The City of Napoleon is working toward modifications for our WWTP disinfection facility. The building is currently open on three sides, with a solid roof and contains two (2) ultraviolet (UV) disinfection channels. The UV units receive fully treated secondary effluent from the WWTP processes under normal conditions and will, on occasion (1-2 times per year), receive the overflow from our 2.5 MG flow equalization (EQ) Basin. Overflow from the EQ basin is combined with the WWTP effluent and meets secondary concentration limits for discharge to the receiving stream.
It is our intention to fully enclose the disinfection facility and are seeking clarification on the classification of that space to ensure the electrical enclosures and devices are rated properly. It is our understanding that the NFPA guideline for facilities conveying and disinfecting secondary WWTP effluent in open channels are not classified Class 1, Div. 1 spaces and do not require explosion-proof enclosures and devices compliant with NEC ... Would the same hold true for the blended effluent from the WWTP and EQ Basin?
If the Class 1, Div. 1 designation is applied, do you have suggestions for modifications we could make to reduce the classification?