长龄期简易填埋条件下污泥基本性质的变化

我国曾经有大量的污泥被随意弃置形成了许多简易污泥填埋场,简易填埋的污泥不受控制的堆放在自然环境中,其性质会随着时间发生变化。本文通过对江苏省某化工企业已经简易填存20年陈污泥的取样分析,发现经过多年的堆存,降解简易填埋陈污泥中的有机质含量仍高于50%；污泥中的pH值维持在8.5～9.0,适合产甲烷菌的生存条件；污泥中的含水率大多在90%以上,且水位线在污泥坑表层0～30cm变动,下部都呈厌氧饱和状态。该简易填埋场中老污泥中重金属Zn和Mn总量较高,但浸出量和渗沥液中的含量都很低,表明重金属不是污泥简易填埋场的主要污染物。渗沥液中COD、BOD₅、TN、NH₄-N、TP大多超标,表明简易污泥填埋场中的主要污染类型为有机污染。简易填埋污泥的渗透系数在10-8cm/s数量级,水分排出困难,不适合采用真空预压或堆载排水加固的方法对场地进行加固施工。

Basic Characteristics of Aged Sewage Sludge in a Simple Landfill

Much sewage sludge have been abandoned randomly in China in the past which generated many non-sanitary simple sludge landfills that were potentially threatening to the environment. For the basic characteristics of aged sludge, a field investigation was conducted at a simple sludge landfill created by a Chemical Enterprise in Jiangsu Province and properties such as the organic matter content, moisture content, pH, total heavy metals, heavy metal leaching amount, permeability coefficient and leachate were tested. The results show that the organic matter content is still higher than 50% even after many years of degradation. The pH value of the sludge lies between 8.5 and 9.0, which fits for living conditions of methanogenic bacteria. The moisture contents within the sludge are higher than 90% and the water table located at a depth of 30cm beneath the surface of the sludge. As a result, anaerobic and saturation conditions exist beneath the 30cm depth. The concentration amounts of Zn and Mn were above the recommended standard levels but the heavy metal concentrations obtained from the leaching test and leachate are very low which indicates that heavy metals are not the major pollutants in simple sludge landfills. Concentrations of COD, BOD₅, TN, NH₄-N, and TP exceeded many times the recommended standard values which indicate the organic pollutants are the major pollutants in simple sludge landfills. The permeability coefficient of aged sludge was 10-8cm /s, which signifies the difficulty in sludge drainage and the unsuitability of the vacuum drainage preloading method for such base reinforcement projects.