Study On Application Of Earthworm In Organic Solid Wastes Treatment

With the rapid development of economy, organic solid wastes are increasing in Chinaand we are paying more and more attention to the treatment and disposal of them. On the onehand, it would have a bad effect on the environment and human health if the organic solidwastes will not be improperly disposed; on the other hand, the potential of organic solidwastes as resource is tremendous owing to their rich organic matter. The technique ofvermicomposting of organic solid wastes not only can reduce the environmental pollutioncaused by waste, but also can reduce the waste of resources. This experiment studied theoptimal formula of vermicomposting different combinations of three melon vegetable strawsrespectively with cow dung and sludge, heavy metal migration and quality test of productafter vermicomposting. Main content and conclusions are as follows:(1)The test conducted vermicomposting of different percentage of sweet potato straw,cowpea straw and tomato straw respectively with cow dung and sluges,and recorded thegrowth and reproduction of earthworm every15days. We determined the physical andchemical characters and seed generation of index of materials. The results are as follow:Average live weight of earthworm increased and then decreased as time went on, andaverage live weight of earthworm of treatment2was992.5mg/ind at15th day that was thehighest in all different treatments. Weight gain multiple of earthworm in all treatmentsdeclined and was0.0118in treatment2at15th day that was the biggest. Cocoon reproductionof earthworm increased and then decreased with the time, and it was0.0911in treatment3at15th day that was the highest. Proliferation multiple of earthworm increased with the time,and it was0.1948at45th day that was the biggest.It showed that there was a decrease in pH, organic matter and increase in EC, totalnitrogen, available nitrogen, total phosphorus, available phosphorus, total potassium andavailable potassium content in all the vermireactors after vermicomposting.The seed generation of index of materials in treatment2,3,7,8,10were more than80%,and it was90%in treatment2that showed material after vermicomposting becamethoroughly decomposed. According to the state of growth and reproduction of earthworm and fertilizer efficiencyand decomposed degree of materials, the best formula of vermicomposting of organic solidwastes were treatment2(10%sweet potato straws+60%cow dung+30%sewage sludge)and treatment3(20%sweet potato straws+50%cow dung+30%sewage sludge).(2) A total of four treatments of different contents of Pb,Ni,Cr,Cd added to the wasteswas carried out and monitored the weight of earthworms per box, weight of materials, thecontents of heavy metal of earthworm and materials and changes of physical and chemicalcharacters of materials before and after treatment. The results are as follow:Biomass of earthworms increased in those treatments of lower contents of heavy metal,but it decreased when contents of heavy metal of materials was higher.There was a decrease in pH, organic matter and increase in EC, total nitrogen, availablenitrogen, total phosphorus, available phosphorus, total potassium and available potassiumcontent in all the treatments after vermicomposting. However, variation value of thesephysical and chemical characters of materials showed a trend of first increase and thendecrease along with the heavy metal contents increasing.The contents of Pb,Ni,Cr,Cd of earthworms in all treatments increased in varyingdegrees. The contents of Pb,Ni,Cr of materials in all treatments increased, but the contents ofCd decreased. The total contents of Pb,Ni,Cr,Cd of earthworms absorbed per box raised,nevertheless, it lessened in materials per box.According to the comparison of K value, there had been a strong accumulation of Cd forearthworm. It could absorb Pb,Ni,Cr of materials, but could not accumulate them.(3) The result of quality test of product after vermicomposting indicated that crudeprotein of earthworm was13.56g/100g in wet weight and54.24%in dry weight. It could notbe used as fish feed for earthworm owing to high contents of heavy metal. It could not beworkable to exploit vermcast as organic fertilizer could be because technical index of it was inthe limit of organic fertilizer in China.The best proportioning of soil and vermcast was4:1assubstrate of romaine lettuce. Not only emergence of lettuce was promoted, but also plantheight and yield of lettuce was highest in this condition.