Study On Condition And Process For Simultaneously Treatment Of Wetland Plants And Sludge By An Earthworm Reactor

In the last decades, ecological wetland technology has been widely used in wastewater treatment and drinking water treatment, and been proved successful in many pilot studies. In the sustainable development point view,, it’s a great strategy to harvest the wetland plants used in the waste water treatment. Meanwhile, as another by-product of sewage treatment, how to take advantage of resource utilization of sewage sludge is a hot point for the modern environmental research. This work was focused on utilizing earthworm reactor as an ecological means for wetland plant and sewage sludge co-treatment, wishing to explore the nutrient changes and pollutant reduction by this procession, the conclusions are as follows:1. The earthworm reactor takes significant effect on Myriophyllum spicatum-sewage sludge co-treatment, compare with the treating effect of different ratio of M. spicatum and sewage sludge under earthworm reactor condition, after30days,30%M. spicatum treatment got the most efficiency treating effect, which the earthworm grows fastest, the waste weight reducing reached to58.6%, volume reducing reached to60.9%, OM decomposition reached to34.3%, meanwhile, earthworm reactor changed the form of nutrients and microbial community structure greatly, the available P, actinomycetes and fungus number were all significantly increased.2. Water content of the wetland plant and C/N for the treating materials could be important factors affecting transforming efficiency of earthworm reactor, therefore, we used4similar wetland plants (M. spicatum, Hydrocotyle verticillata, Jussiaea stipulacea Ohwi, Pistia stratiotes L.) as experimental materials, based on the previous result, chose30%as the best plant ratio, to compare the treating efficiency to4kinds of plant by earthworm reactor treatment, the result shows that, after treatment, the reduction of weight and volume for these4kinds of plants were all more than50%, and also C/N ratio were significantly reduced after treatment, achieved nearly10:1as balance at the end. Considering the treating efficiency, M.spicatum and P.stratiotes were little superior than the other two plants.3. Taking pure sludge as culture medium has some inhibiting effect on cabbage growth, which may also affect the yield of plants and lead to accumulation of heavy metals. However, using wormcast as culture medium can greatly increase the yield of cabbage. The effect of pure sludge treated wormcast or30%plant treated wormcast on the yield and quality of cabbage has no big difference, but there existed large gap of P accumulation of cabbage between these two worm casts. Comparing with paddy soil,2kinds of worm cast increased the yield of the cabbage to147.7%and149.9%separately, but almost had no obvious accumulation of heavy metals, from which we can easily conclude that, the wormcast produced by earthworm reactor can be used as culture mediums for plants.4. As a regulator, perlite addition can improve the efficiency of earthworm reactor and shorten the treatment time. Comparing among2%,4%,8%,16%perlite proportion addition, we found4%perlite treatment took the most effective way.5. Earthworm reactor can decrease the pH of the samples, and help earthworm accumulate some extent of Cu and Cr, but overall, the heavy metal content in earthworm had no side effect on its healthy living. The total heavy metal concentration had no obviously changes, but the available heavy metal content significantly decreased after treatments. The main reason accounted for this was activities of earthworm and microbial can activate the production of small molecule organic acid, which can chelate with the heavy metals leading to its inactivation. Earthworm can also eliminate other environmental pollutants such as tetracycline. Under low tetracycline concentration, earthworm can completely eliminate it in a short time; under high tetracycline concentration, the degradation rate for tetracycline reached more than95%in15days.