Pretreatment Of Waste Activated Sludge With Sodium Iron Chlorophyll Fenton-like System For Enhanced Methane Production In Anaerobic Digestion

Sludge is a by-product of sewage treatment plant,and its generation increases with the increase of sewage volume.Sludge contains a large number of organic matter and microorganisms,which is easy to give stinky smell,owns high moisture content,and is difficult to dehydrate.As a secondary pollutant,it has adverse effect on the environment and human health.Anaerobic digestion can degrade the organic matter in sludge and produce methane,which has certain economic and environmental benefits.However,anaerobic digestion cycle is usually time consuming and methane production is low.Compared with other pretreatment methods,sodium iron chlorophyll combined with hydrogen peroxide?Fenton system of sodium iron chlorophyll?has good conditioning efficiency with low energy consumption,no corrosion to equipment and no residue.Fenton pretreatment with sodium iron chlorophyll could decompose sludge flocs efficiently.By releasing intracellular polymers,the macromolecular organic matter in sludge can be converted into small molecular organic matter,and the bioavailability of organic matter can be improved.Thus,the utilization of organic matter by anaerobic microorganisms can be improved,the anaerobic digestion process can be shortened and the amount of volatile fatty acid can be increased,thereby increasing methane production yield.The purpose of this thesis is to improve methane production in anaerobic digestion by conditioning with Fenton-like system sludge conditioned using sodium iron chlorophyll as catalyst.The main research described in this thesis includes:?1?Soluble polysaccharides,soluble proteins and capillary suction time?CST?were used as characterization parameters to evaluate the sludge disintegration after conditioning with sodium iron chlorophyll Fenton-like system.The effects of sodium iron chlorophyll,hydrogen peroxide and conditioning time on the pre-conditioning effect were investigated.High efficient sludge decomposition is obtained after conditioning with H₂O₂ of 0.02 g/g TS,n?SIC?:n?H₂O₂?of 1:80,and conditioning time of 140 min,and the CST of sludge after conditioning is as high as 750.1 s.?2?Experiments on the effect of sludge pretreated by Fenton-like system with sodium iron chlorophyll on anaerobic digestion and methanogenesis of sludge were conducted,and the mechanism on promotion of methane generation was discussed.This Fenton-like system can treat sludge effectively,release intracellular polymer,degrade macromolecule organic matter into soluble small molecule organic matter,which improve the bioavailability of organic matter in sludge,and enhance the degradation and utilization of organic matter by anaerobic microorganisms.Most of the residual sodium iron chlorophyll participates in hydrolysis and acidification reactions of anaerobic digestion,and increases the production of volatile fatty acids such as propionic acid.It can also utilize the volatile fatty acids to produce methane and improve the efficiency of methane production in anaerobic digestion.The methane yield is 83.34 mL CH₄/g VS,which is higher than 53.15 mL CH₄/g VS of raw sludge.In this thesis,the anaerobic digestion process of sludge for methane production was optimized.The new process of sludge conditioning with sodium iron chlorophyll and hydrogen peroxide system to promote anaerobic digestion and methane production was explored,which provided a new pretreatment method for anaerobic digestion and methane production of sludge,and provided a new route for large-scale use of anaerobic digestion for methane production.