Is Clean Water Vs. Dirty Air a Good Trade-Off?

Do you need to put 5,000 more cars to the road to get clean drinking water?

I find the trade-offs that arise in energy development, environmental protection and human health fascinating. Over the years I’ve written on this topic a few times:

Energy Technologies and Unintended Consequences

Unintended Consequences, Part II: Air vs. Water

Unintended Consequences, Part III: Electricity vs. Water

Today I want to talk about a 160,000 square-foot new water treatment facility in New York that will be going online this year, and how it’s giving us safer water at the cost of a hefty increase in greenhouse gas emissions. I’m referring to the Catskill/Delaware Ultraviolet Light Disinfection Facility, which is in the final stages of construction just north of New York City. The facility will use ultraviolet light to disinfect an average of 1.3 billion gallons of water per day. It’s also going to use a lot of electricity and, as a result, increase greenhouse gas emissions.

Source: NYC Dept. of Environmental Protection

The consequences of this project are neither unintended nor unforeseen. The project was required by Federal and State regulations to maintain the safety of New York City’s water supply, which is one of only a handful of major water supplies in the U.S. that remain unfiltered, according to civil engineer Robert Osborne, who is very into water. Having an unfiltered water supply is a kind of badge of honor. It means your water is exceptionally pure. But Federal and state regulations require water supplies to be protected by other means if filtration is not used. (The New York Times reported that a filtration system for this water supply would have cost up to $8 billion to build millions of dollars a year to operate.)

A project of this magnitude, whose costs are estimated at $1.6 billion, undergoes detailed analysis and planning, including an the creation of an environmental impact statement. The environmental impact statement says that the plant will draw an average of 4.45 megawatts of electric power. By my calculations (4.45MW X 24 hours X 365.25 days X 1000), that will equal about 39 million KWh of electricity annually.

You can calculate the amount of greenhouse gases emitted to provide 39M KWh of electricity in New York using EPA’s eGRID methodology (available via a cool tool on Using my assumption, it comes to over 25,000 metric tons of CO2 equivalent. Taking the EPA’s estimate of the average annual greenhouse gas emissions of an average automobile (5.1 metric tons of CO2E per year) you find that these emissions are the equivalent of putting about 5,000 more cars on the road.

I have no doubt that this particular trade-off (cleaner water for dirtier air) is worth it. The project protects over 8 million people who depend on this water supply from the risk of water-borne contaminants that could cause a significant public health crisis. I point it out not to criticize this project but rather to illustrate the kinds of trade-offs policy makers face all the time.

I’d love to hear your thoughts.



Filed under climate change, emissions, grid, transportation, utilities, water

5 responses to “Is Clean Water Vs. Dirty Air a Good Trade-Off?

  1. Mitra Ardron

    Its an interesting trade off. Doing the math, thats about 0.02 liters/WH which is about 4x more efficient than the most efficient household UV treatment. Since many NYers probably filter or otherwise treat anyway to get the chlorine and since we only drink maybe 5 liters per day out of the 200-500 consumed it would make a lot more energy & financial sense to treat at the tap, and might have the added effect of getting more people off the environmental monstrosity of bottled water.

    • David Schatsky

      Thanks for your comment, Mitra. It’s an interesting point. I wonder what a full life cycle analysis of your suggested alternative would show. Nonetheless, it’s a Federal requirement that determined approach. I would supposed that the Feds have their reasons.

  2. Tom Marting

    I don’t buy the idea that unfiltered water is more pure than filtered water. I agree that UV disinfection is better than chemical treatment, but to me clean means it has been disinfected (no microbes) and pure means a lack of chemical contaminates. UV may break down some organic contaminates, but it will not eliminate as many chemicals as an activated charcoal filter can. Reverse osmosis is a ultrafiltration technology that purifies water nearly as well as distillation, but strips some minerals out of the water. Combining UV disinfection with some other filtration technologies might have been more energy efficient than intense UV alone, but not worthy of a headline.

    • David Schatsky

      Hi Tom. Thanks for your comment.

      Water nerds (a term I use endearingly) in watersheds that don’t require filtering tend to be proud of that fact. This isn’t because they believe that unfiltered water is purer than filtered. It’s just that they like the fact that their water source is free of the contaminants that necessitate filtering. There’s no judgment implied about the quality of the end product.

      The UV process is for disinfecting, not for removing chemicals. I believe the reason that NYC has a pass on filtering is because the water is judged to be relatively free of chemicals and other impurities to begin with.

      Put me down as a fan of Purell, by the way.

      • Tom Marting

        It would be nice if more source waters were as free of impurities. As we get our drinking water from Lake Erie, I think we are a few years away from being able to hit that same standard.

        As we develop life cycle thinking into our corporate culture, we will face similiar choices between environmental impacts like the one you describe above. If we pursue bio-based resins, should we accept less GHG for potentially higher eutrophication? How much it too much?

        What are your thoughts on revealing and making choices like these?

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