The Effect Of Ultrasonic/Hydrogen Pretreatment On The Fermentation And Dehydration Of Sludge

Activated sludge method is currently the most widely used domest ic sewage treatment technology.Sludge produced in the process of activated sludge method has not been properly soluted.High water content of sludge is the main reason of the high cost.There is a large amount of organic matter in the sludge,so discharging is not environmentally friendly and will waste a lot of energy.In this paper,the effect of ultrasonic and hydrogen peroxide on sludge dewatering and fermentation performance was studied to achieve sludge reduction and energy recovery.In order to improve the dewatering performance and subsequent fermentation perform ance of the sludge,the sludge can be conditioned by means of pretreatment to improve the properties and make it more conducive to dehydration and gas production in fermentation.In this paper,sludge from secondary clarifier was used as the research object.The pretreatment was ultrasonic and hydrogen peroxide.The ability of ultrasound and hydrogen peroxide to crack the sludge was investigated.The results showed that when the ultrasonic frequency was 20 k Hz,the ultrasonic time was 8 min.the power was 0~300 W,the SCOD,total nitrogen and ammonia nitrogen in the sludge supernatant will increase as the increasing of ultrasonic power.After treatment for 8 min at 300 W,the sludge supernatant SCOD was increased 842%.As the hydrogen peroxide dosage increased,the SCOD in the supernatant increased first and then decreased,when the dosage is 2.78 mg/L,was increased 251%.The total nitrogen and ammonia nitrogen were increased.After the ultrasonic cracking,the VFAs rises rapidly and highly in the process of fermentation.The amount of methane produced during the digestion process increases significantly.In order to verify whether the combined use of hydrogen peroxide and ultrasound can achieve better result,ultrasonic power,p H value,and amount of hydrogen peroxide were used as variables situation to study the cracking effect and fermentation effect through orthogonal test methods.The results showed that combining ultrasound-Hydrogen peroxide was superior than the two alone.There is a better promoting effect on cracking and anaerobic digestion.When the pretreatment conditions were: p H=10,hydrogen peroxide(30% H2O2)= 2.78 mg/L and the ultrasonic power = 240 W,the gas production of anaerobic digestion for 8 days was increased 70% that before treatment.The sludge was treated as same as pretreatment method to verify the improvement of sludge dewatering performance.After ultrasonic treatment,the sedimentation of sludge was deteriorated.Centrifugal dewatering and filter dewatering were changed when ultrasonic power changed.The centrifugal dewatering effect was best at 180 W,and the dewatering effect was best at 120 W.After the treatment with hydrogen peroxide,the sedimentation performance of the sludge and the dewatering by suction was decreased but centrifugal dewatering improved was decreased.Put the pretreated sludge into the CSTR.After ultrasonication,the sludge fermentation started quickly.However,the later gas production was not as good as ultrasonic hydrogen peroxide treatment.The sludge production after the treatment with hydrogen peroxide alone was lower and the speed was slow.After pretreatment by ultrasonication,the dewatering performance of sludge is improving.The treatment can save the volume of the container.It can also promote t he anaerobic reaction.The treatment can achieve energy utilization and sludge reduction.