Effects Of Organic Matter Release And Sludge Reduction In Anaerobic Digestion Treated By Combination OfUltrasound And Thermal Hydrolysis

At present,China’s urbanization rate is becoming faster and faster,with the improvement of sewage treatment capacity, the sludge emission is increasing fsater.The conventional anaerobic digestion process has the disadvantage of the long period of the long digestion period,the low methane production and the poor effect of sludge reduction.The study on sewage sludge anaerobic digestion promoted by ultrasonic radiation and ultrasound combined with thermal hydrolysis to improve the effect of anaerobic digestion is attracting more and more attention.The paper studied the impact on excess sludge treated by ultrasonic radiation and ultrasound combined with thermal hydrolysis.The conclusion follows:(1).The cavitation of ultrasound can effect sludge properties. With the energy consumption increased,the crack effect increased,and the 20+25kHz dual-frequency >20kHz>25kHz. The crack degree of SCOD is up to 28.7%, the concentration of ammonia and protein solubility were 2.96 and 7.1 times of the original sludge.The reduction rate of TSS and VSS is 24.2% and 21.2%,the average particle size of sludge is reduced by 52.0%.The crack effect increased slowly when the energy consumption is over 12000kJ/kg TS, the (20+25kHz、12000kJ/kg TS) is the best individual sonication conditions to ensure effectiveness as well as reduce the energy consumption.(2).The release of organic matter and the methane production rate is improved by ultrasonic pretreatment,but the effect of sludge reduction increased slowly, With the increase of energy consumption,the peak concentration of SCOD and solubility protein is higher, The maximum ammonia concentration is 6.4 times than the original slufge,the production of methane is 284.02mL/g TS,and is increased by 19.7% than the original sludge. The reduction rate of TSS and VSS is 18.62% and 16.07%,compared with the original mud’s 17.03% and 15.16%, the effect of sludge reduction needed to be improved.(3)The crack effect of ultrasound-thermal hydrolysis technology is significantly better than ultrasound alone.The best effect is appeared with the combination of ultrasound and 80℃ thermal hydrolysis.With the temperature increased, the crack degree of SCOD、the concentration of ammonia and the reduction rate of TSS、VSS increased gradually. The maximum value was achieved to 41%、138.9mg/L、30.9% and 27.7%, Soluble protein concentration reaches a maximum at 80℃.Compared with ultrasound alone crack degree of SCOD increased by 12.8%、and reduction rate of TSS% VSS increased by 7% and 7.1%,the average particle size of sludge is close.(4).The release of organic matter and the methane production rate is improved by ultrasonic pretreatment,and it improved the effect of sludge reduction obviously.The maximum reduction rate of TSS and VSS was increased by 19.17% and 18.71% than the effect of ultrasound alone. With the temperature increased,the concentration of ammonia, the reduction rate of TSS was increasing。The concentration of SCOD、the soluble protein、the VSS reduction rate and methane production decreased after the first increase.The combination of ultrasound and 80℃ thermal hydrolysis reached the best effect of anaerobic digestion.The maximum concentration of SCOD is 5603.4mg/L, which is 12.5% higher than ultrasound alone,the largest amount of methane is 332.5mL/g TS,which is 17.1% higher than ultrasound alone.