脱水污泥生物干化及产物农用性质评价

Bio-drying of Dewatered Sludge and Characteristics Analysis of Bio-dried Products in Agricultural Application

城市污泥的生物干化及产物农用已引起越来越多的关注。本研究探讨了不同调理剂对生物干化堆体温度和产物含水率的影响,分析了干化过程中有机物的降解,及干化产物生物稳定性和重金属含量的变化趋势。结果表明:以稻草为调理剂的堆体最高温度可达67℃,干化产物含水率可从73%降至52%,产物4日耗氧呼吸速率降至10mgO·2g-1DM,显示了较好的稳定性。生物干化过程中,蛋白质和腐殖质含量逐渐降低,而多糖含量比较稳定。生物干化后产物重金属含量有所提高,除Zn部分超标外,其余重金属均未超出《农用污泥中污染物控制标准》(GB4284—1984)规定的限值。

Sludge bio-drying is a variation of aerobic decomposition, in which sludge is dried by the heat generated by aerobic degradation of its organic matters. Recently, more and more attentions are paid on the bio-drying of dewatered sludge and the agricultural application of its bid-dried products. Straw and sawdust are commonly used bulking agents in sludge bio-drying. This study evaluated the effects of the different bulking agents on the variations of pile temperature, water content, organic matters, biodegradability and heavy metal contents for bio-dried products. The results showed that straw was more suitable bulking agent for sludge bio-drying than sawdust, and the pile using straw had a temperature as high as about 67 ℃. The water content of bio-dried products decreased from 73% to 52%, and the 4-day aerobic respiration rate reduced to 10 mgO2·g-1 DM, showing high biodegradability. The contents of proteins and humic matters decreased during bio-drying process, while that of polysaccharides remained constant, which would be attributed to the high protease contents in sludge. The ratios of humic acids/fulic acids both increased for the two bio-drying piles, indicating that the bio-drying process would be suitable for the formation of humic acids. Further study showed that the contents of heavy metals increased during the bio-drying process, while all the heavy metals, except for Zn, did not exceed the maximum permissible contents used for soil（GB 4284—1984）.