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Laboratory simulation tests were conducted to examine the effects of different washing reagents (distilled water, HCl, H3PO4, oxalic acid, and CaCl2) in extracting the heavy metals from contaminated soils left by a chemical plant. The effects of reagent concentration, reaction time, and washing time on the washing efficiency were investigated, and the form variation of test heavy metals was determined before and after HCl washing. Distilled water, H3PO4, and CaCl2 could remove less than 1% of most heavy metals, and the highest removal rate was only 3.58%; while 2 mol HCl x L(-1) could obtain the highest washing efficiency under the optimal conditions, i. e., soil:liquid ratio was 1:3, reaction time was 1 hour, and the soils were washed twice by HCl solution. The removal rates of Cr, Pb, Zn, Cu, and Cd from test soils were 80.75%, 88.69%, 98.00%, 79.33%, and 95.52%, respectively. Among the washing reagents, HCl could effectively remove all forms of heavy metals.

Composting is an effective methodology for the treatment of organic waste like pig manure (PM) before land application. However, nitrogen loss through NH(3) volatilization during the thermophilic phase is one of the major disadvantages of composting. The presence of Cu and Zn in compost arising from pig feed additives is also an issue. In this study the effects of bamboo charcoal (BC) and bamboo vinegar (BV) added to composting piles on nitrogen conservation and immobility of Cu and Zn during PM composting was investigated. Total Kjeldahl nitrogen (TKN) loss and mobility of Cu and Zn decreased with increased BC addition. TKN loss and mobility of Cu and Zn in the treatment with 9% BC at the end of composting significantly decreased by 65%, 35% and 39% respectively, as compared to the control. Addition of BV further decreased TKN loss. After composting, TKN loss in the treatment with 3% BC+0.4% BV was 23% lower than that in the treatment with 9% BC. The final results indicated that by adding BC or BC+BV into PM composting is an effective method to reduce TKN loss and control the mobility of Cu and Zn., (Copyright (c) 2009 Elsevier Ltd. All rights reserved.)

Tea waste is an important part of agricultural solid wastes, because of its various sources and huge amount. The heavy metals removal from waste water by tea waste has been paid much attention by the researchers around the world, owing to the adsorption characteristic of tea waste. In this paper, the research advances in the heavy metals removal from aqueous phase by tea waste were summarized from the aspects of affecting factors, adsorption mechanism, pretreatment, desorption, and regeneration, and the prospects were put forward. It was considered that for the industrialized utilization of tea waste absorbents, further researches should be focused on their adsorption mechanism, pretreatment, desorption and regeneration, technological parameters, and after treatment.

Objective: To investigate the heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) in sludge of twelve wastewater treatment plants (WWTPs) in Zhejiang province of China, and to assess their potential for land application., Methods: Sludge was collected from 12 WWTPs within the province. GC-MS and AAS were used to measure PAHs and HMs contents in sludge., Results: Concentrations of HMs in most of the sludge samples were below the regulatory limits for the sludge to be used in agriculture in China with the exception of Zn in 2 sludge samples and Cd in 1 sample. All 16 PAHs, targeted by the USEPA agency, were found in the sludge from the twelve plants with a total concentration ranging from 33.73 mg kg(-1) to 82.58 mg kg(-1) (dry weight, d.w.). The levels of Sigma9 PAHs varied from 13.87 mg kg(-1) to 61.86 mg kg(-1) (d.w.) in the sludge, far exceeding the limitation value recommended by the Europe Union. The concentration and composition of PAHs in sewage sludge varied and depended mainly on the quantity and type of industrial wastewater accepted by the WWTPs. A significant relationship between the proportion of industrial wastewater received by WWTPs and the total content of 16 PAHs in the sludge was observed., Conclusion: PAHs have become one of the primary pollutants in sludge of Zhejiang WWTPs instead of HMs. It is, therefore, essential to reduce the contents of PAHs before the sludge can be used in agriculture through proper treatment.

Municipal solid waste (MSW) source-classified collection represents a change in MSW management in China and other developing countries. Comparative experiments were performed to evaluate the effect of a newly established MSW source-classified collection system on the emission of PCDDs/Fs (polychlorinated dibenzo-p-dioxins and dibenzofurans) and heavy metals (HMs) from a full-scale incinerator in China. As a result of presorting and dewatering, the chlorine level, heavy metal and water content were lower, but heat value was higher in the source-classified MSW (classified MSW) as compared with the conventionally mixed collected MSW (mixed MSW). The generation of PCDDs/Fs in flue gas from the classified MSW incineration was 9.28 ng I-TEQ/Nm(3), only 69.4% of that from the mixed MSW incineration, and the final emission of PCDDs/Fs was only 0.12 ng I-TEQ/Nm(3), although activated carbon injection was reduced by 20%. The level of PCDDs/Fs in fly ash from the bag filter was 0.27 ng I-TEQ/g. These results indicated that the source-classified collection with pretreatment could improve the characteristics of MSW for incineration, and significantly decrease formation of PCDDs/Fs in MSW incineration. Furthermore, distributions of HMs such as Cd, Pb, Cu, Zn, Cr, As, Ni, Hg in bottom ash and fly ash were investigated to assess the need for treatment of residual ash.

