Calcium Peroxide Combined With Ultrasonic Pretreatment To Improve Methane Production In Sludge Anaerobic Digestion

At present,sludge anaerobic digestion is the most economical sludge treatment method for large sewage treatment plants,which can not only effectively reduce sludge,stability and reuse,but also can recover energy and nutrients and reduce the operation cost of WWTPs.However,in the process of methane production from sludge anaerobic digestion,there is a rate-limiting step?hydrolysis and acidification stage?,so the actual production of methane is not high.Therefore,the sludge pretreatment technology is used to improve the methane production.In recent years,ultrasonic?US?pretreatment has proved to be an effective method at the laboratory scale and has been applied in the real world.This technology is simple to operate and has no secondary pollution.It can not only be used as an independent pretreatment method,but also be combined with other methods for the sludge pretreatment process.Calcium peroxide?CaO₂?is a kind of widely used and safe inorganic compound peroxide.This study reported a new and efficient anaerobic digestion pretreatment method,which combined calcium peroxide?CaO₂?and ultrasonic?US?to pretreat sludge.The experimental results showed that under the conditions of 0.1g CaO₂/g VSS and US?1 W/ml,10 min?,the maximum methane production was 211.90±2.6 LCH₄/kg VSS after 36 days of sludge anaerobic digestion,which was 1.36 times as much as the control,1.19 times as much as the pretreatment with ultrasound alone?1 W/ml,10 min?,and 1.26 times as much as the pretreatment with calcium peroxide alone?0.1 g/g VSS?.CaO₂+ultrasonic technology not only significantly improves the methane production,but also plays a positive role in sludge reduction,and also improves the removal rate of refractory organic pollutants.In this paper,the mechanism of CaO₂+ultrasonic technology promoting the improvement of methane was analyzed and studied from the aspects of exploring the synergistic effect of calcium peroxide and ultrasound,the effect on sludge cell cracking and sludge biodegradability.Studies have shown that ultrasound can promote the decomposition of calcium peroxide,and promote the production of more calcium peroxide and free radicals.CaO₂+ultrasound not only increased the disintegration rate of activated sludge?WAS?,but also increased the proportion of biodegradable organic matter.Therefore,the combined treatment strategy?CaO₂+US?proposed in this study can be used as an alternative pretreatment method for the residual sludge anaerobic digestion system,which not only reduces the energy consumption of ultrasound to a certain extent,but also reduces the dose of CaO₂.Combined action can also effectively remove more refractory pollutants,which is more conducive to the follow-up disposal of sludge,and reduce the possibility of environmental pollution,which may be of great significance for the future operation of WWTPs.