Follow these six steps to calculate ventilation requirements in a wastewater treatment plant (WWTP).
Below is a plan for a hypothetical sludge pump station located in Chattanooga, Tennessee. Because of the climate, heating is required but not included in this example. This building stands alone, far from any other buildings on the site and is a single room.
Step 1: Determine the space classification.
Step 2: Perform the ventilation calculation. Determine the volume of the space and calculate the required supply cfm based on the NFPA 820: Standard for Fire Protection in Wastewater Treatment and Collection Facilities chart that provides the lowest electrical hazard classification.
Step 3: Determine the exhaust flow rate. Because this space is remote and there are no adjacent spaces, there are no concerns about differential pressure to adjacent spaces.
Step 4: Select appropriate equipment for the application. In this case, select a makeup air unit and an exhaust fan.
Step 5: Route ductwork and determine appropriate material type.
Step 6: Provide appropriate sensors and alarm devices.
| Table 2: Electrical area classifications | ||||
| AREA | Classification (NFPA 820-2024) | Classification with ventilation (NFPA 820-2024) | Fire protection measures | Notes |
| Blending basin pump station pump room | Class 1 division 2 Table 6.2.2A row 9A | Unclassified Table 6.2.2A row 9B with 6 ACH | H and FE | Wet and corrosive |
| Abbreviations: ACH: Air changes per hour FE: Portable fire extinguisher H: Hydrant protection | ||||
Table 2: Classification of pump station electrical areas. Courtesy: CDM Smith
