When retrofitting RBCs with SideCar, it is a good time to evaluate the entire RBC system Experience has shown the following areas should be explored and adjusted in many existing RBC plants:
- PRETREATMENT OF WASTEWATER: Accepted design practice dictates that effective preliminary treatment of wastewater must precede RBC’s: screening/primary settling; properly maintained PATT (Primary Anaerobic Treatment Tank); or fine screening/effective grit removal at very minimum. Stringy material hangs on RBC’s looking badly and posing risk of clogging media and snagging the aeration headers. Grit (and all heavy solids) tends to settle in the RBC tanks reducing detention time, restricting flow through passages in interstage baffles and emitting objectionable byproducts of anaerobiosis.
- Split flows accurately as the lack thereof is a serious problem in many plants. Long rectangular weirs are too sensitive; the slightest difference in H creates significant flow imbalance.
- Adjust staging baffles on RBCs to be sure the first stage is not overloaded (PPDSBOD per 1000sf check with RBC Instructions.) Inadequately sized stages, created by too many and/or improperly located baffles, are responsible for many mechanical failures and process problems.
- Religiously inspect and clean RBC tank bottom solids deposits which reduce HRT and become anaerobic. (Please also refer to the RBC IO&M. This problem is exacerbated by marginal pretreatment.)
- Optimize secondary clarifier sludge removal via frequent or continuous wasting or returns.
Minimize sludge blanket to prevent denitrification and “floaters”.
- Control/Minimize/Equalize in-plant returns, i.e. anaerobic digester supernatant liquor, thickener overflows, BFP presstrate, filter backwash, et cetera. Avoid BOD and Ammonia spikes to RBCs.
- Recirculate RBC effluent to PATT (if applicable) for denite and alkalinity recovery.
- Control the FET (Flow Equalization Tank) more efficiently to handle peak flows; explore recirculation of secondary biological sludge to aerated FET.