Effect Of Different Types Of Sludge On Anaerobic Degradation Of Cellulose And Its Strengthening Effect

Cellulose is the most abundant organic matter on the earth.As the most abundant polysaccharide,it is widely distributed in nature.The biomass of plant fibers produced through photosynthesis can reach 1 billion tons per year.It has the advantages of environmental friendliness and reproducibility.However,cellulose is difficult to degradation,which is mainly caused by the complex natural structure and the special lattice structure of lignocellulose.In order to improve the utilization rate of cellulose,this study investigated the effects of different sludge types,initial p H and redox mediators(ROMs)on the anaerobic biodegradation of cellulose,optimizing degrading conditions for anaerobic degradation of cellulose.The floc sludge from domestic sewage treatment plants and granular sludge from paper mills were firstly selected as inoculated sludge in this study.At 35°C,the sodium carboxymethyl cellulose was used as substrate to investigate the effects of different sludge types on anaerobic degradation of cellulose.The results showed that both sludges had good acid-producing fermentation function in the early stage of cellulose degradation and the volatile fatty acids(VFAs)content was above 1500 mg/L.However,the ability of these two sludges to convert volatile acids is different.The flocculent sludge had a lower degradation capacity than granular sludge.The acetate was significantly reduced by the granular sludge on the 18 th day.In addition,their methanogenesis was different at the end of anaerobic degradation.The methane content from floc sludge and granular sludge were 23% and 64%,respectively,which resulted in a low COD removal by floc sludge,while the COD removal reached 21.3% by granular sludge.The effect of initial p H on anaerobic biodegradation of cellulose showed that the content of reducing sugars showed a fluctuation form as culture duration at initial p H of 4.5 to 8.5.However,the reducing sugar content at initial p H 9.5 was relative stable,maintaining for 0.7~0.8 mg/L.The VFAs content at low p H(4.5 and 5.5)was significantly lower than that of volatile acids under neutral and alkaline conditions in the early stage of anaerobic degradation.The hydrogen-producing acetate bacteria using ethanol also had higher activity.The cumulative methane production reached 58.9 m L at initial p H 7.5,which was significantly higher than other p H conditions.The COD removal also reached 48.4% at initial p H 7.5.Although the main microbial groups at initial p H 4.5~9.5 were Methanobacterium,Methanothrix,Macellibacteroides,Petrimonas,Bacteroides,Brooklawnia,Anaerofilum,their relative abundances were different.When AQDS and GO were used as ROMs to enhance the anaerobic degradation of cellulose,the total amount of VFAs was higher than that of control,and butyrate and acetate were the dominant intermediate metabolites.However,the accumulation of VFAs led to a lower p H during the cellulose anaerobic degradation,which further inhibited the activity of hydrogen-producing acetate bacteria and methanogens.Although the hydrogenotrophic methanogens had activity uander AQDS of 80,100,200 mg/L and GO of 50,80,100 mg/L conditions,the activity of hydrogen-producing acetate bacteria and acetotrophic methanogens were significantly inhibited.After 16 day's cultivation,the COD removal in control,different concentrations of AQDS and GO was only 15.3%~25.5%.The analysis of showed that the relative abundance of Methanothrix of the two methanogenic bacteria Methanobacterium in the AQDS and GO in ROMs(except GO concentration of 100 mg/L)was less than that of the control,whereas the relative abundance of the acid-producing bacteria(Petrimonas and Brooklawnia)was higher than the control.