Study On Co-Anaerobic Digestion Of Food Waste And Sewage Sludge Based On Microwave Pretreatment

Food waste(FW) and sewage sludge(SS) have the characteristics of high water content, high content of organic matters and perishable. They will greatly threatened environmental sanitation and human health without appropriate treatment. Anaerobic digestion(AD) is an ideal treatment method for the purpose of harmless, reductive and regenerative FW and SS disposal. However, some problems exist in the practical application, such as low organic loading rate, easy acidifying, low efficiency and unstable reactive process. In order to provide technical support and scientific basis to the development of efficient and stable co-anaerobic digestion technology, batch experiments for co-digestion of FW and dewatered sewage sludge(DS) using microwave pretreatment were carried out to clear the proper pretreatment method and mixing ratio, methane production and organic matter degradation performance were also investigated in this paper.The main results are as follows:Microwave pretreatment was useful for improving the methane production capability and organic matter degradation performance of co-anaerobic digestion system, while it had no positive impact on the appearing time of the peak of the daily yield of methane, the reduction of polysaccharide and the volume reduction. From the view of whole province, the method of making microwave pre-treat to DS was better. When the TS ratio of FW and pre-treated DS was 1:1, the cumulative methane production, maximum daily yield of methane, the methane production per unit VS and COD, the degradation rate of TS,VS and TCOD were 3228.1ml,327.8ml,317.92ml/g VS,199.34ml/g COD,20.14%,48.79%and 55.45%,respectively.Either microwave pretreatment method, the cumulative methane production, maximum daily yield of methane, cumulative methane production rate, the reduction rate of TCOD, SCOD, protein and polysaccharide increased firstly and then decreased with the decreasing of FW content, and got to the highest when the TS ratio of FW and DS was 3:2.For the method of making microwave pre-treat to DS, the cumulative methane production, the methane production per unit VS and COD, the reduction rate of TCOD,SCOD, protein and polysaccharide were 3506.2ml, 338.44ml/g VS, 210.58ml/g COD, 64.59%,85.30% and 72.76%,respectively.While the reduction rate of TS and VS decreased with the decreasing of FW content and got to the highest when the TS ratio of FW and DS was 2:1.During anaerobic digestion process, the degradation of propionic acid was the rate-limiting step of methanogenesis reaction. The method of making microwave pre-treat to DS was more advantageous to the degradation and transformation of VFA and could help weaken the influence of propionic acid. After pre-treating FW, co-anaerobic digestion system was greatly inhibited by propionic acid and it was not good for efficient operation. The protein in the co- anaerobic digestion system was difficult to be degraded and remained a high concentration using different pretreatment methods, then consider add appropriate proteolytic enzyme into the system to better enhance the anaerobic digestion efficiency in the future research.