Hubbell, Roth & Clark, Inc. (HRC) completed a study for the Village of Caro wastewater treatment system recommending improvements to the existing wastewater treatment facilities. The existing treatment facility was designed for a capacity of 1.2 MGD. Due to changes in permit conditions, i.e., more stringent nutrient limits, HRC's study concluded the capacity with the existing rotating biological contactors (RBCs) is approximately 1.0 MGD. With residential and commercial development occurring at a more reduced rate than the original plant had been designed, the 1.0 MGD capacity should be adequate for the Village for the next 20 years. However, to maintain treatment levels in compliance with the permit, renovation of the facility is necessary.

To maintain the collection system infrastructure improvements were recommended for the system's 11 existing pumping stations. These pumping station improvements included providing better access for personnel, spare pumps, variable frequency drives, new flow meters, improved controls, and provisions for standby generators.

HRC conducted an extensive review of the solids handling system at the Caro WWTP. HRC evaluated retention time, solids loading rates, volatile suspended solids destruction rates, and digester gas production. The result of this study indicated that the digester system was adequate for the solids loading but improved mixing was necessary for more efficient operation. A new pumped sludge mixing system is proposed. Also, structural improvements are recommended to extend the useful life of the digesters. This study also recommended that extra heat generated from the sludge heating operation be used to heat buildings near the digester system.

Improvements are planned to many other plant facilities including the preliminary system, with the replacement of the existing influent screening system and grit removal systems.