Treatment Of Sewage Sludge By Earthworms And Microorganisms

Sewage sludge is an organic precipitate produced in the process of wastewater treatment, high nutrient content, with the value and potential of agricultural use, but also contains a large number of pathogens, heavy metals, and other harmful substances such 2as organic pollutants, without appropriate treatment may cause secondary pollution of the environment. At present, the main treatment methods of sewage sludge are landfill, incineration and land utilization, but the risk of environmental pollution and waste of resources exists. The use of earthworms and microbial treatment gets the advantages of high efficiency, rapid and no pollution, but less research in the tropical area. In the present study, analyzes the properties and main pollutant components of the sewage sludge, study the effects of adding cassava dregs to sewage sludge treated by earthworms, effects of earthworms with microorganisms and changes in sludge bacterial diversity. Discussion the effects of earthworms coordination with microorganisms on sewage sludge and tropical agricultural waste, it aims to provide new ideas and research foundation for sewage sludge and agricultural waste resource utilization common in tropics. Following research conclusions were reached:1. Haikou sewage sludge organic matter content is 59.61%, the total amount of nitrogen, phosphorus and potassium respectively 41.17,20.23,20.40 g·kg-1, available nitrogen, phosphorus and potassium content were 1.17,0.44,10.21 g·kg-1; the content of heavy metals did not exceed the standard of agricultural grade A except Zn; ?AHs content of 6.44 mg·kg-1, more than the agricultural use standard limit of 5 mg·kg-1.2. Adding the cassava dregs into sludge, after treated by earthworms, the survival rate, earthworm individual weight and total cocoon production is better than 100% sludge. After treated by earthworms, the organic matter and total nitrogen content of sludge decreased and available nitrogen content significantly increased. Total phosphorus and available phosphorus, total potassium and available potassium content increased highest in group C (80% sludge+20% cassava dregs), which increase the sludge fertilizer best. Content of PAHs reduction were 10.48%,15.44%,29.74% respectively in group A,B,C, earthworm contents were significantly increased respectively 24.59%, 40.19%,51.71%, group C reduce the PAHs content better.3. After treated, organic matter and total nitrogen content decreased in all groups, total phosphorus, total potassium, available N, P, K increased maximum are C3 group (80% sludge+20% cassava dregs+earthworm+EM); the PAHs content of C3 group decreased to a greater extent, the earthworm bioaccumulation of PAHs amplitude is the highest. The results showed that the synergistic treatment had the best effect on increasing the nutrient and PAHs degradation of sludge.4. The bacterial diversity of the best level of classification for "family", after treatment, Cl, C2, C3 group sludge bacterial diversity were higher than those before treatment. On the species composition of it, compared with before treatment, Hyphomicrobiaceae, Rhodospirillaceae and Erythrobacteraceae associated with the decomposition of organic matter and the degradation of pollutants microbial abundance ratio increased, that may be the role of microorganisms to reduce the content of PAHs in the sludge; And collaborative processing C3 group of sludge reduction of PAHs content is the largest, the relative abundance of the Erythrobacteraceae increased the most, suggesting that it may be a greater contribution on the degradation of PAHs.The expression of species also have obvious change after treatment, harmful bacteria such as Flavobacteriaceae, Xanthomonadaceae expression decreased, while Syntrophobacteraceae and Bradyrhizobiaceae are beneficial to the degradation of organic pollutants and improve the content of nutrient elements such as increased expression of microbes, and coordination treatment group mainly Pseudomonadaceae, Paenibacillaceae such as organic matter decomposition, degradation of PAHs, and promote plant growth related expression of microbial quantity increases, Pseudomonadaceae and Paenibacillaceae may contribute more to the increase of nutrient elements and decrease the content of PAHs in the cooperative treatment group.