The city’s drinking water now meets the trihalomethane levels set forth by regulatory agencies. The levels for the past four quarters were below the maximum concentration level of 80 parts per billion. “This progress follows a series of significant updates and process improvements at the water treatment facilities aimed at reducing THM levels and ensuring water quality for Suisun City residents,” wrote City Manager Bret Prebula. Trihalomethanes, a byproduct of chlorine disinfection, can be produced during the pre-chlorination step of the water treatment process. It’s critical for removing organic materials and heavy metals.