Pretreatment, Grease, and Odor Control
What the exam expects
Pretreatment protects the collection system and treatment plant from industrial and commercial discharges. Grease and odor control are the most visible field problems.
Concepts to master
- Pretreatment program elements: local limits, permits, monitoring, enforcement.
- FOG (fats, oils, grease): grease interceptors, hauling, and ordinance requirements.
- Sources of odor: H2S from anaerobic decomposition; also industrial discharges.
- Odor control methods: ventilation, chemical addition (nitrate, peroxide, ferrous salts), biofilters, and covers.
- Corrosion from H2S and the role of sulfate-reducing bacteria.
Traps
A common trap is assuming grease traps are maintenance-free; they require pumping. Another is treating odor at the wrong location - control must address the source, not just the receptor.
Worked example
A restaurant discharges high FOG. The fix is a properly sized and maintained grease interceptor plus an ordinance requiring pumping at a set frequency. Chemical addition downstream treats symptoms, not the source.