Rosendale embraces switch from chlorine to UV for wastewater treatment

A view of the Rosendale Sewage Treatment Plant. (Photo by Lauren Thomas)

Sometimes a delay in implementation of a major infrastructure project can fortuitously result in a better final product, as technology outpaces bureaucracy. That seems to be the case in Rosendale, where millions of dollars’ worth of improvements to the town’s water and sewer systems have been underway, phase by phase, since New York State started making grant funding available to municipalities hard-hit by Hurricane Irene and Tropical Storm Lee in 2011. One of those projects was “hardening” the town’s wastewater treatment plant (WWTP), which had “failed during the storm events because it was overwhelmed without sufficient capacity to accommodate the demand from stormwater inundation and Creek flooding,” in the words of the NY Rising Community Reconstruction Plan issued by the Governor’s Office of Storm Recovery in March 2014.

Rosendale’s initial infusion of NY Rising money specifically for the WWTP was a $500,000 grant for a Stormwater Management Study as the first step in “scoping and implementation of protection measures.” The town retained the services of engineering consultants Barton & Loguidice to conduct the study and design upgrades to the plant. Subsequently, an additional grant of $620,000 was awarded to Rosendale under the Clean Water Infrastructure Act of 2017, constituting a 25 percent match intended to leverage other funds toward the purchase and installation of equipment as part of the $2,480,000 wastewater project. The balance of the cost is to be financed via interest-free loans provided under New York State’s quasi-governmental funding agency, the Environmental Facilities Corporation.


The wheels of state funding grind slowly, however, and Barton & Loguidice just recently completed the initial Stormwater Management Study and associated State Environmental Quality Review process for the upgrade. While these were in process, however, another state agency, the Department of Environmental Conservation, changed the rules with regard to levels of residual chlorine that a WWTP is permitted to discharge into a water body. The daily maximum is now .05 milligrams of chlorine per liter of water, compared to two milligrams per liter previously. “We got the news after the funding application was submitted,” Jason Ballard of Barton & Loguidice told the Rosendale Town Board at its March meeting.

This change in standards forced the engineering firm to reevaluate the entire plan that it was about to recommend to the town, which included improvements to the plant’s backflow valves, clarifiers and tank aeration, as well as to the building envelope to make it more impervious to flooding of the adjacent Rondout Creek, but was, in Ballard’s words, “designed for two milligrams per liter.” Even the earlier standard presented a challenge, he said, but declared “.5 extremely difficult to reach.” To reduce chlorine content to that level would require construction of a separate workspace for WWTP workers to add sodium bisulfate to dechlorinate the water further after treatment. The additional chemical, he said, is “not the most pleasant to work around. The taste stays in your mouth for a while” after handling. Ballard called the dechlorination process “operationally difficult” and “not very user-friendly,” in addition to driving up the project’s pricetag with the construction of a “secondary container” and additional workforce hours.

Confronted with this challenge, the engineering firm came up with an alternative plan — one that, while costlier than the original project, would cost less than the dechlorination option, in addition to being much more environmentally friendly: ultraviolet (UV) disinfection. “A lot of municipalities are switching over to UV now,” Ballard said. He shared a diagram of a tank with a bank of UV lamps suspended in the middle, through which the wastewater would be channeled. “It doesn’t kill the microorganisms. There’s a photochemical reaction with the virus, which damages its DNA so it can’t reproduce. It makes it kind of inert. But it doesn’t change the chemical composition of the water…You can completely discontinue all chlorine.”

Rosendale water and sewer superintendent Terry Johnson responded approvingly, “Anytime you can get away from chlorine…it’s a carcinogen. We test for chlorine daily. It’s easy to go over two milligrams.” Ballard said that, with the UV apparatus, microorganisms including the “indicator bacteria” E. coli, protozoa, viruses and algae would be “all deactivated. It’s 100 percent effective.”

Additional costs incurred by installing a UV treatment tank would include building a “small pole barn with an awning over the top” closer to the creek than the existing structure, noting than an “enclosed vessel for UV would be harder to access” for periodic cleaning of the lamps. Electric lines would need to be run to the tank, and the bulb array would have to be removed each October, when the treatment season ends, to protect the bulbs from freezing temperatures. Some extra storage space would also be needed. Ballard estimated that the entire setup would have a lifespan of eight to 12 years, although the bulbs would need replacement more often than that.

The bulk of the costs of the system improvements, the engineer said, had to do not with the UV treatment tank, but with the hydraulics, and with increasing the height of the walls of the aeration tanks: “We have to make sure we can handle a 100-year flood, when [the Rondout Creek] backs up to the aeration tanks.”

The Town Board responded with enthusiasm to Ballard’s recommendations, despite the increase in costs. “We’re not going to do the dechlorination; you’ve convinced us,” said Town Supervisor Jeanne Walsh. “We love our creek. Let’s do UV; let’s make it happen!” Still to be determined at this point is whether the pending applications for grant funding and interest-free loans can be recalculated to accommodate the changes needed to meet New York State mandates.

There is one comment

  1. Rose and Dale

    Good. Now there will be more chlorine available for New Paltz town/village swimming pool. Nobody has any idea how much chlorine is dumped in that cement pond or its cost because the bills are not public information.
    Walk around the back of the pool, and you can witness the pipes that let out the overflow of chlorinated and contaminated water right into the Millbrook stream and then down into the Wallkill River.
    “…damages DNA.”

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