Wastewater & Stormwater
Wastewater & Stormwater
This domain tests wastewater collection and treatment, effluent permit compliance, biosolids and stormwater controls. In Oklahoma, DEQ issues wastewater and stormwater permits; municipalities and utilities must operate certified systems with qualified operators. Know the treatment train: preliminary screening and grit, primary settling, secondary biological treatment, disinfection, and solids handling. Stormwater is separate: construction, industrial, and municipal separate storm sewer system (MS4) permits control discharges, and sanitary sewage must not enter storm drains.
Core rules and concepts
- Permit limits commonly include flow, CBOD, TSS, ammonia, E. coli, pH, and minimum dissolved oxygen. Monitor at permitted points and report exceedances.
- BOD load (lb/day) = concentration (mg/L) × flow (MGD) × 8.34. Organic load drives aeration and sludge production.
- Clarifier surface overflow rate = flow ÷ surface area; use consistent units. Short-circuiting and solids overload reduce performance.
- Sanitary sewer overflows and bypasses require prompt notification and corrective action under permit and state rules.
- Construction stormwater coverage typically begins with a Notice of Intent and a stormwater pollution prevention plan before disturbance.
Worked example
A plant receives 0.5 MGD with influent BOD of 220 mg/L. Load = 220 × 0.5 × 8.34 = 917 lb/day. If the permitted influent design load is 800 lb/day, the plant is 117 lb/day over design, so check aeration capacity, sludge wasting, and equalization. Do not convert 0.5 MGD to gallons per day before using the 8.34 factor; the factor already pairs mg/L with MGD.
Traps
Using 8.34 with liters or cubic meters; reporting only concentration while ignoring flow; confusing surface overflow rate with hydraulic retention time; and assuming a stormwater NOI is the same as the permit coverage itself.