The Massachusetts Alternative Septic System Test Center monitors a variety of new technologies, but also looks at simple sand and sawdust drainfield bed.
Removing nitrogen from wastewater is a complicated challenge anywhere, but in Massachusetts, George Heufelder is working toward a simple solution. It is not big, not chemical, and not expensive. And it involves sawdust.
Heufelder directs the Barnstable County Department of Health and Environment, which covers Cape Cod. The department also operates the Massachusetts Alternative Septic System Test Center to measure the performance of new technologies. But for nitrogen removal Heufelder turned to an older idea, as he explains to Pumper readers.
Pumper: Do you have a problem with anoxic zones?
Heufelder: There are some embayments stressed by an excess of nutrients, and while we have had some marine life killed by a lack of oxygen, we have nothing like the problem in the Gulf of Mexico.
We’ve known about the nitrite problem here since the early 1990s. We have coarse, sandy soils so nitrogen travels freely as nitrite. Through a great deal of work we have the watersheds on Cape Cod very well mapped, and the conclusion is septic systems are the core of the problem. More than 90 percent of the people on the Cape are served by onsite systems, and in some embayments, septic systems have been identified as more than 80 percent of the problem.
Pumper: Have people considered sewers as a solution?
Heufelder: It is generally true that sewer is the cheaper solution for a high-density population near water. But if the lots are larger and the watershed is large, it’s not so inexpensive.
Onsite will continue to have the major role here, either individual systems or package plants serving 50 or 100 homes. I don’t believe we will ever see 50 percent of the area sewered. And that’s a dream. We probably will never exceed 30 percent.
Pumper: How does this sawdust-based technology work?
Heufelder: What we have at the moment is a soil absorption system beneath which we place various configurations of sand mixed with sawdust. Bacteria that convert nitrate to nitrogen gas colonize the sawdust layer and use cellulose in the wood as a carbon source.
Pumper: How did you get the idea for this?
Heufelder: I learned about this work through talking to people at conferences. This is not a new idea. Agriculture researchers have been studying this method in a vertical configuration for some time to address runoff from crop fields. The Florida Department of Health funded a similar project where horizontal layers of sawdust mix were used to achieve denitrification. I also talked to Will Robertson at the University of Waterloo, who did some work on this a few decades ago, using a similar concept. Basically, I tried to simplify their concepts to make them as simple and inexpensive as possible.
We know you get a lot of treatment out of soil, and if we can enhance some of the qualities in the soils, maybe simple systems can do more than we think they can. I was surprised more people weren’t looking at the concept.
Pumper: How did your tests come out?
Heufelder: We put our first test systems in the ground in December 2014, and the results are promising. The first spring the levels dropped below 5 mg/L. We have three systems in the ground at our testing facility, and we’re thinking of installing some in the field. It’s pretty low-risk when you think about it. You’re just adding a carbon source to the soil, and if it doesn’t clog, maybe you have a winner.
What we need are more tests. The biggest unanswered question is how long the carbon source will last.
I’m not an academic, so I approached Jose Amador at the University of Rhode Island and their Laboratory of Soil Ecology and Microbiology, and George Loomis at the New England Onsite Wastewater Training Center, and we’re collaborating on this work. Also, some people from the State University of New York at Stony Brook are looking at all the bacterial species that populate the sawdust bed so we understand that.
Pumper: How simple and inexpensive is the system so far?
Heufelder: One complexity we had to include was low-pressure dosing to spread the effluent evenly across the drainfield. Without that you’re likely to burn a hole in your denitrification layer by overloading one area. Drip dispersal line works equally well.
Another reason for low-pressure distribution came from our work with personal care products and pharmaceuticals that come through in the wastewater stream. A lot of the endocrine-disrupting chemicals and other contaminants of emerging concern are broken down in that shallow soil layer. That is also where you get good reduction and removal of bacteria and viruses.
Someday someone may come up with a simpler gravity-fed system, but intuitively I don’t think that will happen.
Pumper: How did the center begin?
Heufelder: In 1999, there was a proposal to put experimental systems in people’s backyards, and I asked how the companies knew that these would work. And I said if they didn’t then we would have citizens calling in the middle of the night because of failing systems. So we looked for a place to do tests.
At the same time, Joint Base Cape Cod (which holds the operations for eight branches of the Massachusetts National Guard, U.S. Air Force and U.S. Coast Guard) was replacing its old wastewater treatment plant. They were kind enough to give us space at the old plant site where we could install test systems in the ground, and they let us borrow some of the plant influent to feed our test systems. (Water is returned to the plant with a drain system to prevent any discharge.)
As I reviewed performance data from various commercial units, I was concerned about the data I saw. Everything coming out then had been tested in the South, and we wanted to make sure a New England winter would not slow these systems down.
(The U.S. Environmental Protection Agency) and the state provided money to start the center, but it is now self-funding from the test fees charged to manufacturers. We have tested the systems of just about every major manufacturer, including some from outside the United States, and we have become one of the larger third-party testing beds. We supervise tests as much or as little as a company wants — from samples every hour and sending data daily, to looking at it and telling people if we think something is wrong. We perform NSF tests on request, but we don’t give a seal of approval like NSF. We do write reports at a manufacturer’s request to summarize our data.
Our results — those that companies are willing to make public — are posted online, and people can also look at the performance of various types of innovative and alternative systems installed on Cape Cod.