Prior to the wastewater being discharged to the Millstone River, the wastewater is disinfected. The purpose of disinfection is the destruction of all living organisms; pathogenic and non-pathogenic. Sodium hypochlorite is utilized for disinfection and is introduced into the process right after filtration. The wastewater flows by gravity to the four Chlorine Contact Tanks where it has a contact time for a period of no less than 30-minutes to ensure proper disinfection with a chlorine residual between 1.5 mg/l and 2 mg/l.
In order to protect the aquatic life in the Millstone River the chlorine residual must be removed prior to discharge to the river. Sodium bisulfite is added in the dechlorination chamber which is located at the end of each chlorine contact tank. The chemical reaction removes the chlorine residual.
In addition to the removal of the chlorine residual, dissolved oxygen in the wastewater must be greater than 6.0 parts per million (ppm) to ensure adequate oxygen supply when discharged to the Millstone River. The reaeration tanks are supplied with mechanical surface aerators to introduce oxygen into the effluent if necessary.
The River Road WWTP is regulated under the New Jersey Department of Environmental Protection’s (NJDEP) Pollution Discharge Elimination System permit and must meet the following discharge limits:
– D.O. must be greater than 6.0 ppm.
– CBOD must be less than 8 mg/l on a monthly average (summer limit).
– TSS must be less than 30 mg/l on a monthly average.
– Fecal Coliform must be less than 200 colonies/100ml of sample.
– pH must be between 6.0 – 9.0.
– Ammonia must be less than 2.0 mg/l (summer limit).