Feasibility Study On Bioleached Sludge Treatment By Cultivating Earthworms

With more and more engineering application of sludge bioleaching technology, bioleached sludge has faced with the final disposal or reutlization problems urgently. Compared to the traditional methods such as incineration and landfill, vermicomposting using earthworm to dispose bioleached sludge can not only harvest a great amount of fresh earthworm and but also earthworm casts (earthworm excrement), which promotes the reduction of sludge volume and also generat a higher economic benifits.In this study, bioleached sludge mixed with cow dung at different rates is used to feed earthworms. In order to investigate the practical feasibility and manipuility of vermistabilization, the changes of physico-chemical properties and microbial parameters of sludge-cowdung mixtures before and after vermicomposting were measured. Earthworm growth and cocoon production patterns in these mixtures were also observed during vermicomposting.This thesis mainly composed of four parts. The first part is to introduce the Materials and Methods of vermicomposting with bioleached sludge. The second part exhibits the effect analysis from earthworm processing matched by various auxiliary material and bioleaching sludge. For the third is the cow dung mixed with sludge of earthworm treatment effect.For the last is the design of earthworm processing production.After 70 days by using earthworm to process bioleached sludge directly, we can realize that bioleached sludge is better than garden soil to increase earthworm weight and it increases highest in adding auxiliary material. However, it is inappropriate to feed earthworm directly with bioleached sludge as earthworm may escape and die. Since earthworm processing, organic content is on the decline overall in bioleached sludge,meanwhile EC is increasing, In addition, the pH rises first and goes down later.It is beneficial for earthworm to reproduce by adding cow dung and the best ratio to promote reproduction of cow dung and sludge is 1:3 (fresh weight). The addition of additives on sludge feeding earthworms has some effect, moisture of bioleached sludge increasing can promote the growth of earthworms. Heavy metals in sludge changed after earthworm treatment:Cu, Zn, Pb, Cr, Cd respectively reduced 23.9%、31.5%、32.8%、 28.0%、13.9%,and earthworms can reduce most of the bio-availability of heavy metals.In addition, this paper carry out the process design of the field breeding earthworm. Preliminary thought, total processing bioleached sludge 300 t, need 60 days and the land area of 0.3 hm2. construction investment costs 65180 yuan, the Operating costs 221000 yuan/year. We can harvest fresh earthworm 34.62 t, vermis dung 594 t. We can obtain direct income 297000 yuan/year.