The occurrences of Trihalomethanes (THMs) and heterotrophic bacteria were monitored in water samples from different locations “areas”. The water samples we got them water from (El-Shocake RO plant system, Jazan, KSA) over a twelve -month period to investigate the association between (THMs) and heterotrophic bacteria populations. The sampling sites were chosen to cover the entire distribution pipes network of the El-Shocake RO system approximately more than 200 Km distance. A positive association between some bacterial species and THMs concentrations was found at some locations. Bacterial count of some type bacterial species could be used as an indicator for the presence of THMs in distribution systems.
When we considered the relation between THMs and all identified culture-able bacterial isolates we observed that, the increase the concentrations of the THMs in the water increased the percent of gamma- Proteobacteria classes. The highest THMs values were recorded at water samples collected from the south region of Jazan province which included three main cities El-Ahad, El-Dagarer and Samta. We think that, there are many of yet-unknown bacterial strains “aerobic/anaerobic” which have relations with THMs and further studies on the isolation and identification bacteria using other mechanisms.