Biological Conditioning To Improve Sludge Dewaterability

Biological condition provides an effective option for sludge condition,which has such advantages as small secondary pollution,low cost and environment friendly,to improve the slude dewaterability.However,there is no systematic research on the process parameters in the operation process.The aim of this study was to investigate the process parameters of biological condition to improve the sludge dewaterability.It would have a deep study on the influence of dosing ratio and dosage of S⁰ and FeS0₄,and the aeration rate.In addition,use electrochemistry as a pretreatment method to help carbon source release so as to be better utilized in the biological conditioning process.The results showed that when the ratio of S⁰ and FeS0₄ was 3:7,the solid cake was 15.07%,which was 62.4%higher than that of the control group.The CST reduced to 11.3 s.The pH droped to 2.74.The viscosity reached 360 mPa·s.The Zeta potential increased to-3.06 mV.Moreover,the proteins in the EPS layer denaturalized and precipitated due to the decrease of the pH,and the polysaccharide also released into the supernatant in a large amount.When the mass of the mixture was 20%of the dry weight of sludge,the solid cake reached 18.48%.The CST value droped to 10.6 s,39.1%better than that of the control group.The pH dropped to 2.18,viscosity reached 358 mPa·s,while the Zeta potential reached-1.15 mV.The SCOD in the supernatant has obvious dissoluted and degradated and made the EPS content decrease significantly.Further studies on the aeration affecting the biological conditioning effect were carried out.It was found that the use of aeration rate at 400mL/min·L can reduce the pH of the system to the proper range at a faster rate.The viscosity of the sludge decreased to 275 mPa·s.The Zeta potential reached to-3.59 mV.The solid cake was to 22.6%.The CST reached 11.5 s.The release of organic compounds in the EPS layer was obviously better than other groups.In addition,the sludge was electrolyzed for 5 min using electrolysis voltage of 20 V and electrode spacing of 5 cm,then the biological conditioning was carried out according to the previous experiments.The rate of solid cake increased from 20.0%to 23.0%.The CST decreased from44.1s to 36.7s.The pH value decreased from 3.54 to 3.16.It was worth mentioned that,after electrolysis,the content of polysaccharide which was difficult to be degraded significantly reduced,so that sludge dewatering improved.It was also showed that Thiobacterales,a bacterial that had a significant effect on biological condition,had the highest content of 3.59%in the 5 min group.It showed that the ratio of S⁰ and FeS0₄ was 3:7,the dosage was 20%of the dry weight of sludge,and aeration of 400 mL/min·L was used to improve sludge dewatering.Under the condition of electrolysis voltage of20 V and electrode spacing of 5 cm to electrolysis 5 min,sludge dewatering could get the best improvement.