Improved Study On Anaerobic Fermentation Of Sewage Sludge For Volatile Fatty Acids By Pretreatment With Ultrasonic Coupling Technology

As the demand of sewage concentrated treatment rate is higher and higher, the amount of excess sludge produced by sewage treatment is becoming more and more big. The “water pollution prevention plan of action” recently enacted by the state council request forward demand of sludge disposal by sewage plant: existing sludge disposal facilities should be transformed up to standard before the end of 2017, prefecture-level city and urban sludge disposal rate should be above 90% by the end of 2020. Therefore, urban sludge disposal will be the hot spot and focus in the field of pollution control in the next few years.Sludge anaerobic fermentation is an effective way of sludge innocent treatment and utilization, reduction. However, excess sludge has poor biodegradable nature because of the low content of soluble organic matter and solid. The effect of acidification and reduction is not obvious about excess sludge anaerobic digestion only. This study is about sludge pretreatment by ultrasonic and its coupling technology to get more soluble organic matter in order to improve the sludge anaerobic acidification, fore solving the problem that hydrolyzing is the limiting step of sludge anaerobic digestion. The main conclusions are as follows:1)First of all, the study is about sludge crack and the influence of anaerobic acidification by alone ultrasonic pretreatment, and optimized the parameters of the sludge treatment by ultrasonic. The results show that the content of the solubility of chemical oxygen demand(SCOD) and soluble carbohydrate is increased when the ultrasonic sound energy density and duration is improved, and the release of ammonia nitrogen and phosphate is becoming more. The content of small particles in the sludge is increased and decrement of VSS about sludge is promoted by ultrasonic pretreatment. Ultrasonic pretreatment for sludge anaerobic hydrolysis offers a wide range of initial fermentation substrates, the production of solubility of volatile fatty acids(VFAs) is becoming more after ultrasonic pretreatment. Ultrasonic pretreatment reduces the acidification time that concentration of VFAs was highest about sludge anaerobic. When the sound energy density is 1 W/mL, the optimal pretreatment time is 20 min.2)The release of organic matter is more obvious by the sludge pretreatment of ultrasonic coupling with alkali technology. The content of SCOD and soluble carbohydrates increased significantly when the dosage of alkali(or pH) was improved at same ultrasonic conditions. The production of VFAs is improved at sludge anaerobic fermentation by ultrasonic pretreatment coupling with alkali when the dosage of alkali(or pH) was improved, but the sludge anaerobic fermentation time of achieving highest production of VFAs was extended. In this experiment, the best pH of ultrasonic coupling alkali pretreatment sludge was 10.3)This experiment first studied the influence of sludge crack and anaerobic acidification by the pretreatment of ultrasonic coupling with surface active agent. The results show that the content of SCOD and soluble carbohydrate was increased when the dosage of sodium dodecyl benzene sulfonate(SDBS) or hexadecyl trimethyl ammonium chloride(1631) was improved. The release of the phosphates in sewage sludge was promoted because of SDBS than 1631 at same conditions, and the hydrolysis of ammonia nitrogen was inhibition by 1631.The production of VFAs was improved by the sludge pretreatment of ultrasonic coupling with SDBS or 1631,but was more when SDBS or 1631 separate effect on sludge.