WWTP Gets a Grip on Grease and Powers Up Digester Gas

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WWTP Gets a Grip on Grease and Powers Up Digester Gas

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Grease can cause big problems, but when managed properly, it can also provide big dividends as a renewable energy source. The wastewater treatment plant in West Lafayette, Indiana, has grease in abundance and is making the most of it. In 2012, the plant received an average of 18,000 gallons of grease per month. Although grease deliveries are not always daily, the plant can receive multiple deliveries in one day. One small tanker truck can bring in 2,000 to 3,000 gallons while a large truck can bring in between 4,000 and 5,000 gallons.

When the West Lafayette treatment plant implemented a major upgrade in 2009, they installed two microturbines for generating electricity to make use of the methane produced in their anaerobic digesters. At the same time, they also installed a grease receiving station. This station conveys grease to the digesters to supercharge methane production for the microturbines.

According to Jim Bjork, maintenance supervisor for the West Lafayette Wastewater Treatment Utility, “the initial grease receiving station we installed utilized a traditional septage receiving trap that just couldn’t handle the debris.” The incoming grease varied widely in consistency. Thick grease prevented debris from settling in the metal trap. Thin-consistency grease, on the other hand, would allow most of the debris to flow through into the grease tank. Since there was no grinder on the discharge side of this trap, debris entering the grease tank would get pulled into the grease pump, often causing blockage, severe damage and expensive repair to the pump.

To solve this problem, in 2011 the plant installed JWC Environmental’s Heavy Object Trap. The HOT (model GRS) features an adjustable bar screen with 1/2-inch spacings. As grease trucks unload, all debris is captured with the screen. The liquid grease, unhindered by any solid objects, then flows smoothly downstream, without process disruption.

“The JWCE HOT has significantly reduced the amount of debris being discharged into our grease tank,” Bjork says. “The unit’s bar racks stop rags and lighter debris that flow easily, while the unit’s basket catches heavier debris.”

Since it’s easy to clean the HOT, operators open it frequently to check it, and if needed, clean it before a second truck comes in to off-load. They also run hot water through the unit, which rinses out most of the grease from the basket while retaining the solids.

“Our return on investment has been excellent,” Bjork says. “We now have much better grease screening, which means the grease pump sustains much less wear and tear.”

The West Lafayette treatment plant also uses a really big 4-SHRED horizontal industrial grinder from JWC to homogenize food waste that is brought into the facility from Purdue University’s large cafeterias. The food waste is ground up and pumped into the sludge digesters to also help boost biogas production.

Whether a plant is dealing with grease waste or food waste, JWC Environmental has a Monster solution that can make the process easier, cleaner and more efficient. The HOT is available in six sizes and features an adjustable bar screen with 1/2- or 1-inch spacings. This allows site operators the ability change the capture rate of debris. As grease trucks unload, rocks, rags, knives, plastics and other debris are captured. In many installations a Muffin Monster grinder then homogenizes the liquid grease — breaking clumps into an easy to pump slurry.


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