From The Editor | February 16, 2017

Putting Algae To Work For Sludge Processing

Peter Chawaga - editor

By Peter Chawaga, Associate Editor, Water Online

Putting Algae To Work For Sludge Processing

When the general population thinks about biosolids and sludge, if they do at all, they probably don’t have the full picture in mind. As an aspect of wastewater treatment that the public prefers not to think about, sludge requires a huge amount of effort on the part of treatment plants to process. While that procedure has always been labor-intensive, an innovative use of algae may change things.

Ovivo, a water and wastewater treatment technology provider, teamed up with researchers from the University of Akron to develop its BioAlgaNyx technology, a bioengineered algae for wastewater sludge management.

“Ovivo funded fundamental research in order to establish BioAlgaNyx technology’s capabilities for enhancing aerobic and anaerobic sludge stabilization and digestion and its ability to capture organic carbon from high-strength wastewater,” said a company spokesperson. “In addition, Ovivo has been running field pilots to confirm the technology’s scalability and its effectiveness under actual site conditions.”

Ovivo saw an opportunity to improve the laborious process of sludge handling that has long plagued wastewater treatment operations. BioAlgaNyx utilizes phagotrophic algae, which feed by ingesting particles, as opposed to the phototrophic algae, which feed using photosynthesis, that are typically leveraged for treatment solutions. The technology creates an environment low in dissolved oxygen which encourages the algae to ingest bacteria and dissolved organics. They store the organic carbon as lipids and, without cell walls, can digest it quickly.

“Assuming that a 1 MGD plant generates approximately one ton of waste sludge, the biosolids management poses a significant challenge in terms of resource recovery, treatment, and disposal for these facilities,” the spokesperson said. “BioAlgaNyx provides treatment plant operators a simple option for sludge pretreatment which leads to enhanced digestion rates.”

Ovivo has said that the technology leads to a 20 to 30 percent increase in volatile solids destruction while providing a 50 to 75 percent reduction in sludge holding tank volumes. This can help plants achieve Class B biosolids designation, a U.S. EPA label for treated sewage sludge appropriate for use as fertilizer.

There are other benefits as well, including the lower capital and O&M costs thanks to a smaller digester footprint. Sludge hauling costs should also be reduced with enhanced digestion. Furthermore, plants that adopt BioAlgaNyx have more potential for resource recovery.

“Plants with aerobic or anaerobic digesters can expand their capacity using the existing tankage and plants with co-digestion can now have the option of capturing organic carbon from the sludge and food-grade waste,” said the spokesperson. “The organic carbon can then be converted to phagotrophic algae with high lipid content, which can be extracted and used for biofuel production.”

While many operations turn to thermal hydrolysis to make sludge more digestible, Ovivo claims that this technology is a simpler method for enhancing digester performance. It has run BioAlgaNyx through multiple pilot studies and is confident in its enhancement capabilities for aerobic digestion. In some initial anaerobic digestion runs, the company has seen clear improvement and plans additional testing this summer.

Image credit: "Algae," Quimby--no, not really, but I wish © 2006, used under an Attribution 2.0 Generic license: https://creativecommons.org/licenses/by/2.0/