Knowing what a trickling filter, lagoon, or RBC is only gets you so far. As a Class C operator, your job is keeping one of these processes running well day after day — through summer heat, spring runoff, and winter ice — and recognizing early when something is starting to go wrong. This guide moves from the basic concepts you learned at the Class D level into the routine process control decisions and troubleshooting judgment that define competent operation of each alternative biological process.
Trickling Filter Operation
Recirculation
Recirculation is the practice of pumping a portion of filter effluent (or clarifier underflow) back to blend with incoming raw wastewater before it is redosed onto the filter. Operators recirculate for several reasons at once:
- It maintains a minimum wetting rate over the media during periods of low influent flow, keeping the biofilm cont