By Peter Chawaga
In an increasingly green-conscious world, there are growing concerns around the use of harsh chemicals to treat drinking water. Many do not like the idea of ingesting something that was once dosed with unnatural compounds or the waste and byproducts that are produced as a result.
Biological treatment of drinking water, defined by the use of bacteria to remove contaminants, has emerged as an increasingly popular alternative to traditional use of chemicals. In a recent testament to the future of biological treatment, Nicholas Dugan of the U.S. EPA’s Office of Research and Development presented a webinar called “Capabilities of Biological Treatment for Drinking Water.”
Dugan began his research on biological treatment as a graduate student, investigating the removal of disinfection byproduct (DBP) precursors with biologically-active filters. His work in the field demonstrated the potential for effective treatment combined with minimal DBPs.
“Biological treatment can be a good solution for the treatment industry because it has the potential to remove problematic water quality constituents while minimizing the production of treatment residuals,” Dugan said.
In particular, Dugan presented on biological treatment as a better answer for ammonia, nitrate, nitrite, and perchlorate removal, substances that are all of regulatory interest. While nitrate, nitrite, and perchlorate are traditionally removed through ion exchange, the necessary resins for that process are either single use or require regeneration that produced a waste brine stream. While ammonia is generally treated through biological nitrification in suspended growth processes, Dugan presented case studies in which bacteria attached to sand and gravel filter media did the trick.
“We shared three case studies,” Dugan said of his webinar. “A bench-scale anaerobic/aerobic treatment study that demonstrated removal of nitrate, perchlorate, and bromate in the anaerobic and ammonia for the aerobic; a pilot-scale anaerobic treatment study that demonstrated the removals of nitrate and perchlorate; and a pilot-scale treatment study that demonstrated the removal of ammonia.”
While bench- and pilot-scale studies performed in EPA and academic laboratories as well as field tests have all demonstrated the potential, many treatment plants have yet to embrace biological treatment for drinking water.
“Much of the hesitation to implement these types of processes may stem from concerns about reliability and maintenance or operation issues,” Dugan said. “The continuing education of state primacy and water treatment personnel, combined with successful demonstrations of biological processes at the pilot- and full-scale will, over time, promote the adoption of biological treatment.”
If and when plants do come around, they might face a series of obstacles before they can fully implement biological treatment. Dugan highlighted several operation and maintenance issues to be wary of.
Firstly, there might be need for backup treatment as problems with the microorganisms meant to degrade contaminants are possible. Downstream particulate removal processes might have to be implemented to combat increased turbidity. The effluent from anaerobic processes may need to be aerated to restore dissolved oxygen levels and the processes may require an additional electron donor to support microbial metabolic activity. Both anaerobic and aerobic biological processes might need additional nutrients, like phosphorus, to support a high level of biological activity.
Despite these extra requirements, researchers like Dugan are convinced that biological treatment offers a path to a more sustainable future for water treatment. As the benefits are demonstrated more widely, plants all over the country should start seeing the way.