Study On Degradation Of Volatile Organic Compounds In Sludge Drying By Denitrification

Sludge drying processes produce large amounts of volatile organic compounds.It affects the atmospheric environment.In order to reduce VOCs emissions,This paper propose a method to degrade VOCs from waste gas by denitrifying microorganisms.The efficiency and reliability of the denitrifying biological treatment on VOCs in waste gas were studied.And effects of the factors such as the amount of suction air and the inorganic matter in the dry air were analyzed.The main conclusions are as follows:(1)For the removal of VOCs in residual sludge drying gas,denitrification biological method was significantly better than ordinary biological method.The denitrification device has 12-30%higher removal rate of volatile organic compounds than aerobic devices under different experimental conditions of drying temperature and inlet concentration.Which can effectively reduce the total amount of VOCs discharged into the atmosphere the amount.(2)It was found that both the denitrification and bio-aerobic effects occurred simultaneously in the denitrification device.Under the experimental conditions,the proportion of denitrification in the removal of VOCs is 12-27%.(3)Different sludge drying temperature produces different organic components of the exhaust.Which has a significant effect on the removal efficiency of VOCs in common biological treatment plants,but have little effect on the denitrification device.There are more kinds of VOCs in the exhaust gas at higher drying temperatures,which contain more VOCs with higher molecular weight,more benzene and lipids.These VOCs have more stable chemical properties and are resistant to microbes Metabolic utilization.For some types of VOCs?denitrifying microorganisms have a higher metabolic utilization than aerobic microorganisms.(4)The ammonia nitrogen in the dry exhaust gas is transferred to the liquid phase and converted to nitrate nitrogen by aerobic nitrification.This part of the nitrate nitrogen also provides the nitrogen source for the denitrification reaction.It can save the amount of nitrate added.Under experimental conditions,the ammonia gas in the tail gas provides about 40%of the nitrogen source for the denitrification reaction.(5)The reduction of the denitrification in the device will lead to the decrease of VOCs removal rate.The denitrification state of the denitrification device is affected by the exhaust air volume.When the suction air volume is large,the device dissolved oxygen concentration is high,denitrification reaction is inhibited.and the reduction of the denitrification in the device will lead to the decrease of VOCs removal rate.(6)From the analysis of VOCs composition of dry waste gas,it can be seen that the composition of VOCs in exhaust gas is complicated.There are more drug residues,such as prednisolone acetate,beclomethasone acetate,hydrocortisone acetate and other substances,There are ricinoleic acid and other surfactant substances,dichloromethane and other paint residues.