The secondary effluent is combined into a single channel containing an ultraviolet disinfection system. The UV system consists of two banks of horizontal lamps, each having 176 lamps, four control panels and an effluent flow control gate. In the automatic mode, each bank alternates operating time every 100 hours. both banks will function together when the plant flow exceeds a certain level. Post aeration of the effluent is provided at a cascade aeration structure where the floe cascades down a series of concrete steps prior to entering the Ohio River.
Permit limits and actual average results for the Moundsville facility after 11 years of operation are shown below.
| Parameter | Permit | Actual |
| Flow | 2.34 mgd | 1.61 mgd |
| CBOD | 25 mg/l | 5 mg/l |
| TSS | 30 mg/l | 4 mg/l |
| Ammonia | 15 mg/l | 2.6 mg/l |
| Fecal Coliform | 200 | 28 |