After our recent stories on sewage sludge, the Orange Water and Sewer Authority sent a letter to local governments about their biosolids program.
HOW MUCH: OWASA treats about 8.5 million gallons of sewage and generates about four dry tons of sludge per day. OWASA’s biosolids are produced according to federal and state requirements that allow their reuse as a fertilizer, according to the letter, which was sent to Carrboro Mayor Mark Chilton, Chapel Hill Mayor Kevin Foy and Valerie Foushee, chairwoman of the Orange County Board of Commissioners.
WHERE IT GOES: OWASA has liquid land application permits for a total of 1,156 acres of farm land in Orange, Chatham and Alamance counties. Nearly 90 percent (1,013 acres) is privately owned. The remaining 143 acres are owned by OWASA as part of a 700-acre tract west of Orange Grove Road in Orange County. The maximum amount of biosolids that can be applied to a given field is determined by the nitrogen content of the biosolids and is limited to the nitrogen requirements of the particular crop to which it is being applied. OWASA closely monitors the application rates on each individual field and, historically, has applied at rates well below those allowed by regulation.
TESTING: OWASA'S biosolids are tested for toxicity and certain other characteristics once a year; but trace metals, solids, and nutrients are measured every 60 days. OWASA monitors three times a year for groundwater contamination and measures multiple constituents in plant tissues once a year at OWASA-owned locations that receive biosolids.
The letter cites a 1996 National Academy of Sciences/National Research Council review of EPA’s biosolids management program that found biosolids presents “negligible risk” when conducted according to federal regulations.
OWASA'S CONCLUSION: “OWASA recognizes that some uncertainty still exists about the effects of certain biosolids constituents. We support further study to determine these impacts. However, OWASA also firmly believes that recycling biosolids through a properly managed program in strict compliance with State and Federal permit requirements is a safe, cost effective, and environmentally responsible way of managing this inevitable by-product of the community.”
