In Virginia, Loudoun Water (formerly the Loudoun County Sanitation Authority) approves all specifications and plans for community-based systems in new developments. The developers then deed the systems to Loudoun Water to own and operate. The agency relies heavily on natural wastewater treatment, such as septic tanks, drip irrigation, and recirculating sand filters, which are shown here. Photos: Loudoun Water
In Virginia, Loudoun Water (formerly the Loudoun County Sanitation Authority) approves all specifications and plans for community-based systems in new developments. The developers then deed the systems to Loudoun Water to own and operate. The agency relies heavily on natural wastewater treatment, such as septic tanks, drip irrigation, and recirculating sand filters, which are shown here. Photos: Loudoun Water
The wastewater treatment building at a subdivision in Aldie, Va., is served by a community wastewater system that disperses effluent in a low-pressure distribution system. About half of the effluent is lost to evapo-transpiration from both the grass and the soil. The other half recharges the groundwater approximately half a mile from the closest well. The wastewater treatment system consists of dual-train extended aeration package plants within a building, followed by a deep bed denitrification filter and a low-pressure distribution in aerobic drainfields.
The wastewater treatment building at a subdivision in Aldie, Va., is served by a community wastewater system that disperses effluent in a low-pressure distribution system. About half of the effluent is lost to evapo-transpiration from both the grass and the soil. The other half recharges the groundwater approximately half a mile from the closest well. The wastewater treatment system consists of dual-train extended aeration package plants within a building, followed by a deep bed denitrification filter and a low-pressure distribution in aerobic drainfields.

When the subsurface sewage treatment systems at three condominium developments in Brookfield, Conn., repeatedly failed in the mid-1990s, the physical mess created a financial nightmare for both the condominium associations and the town itself.

Because the associations couldn't pay for the repairs that would eliminate illegal discharges, the Connecticut Department of Environmental Protection ordered the town to do it, a massive undertaking that involves:

A 32-unit development generating 5,400 gallons/day. Estimated repair cost: $625,000

  • A 41-unit development generating 7,300 gallons/day from two onsite treatment systems. Estimated repair cost: $300,000
  • A 162-unit development generating 20,000 gallons/day. The development's monitoring reports showed nine failures between 1993 and 1996. The Department of Environmental Protection determined that the onsite system wasn't developed properly. Estimated repair cost: $1.2 million.

So began a protracted court battle between Brookfield and the state. The town has lost several appeals and faces up to $100,000 in fines if residents don't approve a $1.9 million referendum this month to connect the condominium complexes to the main gravity sewer system with a new sewer line.

It's a hard lesson learned from an era of unprecedented growth in the housing market, when subdivisions were built faster than the infrastructure necessary to serve them. With traditional wastewater treatment plants facing restrictions on their total maximum daily loads (TMDLs), decentralized systems were an attractive way to accommodate growth.

Subdivisions were built with “neighborhood-scale systems” that typically serve up to several dozen homes. Some estimates place the number of new homes in fast-growing urban areas served by decentralized systems at more than one-third.

Decentralized systems are used largely for two reasons: when the main sewer system is inaccessible (or linking to it would not be cost-efficient) and when centralized systems and treatment plants face capacity limitations. They're also a fraction of the cost to build and maintain a centralized wastewater treatment plant.

“We're seeing these mostly in areas of high urban growth,” says Peter Grose, senior vice president of engineering and consulting firm Fuss & O'Neill. “Occasionally we see them mediating an existing problem, such as a densely populated area with existing septic systems that aren't doing the job at effectively removing nitrogen.”

Onsite wastewater treatment systems use processes similar to traditional wastewater treatment plants, relying on both aerobic methods (such as activated sludge, suspended growth, or attached growth with textile filters) as well as anaerobic methods to remove nitrogen. But unlike most centralized systems, they discharge through leaching fields, spray irrigation systems, and constructed wetlands rather than to a river or lake.

“Decentralized wastewater treatment, reuse, and resource recovery are key elements in a significantly more efficient use of water that also entails a lighter environmental footprint as well as more creative open space and lower energy costs,” says Valerie Nelson, director of the Coalition for Alternative Wastewater Treatment. “Systems that rely on soil-based treatment also replenish groundwater aquifers.”

“Some rival the efficiency of a larger treatment plant in removal of organic matter, solids, and nutrients such as nitrogen and phosphorous,” Grose says.

However attractive decentralized systems are, though, what remains is the question of responsibility in the wake of a system failure.

