While most wastewater treatment plants focus on material collected from their own systems, some choose — often for economic reasons — to supplement that with outside waste.

After a major expansion in the late 1980s and an upgrade in the mid-1990s, Glens Falls (N.Y.) Wastewater Treatment Plant found itself in just such a situation. Today, drawing from varied sources, the plant accepts a broad range of materials including grease trap waste, holding tank waste, septage, sewer cleaning debris and biosolids (liquid and cake) from others. That diversity and reliable long-term equipment performance have helped the plant remain viable in serving its city and surrounding areas.

Legacy lives on

Glens Falls, on the Hudson River 45 minutes north of Albany, is a picturesque city of 15,000 and has a thriving base of medical device and medical service industries. The city was home to a huge pigment manufacturing plant that closed in the 1980s, leaving contaminated soil behind. The Glens Falls treatment plant still treats wastewater from the site’s groundwater treatment and collection system.

“That pigment plant was actually a driving force in an expansion that took place here in the mid-1980s,” says Jason Vilander, the plant’s maintenance manager. “A lot of water is used in chemical and dye work — water that couldn’t simply be discharged to the river — so our plant was designed to accommodate that additional volume. The expansion allowed us to move to activated sludge treatment and prompted installation of a fluid bed biosolids incinerator. Unfortunately, the pigment plant shut down during the later part of our expansion, leaving us with a good deal of extra capacity.”

Filling the void

Needing to fill that capacity, Glens Falls began seeking entities looking to outsource water and waste treatment. Today, the plant takes in material from the Town of Queensbury, the Village of South Glens Falls with its Moreau Industrial Park, and a number of businesses.

“We’ve had success in some unlikely places,” Vilander says. “Most of our liquid sludge, for example, comes from Vermont.” That includes large ski resorts, and town and village treatment plants that lack drying beds or digesters for biosolids processing. “We provide that last step for them,” Vilander says. Material also comes from regional correctional facilities.

“Those facilities have their own wastewater treatment systems, complete with belt presses, but that’s as far as they can go with it. So, twice or three times a week, they send us five tons of cake in a single-axle dump truck, and dump it onto a pad. We load that into a receiving station and store it until we have the time and manpower to incinerate it.”

Long-lasting equipment

The benefits of importing material would be moot if the city couldn’t effectively handle what it collects. Vilander says the equipment in many parts of the facility has shown excellent capability and longevity.

“A good case in point would be our sludge pumps,” he says. “We had a pair of Schwing KSP-5 sludge pumps installed during the first plant upgrade. Those pumps, among the first Schwing made for this market, have been outstanding given what they’re asked to do.” They were replaced a few years ago after nearly three decades, not because of wear but because volumes had grown and the plant needed to upsize.

A pair of larger Schwing KSP-10 pumps have increased pumping capability to deal with growth in biosolids handling. The pumps take cake dewatered to about 24 to 26 percent solids and route it for incineration, where 32 tons of cake (a semi-trailer full) is reduced to 100 pounds of ash. A “slip ring,” pipeline lubrication system helps move that volume — the system injects a thin film of water to reduce friction loss in the pipeline and reduce pipeline operating pressures, in some cases by more than 50 percent.

“We work so hard to get all the water out, so it seems a bit contradictory to put some back in, but because we’re running these slip rings at about 20 to 30 percent of their capacity and they come on for only a matter of seconds, we are adding no more than three gallons per hour,” Vilander says. “So the amount of water added is minimal, and it pales by comparison to the improvement in throughput and the fuel savings we achieve with the drier cake.”

Better control

The newer pumps also add versatility: Because they are PLC-controlled, the team can run them in several modes, including pressure, tracking and manual. That means they can automatically control the speed of the hopper screws and the pumps themselves.

“With the old pumps, we could adjust our pressures a bit to get the speed we needed, but we couldn’t get independent control of both components — the screws and the pump,” says Vilander. “Now we can, and it has made a huge difference. Because the pumps run nice and slow and quiet, we’re not seeing the level of maintenance we did with the old ones. I can see these outlasting those previous workhorses.”

The ultimate destination for cake at Glens Falls is the fluid bed incinerator, 18 feet 3 inches in diameter and 44 feet 9 inches high. The unit maintains an effective operating temperature of 1,500 degrees F and uses the cake as the primary fuel — if the cake is dry enough, it burns autogenously.

“If it’s too wet or does not have enough VOC in it, we have to add Btu through an alternative heat source which in the past was fuel oil,” says Vilander. “While the new belt presses gave us a much drier cake, we still had to rely on the fuel oil. As part of an overall cost savings move, we installed a two-part grease system consisting of a concentrator and a storage tank.”

Better in the long run

Doing so dramatically reduced operating costs and gave area businesses a place to discard grease. Now, septage haulers pay a fee to drop off grease, which is then concentrated, thickened and burned. 

“Occasionally we get a load of grease with wastewater added to it, which has to be treated differently,” Vilander says. “So it goes into our storage tank where it is mixed and pumped up to our belt presses, combined with the cake, and moved using the Schwing pumps out to incineration. The grease is now both a fuel source and a small revenue stream.”

Vilander believes the plant’s piston-style pumps have played a major role in running the plant’s solids operation and keeping the plant viable: “Our piston-style pumps were more expensive up front, but we know they will provide decades of good service. I think we’ve already proven that.”