Study On Microwave/Activated Carbon Fiber Coupling Persulfate Pretreatment Of Sludge

The treatment and disposal of excess sludge has always been a difficult problem in the sewage treatment industry.The sludge digestion and dehydration links in the sludge treatment process determine the economic and environmental benefits of subsequent drying treatment and sludge disposal.As we all know,the capillary water and combined water in the excess sludge are difficult to be removed by mechanical method,and the organic matter in the sludge is difficult to be used by anaerobic bacteria,resulting in the problems of poor sludge dewatering performance and low anaerobic digestion efficiency in the actual sludge treatment process.To solve these problems,researchers tried to pretreat the concentrated sludge by microwave heating and adding persulfate,and made some progress in improving sludge dewatering performance and anaerobic digestion rate.Sulfate radical（SO₄^-·）with strong oxidation can be produced by adding persulfate,which can destroy the floc structure and cell structure of sludge.However,due to the low yield of SO₄^-·the treatment cost is high and the reaction speed is slow.The use of microwave heating technology is helpful to improve the yield of SO₄^-·and the increase of activated carbon fiber can improve the efficiency of microwave heating.This study attempts to combine the three effects of microwave activation,activated carbon fiber assisted heating and persulfate strong oxidation to pretreat the excess sludge.Through the experimental design,the effects of the combination of two and three on the anaerobic digestion and dehydration of sludge are studied.The experiment of microwave/persulfate（MW/PS）on sludge pretreatment shows that the increase of microwave power,microwave time and persulfate dosage can improve the sludge cracking effect.The optimum reaction conditions were persulfate dosage of 1.8mmol/gvss and 700W microwave treatment for 240s.In terms of sludge dewatering performance,with the increase of persulfate dosage,the sludge dewatering performance is significantly improved.In terms of anaerobic digestion,the cumulative methane production of sludge treated with microwave/persulfate（MW/PS）increased by 105.30%and 161.60%respectively compared with sludge treated with microwave（MW）and persulfate（PS）alone.The anaerobic digestion performance of sludge treated by microwave and persulfate was significantly improved.The experiment of sludge pretreatment with microwave/activated carbon fiber（MW/ACF）shows that low-power microwave radiation can improve the sludge dewatering performance,but the sludge dewatering performance deteriorates with the increase of microwave power.Compared with the sludge treated by microwave（MW）alone,the addition of activated carbon fiber（ACF）improves the sludge cracking efficiency and shortens the time required to reach the reaction equilibrium.In terms of anaerobic digestion,the cumulative methane production of MW/ACF experimental group was 28.81%higher than that of MW group.The addition of ACF improves the anaerobic digestion effect of MW treated sludge to a certain extent.Using microwave/activated carbon fiber combined with persulfate（MW/ACF/PS）to pretreat sludge,compared with the first two pretreatment methods,the reaction equilibrium time is shortened and the sludge cracking effect is further improved.The experimental results showed that the optimum reaction conditions were persulfate dosage of 1.8mmol/gvss and 700W microwave treatment for 180s.Compared with the sludge treated by MW/ACF and MW/PS under the same conditions,the SCOD value of sludge increased by 120.74%and 46.28%respectively.Compared with the sludge treated by MW/ACF,the sludge dewatering performance is improved.In terms of anaerobic digestion,the content of sludge hydrolysates,volatile organic acids（VFAs）and total cumulative methane production in MW/ACF/PS group were much higher than those in other experimental groups.Therefore,the coupling of microwave,activated carbon fiber and persulfate can further improve the anaerobic digestion effect of sludge.