Known only as “opposite Little Rock” until the Civil War, North Little Rock grew as a crossroads that linked river and overland traffic. Today it is a thriving community of more than 60,000 residents. In 1988, North Little Rock constructed its own hydroelectric plant on the Arkansas River. Its two generators are capable of producing 42 MW at peak conditions, enabling the city to furnish approximately 20% of its own fixed-cost electricity. This puts North Little Rock in the enviable position of offering its residents reasonably priced power. It also creates another opportunity for the North Little Rock Electric Department to exhibit its strong environmental stewardship practices.
North Little Rock Electric Department has been using an Abanaki Oil Grabber (Figure 9) for over 10 years. The system has proven to be a dependable and effective means of removing oil from the plant water before it is discharged back into the Arkansas River. Before Abanaki, a floating skimmer was used at the plant, although it required significant maintenance. Now plant workers appreciate the design of the Oil Grabber Model 8 for its high reliability and its light maintenance schedule.
|9. Keep it clean. An oil skimmer separates oil from water before discharging water back to the Arkansas River, keeping the North Little Rock Electric Department in compliance with its environmental water discharge permit. Courtesy: Abanaki Oil Skimmers
Another advantage of the Model 8 is its easy mounting in a small footprint, making it ideal for cramped quarters. The Oil Grabber Model 8 is situated in a retention sump that catches oil leaks at a rate up to 40 gallons per hour from any hydraulics, always a distinct risk in a hydroelectric facility.
The operation of the Model 8 is very simple. Oil skimmers make use of the inherent surface tension and specific gravity differences between oil and water. These physical characteristics allow the skimming media to attract oil from the water’s surface. A belt, operating on a motor and pulley system, runs through the water. After traveling over the head pulley, the belt passes through tandem wiper blades, where oil is scraped off both sides of the belt and collected in a container.
After the skimming stage, the water is pumped into holding tanks and processed through a dedicated oil/water separator before the water can be released back into the river. The staff noted that this final filtering stage has not been used much since the Model 8 was installed. Since the Oil Grabber was installed, the skimmer removes the majority of the oil from the sump before it is processed further. This means that the separator doesn’t have to run as long and doesn’t need to be cleaned as often.
—Contributed by Abanaki Oil Skimmers.