Study On Waste Activated Sludge Thermophilic Co-fermentation Of Acidification Combined With Food Waste

With the continuous development of urbanization in China,the treatment of municipal solid waste has become a problem that cannot be ignored.The waste sludge and food waste are its main components.It is an important and urgent environmental problem how to deal with the increasing sludge and food waste economically and efficiently.Through co-fermentation,organic matter in sludge and food waste can be converted into volatile fatty acids,which can not only reduce the total amount of sludge and food waste,but also achieve reduction and recycle.In this paper,the mechanical method(ultrasonic-20kHz),alkaline hydrolysis method(pH-10)and biological method(anaerobic-70?)were compared for the purpose of promoting the destruction of sludge microbial floc structure and the dissolution of sludge cells.The test results showed that the sludge had more organic matter release and higher cell death rate under the treatment of alkaline hydrolysis method.The dissolved protein concentration after pretreatment was 5514.43 mg COD/L,and the dissolved polysaccharide concentration was 550.42 mg COD/L.The concentration of VFAs was 1447.14 mg COD/L,the DNA concentration was 1343.3 mg/L,and the cell death rate increased by 45.6%.And in terms of stability and economy,the alkaline hydrolysis method(pH-10)is the best pretreatment method for waste activated sludge.After pretreatment test,The hydrolysis and acidification processes of waste activated sludge,alkaline hydrolysis pretreatment sludge,mixture(mixed by alkaline pretreatment sludge and food waste)at 25?C and 55? were studied by batch and continuous test.The results show that thermophilic and alkaline hydrolysis pretreatment can promote the hydrolysis and VFAs production of sludge and food waste,and the effect of thermophilic is better.The concentration of SCOD dissolved in the mixture was the highest,the SCOD reached 707.46 mg/g VSS at 55? and 564.58 mg/g VSS at 25?.The hydrolysis kinetics of alkaline pretreatment sludge was the fastest at 55?,and the hydrolysis kinetics constant reached 0.0829 d-1.During continuous test,all reactors have stable VFAs production after a certain adaptation period in mesophilic and thermophilic.The mixture has the highest VFAs yield in 55 ?,reaching 274.8 mg COD/gVSS.The VFAs production of sludge,alkaline hydrolysis pretreatment and the mixture at thermophilic compared with at mesophilic were 55.8,1.55 and 1.99 times,respectively.Acetic acid was the most important part of VFA,ranging from 44 to 84.5%.The sludge and the alkaline hydrolysis pretreatment sludge were propionic acid fermentation at 25?;the mixture were all butyric acid type fermentation at 25? and 55?.Based on the results of tests,this paper consider that thermophilic co-fermentation of sludge combined with food watse has significant and stability VFAs production,which is one of the effective methods to achieve reduction and recycle of waste activated sludge.