and the formation potentials of tri-halomethanes and haloacetic acids in chlorination

The effects of addition of calcium hydroxide on aluminum sulphate(or alum) coagulation for removal of natural organic matter(NOM) and its subsequent effect on the formation potentials of two major types of regulated disinfection byproducts(DBPs),haloacetic acids(HAAs) and trihalomethanes(THMs),have been examined.The results revealed several noteworthy phenomena.At the optimal coagulation pH(i.e.6),the coagulation behavior of NOM water solutions versus alum dose,showed large variation and a consequent great change in the formation potentials of the DBPs at certain coagulant doses.However,with addition of a relatively small amount of Ca(OH) 2,although the zeta potential of coagulated flocs remained almost the same,NOM removal became more consistent with alum dose.Importantly,also the detrimental effect of charge reversal on NOM removal at the low coagulant dose disappeared.This resulted in a steady decrease in the formation potentials of DBPs as a function of the coagulant dose.Moreover,the addition of Ca(OH) 2 broadened the pH range of alum coagulation and promoted further reduction of the formation potentials of the DBPs.The enhancement effects of Ca(OH) 2 assisted alum coagulation are especially pronounced at pH 7 and 8.Finally,synchronous fluorescence spectra showed that the reduction in DBPs formation potential by Ca(OH) 2-assisted alum coagulation was connected to an enhanced removal of small hydrophobic and hydrophilic HA molecules.Ca(OH) 2-assistance of alum coagulation appeared to increase substantially the removal of the hydrophilic HA fraction responsible for HAAs formation,prompting further reduction of HAA formation potentials.     

Measurement of semivolatile carbonaceous aerosols and its implications: A review

Measurement of carbonaceous aerosols is complicated by positive and negative artifacts. An organic denuder with high efficiency for removing gaseous organics is an effective approach to eliminate the positive artifact, and it is a precondition for the accurate determination of SVOC by an adsorbent backup filter. Evaluations of different configurations of the organic denuder, and SVOC determined by different denuder-based samplers, both integrated and semi-continuous, are reviewed. A new equation for determination of the denuder efficiency is estimated, considering the efficiency of removing both the gaseous organics that could be adsorbed by the quartz and the gaseous passing through the quartz that could be subsequently adsorbed by the backup adsorbent filter. The origin of OC on the backup quartz filter, behind either quartz or Teflon filter, is quantitatively evaluated by the denuder-based method based on the data published. The backup-OC is shown to be dominated by either gaseous organics passing through the front filter or the evaporated particulate organic carbon depending on the sampling environment.     

强化活性炭处理工艺去除焦化厂生化出水中的氰化物

以某焦化厂生化出水为研究对象,考寨了金属负载活性炭(简称负载炭)和Fenton氧化预处理等强化活性炭工艺对总氰化物(TCN)的去除效果.在TCN批式实验中,对负载炭的金属离子种类和固定方式进行了考察,同时研究了接触时间、DO对游离氰(KCN配水)、络合氰(K3Fe(CN)6配水)及焦化厂生化出水中TCN的去除效果.结果表明,负载金属离子可以有效提高活性炭对TCN的去除量,KI固定后的载铜活性炭对TCN的去除更有效.吸附作用在活性炭去除TCN过程中起着主要作用,同时TCN在活性炭表面也发生缓慢的催化氧化反应.在穿透实验中,采用了小型炭柱穿透和微型快速穿透实验方法,得到的TCN穿透曲线基本相同.含不同比例原煤炭和负载炭的小型炭柱处理经Fenton氧化预处理的焦化厂生化出水时,在18 d的启动阶段后形成生物活性炭柱,其出水能长期达到<城镇污水处理厂污染物排放标准>(GB 18918-2002)规定的要求.载铜话性炭可以提高活性炭工艺对TCN的去除能力,确保处理全程(57 d)出水的TCN达标.     

电吸附技术的新进展

阐述了电吸附技术的原理及特点,介绍了双电层模型的发展,综述了活性炭电极、活性碳纤维电极、碳气凝胶电极、碳纳米管电极及复合电极的制备工艺以及电吸附技术在咸水淡化和去除水中污染物方面的最新应用,并对以后的研究方向提出了建议。     

小型燃油锅炉NOx的排放特征与管理控制

以68台燃油锅炉（≤10.5 MW）NO_x排放实测数据为基础,通过统计分析方法,研究了NO_x的排放特征;通过对比分析,探讨了我国燃油锅炉NO_x排放控制与管理现状,讨论了进一步加强我国燃油锅炉NO_x排放管理控制的可能性与可行性,并提出了相应的管理控制建议。结果表明,NO_x平均排放浓度为318.2 mg/m³,     

新型类Fenton催化剂用于酸性红B染料废水处理的研究

为了解决Fenton试剂反应前后需要调节pH值、催化剂不能重复利用的问题,本实验以酸性红B溶液作为模拟染料废水,探索以硫铁矿烧渣作为非均相催化剂进行类Fenton反应的催化活性,研究了H2O2投加量、催化剂投加量、pH值、反应时间对酸性红B去除效果的影响。在双氧水(H2O2质量分数为30%)投加量为30 mL/L、催化剂投加量为30 g/L、pH值在1~11范围内,反应4 h,浓度为200 mg/L的酸性红B去除率均达到95%以上,且反应后pH值在中性范围。实验结果表明,该非均相类Fenton反应体系对pH的适用范围广,且催化剂易于沉淀分离,反应数次后依然保持较高催化活性,能重复利用。     

