Study On The Recycling & Resource Utilization Technology Of Biogas Slurry From Perishable Organic Waste

With the rapid development of social economy and the continuous improvement of people’s living standards,the amount of perishable organic waste has been increasing.Anaerobic fermentation technology can effectively degrade organic matter and produce biogas for the biotransformation and resource utilization,,so it is now widely used in variety of industrial processing.The biogas slurry formed in the process of anaerobic fermentation can not be effectively treated and exploited due to its large output,complex composition,limited treatment and utilization technology,and the safety risks as well.According to the physicochemical properties of biogas slurry,coagulation and coagulation/ultrafiltration processes were used to treat biogas slurry in this thesis.The treated biogas slurry was used for seed soaking and hydroponics of biogas slurry,which is expected provid a theoretical basis with the practical experience for the resource utilization of biogas slurry from perishable garbage.The main conclusions are as follows1)Coagulation treatment can remove most of suspended solids in biogas slurry,reduce the turbidity,COD and heavy metal ions content of biogas slurry for water purification and reclamation.In the coagulation process,when using PAC as the coagulant with CTS and PAM as coagulation aids,respectively,the effect of CTS as the aid for the removal of Cu²⁺and Cd²⁺is better than that of PAM.When the initial p H is 7.0,the dosage of PAC is 0.75m L·L^-1and PAM is 9.0mg·L^-1,the removal rates of TN,COD and turbidity are 42.01%,44.56%and 99.72%,and the removal for Cu²⁺and Cd²⁺are 42.73%and 18.85%respectively.In the same condition for the initial p H of biogas slurry and 0.75m L·L^-1 of PAC dosage with 15 mg·L^-1 of CTS as the aid,the removal rates of Cu²⁺and Cd²⁺can reach 65.67%and 70.06%respectively,which are better than those for other p H conditions.2)The turbidity removal rate of biogas slurry by coagulation/ultrafiltration combined process is more than 99.8%.In this context,factors such as coagulant dosage,p H and coagulant aid types are no longer the limiting factors for the turbidity removal,and the changing trend and removal law for other water indices are consistent with those for coagulation treatment.In the coagulation/ultrafiltration combined process,when the initial p H of biogas slurry is 7.0,the dosage of coagulant PAC is 0.75m L·L^-1,and the coagulant aid PAM is 9 mg·L^-1,the removal rates of TN,COD and turbidity were 43.63%,51.72%and 99.80%with the removal for Cu²⁺and Cd²⁺being 46.51%and 20.78%,respectively.In the conditions for the original p H of biogas slurry,when the dosage of CTS and PAM are 15mg·L^-1 and 12mg·L^-1,the removal for Cu²⁺and Cd²⁺can reach 74.09%and 82.54%,respectively after ultrafiltration.The treatment effect of coagulation/ultrafiltration combined process is better than that of coagulation process,but the production costs will increase while the removal rate of water index is improved.In addition,the removal rates of TN and COD by coagulation treatment account for about96.29%and 86.15%,respectively,indicating that the removal of pollutants by coagulation process is dominant.3)The experiment of biogas slurry resource utilization includes seed soaking and hydroponics using the biogas slurry.High concentration of biogas slurry can inhibit the germination and growth of mung bean and wheat.When the concentration dilution range of biogas slurry is 0～30%and the germination time is 1.5d,the germination rate of mung bean is above 99.33%;When the concentration dilution range of biogas slurry is 0～40%and the germination time is 2d,the germination rate of wheat is above 96%.However,when the concentration of biogas slurry was 100%,the germination of both mung bean and wheat failed.With the growth of mung bean and wheat,the initial biogas slurry concentration was 5%,and the biogas slurry concentration after treatment was 10%,which is the optimum concentration for hydroponics in the experiment.