Thesis (M.Sc.)--Chulalongkorn University, 2005

WASP 6.0 (EUTRO) was applied to estimate the carrying capacity of Pak Phanang River on organic waste loading. The achievement of water quality goal was set to maintaining a DO concentration of 4.0 mg/L according to the river class 3 of Thailand's surface water quality standard. The average annual organic waste loads was estimated from secondary data collected in 2002 to 2003, as 2,978 kg/day. The results showed that loading capacity of the river from Mai Siap weir to Kuan kreng swamp forest was 1,175 kg/day which can receive additional load about 7 times of the existing loads. Loading capacity of the river from Kuan Kreng swamp forest to Klong Chian Yai was 130 kg/day which requires 80 percents treatment of the existing loads. Loading capacity of the river from Klong Chian Yai to Uthokvibhajaprasid Gate was 874 kg/day which requires 60 percents treatment of the existing loads. Consequently, it was calculated that total loading capacity of Pak Phanang River was 2,179 kg/day.