STUDY OF THE FORMATION OF REGULATED TRIHALOMETHANES DURING CHLORINATION AND CHLORAMINATION BY THE SOIL-EXTRACTED DOM FROM THE CEDAR LAKE WATERSHED

Author

Sajjan Nhuchhen Pradhan, Southern Illinois University CarbondaleFollow

Date of Award

6-1-2021

Degree Name

Master of Science

Department

Civil Engineering

First Advisor

Fakhraei, Habibollah

Abstract

The Cedar Lake watershed in Southern Illinois has upland forests as a major land-cover type along with fined-grained soil, having moderate water transmission rate. As naturally occurring organic carbon forms in the soil underlying the upland forests, the dissolved organic matters (DOM) release to the lake. Dissolved organic carbon (DOC) is an important water quality parameter as it undergoes reaction with disinfectants, such as chlorine and chloramine, to form potentially carcinogenic disinfection by-products (DBPs) during water treatment process. In this study, soil samples from organic and mineral layers at six different spots were collected within the Cedar Lake watershed. The soil samples were processed in the laboratory to extract DOC from mineral and organic horizons. The soil samples were air dried, sieved to < 2 mm and soaked in deionized water overnight while stirring gently. The soil solution was poured off, centrifuged and filtered with 0.45-μm nylon membrane filters to obtain the DOC stock solution. DOC solutions were prepared by diluting the DOC stock solution at different levels. Then the solutions were chlorinated and chloraminated under variable environmental factors including temperature, disinfectant dose, bromide concentration, and pH. Analysis of THMs were done using headspace GC-MS by following the EPA Method 5021A in combination with determinative method 8260. The results showed that chlorination produced far more THMs compared to chloramination. The study revealed that the concentration of total trihalomethanes (TTHMs) noticeably increased along with increases in DOC concentration, reaction time and disinfectant dose both in chlorination and chloramination processes. Bromide level in the DOC impacted the concentration of Br-THMs formed during chlorination while pH and temperature had moderate impact on formation of TTHMs. The preliminary water quality parameters, such as DOC level, EC, TDS, turbidity, UV254, bromide level and SUVA, showed strong positive correlation with TTHMs in chlorination experiment.