New insights into the evaluation of anaerobic properties of sludge: Biodegradability and stabilization

Evaluating anaerobic biodegradability of sludge and then identifying the stabilization of digestate is necessary in sludge treatment and disposal. 48 sludge samples from 24 typical waste water treatment plants (WWTPs) in 11 provinces in China were selected to investigate the relationship between Biochemical Acidogenic Potential (BAP) test and Biochemical Methane Potential (BMP) test. The volatile fatty acid (VFA) production obtained from BAP tests was found linearly related to the ultimate methane production from corresponding BMP tests. Satisfying results were obtained with Pearson correlation coefficient as 0.929 and R² value as 0.76. Furthermore, the physio-chemical characteristics (FCI, SUVA₂₅₄, E₄/E₆) of supernatant, which were associated with humic-like substances (HS), were investigated before and after BMP tests. Through which a new criterion (FCI>1.50, SUVA₂₅₄>1.10, E₄/E₆<4.0) was proposed to evaluate the stabilization level of anaerobic digested sludge.     

污泥中重金属性质分析及处理方法实验研究

选取典型城市污水厂污泥进行重金属总量及形态分析，确定超标重金属的含量、形态，并选择重金属稳定化方法对污泥中的重金属进行了初步实验。通过实验，结果证明了重金属的稳定化是污泥农用中重金属控制的有效方法，并给出了进一步研究的目标和建议。     

10万m3/d污水处理厂新型稳定塘工艺技术经济分析

介绍了沙营污水处理厂稳定塘工艺的构成特点及2年来实际运行效果。效益分析表明,新型稳定塘工艺通过在厌氧塘安装弹性填料、在好氧塘增加表面曝气机,在养鱼塘放养各类鱼苗、在生态塘种植莲藕、芦苇,从而形成了人工可以控制的生物氧化过程来处理城市污水,具有基建投资省、维护管理方便、运行费用低等特点,在土地资源丰富的中小城市具有良好的应用前景。     

World copper market, 1973–1982, and international stabilization policies

This article critically examines international price stabilization policy in relation to the main features of the world copper market and the structural changes that have affected the industry in the decade up to 1982. The first section summarizes the main features of the world copper market, briefly discussing the principal structural changes; the second part examines the recent pattern of investment in copper and changes in ownership of some copper producing companies resulting from the need for improved cash flows due to the adverse effects of the recession; and the third part analyses the practical and theoretical issues relating to the question of price instability. A number of formidable problems are likely to arise from such price stabilization policies and it is concluded that it is because of these difficulties that the policies have not been implemented. Consequently, international commodity agreements designed to minimize or avoid price instability have proved difficult to conclude. New questions on which consensus is likely should be examined to promote intergovernmental co-operation, and hence market stability. With that end in view, this article lists some new questions that could form the basis of an agenda for exploratory intergovernmental discussions on copper.     

Heavy metal and nutrient changes during vermicomposting animal manure spiked with mushroom residues

A pilot-scale trial of four months was conducted to investigate the responses of heavy metal and nutrient to composting animal manure spiked with mushroom residues with and without earthworms. Results showed that earthworm activities accelerated organic matter mineralization (e.g. reduction in C/N ratio, increase in total concentrations of N, P, K) and humification (e.g. increase in humic acid concentration, humification ratio and humification index). Despite composting increased total heavy metal (i.e. As, Pb, Cu, Zn) concentrations irrespective of earthworm, the availability of heavy metals extracted by DTPA significantly (P < 0.05) decreased particularly in treatments with earthworms introduced. The shift from available to unavailable fractions of heavy metals was either due to earthworm bioaccumulation, as indicated by total heavy metal concentrations being higher in earthworm tissues, or due to the formation of stable metal-humus complexes as indicated by the promotion of humification. Our results suggest that vermicomposting process could magnify the nutrient quality but relieve the heavy metals risk of agricultural organic wastes.