Increased loading of ammonium to the SFE is largely the product of the Clean Water Act requiring the conversion of WTP’s to secondary treatment resulting in discharge of N as ammonium. With the exception of Stockton, major cities in the Northern SFE and Delta do not carry out advanced secondary treatment and discharge N primarily in the form of ammonium rather than naitrate. As of 2006, 75% of the effluent released by Delta treatment plants was processed only to the secondary level (Brooks et al., 2011). Approximately 90% of the total N in Northern SFE originates from a single point source, at the Sacramento Regional WTP (SRWTP), which discharges approximately metric tons of N per day, largely as ammonium, to the Sacramento River
Jassby, 2008
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