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Background
The scenic Illinois River is currently experiencing high levels of phosphorous that promote excessive algae growth and impair water quality. Headwaters of the Illinois are located in Northwest Arkansas (NWA), and the river meanders into Northeast Oklahoma to form beautiful Lake Tenkiller. Since no single source of the pollution can be identified, the states of Oklahoma and Arkansas have been working together to establish a statement of joint principles and actions to address the problem of high phosphorous loading in the Illinois River Basin.
Problem
Oklahoma desired that the Illinois River Basin phosphorus limit be set at 0.037 mg/L for National Pollutant Discharge Elimination System (NPDES) permits, and the Environmental Protection Agency (EPA) has agreed that this level should be the target for 2012. However, it was argued by both NWA and Northeast Oklahoma officials that current technology was not capable of meeting such stringent levels, and an interim compromise of 1.0 mg/L by 2009 was adopted.
Tremendous growth in NWA and Northeast Oklahoma is driving many municipalities to consider wastewater treatment plant expansions/upgrades in the near future. Although the targeted goal of 0.037 mg/L has not been officially adopted, the possibility of such stringent levels has presented many municipalities with a tough decision. Should these municipalities design for the interim 1.0 mg/L level and risk being out of compliance within a few years, or find a technology that can reach the desired 0.037 mg/L level and ensure compliance now and in the future?
Solution
With a desire to be a proactive leader, Siloam Springs, AR has taken the initiative to find that technology. The recent and anticipated growth of Siloam Springs and the surrounding area is driving the city to upgrade their existing wastewater treatment facility, and they are looking to have a 6 MGD WWTP online by 2009.
Siloam Springs sought out Garver Engineers to help them find a technology that could meet the anticipated 2012 phosphorous level of 0.037 mg/L. It was determined that the most likely candidate for achieving such stringent levels would be a
combination of biological nutrient removal (BNR) and a membrane bioreactor (MBR). In a 2006 pilot study conducted at Siloam Springs WWTP, two industry-leading membrane manufacturers took the challenge of meeting these levels. Two pilot-scale secondary plants, including BNR and MBR, were constructed at the site. After an optimization period, the plants were run side-by-side for a 6-week demonstration period. During this time, operational data was collected via online instrumentation and water quality testing data was conducted by a third-party certified lab.
The data obtained from this pilot study proved that MBR technology in combination with BNR can have a part in helping save the scenic Illinois River, by providing an effluent with extremely low phosphorous levels. This data proves that current technology does exist for achieving phosphorous levels of 0.037 mg/L and lower. In addition, the data shows that this technology can prove cost-effective, while providing an effluent suitable for reuse purposes.
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