ON THEIR OWN TERMS

Although in most cases developers install the community systems and operations firms are contracted for maintenance, some cities and counties operate and maintain the systems themselves.

In Loudoun County, Va., where about 1,000 of 57,000 sewer connections are decentralized, officials took matters into their own hands, dictating the terms under which decentralized systems can be installed.

The utility works with developers to ensure that design standards of their chosen vendors comply with state collection and treatment regulations and are efficient and reliable. Loudoun Water (formerly the Loudoun County Sanitation Authority) also works with the local health department that oversees the subsurface discharging systems.

The county's board of commissioners created the public utility in 1959 to provide water and wastewater services to unincorporated areas just as the historical farming community northwest of Washington, D.C., was at the verge of a boom in suburban sprawl.

“Only individual systems or community-based systems are allowed, and they are only allowed to be operated publicly,” says Todd Danielson, manager of community systems. “It comes from a history of nightmares trying to fix problems with improperly installed septic systems.”

Not until the early 1990s did the board of supervisors adopt a general plan that allows cluster developments in the formerly rural areas of the county. When property values skyrocketed at the end of the decade, developers began moving in with community-based systems.

Loudoun Water owns and operates eight community-scale systems that discharge 10,000 to 125,000 gallons/day each, and it operates another eight (which are owned largely by schools, other towns, and businesses) that discharge 4,000 to 250,000 gallons/day each. Homeowners pay Loudoun Water quarterly based on how much water their subdivision uses.

Although some states regulate decentralized community systems, there are no federal standards to ensure that developers install systems that operate properly. Loudoun County's approach — owning and operating the systems after approving design — is rare.

In addition to the sporadic state permitting issues, most community-scale systems are surface discharge systems that require a National Pollution Discharge Elimination System permit, but they also can be subsurface discharge systems, which are permitted through local health departments. There's also the question of certification — in most places, operators of decentralized systems don't need any type of certification — and oversight to ensure that private developers follow a standard.

“When package plants came out in the 1980s, people didn't know how to operate them, and they got a bad rap,” Danielson says. It didn't matter to most communities, because the EPA was offering grant money to help fund the expansion of centralized wastewater systems. Now that that funding is no longer available, and suburban sprawl is at a crossroads, “people are starting to look at lower-cost alternatives.”

FINANCIAL ASSURANCES ARE KEY

In 1998, after a land transfer with the state, the town of Newtown in Connecticut spent $100,000 to install a community-based system servicing six houses.

Public Works Director Fred Hurley thinks it was a smart move. “The septic systems were failing, but it just wasn't commercially feasible to bring those houses onto the centralized system,” he says. Homeowners pay a quarterly assessment to the town's Water and Sewer Authority to offset the costs of operations and maintenance.

That system, along with a $200,000 system consisting of two duplex grinder pumps that feed into the centralized system from a 60-unit trailer park, are operated by United Water/Suez, which also operates and maintains the town's main wastewater treatment plant.

Hurley acknowledges that the town learned from the legal battle in nearby Brookfield. In Newtown developers must provide financial assurance in the event of a system failure, a sort of escrow account that guarantees funding for repairs.

The Water and Sewer Authority also oversees a maintenance fund supported by condominium association fees at a privately maintained community system for a 60-unit condominium development that was installed privately in the late 1990s. The fund is tapped whenever maintenance is required.

“The town conducted a full engineering analysis of the soils, examined the design of the system, and ensured there would be adequate funding reserves deposited annually to maintain it and provide for replacement of the system,” Hurley explains. “It lowered the town's exposure to virtually zero.”

Requiring financial assurance from developers is still largely new territory, says Grose, who explains that the goal is to have the benefitting property owners pay for the upgrade to a community-based decentralized system, “or the city brings in sewers and levees benefit assessments like it would with any sewer user.”

To convince the public and elected officials that a decentralized system should be part of the overall waste-water-treatment mix, Danielson advocates what he calls “triple bottom line accounting.”

“Look at the numbers, but also look at the impact on the environment and the impact on society,” he explains. “Put a dollar value on how you're affecting the environment and society. For example, what's going to be the cost on the neighborhood of ripping up the streets to put in a new sewer line? With major infrastructure improvements, you're working on a 20-year cycle, you're carrying all that additional cost to operate and maintain these idle facilities in some manner until you build them out.”

Decentralized systems should be evaluated alongside other treatment options, says Jeff Moeller, senior program director for the Water Environment Research Foundation.

“Decentralized systems are no longer a stopgap for outlying areas,” he says. “And centralized systems are no longer a one-size-fits-all solution.”