Study on Dewatering Process of Biogas Residue Enhanced by Rolling Soft Pressing Coupled with Starch Modified Organic Flocculant
In this study,a new technology of digestate dewatering was developed by coupling starch-modified organic flocculant with roller soft-pressing process.The effects of different proportions and dosages of starch and organic flocculant on digestate dewatering performance were evaluated by measuring the water content,solid content,and digestate specific resistance of the vacuum-filtered mud cake.The results showed that when the proportion was 1∶0.5 and the dosage was 0.4 mg,the starch-modified organic flocculant reduced the water content of the digestate to 67.4%,decreased the filter specific resistance by approximately 63.6%,and significantly improved digestate dewatering performance.Analysis of the change in zeta potential before and after conditioning revealed that the digestate|ζ|potential decreased to 0.53 mV.Through improvements to traditional roller pressing dewatering technology,the study investigated the effects of dry weight,feed solid content,flocculant concentration,contact area between the roller and filter membrane,and pressing pressure on the dewatering rate.The optimal dewatering process was determined to be:friction area 0.314 m2,pressing pressure 5 kg,dry weight 33.3%,feed solid content 0.6%,and flocculant concentration 0.2%.This process achieved a digestate solid content of 39.63%,providing relevant process parameters for the promotion and application of this technology.