An All-Time Low: A New Plant in Arkansas Meets Stringent Phosphorus Removal Requirements

by The Burns & McDonnell Team on August 26, 2011

Northwest Arkansas Wastewater Treatment Plant

 

 

 

When it comes to phosphorus in our streams and lakes, less is almost always better. Phosphorus occurs naturally in ecosystems and is an essential nutrient for plants. Agricultural activities — such as use of fertilizers and animal manure to increase crop yields — and phosphorus discharged from wastewater treatment plants, however, can damage the delicate balance in wetland or aquatic environments. The results of phosphorus pollution can be algal blooms, oxygen deficits or hypoxia, and even declines in desirable aquatic life.

Because of its harmful effects on the environment, the EPA requires some wastewater treatment facilities to limit amounts of phosphorus discharged into streams and lakes based on maintaining water quality at acceptable levels.

Northwest Arkansas has a combination of rapid growth and development resulting from the region’s retail business activities, plus a significant poultry industry and agricultural economy. Municipal wastewater discharges with elevated levels of phosphorus and agricultural activities combined adversely affect water quality in streams and lakes. To share the challenge and burden of meeting new EPA mandates to reduce discharges of phosphorus from its wastewater treatment facilities, several cities in northwest Arkansas came together in 2002 to form the Northwest Arkansas Conservation Authority (NACA). The organization’s mission was to work together to create affordable, sustainable ways to treat and dispose of phosphorus-laden wastewater effluent and residuals.

What began as something small quickly turned into something big, and NACA decided to open a new wastewater treatment facility that could handle the region’s excess wastewater, which smaller plants could not treat efficiently. This facility would be state-of-the-art and sustainable, and it would be able to process 4 million gallons each day. Burns & McDonnell was contracted to evaluate sites and design the new plant, developing a plan to meet the EPA phosphorous requirements of 1 part per million or less in the wastewater effluent.

However, the EPA threw NACA a curveball by lowering the phosphorus limit to 100 parts per billion, 10 times lower than first expected, after the construction bids for the new plant had been received. Burns & McDonnell moved quickly and revised original schematics to meet the new requirements. The result was a plant that opened on time and under budget, but most significantly, the facility meets the new EPA discharge requirements, producing water that has been producing effluent with phosphorus levels of just 60 parts per billion.

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