Wastewater municipality saves $6 million by reducing lagoon biosolids by 68 million gallons in one year
The influent to the wastewater system was primarily municipal, with some commercial and industrial sources (25%) for a total of 2.8 million gallons a day. Each primary lagoon – Ponds 1A and 1B – was estimated to hold 25 million gallons of water.
A sludge judge was performed on the primary lagoons as a baseline. The overall lagoon depth averaged 10 feet with 2 feet of freeboard. It was determined that the sludge blanket was greater than 5 feet in several locations in both primary lagoons, Pond 1A and Pond 1B. The high average sludge-blanket depth significantly reduced the primary lagoon’s overall capacity.
A biostimulant was selected to support the reduction of the organic solids in the system. The liquid biostimulant was added via peristaltic pump to the lagoon inlets. Initially the dose applied was 7 ppm and was eventually decreased 10 months later to 5 ppm. A maintenance dose of 3 ppm was established 2 months later.
Measurements used to calculate sludge removal are shown in Table 1 below. These values correlated to about 9,375,000 gallons of sludge removal or about 2,800 truckloads. An additional 57.4 MG/Year of solids were treated in addition to what was removed resulting in a total sludge removal of 66.8 million gallons of sludge, or 17,800 dry tons. At a cost of $340/dry ton for hauling offsite and disposal, the estimated savings was $6,066,000.
Table 1 – Sludge Removal Calculations
• $6 million cost avoidance in dredging, hauling, disposal costs.
• 45% reduction of sludge depth
• Equivalent of 17,810 dry tons of sludge removed