Roxboro Kiwanians learn about wastewater treatment
At the Dec. 2 meeting of the Roxboro Kiwanis Club, Crystal Shotwell, pretreatment coordinator for the Roxboro wastewater treatment plant¸ spoke about the facility. A Person County native, she is a graduate of Roxboro Christian Academy and received an associate degree from Alamance Community College. She worked in Chapel Hill for seven years before returning to Roxboro for employment by the city.
She informed the club that the wastewater treatment plant has 10 employees and operates on a 24 hour basis. A Grade1 certification from the State is required for all employees, and four of them hold advanced Grade 4 designations.
The facility was built in 1964 and upgraded in the 1980s. It has a 5-million-gallon capacity, but is only treating about 1.8 million gallons a day since a number of large-volume industries are no longer in operation. Septic tank discharge at the plant is allowed only for Person County residents.
From an operational standpoint, Shotwell indicated influent is screened to remove suspended solids and hourly samples are taken. The applicable permit requires that certain pollutants be analyzed, and flow must be measured. These data are reported monthly to the N.C. Division of Water Quality.
The next step in the process is the aeration basin, where micro-organisms break down pollutants. Everything then flows to secondary clarifiers to facilitate settling of solids. There are three clarifiers, each 70 feet in diameter, with skimmer arms. An aerobic digester is used to deal with solids. These are processed by a digester and are dried on-site in lagoons before being hauled away.
A new centrifuge has been acquired which, when in operation, will speed up this process, perhaps allowing haul-off every 6 months. An outside contractor tests for metals and the sludge is then applied as fertilizer. The land to which it is applied must then lie fallow for 18 months before being planted with crops.
Treated water flows to a disinfectant tank which uses sodium hydrochloride. Testing is done for 24 hours for a variety of pollutants. Chlorinated water must be de-chlorinated before flowing into Marlowe Creek, Shotwell said.
A pretreatment program operated by the city helps local industry deal with their permitted waste, with state control and local supervision. Its oil and grease program works with restaurants, nursing homes and other commercial locations which are required to have grease traps which must be cleaned on a regular basis. Educational programs are available for residential uses.
A mercury minimization plan works with businesses, doctors and dentists to be sure mercury does not go into the creek. In response to a question, Shotwell pointed out that stormwater drains, as opposed to wastewater drains, go directly to Marlowe Creek.