Is Drip Dispersal a Solution for Small-Scale Municipal Treatment?

The technology was developed for large agricultural irrigation use. But in the past decade, it's found acceptance in wastewater municipal systems.

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Editor's Note: This article is part of a profile on the Fairfield Glade Community Club. Watch for a special feature in the July 2015 issue of Treatment Plant Operator. Not a subscriber? Take care of that right here and now. Click here to have TPO delivered monthly to your mailbox.

A Fairfield Glade Community Club drip dispersal project in Tennessee was not the first for Jim Prochaska and Glenn Marcum. And it certainly won’t be the last.

Prochaska’s company, JNM Technologies, collaborated with Marcum’s company, EcoStruct Group, and Rutherford Utility Company on a design-build approach to the 250,000 gpd Fairfield Glade drip project, which serves a private resort community and disperses effluent from a facultative lagoon system.

Marcum and Prochaska see a bright future for drip dispersal in private as well as municipal utility applications. A drip dispersal system pumps effluent at low pressure through shallow-buried flexible plastic tubing in a dripfield. The tubing, containing evenly spaced emitters, distributes the effluent uniformly at a rate within the soil’s capacity to absorb it.

Gaining favor
The technology was developed for large agricultural irrigation projects and has been widely used in wastewater applications, such as small commercial and housing clusters and individual homes. In the past decade, it has started gaining acceptance in municipal projects. 

“I’ve been working with drip dispersal for the past 25 years or so,” says Prochaska, president of JNM and an engineer who functions as a designer and trainer on projects. “Acceptance has been an issue. It’s been mostly a problem of regulations and people being unfamiliar with the technology. We’ve been doing a lot of education, and we’re getting to where enough of these systems are installed, in enough states, so that the value is becoming clear.

“It’s a very efficient and good way to reintroduce treated wastewater to the natural environment. The technology is earth-friendly. There isn’t a lot of preparation unless the site is highly vegetated. When you’re done installing a system, you can put a park on top of it. It’s not so delicate that you can’t use the land.”

Municipal niche
Drip dispersal has potential for municipal systems largely because of tightening NPDES stream discharge permits. Lagoon systems, which serve many small communities, now often have difficulty meeting new ammonia limits, Prochaska observes.

“So they end up having to invest in a treatment plant, which negates the reasons why they went with a lagoon to begin with: simplicity and low cost," he says.

Applying effluent to the soil for further treatment is an alternative. Spray irrigation is one way of doing that. It is simple and inexpensive, but it has limitations, says Prochaska.

“The main drawback of a spray system is runoff, which you absolutely can’t have," he says. "And spray is only good for warmer months of the year. In the Midwest and the northern states, it’s a system the community really can’t rely on.”

Drip dispersal, on the other hand, isn’t weather-dependent.

EcoStruct’s Marcum, a contractor who handles installations, sees another niche in states including Tennessee, where certain streams have exceeded total maximum daily loading (TMDL) limits for nutrients, and regulators no longer allow point discharges.

Making it happen
One obstacle to drip dispersal systems is cost. Communities that use lagoons are typically small and rural and lack funds for major projects. Larger municipalities also have cost constraints and, while they have the bonding power needed to implement projects, they need to be convinced of drip dispersal’s effectiveness, says Prochaska.

Still, Marcum and Prochaska have collaborated on some substantial drip projects.

“We did a quarter-million gpd system a few years ago,” Prochaska says. “We’ve done half-million gpd systems. We have seen systems up to 1 mgd, and we have quoted on jobs in the 2 mgd range – they just haven’t gone the ground yet."

Marcum, meanwhile, reports he has been involved in municipal projects totaling 700,000 linear feet of drip tubing in the past two years.

Prochaska and Marcum typically install Bioline drip tubing (Netafim USA). Upstream filtration of the effluent prevents clogging of the tubing emitters — for that purpose the collaborators use 100-micron Ring Disc (Arkal Filtration Systems).

“The other important thing is controls,” Prochaska says. “We’re trying to take that to higher levels, moving toward less wire and more radio technology. It helps to have Web-based control so that, for example, from my office in Texas, I can look at the systems we’ve installed and help the operators solve problems — or even make the correction from my desk many miles away.”


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