Study On The Growth And Reproduction Of Earthworm In The Process Of Treating Activated Sewage Sludge In Wastewater Plant

With the development of economy, the treatment of sewage sludge has become a serious problem that must be solved quickly all over the world. Eisenia foetida as one kind of soil macrofauna, has been widely used on the treatment of organic wastes, including garbage, manure, and sewage sludge and so on, because of its unique physiological function.The paper studies on the growth and reproduction of earthworm (Eisenia foetida ) in the process of treating the activated sewage sludge in wastewater treatment plant in Changchun. The aims of this study is to find out the best mixture for growth and reproduction of earthworm in the experiment of mixture of sewage sludge ( freezed at 4℃for 110 days) and cow dung (not fully fermented) (SS+NFCD), and fresh sewage sludge and fully fermented cow dung (FSS+FCD). It provides a scientific basis for the application of earthworm to treat sewage sludge, and lays the foundation for the study of the growth and reproduction of earthworm in the process of treating the activated sewage sludge in urban wastewater treatment plant. So this study is more important theoretical and practical significance.The SS+NFCD is mixed in CD (100% cow dung), 1:1, 2:1, 3:1, 4:1, 5:1 and 1:0 (sewage sludge: cow dung at dry weight) respectively; the FSS+FCD is mixed in 1:1, 2:1, 3:1, 4:1, 5:1 and 1:0 (sewage sludge: cow dung on dry weight) respectively. 4 duplications and1 control sample lasts for 60 days.The results showed that: after 42 days, all the earthworms died in sewage sludge which was freezed at 4℃for 110 days, and there are a large number of earthworms died in SS+NFCD. In SS+NFCD, earthworms died on the first week, more in 1:1 and 2:1, and less in 3:1 and 5:1, earthworms in CD and 4:1 have no death. Earthworms in fresh sewage sludge and FSS+FCD can grow and reproduce normally, without escaping or death.In SS+NFCD, the average individual weight increment, net weight increment of earthworms in the end, multiple of weight increment and growth rate are all the highest in 1:1, and the cocoon production every week, total cocoon production and the mean hatching rate are higher in 3:1 than the others.In FSS+FCD, the average individual weight increment, net weight increment of earthworms in the end, multiple of weight increment and growth rate are all the highest in 4:1, and the cocoon production every week, total cocoon production and the mean hatching rate are higher in 1:1 than the others.Comparing the growth and reproduction of earthworms of the 4 best treatments, I found that 1:1 in SS+NFCD is the best mixture for growth; 1:1 in FSS+FCD is the best mixture for reproduction. The results of the parallel test showed that: the earthworms can live 85 days mostly in SS+NFCD, and can live more than 100 days in FSS+FCD. The best mixture for the growth and reproduction of earthworms is 1:1, which is composed of fresh sewage sludge and fully fermented cow dung.