Objectives By analyzing the monitoring data on sewages discharged from medical institutions in Changzhou City in 2008-2011, to search for the critical issues existed in the waste water system and to correct it in the future operations.

Methods A retrospective analysis was conducted on the monitoring data of 131 sewage samples obtained from Changzhou Center for Disease Control and Prevention in 2008-2011. The eight items of examination were enteropathogenic bacteria (Salmonella and Shigella), faecal coliforms counts, volatile phenol, suspended material, pH, chemical oxygen demand (COD), ammonia nitrogen and total residual chlorine.

Results The overall qualified rate of the sewage data was 23.6%, which was 20.0%, 20.6%, 18.9% and 32.5%, respectively in the four years. No enteropathogenic bacteria (Salmonella and Shigella) had been detected in waste water from medical institutions for infectious or non-infectious diseases. The qualified rates of both volatile phenol and suspended material were 100%. The qualified rates for faecal coliforms counts, pH, COD, ammonia nitrogen and total residual chlorine were 99.2%, 95.4%, 94.7%, 46.2% and 24.4% respectively. The qualified rate for total residual chlorine was the lowest.The qualification of total residual chlorine in 99 of 131 sewage samples was not acceptable. The value of total residual chloride in 27 of 99 (27.2%) sewage samples was lower than the standard and the value of other 77 samples was higher than the standard limits. The highest value of total residual chloride was 918.28 mg/L, which was 115 times higher than the standard limits. The qualified rate of ammonia nitrogen was also low, just only 46.2%.

Conclusions The overall situation of the sewage discharged from medical institutions was not optimistic. Currently, the main issue of sewage disinfection is excessive adding disinfectants and the facilities and process for wastewater treatment in the hospital for infectious diseases not met the requirements of discharging sewages.