| At present, hydrolysis and acidification process is mainly for high-volatile(VSS/TSS>50%) sewage sludge, therefore strengthen hydrolysis and acidification oflow-volatile (VSS/TSS<40%) sewage sludge is worth to concern. In this study, the combinationof low-intensity (ultrasonic density≤0.570W/mL and ultrasonic time≤3min） ultrasonictreatment and a moderate alkaline (pH≤10.0) adjustment was used to strengthen hydrolysis andacidification of low-volatile sewage sludge, sludge resources and stabilization were reached.The following contents were studied:(1) The influence of treatment pHs, ultrasonicdensities and ultrasonic time in hydrolysis and acidification process of low volatile sludge wasresearched, the major indicators were the release of organic matter and the activity of enzymes.(2) The relationships between sludge resources and stabilization in the process of low-volatilesludge’s hydrolysis and acidification were studied.(3) Factors of combination in hydrolysis andacidification process were analyzed.The results have shown that:(1) Under the way of ultrasonic treatment before pH adjustment, it was more helpful to thetransformation of organic sludge and VFAs generation for low-volatile (VSS/TSS<30%) sludgewhen the ultrasonic density was0.190W/mL, the ultrasonic time was3min and the pH was9.5.(2) The low-volatile (VSS/TSS=27%) sludge’s pH was adjusted to8.0,9.0,9.5,10.0withthe ultrasonic density0.190W/mL and ultrasonic time3min, in the fermentation system we gotthe variation of SCOD concerntration on the forth day was: PH9.5> pH10.0> pH9.0> pH8.0;In the process of hydrolysis and acidification, different pH value had a great influence on thespecies of volatile acid. High pH values had an inhibitory action on dehydrogenase activity;(3) On the forth day, when the low-volatile sewage sludge (VSS/TSS=25%) was treatedby ultrasonic density0.190W/mL, ultrasonic time3min, and pH9.5, the highest concentrationof soluble protein and carbohydrate reached2493.5mg/L and366.56mg/L, respectively; At day0, the effects of different ultrasonic time of α-glucosidase activity was in the order:3min>5min>1min;(4) Under the condition of ultrasonic density0.076W/mL,0.190W/mL,0.380W/mL,0.570W/mL, ultrasonic time3min, and pH value9.0, on the fifth day sludge (VSS/TSS=25%)hydrolysis and acidification, when ultrasonic density were0.076W/mL and0.190W/mL, thereduction rate of VSS reached19.24%and16.38%, respectively; It was favorable for somehydrolase enzyme activity increasing when the ultrasonic density was0.380W/mL; It wasbeneficial to the increase of SCOD,soluble proteins and carbohydrates, when the ultrasonicdensity was0.190W/mL;(5) Ultrasonic treatment was conducive to the increase of protease, α-glucosidase, alkalinephosphatase, acid phosphatase and dehydrogenase activity for the original sewage sludge; The combined action or only alkaline adjustment was beneficial to the increase of acetate kinaseactivity;(6) By fitting analysis, in the process of SCOD release, we got: the role of hydrolyticacidification time> pH effect>VSS0effect> the role of ultrasonic time> the role of ultrasonicdensity; The VFAs generated process was: the role of hydrolytic acidification time>VSS0effect>pH effect> the role of ultrasonic time> the role of ultrasonic density; And in theprocess of protein release, we got: hydrolytic acidification time> pH effect> the role ofultrasonic density> the role of ultrasonic time> VSS0effect.Therefore, for the hydrolysis and acidification of low volatile sludge (VSS/TSS between30%and40%), the optimal ultrasonic density, ultrasonic time and pH conditons were0.190W/mL,3min and pH9.0. When the optimum conditions were taken for the hydrolysis andacidification of low-volatile sewage sludge, the ThODHAc/ThODVFAsreached88.03%, HAcconcentration reached2460.88mg/L and VSS reduction rate reached32.06%; On the sixth dayhydrolysis and acidification of the low-volatile sewage sludge, it could get both a higerconcentration of acetic acid and a greater degree of stability. |
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