State of the Planet

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Nitrogen and Wastewater: Kartik Chandran interview Part 2

Kartik Chandran interview Part 1

What are you working on with regard to nitrogen in wastewater treatment?

One of the programs that I lead at Columbia is the Wastewater Treatment and Climate Change program.  We are looking specifically at the emissions of nitrous oxide and the metabolic level mechanisms of nitrous oxide emissions in wastewater treatment.  The idea there is to remove nitrogen from the waste stream, but not at the expense of blowing nitrous oxide into the atmosphere.

Although nitrogen in some forms is an essential ingredient of life,
nitrogenous compounds including ammonia, nitrite and nitrate are directly toxic to human and animal life.  Nitrous oxide is also a potent greenhouse gas which is about 300 times as powerful as CO2.   If the nitrogen is not removed from the wastewater streams, it contributes to algal and bacterial growth in receiving water bodies and ultimately the phenomena of ‘eutrophication’ and ‘hypoxia’ and overall degradation of water quality.

Nitrogen is one of the most challenging compounds to remove from wastewater, because the bacteria that remove nitrogen are quite slow growers, and are also sensitive to all kinds of environmental factors.

In what way are your experimental designs being applied in the United States or elsewhere?

With the experimental designs, or what we call the process technologies – what we are after is energy efficient nitrogen removal bioreactor operations, for example.

We develop process technologies in our lab which then are implemented at full scale, for example by the City of New York and all around the country.  These are licensed, patented and then implemented for sustainable wastewater treatment. When I say sustainable, it’s sustainable engineering design – cost efficient, energy efficient.

As part of the nitrous oxide research program we are also coming up with process designs that remove nitrogen from both the liquid and gaseous space.  Not one against the other.  This is actually going into place all across the United States.

There are groups around the world doing this kind of work, and we are coming up with somewhat consistent recommendations.  We work with all the major utilities, in the US.  We have collaborations with Dutch utilities, and also Water Services Municipality of Australia where they’re giving us access to plants in Queensland. This is truly a global effort.

One of the most important issues emerging is the lack of adequate wastewater treatment for nitrogen removal in the developing world.  One of the things we should keep in mind is we should not make all the mistakes again in the developing world that we’ve made in the United States, which is what we’re working towards in some of these sustainable technologies.  We can really leapfrog everything that’s happened here, before we put them out in the developing world.

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