Structure and treatability of organic nitrogen-enriched drinking water.

摘要

Wastewater discharge, agricultural runoff, and algal blooms have led to increased nitrogen-enrichment of drinking water sources. Nitrogen-enrichment will change the structure of dissolved organic matter (DOM), where dissolved organic carbon (DOC) concentration is roughly ten-times that of dissolved organic nitrogen (DON). Drinking water regulation of carbonaceous haloforms, created during disinfection, has focused the industry on DOC removal. Consequently, DON occurrence and treatment has been overlooked. The goal of this research was to develop capabilities to determine the structure and reactivity of major DON pools present in impacted drinking water supplies affected by wastewater discharges and algal activity. This goal was achieved by performing seven research objectives elucidating DON occurrence, composition, and its propensity to form nitrogenous disinfection by-products (N-DBPs) in impacted drinking waters.;A nationwide survey of 16 impacted drinking waters, revealed an average raw water DON concentration of 290 micrograms nitrogen per liter and 206 micrograms nitrogen per liter in the treated water. Total amino acids (TAAs) accounted for, on average, 15 percent of the raw water DON and 4.1 percent in the treated waters, statistically indicating treatment preferentially removed TAAs over DON. Flocculation and sedimentation physically removed the largest mass of TAAs while oxidants decreased TAA concentration through chemical transformation. This study revealed that impacted source and treated waters are more nitrogen-enriched than average.;Organic nitrogen-enriched DOM was isolated from seven nitrogen-enriched waters (two wastewaters, two surface waters, and two laboratory generated). The isolation method enriched biogenic colloids, hydrophobic neutrals, amphiphilics, and hydrophilic bases with organic nitrogen. Biogenic colloids were composed of cellular debris and accounted for 20 to 60 percent (mass basis) of the DOM. The nitrogen-enriched DOM isolates formed more N-DBPs than nitrogen-depleted DOM. Wastewater DOM produced greater yields of cyanogen chloride than surface water DOM and about half of the incorporated nitrogen originated from the applied inorganic chloramine oxidant. Highly nitrogen-enriched hydrophilic bases had the highest yield of Nnitrosodimethylamine. Organic colloids and one hydrophilic base produced chloroacetonitrile which was unique to these isolates. While N-DBPs are currently unregulated, this dissertation builds a foundation of knowledge of existing treatment efficiency and DBP management.