A wastewater treatment system gets a clean wrap from the Board of Health, and precast concrete was the solution.
By Greg Snapper
More than 30 percent of Massachusetts homes are equipped with on-site wastewater treatment systems. Considering the state’s 6.5-million population, that’s a lot of septic systems – and every one of them must follow the Massachusetts Title V State Environmental Code, a collection of clean-water regulations designed to protect state residents.
This spring, a Harvard, Mass., homeowner faced Title V head on. As part of a planned property transfer, an inspection revealed that the home’s aging wastewater treatment system needed to be replaced. And under Title V, the Board of Health must approve a fully operational on-site wastewater treatment system before a home may be sold.
Fortunately the homeowner had several options – some more expensive and less appealing than others – but chose a self-sufficient precast concrete wastewater treatment plant as a replacement and got some financial breathing room as well.
Pio Lombardo, P.E., president of environmental engineer company Lombardo Associates Inc., Newton, Mass., said an original proposal for a mounded treatment system was aesthetically unappealing and too costly. But Lombardo offered a custom design to get the homeowner back on the selling track. “The client was pleased with what we proposed – a mini high-quality wastewater treatment plant.”
Lombardo’s treatment systems have grown in popularity since the first one was installed in 1995. They provide an independent alternative to the underdeveloped sewer systems in many New England cities like Harvard. For this particular project, the entire system was assembled at E.F. Shea, New England Concrete Products Inc., Wilmington, Mass. Shea cast a 1,500-gallon monolithic septic tank to house an aerobic trickle filter manufactured by a Clearwater Waterloo biofilter distributor in Ipswich, Mass. Shea also cast a 2,000-gallon monolithic pump chamber for emergency storage to comply with Massachusetts’ requirements for at least one day’s overflow storage in the event of a failure.
Shea’s tanks are monolithically poured structures. Clearwater’s 26,000-pound biofilter is installed inside the largest tank, with the biofilter’s presence indicated by green covers. Additionally, two dosing chambers were cast – a 2,000-gallon and a 1,000-gallon – along with a 1,500-gallon septic tank. A 1,500-gallon two-compartment tank and a second 1,000-gallon compartment tank house nitrogen removal media that converts the nitrate present in the wastewater to nitrogen gas, which escapes into the atmosphere. Working together, all precast components comprise the residence’s mini wastewater treatment system.
“The Waterloo biofilter was the biggest element, so they actually built the filter within the monolithic structure,” said Joe Garrigan with J&P Construction, Littleton, Mass. Clearwater assembled the biofilter inside the 2,000-gallon monolithic septic tank. Its foam media components, pumps and trickling filter were also installed at the plant, which allowed for a smoother transition at the installation site.
“What is great is that Shea allows us to go over to their yard, preassemble our biofilter units and create the entire system in the plant,” said Mark Cottrell, Clearwater engineer. “This limits the amount of assembly on site.”
Fewer man-hours translates into fewer dollars spent for the client. Lombardo said the Harvard system, which handles up to 660 gallons per day and serves two houses, cost approximately $60,000 in comparison to the client-rejected mounded system proposal, which would have cost $90,000. Lombardo said this particular project had several logistics to overcome. Several permits were required, and approval of the system from the Board of Health was mandatory. Future projects will typically run $45,000 for clients, Lombardo says, but each project is specific to several factors: septic needs, state and city clean-water regulations and permit requirements.
“We’ve installed about a dozen so far, with more requests in Massachusetts, Maryland, California and Florida,” Lombardo said. Lombardo’s sales typically pop up in the northeastern United States due in part to geological conditions and the lack of developed sewer systems.
At the Harvard site, the soil type varies dramatically due to the ecological wash from the glacial periods, and there’s no sewer line access for the residence, Garrigan said. “The land changes quickly from bedrock in one area to glacial till, then sand – it varies so much,” he said. “It’s an interesting area when you’re going to dig, because you never know what to expect.”
The ground composition at the Harvard site caused an installation issue, as this Massachusetts region is clay-rich and slow to drain. “This is the reason Lombardo’s system was effective,” Garrigan said.
The business of doing business
Afterthoughts on where “it” goes after being flushed are generally fleeting, but there’s much more to the business of doing one’s business – especially when considering this system.
Cottrell described the step-by-step process where precast and purification work together from flush to finish.
Following the flush, the wastewater flows into a precast monolithically poured 2,000-gallon septic tank equipped with an effluent filter, which keeps the solids from exiting the tank. Next, the high head pump time-doses the biofilter about every 12 minutes for 30 seconds if suitable water levels are present. The mechanism transfers small doses of effluent to the biofilter, where the water treatment occurs in a sponge-like effect. While circulating through the biofilter, effluent is sprayed with water onto the foam cube media. This water/effluent mixture saturates porous 2-inch foam cubes, where microorganisms and bacteria grow and metabolize the organics and certain forms of nitrogen from the wastewater as a food source before discharge of the liquid portion to a soil absorption system.
“In this specific system, the filter is used to reduce biological oxygen demand, total suspended solids and convert ammonia to nitrates,” Cottrell said. “To remove nitrogen completely is a two-part process. We take it through the first and then (Lombardo) takes care of second step.”
Lombardo Associates Inc. provides a component in the treatment process called Nitrex, a carbon-rich, low-oxygen environment that will denitrify the nitrates. Additionally, Lombardo has gone one technological step further in the treatment process by using UV lights in the treatment process. Wastewater passes over UV light tubes and threatening viruses and bacteria are destroyed. The bulb is replaced yearly by a Clearwater service provider. After wastewater passes through the entire disinfection unit, it leaves the mini wastewater treatment system via drip irrigation, which replaces the standard pipe and stone leach field. These small irrigation lines operate 8 inches below the surface and release small doses of the nearly potable water into the ground. The treatment is then complete.
No one may be thirsty enough for that particular water, but it is a testament to how precast concrete and biological filtration work hand in hand, providing alternative solutions to real-world challenges. This alternative system helped release the homeowner from the long arm of Title V and the new treatment system received approval from the Board of Health in July.