Enhanced Acid Production Of Waste Activated Sludge Fermentation By Calcium Peroxide Combined With Thermal Pretreatment

With the improvement of the living standard of urban residents and the rapid development of industry,the output of domestic production wastewater is also rising.There will be a large amount of surplus sludge(Waste activated sludge,in the process of wastewater treatment in sewage treatment plant.If these surplus sludge is not treated in time,it will bring adverse effects on environment and human health.Anaerobic digestion is a common sludge treatment and disposal method,which can convert organic matter from sludge to high added value products,such as hydrolytic acidizing stage,volatile fatty acid?Volatile fatty acids,abbreviated as VFAs?.It has a good application prospect in the disposal of surplus sludge.However,due to the slow rate of hydrolysis and acidification,and the utilization of methanogenic bacteria,the accumulation of volatile fatty acids was less.Therefore,increasing the yield of volatile fatty acids has become a research hotspot.In this paper,the residual sludge produced by the secondary sedimentation tank of sewage treatment plant was taken as the research object,the effect of adding CaO₂ on the fermentation of surplus sludge,the effect of CaO₂ co-heating pretreatment on sludge cracking,and the combined pretreatment of residual sludge fermentation acid production were investigated.The main conclusions include:?1?The addition of CaO₂ can promoting the cracking of sludge and the dissolution of organic substances.The dissolving effect of sludge and the concentration of volatile organic acids in fermentation broth increased with the increase of CaO₂ dosage.When the dosage was 0.3g/gVSS,The concentration of volatile organic acids in fermentation broth reached the maximum value of 2600 mg/L on the 7th day.At this time,acetic acid accounted for 69.49%of the six acids produced.After fermentation,the removal rate of VSS in sludge increased with the increase of dosage,and the removal rate of VSS reached32.83%when 0.3g/gVSS CaO₂ was added.The increase of dosage promoted the release of ammonia nitrogen and phosphate.?2?It was found that SCOD,soluble protein and soluble polysaccharide in the residual sludge increased obviously with the increase of heat treatment temperature and the increase of CaO₂ dosage,but the protein concentration would decrease after 1 hour,and the concentration of soluble protein and soluble polysaccharide in the residual sludge would decrease with the increase of heat treatment temperature and the increase of CaO₂ dosage.After 1.5h,the increasing trend of SCOD and polysaccharide was no longer obvious.When treated with 0.3g/gVSS+90?for 1.5h,the concentrations of SCOD,protein and polysaccharide were5641mg/L?3596mg/L and 1028.6mg/L??3?The acid production performance of sludge treated with CaO₂ combined with heating was significantly improved.The results showed that the accumulation of volatile fatty acids in the experimental group at 0.2g/gVSS+90?was the largest on the 7th day of fermentation,and the accumulation of volatile fatty acids reached 3101.7mg/L.Compared with CaO₂,added with 0.3g/gVSS alone,the yield of volatile fatty acids increased by19.3%.After pretreatment and then fermentation,the specific resistance of sludge was further increased to 2.7×10¹⁴ mg/kg.Through high-throughput sequencing,it was found that CaO₂ alone and combined pretreatment could decrease the richness of the community,but the abundance of hydrolytic acid-producing bacteria would increase,and the increase of dominant bacteria would be beneficial to the fermentation of acid-producing proces.