Application Of Biosurfactant In Aerobic Composting Of Sewage Sludge

Sewage sludge is scrap in the process of urban sewage treatment. In recent years, with the increased of the urban treatment capacity, the reasonable disposal of sewage sludge became the urgent problem. Urabn sewage sludge is one of the most renewable resources in solid waste. Sewage sludge composting with good economic and environ mental benefits is am important method for sludge treatment and disposal. High temperature aerobic composting is widely used for its high efficiency, short cycle and low operating cost. Currently, the main disadvantages of sewage sludge composting are low nutrient content and high heavy metal content that become key restrict factor of its application in farmland. So, how to reduce the period of sewage sludge compost, accelerat fermentation speed and increase the nutrient content in sewage sludge are very important to the utilization.Biosurfactants mainly are producted by microbial metabolism in the secretion of biologically active metabolites.Compared with chemical surfactant, biosurfactant has a low toxicity to ecological system of Earth and can be biodegraded by microorganism. The biosurfactant can change surface properties of solid-liquid interface and ameliorate the microenvironment of the microorganism to improve the composting efficiency. Previous studies have shown that appropriate surfactant can promote the growth of microorganism fermentation metabolic and enzyme production ability. The researches on the application of biosurfactant in composting of sewage sludge have not been reported.The study focused on the effect of rhamnolipid biosurfactant application on static forced-aeration composting of excess activated sludge. During the30-day composting tests, significant changes of the temperature caused by the two treatments were defined as three stages including a mesophilic period, a thermophilic period and a maturing period for the compost process. The warming rate of the treatment with rahmnolipid at0.015%as well as its moisture content was higher than that of the control. The rhamnolipid addition increased the microbial population. At the end of the composting, the GI(Geimination Index) reached53.70%and50.80%respectively, indicating that addition of rahmnolipid accelerated the decreasing of the compost rhamnolipid. However, due to the enrichment effect, the heavy metal concentration was slightly higher than that of the control one. The experimental indicated that the addition of rahmnolipid can improve the microenvironment of compsting, and as a result, accelerate the composting process and improve the quality of composting products.