A Customized Clarification System Eliminates a Costly Settling Pond and Pumps Fines To a Final Stockpiling Location.
By Carol Wasson
The management team at the P.J. Keating’s Quarry operation in Acushnet, Mass., said it made a wise decision to invest in a customized clarification system that eliminates the need for settling pond maintenance. The system pumps fines more than 1,000 ft. to a final stockpiling area. For its Acushnet quarry operation this means a major cost savings in labor, equipment, fuel and valuable water resources – and a future ability to open up additional reserves where its former settling pond had been.
“Anybody who washes aggregate has a costly fines and silt disposal challenge, and the biggest payback from what we’ve done is pumping – versus hauling silt – to a stockpiling area. We no longer have to move it with machinery,” said Larry Kelly, Southern Operations manager for P.J. Keating.
Prior to the installation of the clarification system, the crew had to muck out the pond with a loading shovel and haul the material via dump trucks to a storage area. “This was a very costly and messy task as the fines and silt material is more than 70-percent liquid. Plus it was always performed on overtime.” said Aidan Kilcoyne, Acushnet site manager.
He goes on to explain that mucking the pond required up to six pieces of equipment, eight hours of labor per week during production season, and three full weeks of labor during the off-season. “So the clarification system has delivered a huge savings, not only in dollars but also in wear and tear on the equipment. Running equipment in the silt pond is not the ideal situation,” he said.
While doing extensive research on the process of thickening silt with the use of flocculants, the P.J. Keating team came across Milwaukee-based Clearwater Industries, a company that provides turnkey solutions, site and water analysis, chemical selection and complete clarification systems that are custom-designed for each specific aggregate application.
“We chose Clearwater Industries for a number of reasons, the biggest being that unlike their competitors, they could customize the system to fit on a smaller footprint. Beyond saving on space, this minimized our capital investment in pouring a concrete foundation, made installation far easier, and allows us to maximize our footprint for future quarry development,” said Kilcoyne.
“The system requires a footprint of 35 ft. by 16 ft. Competitive systems would have required up to 48 ft. in foundation length,” he said.
Clearwater Industries engineered a high-compaction clarification system that allows the operation to take a dirty water stream and produce clean water immediately, while concentrating the fines or solids to a thick state. To obtain a greater compression of mud and a drier consistency, the system features two tall, cylindrical aging tanks. Driven by a 10-hp motor, a hydraulic drive system operates an internal mud rake and knife gate valves in each of the two tanks.
Processing up to 2,400 gal. of water per minute, the system is combined with a dry polymer feed system, polymer mixer, and polymer injection pump. “Unlike many of their competitors, Clearwater is a one-stop shop in that they build their own polymer systems,” said Kilcoyne.
Solids discharge and transfer is handled by two 6-x 6-in. progressive cavity mud pumps driven by 30-hp electric motors with gear reducers. These are the pumps that allow the thickened material to be pumped through a 10-in. pipeline more than 1,000 ft. to the final stockpiling area.
Kelly said that his concern before committing to a clarification system was whether material could be pumped such a long distance. “We were able to visit two other Clearwater installations, one which is pumping its solids more than 2,000 ft. Once we found out we could pump that far, we knew that we just needed to manage our stockpiling area to make sure it dried out enough. It’s hard to believe that we can now move this material with two pumps versus haul trucks. Now we can reallocate our people and our equipment,” he said.
Customization of the system also included certain components – the main control panel, the hydraulic drive system, and the polymer make-down system – being housed to protect them from the elements. Clearwater accomplished that with the use of a shipping container that was sandblasted, primed, painted, heated and insulated. Installation also included wiring for lighting and a service door for entry. Additionally, the container has ample room to store pallets of polymer, keeping them dry and warm.
Kelly said that Clearwater also made modifications to meet P.J. Keating’s stringent safety requirements, such as putting in a stairway, rather than a ladder, to access the top of the clarifier.
“We didn’t have a very big window in getting this system installed before the start of the production season, but Clearwater performed very well on delivery, installation, startup and training. Their technicians remained onsite until everybody was comfortable. Ultimately, it is an automated system. You put in the correct amount of polymer and the system takes care of the rest,” said Kilcoyne.
“We have a complete system with 80 percent of our water being recycled. Along with the reuse of the water, and the decrease in emissions from running less equipment, we are seeing considerable environmental benefits as well. And, our goal is to eventually use the pond area for developing additional quarry reserves,” said Kelly. “So we are very pleased with the total package. Some operations in the New England region have polymer systems, but I am not aware of any others who are actually pumping fines to a ‘final stockpiling’ area.” E