EFFECT OF DIFFERENT BULKING AGENTS ON TRANSFORMATION OF NITROGEN DURING SEWAGE SLUDGE COMPOSTING

Rice straw,sawdust and tree leaves were used as bulking agents to investigate the changes in temperature,total N,NH~+_4-N and NO~-_3-N during sewage sludge composting by artificial turnover protocol.The results showed that using rice straw or rice straw plus sawdust as bulking agents was beneficial to killing the pathogens and accelerating composting due to faster temperature increase and a longer high-temperature period.Water soluble NH~+_4-N increased to the maximum on the 14~(th) day of composting,followed by a rapid decline thereafter.The content of NO~-_3-N started to rise gradually 14 days after the commencement of composting.Contents of NH~+_4-N and NO~-_3-N in the composting piles with sawdust or tree leaves were lower than those in the piles with rice straw or rice straw plus sawdust.Total N in the piles decreased during composting due to loss of NH_3 through volatilization,mainly in the first 28 days of composting.Sawdust helped to decrease N loss.