Effect of Earthworm Biological Treatment on Nutrients and Heavy Metals of Paper Mill Sludge

Paper mill sludge contains a lot of nutrients and heavy metals.We studied the change of nutrients and heavy metals after the earthworm treatment in paper mill sludge of different earthworms addition rates in the incubation experiments.The results showed that the appropriate addition rate was 22.5 gram earthworm per kilogram paper mill sludge.After 84 days of the earthworm treatment,the organic matter of the sludge decomposed strongly and the highest resolution ratio reached 24.95 %;total N,total P and total K increased,and their maximum increments were separately 2.65 g kg-1,0.65 g kg-1 and 0.32 g kg-1;the maximum decreases of available N,available P and available K were 24.78 %,30.40 % and 10.77 %,respectively.The maximum removal rates of total Mn,Cu and Zn reached 28.80%,28.80% and 35.34%,respectively,and the maximum increments of total Mn,Cu and Zn in earthworms were respectively 8.03 %,23.49 % and 27.06 %.The K-values of total Mn,Cu and Zn of earthworm were all lower than 1.0 and ordered as Mn Zn Cu,which suggested that the earthworm could significantly absorb Mn,Cu and Zn in paper mill sludge.