Application Note

Determination Of Trihalomethanes (THMs), Trihaloacetic Acids (THAAs), And Other Disinfection By-Products (DBPs) In Drinking Water

Source: Hach

The determination of Disinfection By-Products (DBPs) has become extremely important to drinking water companies due to the newly imposed regulatory testing requirements by the EPA1. The difficulty and expense involved in regulatory testing has necessitated the need for a low cost, simple, quantitative test for DBPs that can be done in real time. The new method, THM Plus2, allows for the screening of chloroform, also called trichloromethane (TCM), dibromochloromethane (DCBM), bromodichloromethane (BDCM), tribromomethane (TBM), trichloroacetic acid (TCAA), dichlorobromoacetic acid (DBCAA), bromodichloroacetic acid (BDCAA), tribromoacetic acid (TBAA), chloral hydrate (CH), 1,1,1-trichloro-2-propanone (111 TCP) and 1,1,1-trichloroacetonitrile (TCAN). No extraction or concentration steps are required. No hazardous materials are used or generated in the proposed method. The new colorimetric method can be used to quickly adapt to changing influent water characteristics and to establish trending data for the formation of DBPs throughout the distribution system. Multiple samples from across the United States were analyzed in comparison to the three EPA Methods for DBPs to validate the new method.

The EPA’s new D/DBP Rule for total trihalomethanes (TTHMs) and haloacetic acids (HAAs), in combination with the complexities and cost of approved testing methods, has created the need for a new simplified method of analysis. In order for a water utility to efficiently manage its disinfection process, real-time data analysis for THMs and THAAs plus other DBPs such as CH, 111-TCP, and TCAN is critical. Most small utilities do not have the equipment or budget to perform the three methods that are required to test for the major DBPs. In addition, the turn-around time for these tests can be anywhere from one to three weeks. A complete DBP screening encompasses three separate EPA methods, as outlined in Table 1, in contrast to the proposed method described in Table 2 that screens for multiple DBPs.