Study On Emission Characteristics Of Ammonia And Volatile Sulfur Compounds During Sludge Aerobic Composting And Ammonia Adsorption Separation

During sludge aerobic composting process,a great deal of odors are emitted.NH₃ and volatile sulfide compounds?VSCs?are dominant odors during sludge aerobic composting.Generally,VSCs included hydrogen sulfide,methyl mercaptan,methyl sulfide?DMS?,carbon disulfide,and dimethyl disulfide?DMDS?.Odors not only are a major health risk to plant staff exposed,but also pollut the ambient air around the plan.At present,there is still a lack of systematic research about on-site odor emission during sludge aerobic composting at home and abroad,including NH₃ and VSCs emission amount and emission characteristic.In addition,there is also a lack of in-depth and systematic study on the assessment of the odors impact from sludge aerobic composting plants on human sensory and health.In this manuscript,the odor emission during sludge aerobic composting was monitored by the static box method.Variation in emission rate of NH₃ and five VSCs in different seasons was identified,and results revealed that emission amount of NH₃ and VSCs increased with the increasing ambient temperature or the increasing aeration frequency.NH₃,DMDS,and DMS were key odors during sludge aerobic composting,and their emission amount concentrated in the first half of composting cycle,which accounted for 63%?81%of the totals.In addition,nitrogen loss,sulfur loss,and carbon loss were studied.According to assessment methods of odor intensity,odor active values,etc.,aerobic composting workshop was the polluted most seriously site,followed by stacking yard.In the composting workshop,NH₃ reached a degree of 5,and both DMDS and DMS reached a degree of 4.Although[NH₃]was far higher than[DMS]and[DMDS]in the composting workshop,odor contribution of DMS and DMDS contributed 72.12%?92.44%of the total OAV.Based on permissible concentration-time weighted average?PC-TWA?,human risk from odors was assessed.It revealed NH₃ and DMDS in the composting workshop could harm human health.NH₃,emitted from the sludge aerobic composting,was studied for adsorption and separation by adsorption method.NH₃ molecularly imprinted adsorbent was successfully prepared by precipitation polymerization and acid-base hydrolysis method.The adsorption capacity,selectivity and stability of NH₃adsorption were discussed.The results showed that the separation factors were 3453?NH₃/DMS?and5210?NH₃/DMDS?.Inlet[NH₃],humidity,inlet gas flow rate,adsorption temperature,etc.were used for stability experiments.It revealed that NH₃ adsorption capacity can be maintained between 5.59 and 7.84mmol·g^-1.The study on the mechanism of NH₃ molecularly imprinted adsorption showed that the adsorption force between molecularly imprinted adsorbent and NH₃ was mainly chemical adsorption,also included a variety of hydrogen bonds and physical synergy.The components of NH₃ adsorbent were optimized.In order to ensure the adsorption function of NH₃adsorbent,using response surface method-central composite design fitted second-order response surface model to optimize the preparation process parameters by“Design-Expert”software.When environment-friendly ethanol instead of toluene as pore forming agent was used to prepare adsorbent,NH₃ adsorption capacity still reached up to 7.20 mmol·g^-1.Moreover,the reagent cost was reduced by about 75%,and the preparation time was shortened from 5.5 days to 3 days.