Vol. 18, No. 13 June 30 - July 13, 2005


Plant Foes Make Case for New Form of Filtration


As blasting continues in Van Cortlandt Park, and the hole in the former driving range deepens, one environmental group holds out hope that it can convince a an appeals court that there is a better filtration technology than the one the city is planning to use.

The Croton Watershed Clean Water Coalition (CWCWC) is suing the city over the process by which the Department of Environmental Protec-tion (DEP) selected Dissolved Air Flotation (DAF) technology for the plant. The group presented its final oral arguments to an appeals court in Brooklyn on June 23, and is now awaiting the court’s decision.

None of the three other lawsuits fighting the plant has yet been successful, and the Friends of Van Cortlandt Park has dropped its suit entirely. The two other groups are considering appeals. 

CWCWC claims the city must reevaluate its choice of filtration technology for the Van Cortlandt Park plant in light of recent advances in the field of membrane filtration. If CWCWC wins, the city could be required to conduct another study comparing the impacts, costs and benefits of a membrane filtration plant to those of the dissolved air filtration plant being built right now.

The DEP favors dissolved air flotation technology but CWCWC insists membrane technology is a more economical and environmentally friendly choice that would result in a much smaller facility.

In a DAF plant, a combination of chemicals and air bubbles are injected into unfiltered water. The chemicals cause pathogens to cluster together and the air bubbles carry them to the surface where they are skimmed off the top. A membrane filtration system pushes unfiltered water through a series of membranes, plastic barriers with tiny holes in them, similar to microscopic coffee filters or sieves. These membranes allow water to pass through while stopping bacteria and other non-water pathogens.

At the center of the argument are the State Environmental Quality Review Act (SEQR) and the City Environmental Quality Review Act (CEQR), which require agencies to study the environmental impacts of any projects, and thus minimize overall impacts.

Charles Sturcken, a DEP spokes-man, says that DEP water quality scientists and engineers already performed a study in 1997, which they finalized before they released their final Environmental Impact Statement on the proposed plant in 2004.

“They decided that dissolved air flotation is the best way to filter this particular water system,” Sturcken said.

But Dr. Audrey Levine, a specialist in membrane filtration working with CWCWC, says membrane technology has undergone revolutionary advances since DEP conducted their study.

“When you look at it, it doesn’t make sense to embrace this DAF technology right away,” Levine said at a public forum on membrane filtration at St. Ann’s Church in Norwood. “You need to do [another] analysis.”

The state’s deputy comptroller, Kenneth Bleiwas, also requested a new analysis in an official letter to DEP Commissioner Christopher Ward last September.

“Considering the rate at which this technology appears to be advancing,” Bleiwas wrote,  “it seems appropriate for DEP to review this alternative filtration system based upon the most recent scientific data available.”

DEP sent a seven-page response to the comptroller’s office in January, which explained the decision to use DAF technology and concluded that a membrane plant could not, efficiently and cost-effectively, meet treatment goals for the Croton water supply.

For many years, CWCWC was firmly opposed to the construction of any filtration plant because they believed that a plant would encourage development and pollution in the watershed upstream. That position led many Bronx activists, who supported the construction of a plant outside the Bronx, to part company with CWCWC. But CWCWC says they began researching membrane filtration in 2003 after their lawyer in Washington, D.C. told them a plant would be needed to meet stricter water quality standards. With this in mind, they decided to challenge what kind of plant would be built.

“[Membrane filtration] is a clean, simple, direct way of stopping pathogens which can make people very sick,” said Dr. Marian Rose, president of CWCWC.

And James Bacon, an attorney for CWCWC, says that after the cost of a new environmental impact survey and the cost of undoing all the work that has already been done in Van Cortland Park, the city would save at least $600 million by constructing a membrane filtration plant. Addition-ally, a membrane plant would be one-third the size of the DAF plant, he said, citing a quote from membrane manufacturing giant Zenon Inc. 

The DEP challenged that assertion in a June 16 statement to Bronxites for Parks, a Norwood group, saying that, while membrane filtration is good for small-scale plants, DEP studies indicate a membrane plant for the Croton reservoir would have to be larger and would thus be more expensive and closer in size and cost to the present DAF plant.

“We’re confident that we will win,” Sturcken said in response to a question about the costs of another survey. Should they lose, he said, “we’ll have to go back and rethink a lot of things.”

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