Effect of Preformed Chloramines and Chlorine to Ammonia Ratio on the Formation of N-nitrosodimethylamine (NDMA) in TRWD East Texas Raw Water Delivery System
Effect of Preformed Chloramines and Chlorine to Ammonia Ratio on the Formation of N-nitrosodimethylamine (NDMA) in TRWD East Texas Raw Water Delivery System

Author: Khidir Hamad

Publisher:

Published: 2015

Total Pages: 82

ISBN-13:

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Tarrant Regional Water District (TRWD) pumps untreated raw water from Richland Chambers and Cedar Creek reservoirs in East Texas to provide water to several customer cities including Arlington and Fort Worth. TRWD adds chloramines to the pipeline to combat biofilm growth, that reduces pipeline capacity and increases pumping costs, and to control zebra mussels, that clog intake structure screens and the pump wet wells. However, addition of chloramines leads to the formation of Nnitrosodimethylamine (NDMA), a potent carcinogen, by reaction of chloramines with nitrogenous organic precursors possibly present in the raw water. NDMA formation presents a challenge to TRWD because potential regulation of NDMA and other nitrosamines will force TRWD and other utilities alike to seek treatment options. Because post treatment removal of NDMA is ineffective and expensive, the best strategy is to optimize conditions to minimize NDMA formation and to eliminate nitrogenous NDMA precursors in the system. This research examines the effect of preformed chloramines and chlorine to ammonia mass ratio on NDMA formation in the District's current and future pipelines.

Ammonia from Chloramine Decay
Ammonia from Chloramine Decay

Author: Gregory W. Harrington

Publisher: American Water Works Association

Published: 2003

Total Pages: 152

ISBN-13: 9781583212837

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This research report focused on the evaluation of the effects of pH on the inactivation of AOB by chloramines and effects of NOM removal and pH on the rate of ammonia release from the chloramine decay. It was found that water utilities should consider employing pretreatment practices that achieve great stability of chloramine residuals. in order to offset the expenses of periodic strategies to deal with nitrification. Other alternatives to consider for nitrification control are advanced NOM removal strategies or alternative pH values for water entering the distribution system.

NDMA Formation During Drinking Water Treatment: Veterinary Antibiotics as Precursors, the Effect of Natural Organic Matter and the Significance of Treatment Practices
NDMA Formation During Drinking Water Treatment: Veterinary Antibiotics as Precursors, the Effect of Natural Organic Matter and the Significance of Treatment Practices

Author: Shannon Roback

Publisher:

Published: 2015

Total Pages: 157

ISBN-13:

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Nitrosodimethylamine (NDMA) is a nitrosated amine that has been associated with a 10-5 increase in lifetime cancer risk at the ng/L level. NDMA may be formed from a variety of anthropogenic amine precursors during drinking water treatment utilizing chloramines as a disinfectant. In this dissertation, ten veterinary antibiotics were tested for their ability to form NDMA. The antibiotics were tested at different pH, temperature, chlorine to ammonia weight ratio (Cl2/NH3) and time to determine the impact of these factors on formation. Molar conversions ranged from 0.04 to 4.9 percent, with antibiotics containing more than one dimethylamine (DMA) functional group forming significantly more NDMA. The highest formation for most of the compounds was seen near pH 8.4. The effect of Cl2/NH3 ratio, temperature, and hold time was somewhat varied for each chemical, suggesting that the effects of these parameters were compound-specific. This suggests that large-scale farming run-off may be a new source NDMA precursors. NDMA formation is slowed by the presence of natural organic matter (NOM). It is not currently known which components of NOM are responsible for the reduction in NDMA formation. In this dissertation, water containing NOM was fractionated into different MW size groups or separated based on polarity. The high molecular weight NOM fractions (> 10 kDa), polar and charged components were shown to be the most effective in reducing the amount of NDMA formed. Some precursors have high sorption coefficients to NOM, which is the likely mechanism for reduction of NDMA formation from these compounds. Lastly, NDMA formation can be highly impacted by numerous factors relevant to drinking water treatment. In this dissertation, water samples and treatment plant data were collected from approximately 20 drinking water treatment plants in the U.S. and Canada over 2 years. Linear mixed effects models with random intercepts, which account for variability between treatment plants, were used to assess variable significance and create predictive equations. UV254 concentration in the plant influent, sucralose concentration, polyDADMAC concentration, pre-chlorination time, Cl2/NH3 ratio, use of GAC, water pH, and biofiltration were associated with NDMA concentration in the distribution system.

Factors Affecting the Formation of NDMA in Water and Occurrence
Factors Affecting the Formation of NDMA in Water and Occurrence

Author: Richard Louis Valentine

Publisher: Amer Water Works Assn

Published: 2005-01

Total Pages: 252

ISBN-13: 9781583213780

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The USEPA has classified NDMA (N-nitrosodimethylamine) as a probable human carcinogen. It is suspected that chlorination and chloramination may be contributing factors in NDMA formation. This study surveys the levels of NDMA in selected drinking water, recycled water, and wastewater, and describes how various treatment processes impact NDMA formation.

Stability, Formation Potential and Removal of N-nitrosodimethylamine (NDMA) in Drinking Water
Stability, Formation Potential and Removal of N-nitrosodimethylamine (NDMA) in Drinking Water

Author: Xiaoyan Qin

Publisher:

Published: 2005

Total Pages: 65

ISBN-13:

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NDMA stability under various water treatment conditions were tested under both laboratory and field conditions. NDMA concentrations were determined in the laboratory by varying temperature, alkalinity, TOC, pH, free chlorine and monochloramine. The results indicated no NDMA degradation occurred while varying these parameters, except for monochloramine, where NDMA increased when treated with monochloramine. Field work included monitoring four utilities quarterly for a year. Seasonal variation and the stability of NDMA in the distribution systems were studied. Unfortunately, the NDMA formation level was low and no trend could be determined. The use of UV for the destruction of NDMA was evaluated. NDMA degradation by UV was a pseudo-first order reaction. NDMA was reduced from 100 ng/L to 10 ng/L with 1000 mJ/cm 2 UV dosage. The results confirmed that UV is a feasible technique for NDMA removal. pH did not have any significant effects. A total of sixty Missouri lake water samples were treated with 1 mM monochloramine for 2 days and 7 days to evaluate NDMA formation potential. NDMA was formed in almost all lake samples, the differences of the formation level and rate may indicate the existence of different NDMA precursors in these lakes. There was a positive correlation between NDMA formation and DOC concentration.