Effects Of Sodium Hypochlorite Pre-treatment For The Anaerobic Digestion Of Sludge

Hydrolysis acidification stage is the bottleneck of the whole anaerobic digestionprocess. For preprocessing of sludge we can obtain effects such as destroying thesludge floc structure, speeding up the break of extracellular polymers and release andhydrolysis of intracellular organic materials of excess sludge; accelerate thehydrolysis acidification process, improve the efficiency of anaerobic digestion,shorten the digestion period, so as to improve the anaerobic digestion performance,increase gas production and shorten the sludge retention time, lower energyconsumption. In this paper, we use sodium hypochlorite to pretreat the excess sludgeand study the effect of pretreatment and influence on the subsequent anaerobicdigestion performance.For the pretreatment of sludge experiment, the concentration of sodiumhypochlorite, the processing time and the influence of pH was analyzed. Theexperiment result indicated that, the concentration of organic matter released into thewater phase improved with the increase of the available chlorine dosing and theincrease of processing time and the rise of pH in a certain range,. We made theconcentration of sludge4g/L. When adding the active chlorine concentration is14.5mg/g SS and the processing time is4hours, SCOD increased to348.1mg/L; Theconcentration of TP up to22.9mg/L and TN up to51.2mg/L; The concentration ofpolysaccharide and protein increased232.8%and611.3%each other. The organicmatters increased with the increase of pH under the conditions of the best dosingquantity and reaction time.The characteristics of sludge and methane production before and afterpretreatment was analyzed compared with undisposed sludge. It showed that averagedaily rate in anaerobic digestion of excess sludge is34mL, increased by9.80%thanthat of without pretreatment. The gas production rate is1055mL in anaerobic digestion after the pretreatment, which is122mL more than the other. The maximumof the gas production rate occurred4days earlier than the original sludge. Thisindicates that using NaClO to pretreat the excess sludge can accelerate the speed ofanaerobic digestion and shorten sludge retention time. SCOD is a parametricrepresentation the degree of hydrolysis and solubilization of sludge in anaerobicdigestion. The experiments showed that catalyzed by traces of sludge in pretreatmentof sludge, The concentration of SCOD with a maximum of487mg/L after treatmentwas higher than that of sludge without pretreatment, and were about0.12times higherthan that of the untreated.