利用保水剂调节污泥发酵起始水分的研究

为解决生活污泥资源化利用中好氧堆肥的水分过高问题,采用添加保水剂的方法对堆体的初始水分进行调节。试验将生活污泥和木屑按C/N为16∶1混合后,通过添加不同量的保水剂,设置成理论初始含水率分别为46%、54%、56%、58%和68%的5个处理。在堆肥过程中,对堆体温度、p H值、EC值、有机质、总氮、铵态氮、硝态氮以及产物的腐熟度指数(GI)等指标进行了测定。实验结果表明:通过添加保水剂调节污泥堆肥的起始水分含量对促进堆肥的好氧发酵过程是完全可行的;适宜的起始堆体含水率有利于发酵过程温度的升高和养分的转化,也有利于产品各项理化指标和养分指标的实现;根据原料和辅料的碳氮比确定混合配比后,可依据拟采用的保水剂在污泥中的吸水倍率,通过理论计算得到将混合原料起始含水率调整到适宜值时所需添加的保水剂量。根据本试验结果得出,在利用保水剂调节污泥堆肥起始水分时,将理论初始含水率设定在54%左右是较为合适的。

Study on regulation of sewage sludge water content by water retaining agent at the initial stage of composting

The high water content of sewage sludge could compromise temperature increases during the fermentation process, which is an obstacle for its recycling use. Water retaining agent (WRA) is a new type of functional polymer material, which could absorb up to a thousand times its own weight in water. In the present study, polyacrylamide, which can absorb as much as 75.3 times its own weight of water in the sewage sludge, was used as a common WRA to adjust the initial moisture content of compost piles. To implement the experiment, first, sewage sludge and sawdust were mixed to achieve a carbon (C) to nitrogen (N) ratio of 16:1. WRA was then mixed with compound feedstock at 0.614%, 0.456%, 0.423%, 0.377%, and 0% on a weight basis. In this way, the initial compost pile water contents of 46%, 54%, 56%, 58% and 68%were obtained, respectively. In the composting process, the parameters measured include temperature, pH, electrical conductivity (EC), maturity index (GI) and contents of organic matter, total nitrogen (TN), ammonium-N (NH₄⁺-N), nitrate-N (NO₃^--N) of the compost piles. The results showed that a suitable moisture condition for the aerobic fermentation of sewage sludge could be created using WRA in the composting. The most appropriate initial moisture content was 54% for optimum compositing, which promoted a temperature increase and the transformation of nutrients during fermentation, and facilitated the formation of good physical and chemical properties of products. Thus, for specific feedstock with known C/N ratios, the required dose of WRA could be calculated to obtain optimum theoretical moisture contents for the subsequent fermentation process.