Variations of disinfection by-product precursors of stream systems in north Missouri watersheds of drinking water supply reservoirs

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Dissolved organic matter (DOM) and its potential to form disinfection by-products (DBPs) during water treatment are of great public health concern. The link between temporal patterns of terrestrial DOM quantity and quality of stream systems in north Missouri watershed of drinking water supply reservoirs was explored to assess catchment controls on stream water DOM chemical composition and reactivity in DBP formation. TCM (trichloromethane) was the dominant of trihalomethane (THM) species and trichloroacetic acid (TCAA) and DCAA (dichloroacetic acid) were the dominant of haloacetic acid (HAA) species formed in chlorinated stream water samples. N-nitrosodimethylamine (NDMA) formed in chloraminated stream water samples. Catchment land uses and soil characteristics of northern Missouri and their impact on watershed hydrology were the most controlling factors of terrestrial DOM transport and transformation in Northern Missouri sub-watersheds. DOM chemical interactions with clay mineral soil surfaces along water flow paths and residence time within catchments were in large responsible for variations of stream water DOM chemical composition. The chemical and structural reactivity of TCMFP, TCAAFP, DCAAFP and NDMAFP precursors in North Missouri stream water DOM were intrinsically coupled together and both seasonally varied in function of mixed effects of anthropogenic land uses and hydrogeochemical sorption processes within catchments that controlled aromaticity and organic nitrogen contents of North Missouri stream water DOM. Organic nitrogen and aromaticity contents of precursor organic moieties in north Missouri stream water DOM controlled DBP formation potentials. Hydrophobic nitrogen-rich aromatic compounds gave the lowest TCM, TCAA, DCAA and NDMA formation potentials, respectively. Hydrophobic carbon-rich aromatic TCMFP precursors were the most reactive with respect to chloroform formation potential. Hydrophilic nitrogenous aliphatic organic micronutrients were more potent TCMFP precursors than hydrophobic and hydrophilic nitrogen containing aromatic organic compounds. Nitrogenous aliphatic micronutrients and nitrogen-rich aliphatic compounds had the largest NDMAFP and DCAAFP yields, respectively. Hydrophilic nitrogenous aromatic organic micronutrients and hydrophilic nitrogen containing aromatic organic compounds facilitated TCAA formation potential compared to more hydrophobic nitrogen containing aromatic compounds. Understanding of how north Missouri catchment anthropogenic land uses affect the mobilization of precursor material can help in establishment of effective monitoring programs. Evaluating DBP chemical and structural transformations during their transport to drinking water sources can help to implement effective watershed management policy to reduce DBPs transfer from watershed to drinking water sources.