YANGMin,SHANGWei,LIPeng-feng,et al.Influencing Factors of Sodium Hypochlorite Disinfection and Its Optimization in Municipal Wastewater Treatment Plants[J].China Water & Wastewater,2022,38(9):76-81.
Influencing Factors of Sodium Hypochlorite Disinfection and Its Optimization in Municipal Wastewater Treatment Plants
China Water & Wastewater[ISSN:1000-4062/CN:12-1073/TU]
volume:
第38卷
Number:
第9期
Page:
76-81
Column:
Date of publication:
2022-05-01
- Abstract:
- The main influencing factors of sodium hypochlorite for disinfecting the effluent from a filter of a typical municipal wastewater treatment plant were systematically analyzed, and the disinfection process was optimized according to the characterization indexes of effective chlorine dosage and disinfection performance. Effective chlorine dosage, contact time, mixing conditions and the number of fecal coliforms had significant effects on disinfection performance, while ammonia nitrogen had little effect on disinfection performance. The influence of temperature on disinfection performance under static condition was significant, while that under agitation could be ignored. When the stirring and contact time was no less than 10 min, effective chlorine dosage of 0.75 mg/L could ensure that the number of fecal coliforms in the effluent of the filter after disinfection reached the first level A criteria specified in the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB 18918-2002). The number of fecal coliforms in the effluent from typical advanced treatment processes decreased significantly along the process. Compared with the number of fecal coliforms in the effluent from a secondary sedimentation tank, that in the effluent from the filter was decreased by 85% on average. For municipal wastewater treatment plants that require to meet the first level A standard or more strict standards, the optimized effective chlorine dosage for disinfection of the effluent from filter was 1 mg/L when the contact time was no less than 10 min. When the contact time was less than 10 min, the effective chlorine dosage for the disinfection could be increased to 1.25 mg/L. The optimized effective chlorine dosage (1-1.25 mg/L) was significantly lower than the average effective chlorine dosage (3.69 mg/L) of the surveyed municipal wastewater treatment plants required to meet stricter discharge standards. When the effective chlorine dosage was 1 mg/L, the residual chlorine in the effluent from the filter for 30 minutes contact (0.02-0.16 mg/L) was significantly lower than that (1.12 mg/L) in the effluent from the surveyed municipal wastewater treatment plants required to meet stricter discharge standards in China, and the ecological safety risk of the tail water was significantly reduced.An optimized disinfection rapid characterization index [oxidation reduction potential (ORP)] and an operation control parameter (ΔORP) were innovatively proposed, and the referential ΔORP for different contact times of the effluent from the filter under the effective chlorine dosage of 1 mg/L were proposed.
Last Update:
2022-05-01