| Land utilization of municipal sewage sludge is restricted by heavy metals. For this problem, Our research group developed microwave chemical leaching and pre-acidification microwave chemical leaching to remove the heavy metals. For a more comprehensive analysis of the influence that two processes have to concentrated sludge about their related indicators of land utilization, this article evaluates and analyzes physical and chemical indicators, safety indicators, biological indicators, nutrition indicators mainly of concentrated sludge and the sludge from processes according to the standards about land utilization of sludge that executing now in our country.The main results are as follows:The sludge of the processes are weakly acidic, which is more suitable to improve the p H of alkaline soil. The moisture content of the sludge drop to about 70%. The processes also make dewatering performance better. The sludge of the processes meet the granulation conditions after dewatered, and the particle size is bigger. The nature of the sludge is basically stable after the processes, and the sludge could be applied to the soil which would enhance water retention capacity of soil。The content of of heavy metals are reduced after the processes, and the removal rate of sludge after microwave chemical leaching is slightly higher than the sludge after pre-acidification microwave chemical leaching. The biological effectiveness of the sludge is lower after the processe, and the migration ability of Pb and Cd is weakened too, the latter processes can weaken the migration ability of Zn. The removal amount of mineral oil and Ba P is less,the removal amount of mineral oil after the latter process is more than the former, which is not happen to Ba P. The pollutant content are reduced after the processes, and the manure coliforms and ascaris eggs are almost killed, which ensure the hygiene and safety of soil after be appliedsludge. The seed germination rate and GI are higher that indicate the toxicity of the sludge to plants is lower. All of the indicators after two processes conform the standards about land utilization of sludge, reducing the influence of the sludge on the soil ecosystem.The content of of N and organic matter are slightly higher, while little P and K are missed. Compared to organic compound fertilizer, the content of of N and P are enough, there is only a slight lack of K and organic matter, but the sludge would be good low organic fertilizer when add a small amount of K. |
