Membrane filtration OK for Bellwood reservoir
New system will replace traditional filtration with powdered coal and fine sand
A seven-month pilot study at the Bellwood Water Treatment Plant has shown that membrane filtration is a good fit for the water from Bellwood reservoir and that equipment from the Pall Corp. is the best fit among several brands tested, Altoona Water Authority officials said Tuesday.
Membrane filtration is classified as “innovative” by the state Department of Environmental Protection and thus requires a pilot study when it will replace other filtration technology, according to Water Treatment Supervisor Tobias Nagle.
At Bellwood, membrane filtration will replace traditional filtration with powdered coal and fine sand — the same kind of filtration used at the authority’s six other water treatment plants.
Membrane filtration is more absolute than filtration by coal and sand. Pollutants larger than the tiny holes in the membranes can’t get through and are trapped and washed away.
By contrast, coal and sand filtration requires vigilance from treatment plant employees, who must add the correct amounts of coagulant to bind with pollution particles before water enters the filters, so the particle profiles are enlarged and the particles can be trapped.
Employees at the Bellwood plant do a fine job keeping the finished water in compliance with government standards, consulting engineer Mark Glenn of Gwin Dobson & Foreman said. But they sometimes struggle to maintain that compliance after rainstorms, when turbidity, other contaminant levels and acidity are high because of Bellwood’s big watershed, which includes old strip-mined areas, Glenn said.
The membrane filtration should help ease the stress, he indicated.
At the beginning of the pilot study, officials were hopeful they could dispense with coagulation but discovered they still need it to handle manganese, according to Nagle.
Ozonation, the initial treatment, oxidizes some manganese, so the membranes can capture it, but ozonation leaves much of the metal in dissolved form, so that it is small enough to slip through.
Adding coagulants to bind with the manganese, enlarging the metal’s profile, solves that problem.
The authority must advertise for bids for the actual filtration system to be used in the plant.
They will write their specifications so bidders will need to mimic the Pall equipment, according to Nagle and staff engineer Mike Sinisi.
The membrane equipment manufacturer would be a subcontractor to the general contractor, and the authority would reserve the right to choose the membrane manufacturer by means of bid alternatives, Glenn said.
The specifications will call for openings in the membranes no bigger than 0.1 micron.
The authority recently submitted the results of the pilot study to DEP for approval.
The filtration system will cost about $3.2 million — part of the estimated $8.5 million total cost for the treatment plant renovation.
Gwin should complete design for the renovation in the fall or winter.
Workers should begin construction in 2019, completing the job at the beginning of 2021, according to Glenn.
The $12 million dam project should begin and end at about the same times, he said.
The authority will look to Pennvest for funding, with a single application for both projects, according to Glenn.
Mirror Staff Writer William Kibler is at 949-7038.