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This study evaluated theformation of hydrazine during the chloramination of water and wastewater.The study began with the refinement of an existing hydrazine analytical method to allow forlow-level detection in water. The method was modified to allow for the reliablequantification of hydrazine concentration in water down to 5 ng/L. Stability tests were thenconducted and they showed that hydrazine is stable in water up to 48 hours, especially withdecreasing temperature.A detailed hydrazine formation model was developed based on information reported in theliterature. The model accounts for the effect of chloramine concentration, ammoniaconcentration, pH, and contact time on the formation of hydrazine. The model suggestedthat the maximum level of hydrazine formed is independent of the concentration ofchloramine present in the water. Hydrazine formation modeling suggested the following:less than 5 ng/L hydrazine is expected to form in waters containing freeammonia-nitrogen levels below 0.5 mg/L and a pH below 9.0;hydrazine levels in chloraminated wastewaters containing more than 5 mg/L freeammonia-nitrogen are expected to be greater than 40 ng/L at pH levels at orabove 9.0; and,hydrazine formation increases dramatically with increased water pH. Forexample, with 2 mg/L free ammonia, an increase in pH from 9.0 to 9.5 increaseshydrazine formation from 15 ng/L to 80 ng/L.Limited hydrazine formation tests were conducted under varying chloramine and ammoniaconditions. The results showed that no quantifiable hydrazine level was formed under typical drinking water chloramination conditions. However, at elevated ammonia and pHlevels, hydrazine levels formed reached 584 ng/L. The model developed in this study seemsto under-predict the levels of hydrazine formed. However, this could be due to the highsensitivity of hydrazine kinetics to the pH of the water. Includes 22 references, tables, figures.

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Edition: Vol. - No. Published: 06/17/2005 Number of Pages: 18