Effects of the arbuscular mycorrhizal fungus Glomus mosseae on growth and metal uptake by four plant species in copper mine tailings

A greenhouse experiment was conducted to evaluate the potential role of arbuscular mycorrhizal fungi (AMF) in encouraging revegetation of copper (Cu) mine tailings. Two native plant species, Coreopsis drummondii and Pteris vittata, together with a turf grass, Lolium perenne and a leguminous plant Trifolium repens associated with and without AMF Glomus mosseae were grown in Cu mine tailings to assess mycorrhizal effects on plant growth, mineral nutrition and metal uptake. Results indicated that symbiotic associations were successfully established between G. mosseae and all plants tested, and mycorrhizal colonization markedly increased plant dry matter yield except for L. perenne. The beneficial impacts of mycorrhizal colonization on plant growth could be largely explained by both improved P nutrition and decreased shoot Cu, As and Cd concentrations. The experiment provided evidence for the potential use of local plant species in combination with AMF for ecological restoration of metalliferous mine tailings.     

Oasis land-use change and its environmental impact in Jinta Oasis, arid northwestern China

Land use change resulted in land degradation is a focus of research on global environmental changes and plays a significant role in the stability and economic development of oases in arid regions of China. Jinta Oasis, a typical oasis of temperate arid zone in northwestern China, was investigated to assess land-use change dynamics during 1988–2003 with the aid of satellite remote sensing and GIS, and to explore the interaction between these changes and oasis environment. Six land-use types were identified, namely: cropland, forestland, grassland, water, urban or built-up land, and barren land. The results indicate that cropland, urban/built-up land, and barren land increase greatly by 30.03, 13.35, and 15.52 km², respectively; but grassland and forestland areas decrease rapidly by 58.06, and 1.76 km², respectively. These results also show that obvious widespread changes in land-use occur within the whole oasis over the study period and result in severe problems of environmental degradation (i.e. land desertification, decline of groundwater, and vegetation degeneracy).     

Combined effect of adsorption and biodegradation of biological activated carbon on H2S biotrickling filtration

In order to evaluate the combined effect of adsorption and biodegradation of H(2)S on activated carbon surface in biotrickling filtration, four laboratory-scale biofiltration columns were operated simultaneously for 120h to investigate the mechanisms involved in treating synthetic H(2)S streams using biological activated carbon (BAC). The first three columns (A, B, C) contained a mixture of activated carbon and glass beads, with the carbons (BAC or virgin activated carbon (VAC)) and conditions (with or without liquid medium recirculation) differentiated. The last column (D) used 100% glass beads with liquid medium recirculation. Air streams containing 45ppmv H(2)S were passed through the columns at 4s of gas retention time (GRT) and liquid flow rate was set at 0.71mlmin(-1). Column D got its breakthrough in 3min of operation, indicating a negligible contribution of glass beads to the adsorption of H(2)S. The removal efficiency (RE) of Columns B and C using VAC dropped quickly to 30% within the first 8h, and afterwards continued to drop further but slowly. Column A using BAC stayed at 25% of RE throughout the operation time. A thorough investigation of the H(2)S oxidation products, i.e., various S species in both aqueous (recirculation media) and solid phases (BAC and VAC), was conducted using ICP-OES, IC, XRF, and CHNS elemental analyzer. BAC demonstrated a better performance than columns with adsorption only. Water film was found to enhance H(2)S removal. The percentage of sulphate in the total sulphur of the BAC system improved to twice of that of VAC system, indicating sulphate is the main product of H(2)S biofiltration. The observed pH drop in BAC system double confirmed that the presence of biodegradation in the biofilm over carbon surface did profound effect on the oxidation of H(2)S, compare to the systems with adsorption only.     

PM<Subscript>10</Subscript> emissions from industrial coal-fired chain-grate boilers

Industrial coal-fired boiler is an important air pollutant emission source in China. The chain-grate boiler is the most extensively used type of industrial coal-fired boiler. An electrical low-pressure impactor, and a Dekati® Low Pressure Impactor were applied to determine mass and number size distributions of PM₁₀ at the inlet and the outlet of the particulate emission control devices at six coalfired chain-grate boilers. The mass size distribution of PM₁₀ generated from coal-fired chain-grate boilers generally displays a bimodal distribution that contains a submicron mode and a coarse mode. The PM in the submicron mode for burning with raw coal contributes to 33% ± 10 % of PM₁₀ emissions, much higher than those for pulverized boilers. And the PM in the submicron mode for burning with briquette contributes up to 86 % of PM₁₀ emissions. Multiclones and scrubbers are not efficient for controlling PM10 emission. Their average collection efficiencies for sub-micron particle and super-micron particle are 34% and 78%, respectively. Operating conditions of industrial steam boilers have influence on PM generation. Peak of the submicron mode during normal operation period is larger than the start-up period.

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