Research On The Enhenced Humification In Primary Stage Of Sewage Sludge Composting

Sewage sludge treatment is becoming a particular problem in environmental protection.Because of its convenient operation and low cost,composting is wildly used to dispose the sludge.However,the low concentration of humic acids comparing with organic and chemical fertilizer limits the reusing of compost.Raising the concentration of humic acids could shorten the production period and increase economic benefits.Plackett-Burman experiment was used in this study to filter the influence factor.Temperature,catechol,glutamate,metallic oxide,bentonite,dosing time was considered to be the influence factors of the humification.Temperature and metallic oxide was confirmed increase the concentration of humic acids.In further study,humification rate was enhanced with the temperature rising within the composting temperature range.And 50 mg per grams of MnO2 in sludge could increase the concentration of humic acids in sludge.Meanwhile,100 mg and 150 mg per grams of MnO2 didn't take any effectMaillard reaction was consumed to make great contribution to synthetize humic acids in the start period of composting.Reducing sugar,the most important substrate of the reaction,was tested and analyzed by HPLC.The result shows cellobiose is the main reducing sugar in sludge.And in the first 6 days of composting,the cellobiose decrease rapidly with the humic acids increase.Cellopentose was found raise during the compost which may originate from bulk agent.Fructose remained in a low level during the whole process,and the other reducing sugar wasn't detected.Four ratios of sludge and bulk agent(9:1,6:1,3:1 and without bulk agent)was designed to validate the cellulose of bulk agent and the aerobic condition will accelerate the humification process.The conclusion shows the ration of 6:1 and 3:1 was most appropriate for humic acids formation.The high temperature duration,the addition of MnO2 and the appropriate ration of bulk agent with cellulose was shown to accelerate the humification process during composting.