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Phosphorus Compliance Best Solutions: The engineers role in developing recommendations

As improving water quality remains a priority in Wisconsin, many wastewater treatment facilities (WWTF) are seeking new and innovative ways to achieve ultra-low effluent phosphorus levels. On Thursday, May 30, 2019, Waupun Utilities hosted an open house at its WWTF to showcase a pilot-scale Advanced Biological Nutrient Recovery (ABNR) system by CLEARAS Water Recovery. The algae-based system is capable of recovering phosphorus and nitrogen into harvested algal biomass, with anticipated annual biomass revenues of $500,000.  

Applied Technologies, Inc. (ATI) conducted the required evaluation to recommend ABNR as the preferred compliance alternative. ATI worked closely with Waupun Utilities to review data, conduct research, develop cost estimates, complete evaluations, and secure funding to support the installation of the ABNR system.

About Advanced Biological Nutrient Recovery

ABNR is a biological wastewater treatment solution that uses algae to consume overabundant nutrients and achieve ultra-low nutrient levels. The nutrients targeted for recovery are primarily phosphorus (P) and nitrogen (N), as they are detrimental to watersheds. The ABNR system utilizes four phases: 1) Mix, 2) Recover, 3) Separate, and 4) Harvest.

1) Mix

A blend of algae and other microorganisms are combined with carbon dioxide and the nutrient-rich (N and P) wastewater, forming the Mixture Flow.

2) Recover

The Mixture Flow enters the photobioreactor (PBR) and the algae go to work. A series of glass tubes nurture photosynthetic algal growth by providing natural sunlight and an LED light source. The algae rapidly consume phosphorus, nitrogen, and carbon dioxide resulting in clean, oxygenated water.

3) Separate

An ultrafiltration system separates algae from the clean water. The clean water can then be discharged or reused. A portion of the algae is returned to the Mix phase, while the remainder moves to the Harvest phase.

3) Harvest

The algal biomass is dewatered and dried to be utilized in a wide variety of markets. In fact, a developing market opportunity is the use of dried algal biomass to produce biofoams for shoe insoles. 

Determining the Best Solution to Phosphorus Compliance

Wastewater treatment facilities (WWTFs) across the State of Wisconsin are evaluating and upgrading their facilities to comply with the WDNR’s water quality-based effluent limits (WQBELs). WQBELs are intended to protect public health and improve watersheds across the State. A broad spectrum of technologies and strategies must be examined to determine the most cost-effective approach for each individual WWTF.

Waupun Utilities was proactive in investigating its compliance options. In order to comply with monthly average limits, the Utility needed to reduce its previous phosphorus discharge concentration level by roughly 95%.

ATI worked with Waupun Utilities to identify and evaluate potential treatment alternatives for technical and financial feasibility. Based on its high levels of soluble non-reactive phosphorus (SNRP) and ultra-low effluent limits, operational improvements like chemical phosphorus removal were determined to be insufficient. ABNR emerged as the preferred option based on its life cycle costs and favorable qualitative factors. The ABNR system also featured guaranteed SNRP removal, chloride reduction, and the potential for considerable biomass revenue.

After Waupun Utilities decided to proceed with the recommendation, the ATI team sought funding through a USDA Rural Development Grant to assist with project costs. The grant application, which was approved in September 2018, secured a $10 million grant for construction of the full-scale ABNR facility.

The pilot-scale ABNR system began in April 2019. The system treats roughly 10,000 gallons/day, with a total processing time of approximately 85 minutes. For the first three weeks, the average phosphorus loading rate was around 80 lb/MG-d, which was slightly less than the anticipated design loading rate. The average phosphorus effluent concentration was less than the anticipated limit of 0.05 mg/L.

The goals of the continuous pilot are to: 1) Demonstrate that the system can meet the effluent nutrient limits, and 2) Confirm the design rates used for full-scale operation. If the pilot meets these goals, Waupun Utilities plans to install a full-scale system with start-up in 2023. The full-scale ABNR system is expected to produce 4,500 lbs of algae per day, which will then be dewatered and dried and marketed to several different industries. With anticipated annual biomass revenues of $500,000, the ABNR system is a resource recovery process that is poised for success.

About Applied Technologies, Inc.

Applied Technologies, Inc. is a multi-discipline consulting firm specializing in water and wastewater management, renewable energy, architectural design, and civil and structural engineering. With offices in Wisconsin and Illinois, ATI serves municipal and industrial clients locally and internationally. 

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