City of Litchfield, Minnesota
Expansion of the City of Litchfield’s major industry coincided with more stringent effluent limits. A detailed review of the existing trickling filter/activated sludge facility served as a basis for maximizing all unit processes and selecting improvements with the lowest impact to community and industrial user rates. Bolton & Menk prepared a Facility Plan and provided engineering and construction services for the wastewater treatment facility improvements.
The facility’s overall treatment capacity was more than doubled with the addition of intermediate clarifiers, trickling filter upgrades, aeration equipment, replacement of the media filtration and chlorine disinfection system, and expansion of the biosolids process. Biosolids improvements not only provided additional liquid storage, but also modified the current two-digester system to allow parallel or series operation. A floating gas holding cover, mixers, and a heat exchanger on Digester No. 2 provided additional digestion capacity and allowed the city to use the methane gas.