Volume 49 Number 3

Reduction and regrowth of total coliform bacteria, fecal coliform bacteria, and E. coli after chlorine and peracetic acid disinfection in the hospital effluent

Supavita Suwannasin^a, Siranee Sreesai^a,b,*, Chaowalit Warodomrungsimun^a,b, Chatchawal Singhakant^a,b, Wannee Magun^c

 
ABSTRACT:     Hospital wastewater is an important source of pollutants resulting from medical activities. It has a high vulnerability towards the outbreak of several diseases. The aim of the study was to investigate the disinfection efficiency of different dosages and contact times of chlorine and peracetic acid (PAA) to reduce the contaminated microbes. The consequences after treatments such as regrowth capacity, disinfection by-products, and water quality were also observed. The result showed that in all fourth-time samplings of effluent, its physical, chemical, and biological characteristics exceeded the standard requirement and needed further treatment before discharge. The disinfection experiments were run in parallel among 3 chlorine dosages (1.388, 1.588, and 1.988 mg/l) and 3 PAA dosages (5, 10, 15 mg/l) at contact times of 15 and 30 min. PAA performed faster than chlorine from the beginning, after that, they all provided similar microbial reduction around 2.38?4.47 log 10 MPN/100 ml. Chlorine provided higher efficiency in reducing total coliform while PAA was greater for E. coli. The efficiencies increased as contact time was increased. PAA exhibited higher physical and chemical treating capacities than those of chlorine. The study suggested that chlorine at 1.528 mg/l and/or PAA at 5 mg/l, at a contact time of 15 min, are suitable microbial treatments for this effluent. These suggested conditions could improve all water quality parameters to meet the standard requirement and inhibit regrowth of microbes during the three-day incubation period. The stakeholders should also continue to monitor effluent characteristic variation and treatment conditions regarding the application of these infectants.

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* Corresponding author, E-mail: siranee.sre@mahidol.ac.th

Received 1 May 2023, Accepted 3 Dec 2023