Effect Of Low-temperature Thermo-alkaline Pretreatment With Alkyl Polyglucosides (APG) For Low-organic-content Sludge On Anaerobic Digestion

Anaerobic digestion(AD)is one of methods for waste activated sludge treatment and disposal.Stabilization,harmless,reduction and recycling of sludge could be fulfilled by AD.And an effective pretreatment is able to improve its efficiency.The low temperature thermo-alkaline pretreatment has been proved to be an effective method which is full of application potential.In present essay,the pretreatment method was optimized by adding a new kind of green surfactant alkyl polyglucosides(APG)into pretreatment system,and effect of which on AD was studied.It was indicated in an orthogonal experiment of low temperature thermo-alkaline pretreatment with APG that,pH was the most significant factor,and temperature was the second.APG concentration had a significant influence on both organic matters which dissolved mainly from the extracellular polymeric substance(EPS),and phosphorus which came from almost cellular interior.Combine the effect of pretreatment and energy consumption into consideration through the supplementary tests,the pH,temperature and time were made to be 11,60? and 60 min.Under this condition,more APG led to more dissolution of organics and phosphorus.However,when APG concentration reached 18 g/L,more APG inversely lowered the concentration of soluble organic carbon,while soluble phosphorus increased.And in AD,APG at above critical micelle concentration(CMC)inhibited aerogenesis due to that APG micelles inhibited the activity of methanogens.As a result,3.0 g/L was chosen as the optimal APG dosage in pretreatment,when APG concentration in AD system was 1.8 g/L.Under this condition,methanogens had an adaptive phase of 13 days,but the gas production volume,methane yield and organics utilization rate reached their respective peaks.For the problems that there was an adaptive phase in aerogenesis and that the stable phase of aerogenesis was short,a single-stage continuous AD reactor whose volume was 1 L and dilution rate was 0.3 / d was designed in theory to overcome those disadvantages.The treatment and disposal of digested sludge was discussed to be: the fermentation supernatant should go back to equipment for urban sewage treatment after removing phosphorus by struvite precipitation reaction,and digested sludge consisted of struvite crystal and residual solid could be composted to change into high-quality organic fertilizer for agricultural use.