Which water source generally results in higher TTHM formation due to organic material presence?

Surface water is the correct choice for the water source that generally results in higher formation of total trihalomethanes (TTHMs) due to the presence of organic material. Surface water, such as rivers, lakes, and streams, often contains higher levels of dissolved organic matter compared to groundwater sources like wells or spring water. This organic material can react with chlorine or other disinfectants during the water treatment process, leading to the formation of TTHMs, which are byproducts of disinfection.

The presence of vegetation, decaying organic materials, and runoff from land can contribute to an increased organic load in surface waters. When water treatment facilities apply chlorine to disinfect surface water, the reaction with these organic compounds results in the formation of TTHMs. Consequently, effective water treatment and management strategies are essential when using surface water sources to reduce TTHM levels and ensure safe drinking water.