Occurrence, molecular weight and treatability of dissolved organic nitrogen

Research in the drinking water field over the past quarter century has focused on dissolved organic carbon (DOC), overlooking the presence and potential significance of dissolved organic nitrogen (DON). The goal of this dissertation is to develop and apply methodologies for assessing DON occurrence and removal during water treatment. Bulk DON characteristics, DON removal during coagulation, and oxidation reactions with common disinfectants were studied. The present research used both well-developed DON analytical methods from the fields of ecology and an innovative dialysis-based pretreatment method. Samples with dissolved inorganic nitrogen/total dissolved nitrogen ratios exceed 0.6 mgN/mgN require the dialysis pretreatment based on statistical analyses.; The average DON concentration from two seasonal sampling campaigns of 28 water treatment plants (WTPs) was 0.19 mg/L in raw waters and 0.15 mg/L in finished waters. The DOC/DON ratios of raw waters averaged 18 mg DOC/mg DON. DON removal during water treatment closely mirrored that of DOC. The molecular weight (MW) distribution of DON roughly parallels that of DOC. Higher MW fractions (>10,000 Daltons) were preferentially removed across the full-scale WTPs. WTPs using cationic polymers during coagulation removed higher percentages of DON. Bench-scale tests validate these field observations; cationic polymer could increase DON removal by 5 to 20% over alum alone, especially at low alum doses (0--4 mg alum/mg DOC).; Organic chloramines formation in the presence of free chlorine was rapid (<10 min) whereas morochloramine required about 24 hours. The average organic chi oramine yields were 1.1 and 0.3 mg Cl2/mg DON/mg Cl2 consumed upon addition of free chlorine and monochloramine, respectively. Organic chloramine yields increased as DOC/DON ratios decreased. Either higher MW (>10,000 Daltons) or lower MW (<10,000 Daltons) DON formed organic chloramines. Natural organic matter (NOM) isolates with higher nitrogen content exhibited lower chloroform and higher nitrogenous disinfection by-products formation compared against NOM isolates with less nitrogen content. Colloidal and other nitrogen-enriched NOM isolates exhibited higher N-nitrosodimethylamine yields (0.2--7 nmol/mg DOC) as compared against hydrophobic acid isolates (<0.2 nmol/mg DOC) upon monochloramine addition. N-nitrosodimethylamine did not form during chlorination of nitrogen containing NOM isolates.