May 9, 2002 -- The City of Keene, N.H., has had some success treating municipal wastewater at its plant using bioaugmentation, a process designed for smaller treatment plants.
Harnessing the natural benefits of bioaugmentation at municipal wastewater treatment plants (WWTP) can provide facility managers an effective way to maintain strict EPA process and effluent standards on a tight operations budget.
Vigilant monitoring keeps processes within a facility functioning efficiently, and even more importantly within EPA guidelines. However, federal EPA standards affect large and small municipal treatment plants differently, and the science of bioaugmentation offers a way for smaller plants to offset some innate disadvantages.
"We serve a small town of about 25,000 people and discharge our clean water into a very small river. Because many WWTPs in larger areas have much larger bodies of water to discharge into, diluting their wastewater effluent is much easier, while smaller plants like ours face some pretty stringent requirements due to lower loading capacity," said Donna Hanscom, the Laboratory and de facto Operations Manager for the City of Keene, NH, WWTP.
Operated by the Keene's Department of Public Works, the plant is a Grade IV secondary treatment facility that handles primarily domestic wastewater from Keene and a couple smaller surrounding communities.
Using an activated sludge process with biological nitrification, the plant is permitted to treat an average daily flow of 6 mgd. The discharge permit, issued by the U.S. Environmental Protection Agency and the State Department of Environmental Services, allows the plant to treat a maximum influent flow up to 15 mgd with secondary treatment prior to discharge.
"Permitting and regulation are the real limits on our facility's operation," Hanscom said. "The end result is given to us via the EPA limits, and we have to determine the means to achieve them. Basically, we have to reverse engineer processes like nitrification to meet the EPA guidelines."
The overall treatment process includes grit removal, primary settling, secondary aeration, flocculation, final settling, and disinfection by ultraviolet light. Solids collected from the primary and secondary systems are thickened and combined in mixing tanks, and after further processing by the belt filter presses, biosolids are trucked to the city landfill while the plant effluent is discharged into the Ashuelot River.
Since the Keene WWTP uses biological treatment, its processes rely on naturally occurring bacteria - which Hanscom and others in the industry often refer to as "bugs." In specific cases where the bugs aren't growing the way they need to, she uses bioaugmentation.
According to Hanscom, the fermentation process that breeds the bacteria is very sensitive to temperature. While the bacteria levels are typically fine when the population remains heavy, such levels aren't always sustainable year-round.
"One of the primary substances we remove from the wastewater is ammonia, which is highly toxic to the fish in the river. There are two very specific types of bacteria that will convert the ammonia to a non-toxic nitrate, and we don't have a difficult time growing those bacteria when the weather's warm," she said.
However, if the naturally occurring bacteria population suffers a setback in the winter when it's cold, repopulating them is a large problem.
"When we need to restart the nitrification process that removes the ammonia during the winter months or whenever other conditions throw it off, that's when we typically purchase nitrifying bacteria. Over the years we've tried a number of different products, and frankly the bugs we use now are expensive, but we've found the cheaper ones to be a waste of money," she said.
Illustrating the value that the environmentally conscious Keene City Council and citizenry place on ecologically sound wastewater treatment, she explains that they have funded treatment technologies that are more expensive than that required by earlier EPA standards.
"We installed a UV disinfection system to replace chlorine wastewater treatment long before it was required by federal regulations. Even though it had higher capital costs it was the better ecological choice," she said.
The bioaugmentation product that Hanscom has come to rely on is BI-Chem® 1010N 20xS, a cold-stored and cold-shipped liquid concentrate of ammonia- and nitrite-oxidizing bacteria produced by Novozymes Biologicals, Inc.
Designed to reduce the time and effort involved in the nitrification start-up process, 1010N 20xS is produced from naturally occurring strains and is not a genetically engineered product.
Novozymes Biologicals is focused on the development of natural microbial solutions for a wide range of industries including waste treatment, sanitation, and industrial cleaning, as well as consumer and agricultural uses of environmental biotechnology.
Managing treatment operations at the Keene plant since it opened 15 years ago, bioaugmentation has actually been part of Hanscom's strategy since the beginning.
"We originally started trying to build up nitrifying bacteria in March, and as you can imagine New Hampshire is rather cold in March. When we realized that we weren't going to be able to build up an effective population because of the temperature we started augmenting," she said.
Keene's original plant permit only required the plant to perform the nitrification reaction in the warm summer months, between May 1st and October 1st. But when their next permit was issued it required year-round nitrification, which eliminated the start/stop nature of the earlier process, but presented the challenge of managing nitrification through the cold winter months.
Hanscom said that with the help of bioaugmentation she's learned that it is possible to defy conventional wisdom using natural microbial agents like 1010N 20xS to perform tasks in the plant that for many years the literature didn't accept as practical or even possible.
"When we were given our first permit to nitrify year round, the conventional wisdom was that there was no way you can do that in New Hampshire in February. We said, 'gee you're probably right,' but we tried and with the right product we were able to make it work," she said.
Hanscom said that it isn't the sort of task that needs to be performed on a daily or weekly basis, explaining that if a plant has to use nitrifying bacterial supplements on too regular a basis they likely have bigger problems. However, as a "cure" for process interruptions and the disturbances caused by seasonal factors, she is convinced that bacterial supplementation is an invaluable tool.
"The nitrifiers are more sensitive than the other bacteria, and we usually use bioaugmentation about once a year, when something unexpected happens and we lose our nitrification process," she said. "We typically add them over the course of about three to four days, at a gallon a day, and that's all it usually takes to get the population right back up where it needs to be."
Another feature she highlighted was the level of customer service demonstrated by distributor Maryland Biochemical and Novozymes Biologicals, who jointly arranged a review of the Keene plant's treatment systems and offered process suggestions.
"They allowed us contact with the Novozymes' biological process experts at the manufacturing level, offering us the kind of help the others just didn't provide. Despite the higher price of 1010N relative to the other products, this made them by far the most attractive option," she said.
During the evaluation, Novozymes' process experts recommended specific chemicals and offered advice to help determine the appropriate level of buffering capacity to mitigate the generation of acidic components during nitrification and maintain the proper (neutral) pH balance.
Whenever she has a problem with nitrification, or any other plant process, Novozymes and the bioaugmentation products she regularly depends on have been helpful.
"Bacteria, like people, don't respond well to inconsistent food sources. I've tried a lot of canned bacteria products, and will recommend Novozymes and 1010N to any plant that needs help starting up or managing their nitrification process," Hanscom said.
For more information about Novozymes Biologicals Inc., visit its web site at www.novozymes.com.
