Vorelodos Aerobic Digester, reduces nutrient return and improves energy efficiency

City of Green Lake Wastewater Treatment Plant

Green Lake, WI


Faced with rising operating costs due to increasing energy and chemical prices as well as stricter effluent permit limits, many operators and engineers are turning to sensors and automation as a means to enhance treatment performance and reduce operating costs while limited capital expenses.


An advanced process control solution was implemented in an aerobic digester in Green Lake, Wisconsin. By controlling the process in a smarter way, the solution significantly reduced phosphorus and nitrogen in the returns to the main treatment process and reduced energy consumption

The Vorelodos digester system has four zones operating in series, two in the east digester and two in the west digester. Waste activated sludge is automatically pumped from the ICEAS system into the east digester approximately every two hours. The supernatant from the digester is returned to the SBR through the telescoping valve and is manually initiated four days per week. A sludge pump is used to remove sludge from the west digester once per week.

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