A comparison of chemical MSW compositional data between China and Denmark

Chemical waste compositions are important for municipal solid waste management, as they determine the pollution potentials from different waste strategies. A representative dataset for chemical characteristics of individual waste fractions is frequently required to assess chemical waste composition, but it is usually reported in developed countries and not in developing countries. In this study, a dataset for Chinese waste was established through careful data screening and assessment, named as CN dataset. Meanwhile, a dataset for Danish waste（DK dataset） was also summarized based on previous studies. In order to quantitatively evaluate the reliabilities of CN and DK datasets, the chemical waste compositions in four Chinese cities were estimated by utilizing both of them, respectively. It is indicated that the usage of CN datasets led to significantly lower discrepancies from the actual values based on laboratory analysis in most cases. Within the datasets, the moisture contents of food waste, paper, textiles, and plastics, the carbon content of food waste, as well as the oxygen content of plastics would induce significant divergences, which should be paid special attention when gathering the information. In addition, the fractional waste compositions in China showed similar features with other developing countries but differ significantly with developed countries. Thus the above-mentioned conclusions could also be true in other developing countries.

污泥焚烧灰磷回收制备蓝铁矿

污泥焚烧灰是很有前景的磷(P)回收原料.本研究提出新的磷回收途径:污泥焚烧灰富磷浸出液经Mg/Fe-水滑石吸附、NaOH溶液脱附,脱除Ca等杂质离子后制备高价值的蓝铁矿(Fe_(3)(PO_(4))_(2)·8H_(2)O).通过正交实验,获得了脱附液制备蓝铁矿的最佳条件:温度10℃、pH 6、Fe/P摩尔比为1.5.在该条件下,评估了脱附液初始P浓度和干扰离子Al^(3+)对固体产物蓝铁矿纯度的影响.结果表明,初始P浓度越高、Al^(3+)浓度越低,获得的固体产物蓝铁矿相对纯度越高(达97%);随着Al^(3+)浓度增加,产物蓝铁矿纯度下降,Al^(3+)浓度为532 mg/L时,固体产物中不再含蓝铁矿成分.本研究为有效回收污泥焚烧灰中的磷并制备高价值的蓝铁矿提供了理论依据.

Phytotoxicity and groundwater impacts of leaching from thermal treatment residues in roadways

The use of coal fly ash（CFA）, municipal solid waste incinerator bottom ash（MSWIBA） and flue gas desulfurization residue（FGDR） in road construction has become very common owing to its economical advantages. However, these residues may contain toxic constituents that pose an environmental risk if they leach out and flow through the soil, surface water and groundwater.Therefore, it is necessary to assess the ecotoxicity and groundwater impact of these residues before decisions can be made regarding their utilization for road construction. In this study,the physico-chemical characteristics, leaching and phytotoxicity of these residues were investigated. Specifically, multivariate analyses were used to evaluate the contributions of the leaching constituents of the CFA, MSWIBA and FGDR leachates to the germination index of wheat seeds. B, Ba, Cr, Cu, Fe and Pb were found to be more toxic to the wheat seeds than the other heavy metals. Furthermore, the leached concentrations of the constituents from the CFA, MSWIBA and FGDR were below the regulatory threshold limits of the Chinese identification standard for hazardous wastes. Analyses conducted using a numerical groundwater model（Wisc LEACH） indicated that the predicted field concentrations of metals from the CFA, MSWIBA and FGDR increased with time up to about 30 years at the point of compliance, then decreased with time and distance. Overall, this study demonstrated that the risks resulting from MSWIBA, CFA and FGDR leaching could be assessed before its utilization for road construction, providing crucial information for the adoption of these alternative materials.