Biological Filtration: The Future Of Drinking Water Treatment?
For years, Canada's aboriginal communities struggled to deal with poor-quality drinking water.
Their cold, brackish groundwater was packed with high levels of calcium, arsenic, and a variety of other contaminants, and was nearly impossible to treat effectively. At one point in 2006, there were 86 First Nations in Canada under boil-water advisories, according to Health Canada.
Many had given up on the idea that these aboriginal communities would ever have truly safe, clean drinking water. As a last resort, a group of scientists decided to try an unconventional method that had struggled to gain acceptance for decades — biological drinking water treatment.
“We looked at a string of conventional treatments, and they didn’t work,” says Hans Peterson, a microbiologist and the Safe Drinking Water Ambassador for the Safe Drinking Water Foundation in Canada. “Biological filtration has not been historically accepted, at least not in North America, but it showed promise and is up and coming.”
Peterson and his group designed a water treatment system that uses naturally occurring bacteria instead of chemicals to remove contaminants from water, and then treats the water a second time by reverse osmosis (RO). Conventional RO systems using chemical disinfectants were attempted in the First Nations previously, but the RO membranes had to be replaced after just one year due to chemical and microbial fouling. The RO membranes in Peterson’s new integrated biological and reverse osmosis membrane (IBROM) treatment system could last up to 20 years.
“For water that is as bad as this was, using RO is absolutely necessary,” says Peterson. “So we designed a system that could optimize that process, and that had to be a biological treatment system.”
Today, 16 full-scale treatment plants in Canadian First Nations utilize Peterson’s IBROM treatment system. Boil advisories have been lifted all over the country. Treating the poor quality water in Canada would have never been possible without the use of bacteria, Peterson says.
“Biological treatment is going to be the future of drinking water treatment,” he says.
Peterson isn’t the only one who believes in the advantages of biological drinking water treatment, which has been growing in acceptance and popularity over the last five to ten years.
“More and more utilities are implementing it, you are seeing it discussed at conferences, regulators are tuned into it and are starting to develop guidelines around it,” says Jess Brown, the chair of the Biological Drinking Water Treatment Committee for the American Water Works Association (AWWA). “People think of biological treatment as a wastewater process. But really it is a very natural and effective process.”
Compared to other drinking water treatment technologies that sequester contaminants and then remove them, biological treatment destroys contaminants entirety and is able to remove multiple contaminants at the same time. This cuts down on sludge production and bacterial regrowth. Biological treatment can be used to remove natural organic matter, color, chloroform, perchlorate, nitrate, nitrite, bromate, iron, manganese, selenate, chromate, arsenate, and a variety of other contaminants. It eliminates the need for chemical oxidation prior to filtration or settling, eliminates the need for chemical reduction methods, and produces innocuous end-products, thus reducing the risk of a contaminated concentrate stream.
“In conventional treatment systems there is a constant battle between disinfection and disinfection byproducts (DBPs),” says Brown. “With biological treatment there are minimal to no chemical additions required, so you remove disinfection byproduct precursors.”
Cutting back on chemicals can save a treatment facility a significant amount of money as well, says Peterson.
“We have a surface water plant that used to use $15,000 worth of chemicals per month. Now, with the biological filtration system they only use $100 worth,” says Peterson. “With a conventional treatment system the footprint is just too high and the water quality is too low.”
Implementing a biological drinking water system is fairly simple; it is a basic “old school filtration system,” says Brown. But the relative rarity of the technology up until now does present some obstacles. A lack of education is the biggest challenge.
“There are no current manuals of practice or guidance manuals,” says Brown. “So when you start out, you can’t go and get a manual and that feels less comfortable. But that will change.”
In Canada, Peterson and his team have worked diligently to get operators up to speed. An apprenticeship program has been created, as well as several training programs and guides.
“You can’t take a cookbook off the shelf and do this,” says Peterson. “We are writing the cookbook as we speak.”
The AWWA is also working to educate the public. In March they hosted the 2013 Biological Treatment Symposium, which focused on the benefits of engineered and passive biological treatment systems from research and utility perspectives. Over 30 different technical sessions were offered.
As with any new technology, startup costs may also hinder some utilities. In large cities with a lot of water infrastructure, a dramatic change like moving to biological treatment would involve pilot testing, which could be expensive. Right now the technology is best for smaller, rural communities struggling with water quality, says Peterson.
Many academics and industry researchers have dedicated their time to making biological treatment more accessible and easier to understand. As manager of Carollo Engineers’ Research Group, Brown leads the firm’s biological drinking water treatment initiative. Other firms have similar initiatives.
“We’ve really been digging into the nuts and bolts of this and we understand it better,” says Brown.
Brown feels that now, more than ever, is the time for biological drinking water treatment to come to the forefront. Costs of handling water treatment residuals are rising, there is a greater push for green technologies, more regulations limiting the formation of DBPs, and new contaminants that are particularly responsive to biological degradation are on the rise— all factors that make biological treatment an effective solution.
“We get calls weekly from people interested in biological drinking water treatment,” says Brown. “There are still a lot of folks that are hesitant, but I think as we grow the number of plants out there that are using it, we will start to see it a lot more. There is a big, big push in the industry to go toward this.”