AWWA WQTC58812

Three kinetic stages were observed for the chlorine exposure-trihalomethane relationship for two enhanced coagulated waters. There is a fast initial increase of Total Trihalomethane (TTHM) concentration for contact time (CT) < 10 mg-min/L, followed by a linear increase of TTHM concentration up to a CT of 200 mg-min/L and finally followed by another slower linear increase up to a CT of 10,000 mg-min/L. Also, for both waters the chlorine exposure - TTHM relationships were independent of chlorine dose for CT < 200 mg-min/L. For the temperature studies disinfection requirements had a greater impact on the CT than TTHM, DCAA and TCAA formed for CT < 200 mg-min/L. pH impacted the CT - THM and TCAA formation relationships for CT < 200 mg-min/L. Treatment decreased the TTHM, dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) concentrations as a function of CT. Ultraviolet absorbance (UVA) was a good indicator for the CT-THM, DCAA and TCAA relationships for the enhanced coagulated and granular activated carbon (GAC) treated waters and less so for the raw water and ozonated/biotreated waters. In some cases temperature, pH and treatment had greater impacts on the CT - DBP relationship for CT > 1,000 mg-min/L These impacts could be more important for more resistant protozoa, such as Cryptosporidium parvum oocysts, which require higher chlorine exposures. Includes 5 references, tables, figures.