Abstract:
Effects of the hospital size and the type of wastewater treatment plant on the effluent quality was carried out. The effluents discharged from 12 hospitals in Bangkok Metropolis were analysed. The results showed that the effluent quality did not depend on the size (or number of bed) of the hospital but on type of the wastewater treatment process. Almost all of the hospital could not produce effluent with quality conforming to the standards established by NEB. The activated sludge system was better than other processes, namely, septic tank and onsite aerobic package unit in terms of the effluent quality, since its effluent was closer to the standards than the rest. In the 50-120 beds group, the average BOD, COD and SS of the effluent from septic tanks were 189.7, 352.9 and 79.0 mg/l, respectively, where the corresponding figures for the hospitals which treated their wastewater by aerobic package unit was 281.3, 119.3 and 38.3 mg/l. Similarly, the effluent quality from the activated sludge system was 43.6, 97.7 and 18.6 mg/l. In 121-500 beds group, the average BOD, COD and SS of the effluent from septic tanks were 176.0, 306.8 and 20.5 mg/l, respectively, where the corresponding figures for the hospitals which treated their wastewater by aerobic package unit qwas 121.5, 210.2 and 41.3 mg/l. Similarly, the effluent quality from the activated sludge system was 45.5, 88.8 and 16.7 mg/l. In group of the hospital which has more than 500 beds the average BOD, COD and SS of the effluent from activated sludge system was 47.1, 103.0 and 9.3 mg/l and the effluent quality from septic tanks were 142.3, 175.6 mg/l.