Can I discharge reject water containing arsenic or uranium from my reverse osmosis (RO) treatment system to my Title 5 septic system?
The answer depends upon the type of RO treatment system, the concentration of arsenic and uranium in the raw water and the use of the property. On-site discharges of RO reject water from Point-of-Use (POU) (i.e. treating only the water that flows to the kitchen sink) drinking water treatment devices at one- to four-unit residential properties may typically be discharged to a Title 5 septic system, but only if the following raw (untreated) water concentrations limits for arsenic and uranium are met: • total arsenic concentration is less than 1 milligram per liter (mg/L) or 1 part per million (ppm) in the raw (untreated) water; and, • uranium concentration is less than 0.300 mg/L or 300 parts per billion (ppb). POU devices that are used at properties composed of greater than four residential units or are used for purposes other than residential use may not discharge to a Title 5 septic system. Point-of-Entry (POE) (i.e. treating all of the water that enters the house) drinking water trea
