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Case Study

Bakery – Waste Pretreatment Plant

Grease Digestion and Degradation of Carbonaceous Biological Oxygen Demand

Problem

A major full-service bakery in Northern Ohio has a pretreatment plant for bakery waste before discharging wastewater to the local village treatment plant. The average daily wastewater influent to the pretreatment plant has a concentration of 6,000 to over 100,000 mg/l Carbonaceous Biological Oxygen Demand; average suspended solids of 6,000 mg/l and oil and grease concentrations of 800 to 1,000 mg/l.

The average daily flow through this plant is 15,000 to 25,000 gallons. This waste is treated aerobically in an activated sludge system consisting of two 50,000 gallons aerated tanks in series. The waste is then pumped from the second aeration tank onto a gravity belt with polymer being injected into the waste stream.

The objective of adding an Organic Product to this system was to try to increase the biological activity and further reduce the oil and grease.

Solution

An Organic Product was added to the system with an initial charge of 2 gallons, and then 1 quart per day added for a 10-day period. The maintenance dose was then reduced to 1 pint per day.

Conclusion

The second aeration tank took on a darker brown color, and there is no longer a grease buildup on the paddles of the gravity thickener belt. The dosage of polymer was been reduced by approximately 70%.

The average effluent discharge to the local village POTW (publicly owned treatment works) has a CBOD average of less than 200 mg/l, TSS of 200-400 mg/l and an average oil and grease of 15 mg/l or less.