The transformation of heavy metal forms during sewage sludge bioleaching with elemental sulfur as substrate was investigated. The sequential selective extraction procedure was an effective way to reflect the variation in heavy metal forms. The exchangeable form of Cu, Pb and Zn after bioleaching accounted for 81.6, 40.2 and 75.8%, respectively. Cu at initial sludge mainly existed as sulfide precipitate form, most of which turned to exchangeable form during bioleaching, and was solubilized mostly by direct mechanism. The original forms of Pb and Zn were mainly carbonate precipitate and organically bound. Most of the carbonate precipitate Pb transformed into exchangeable form but a little of organically bound Pb. Pb was dissolved from the sludge due to transformation of carbonate precipitated and sulfide precipitated to exchangeable form by cooperation of both direct and indirect mechanisms. A majority of exchangeable Zn was transformed from organically bound and carbonate precipitated forms, and the bioleaching mechanism of Zn was mainly indirect. After bioleaching, the sewage sludge could be applied to land more safely because the heavy metals mainly existed in stable forms. The exchangeable Cu and Pb achieved an obvious increase at pH about 2, while exchangeable Zn showed higher percentage at pH about 3. The transformation of chemical forms for Cu had good relationship with ORP during bioleaching, but Zn was not influenced by ORP of sludge, which appeared to have high bioleaching efficiency at ORP less than 200 mV.

A greenhouse experiment was carried out to compare differences in potential activities of ammonification, nitrification and denitrification in rhizosphere and bulk soil in a heavy-metal-stressed system. Exchangeable fractions of Cd, Cu and Cr were all higher in the rhizosphere of maize than in bulk soil. Results showed that the mineralization of N in soil was stimulated by low concentration of Cd. Addition of Cd at low levels stimulated the ammonifying and nitrifying activity in soil, while inhibitory influences were shown at high levels. Nitrifying bacteria was proved to be the most sensitive one, whilst the effect on denitrifying bacteria was very limited. Comparing Cd, Cu and Cr(VI) at 20 mg/kg soil, Cd was the most effective inhibitor of ammonification and denitrification, while Cr(VI) had the strongest inhibitory influence on nitrifying activity. Root exudates played important roles on the different exchangeable metal fractions and bacterial activities between rhizosphere and non-rhizosphere. Nitrate was the main form of mineral N in soil, as well as the main form of N absorbed by plants, but the formation and relative absorption of ammonium were promoted in response to high Cd exposure.

The effect of elemental sulfur concentration on bioleaching of Cu, Zn and Pb and loss of fertilizer value from sewage sludge was investigated in flasks by batch experiments. The results showed that the ultimate pH of sludges with 3-5 g/L of sulfur added was about 1.3 and the production of SO4(2-) had good correlation with the elemental sulfur concentration. The sensitivity of removal efficiency of metals to sulfur concentration was: Pb > Cu > Zn. The sulfur concentration except for 3-5 g/L had significant effect on the solubilization of Cu, Pb and Zn. The highest solubilization efficiency for sludge with 3 g/L of sulfur was 87.86% for Cu, 32.72% for Pb and 92.14% for Zn, which could make the treated sludge easily meet the metal limitations for land application. The sulfur concentration of 3 g/L was enough for the solubilization of all three heavy metals. The influence of sulfur concentration on solubilization of total nitrogen and potassium from sludge was negligible, but that on solublization of total phosphorus was of great importance. The loss of nitrogen, phosphorus and potassium of sludge with 3 g/L of sulfur by bioleaching was 38.2%, 52.1% and 42.8% respectively, and the sludge still remained satisfactory fertilizer value after bioleaching.

Spatial distribution of heavy metals, arsenic and organic matter in recent sediments in the Hangzhou section of the Grand Canal and their relationships were analyzed. The results showed that the concentrations of heavy metals and organic matters varied widely along the canal, and the average geological accumulation factors decreased in the following orders: organic carbon(2.6), zinc(2.1), cadmium (2.0), copper(1.5), lead(1.1), nitrogen(0.9), mercury (0.8), phosphorus(0.4), arsenic(0.2) and chromium(0). Content of heavy metals and organic carbon in the top 10 cm layer were lower than that of lower layers, except for mercury and organic carbon in the S9 section. Contents of organic carbon in the top 50 cm layer of the mud sediments are significantly higher than those underneath. In the bottom mud layer, there is a concentration peak of the pollutants. In the mud sediments of the canal, cadmium mainly occurred in the Fe and Mn oxide fraction, copper in the organic fraction, lead in the Fe and Mn oxide fraction, and zinc in the carbonate and the Fe and Mn oxide fraction.