Algae Joins The Fight For Nutrient Removal
Wastewater treatment plants have found the unlikeliest of allies in their struggle against nitrogen and phosphorous.
While algal toxins have been climbing the list of contamination culprits lately, sparking a health crisis in Toledo and inspiring an EPA health advisory, a new study has found a way to utilize the organisms for the powers of good.
The study, “phycoremediation strategies for rapid tertiary nutrient removal in a waste stream,” concludes that nutrient removal efficiencies of up to 100 percent are achievable with the aid of algae.
It was conducted by a team led by principal investigators Katherine C. Filippino and Margaret R. Mulholland of Old Dominion University.
“While examining how water resource recovery facilities’ (WRRF) discharges and other nitrogen sources fueled algal growth in the environment, we came up with the idea that since algae are so good at scavenging nitrogen in the environment, maybe algae should be brought into the wastewater treatment plant and be used to treat or polish wastewater,” said Filippino.
A New Method
Biological solutions for removing nutrients from wastewater are nothing new, with algae-based methods like integrated pond systems already well-established at municipalities with enough room to house them. Filippino’s team sought to develop a technology that could be implemented at plants with a smaller footprint and continuous flow conditions, which would also allow for easy removal of the algae after treatment and before discharge.
To accomplish this, the research team encapsulated the algae inside of sodium alginate, a gum derived from brown seaweed.
An executive summary of the research from the Water Environment Research Foundation (WERF) concludes that “algal encapsulation would allow WRRFs to maintain the existing footprint, have scale-up potential, improve effluent quality, remove nutrients, have a low hazard exposure, have available parts and equipment and low capital and operating costs.”
With this method, nutrient removal can be achieved in six and a half hours of hydraulic retention time. The high efficiency level is achieved with wavelength-specific submersible LEDs to encourage algae growth, a consistently maintained pH level, and constant mixing.
Employing Algae
With flexibility in the types of algae and encapsulation used, Filippino said any utility could employ the method. As for its touted affordability, she does not yet have an exact estimate.
“Since this technology hasn’t been scaled up to a pilot project yet, that’s a difficult question to answer,” she said, when asked how much implementation would cost. “Ultimately, the initial capital investment could be large, but once maintained, it should be a self-sustaining process with possibilities for reuse and recycle.”
The resulting biomass of algae created in the process can be reclaimed and used as feedstock, biofuel or fertilizer.
While there is cause for optimism around the budding technology, there is still much work to be done before it arrives in the hands of plant operators.
“There are still obstacles to overcome,” said Filippino. “We are seeking funding to test this technology on a larger, pilot scale. But once that work is completed, this technology could be adopted in urban and suburban plants seeking to reduce their nutrient loads with little energy output, low carbon footprint, and high potential for reuse and recycle.”