Trihalomethane formation potential of shrimp farm effluents in Chachoengsao Province, Thailand

Shrimp farm effluents along Bangpakong River in Chachoengsao Province, Thailand, were evaluated for their trihalomethane formation potential (THMFP), which were shown to be in the range of 810-3,100 µg/L. Samples from river locations, both upstream and downstream from these selected farms, were also tested for their existing THMFP. These river samples were illustrated to have notably lower level of THMFP than the shrimp farm effluents. The downstream concentration was, however, found to be significantly higher than the upstream (as much as 5 times). This indicated that the contamination of shrimp farm effluents could have increased the formation potential of THMs in the natural water source. The experimental results showed a positive correlation between salinity and THMFP. The formation of various THM species depended significantly on the level of salinity in the water sample. Low salinity (0-5 ppt) often led to a high formation of chloroform and bromodichloromethane while high salinity (5-15 ppt) resulted in a great quantity of dibromochloromethane and bromoform. FTIR spectra of the samples before and after chlorination suggested that the functional groups involved in the reaction were hydroxyl group, amines group, aromatic ring, aliphatic chloro compounds and aliphatic bromo compounds, whereas C-O was the product from the reaction