Wastewater.
It's what gets flushed down the toilet, rinsed down the drain,
and produced by places such as factories, workplaces, and homes.
According to the U.S. Environmental Protection Agency,
the average person uses about 100 gallons of water a day
with almost all of it turning into some form of wastewater.
Of the hundred gallons per capita per day of wastewater we produce,
we are drinking about a gallon per day per capita.
So essentially, wastewater is the one gallon
of human waste produced per capita per day,
diluted with 99 gallons of non-human waste.
Because wastewater contains pollutants and contaminants,
most communities send it to treatment plants to be processed.
The water has to meet federal, state,
and local standards before it's released back into the environment.
Wastewater is one part of the human water cycle,
which describes the many ways people interact
with nature's hydrologic cycle to meet our needs
for water, food, and energy.
While water treatment plants are a necessary part of public health
and environmental safety, they require a great deal of energy
and resources to operate.
In the U.S., we devote about three to six percent
of the national energy budget on the enterprise of clean water.
Kartik Chandran is a professor of Earth and Environmental Engineering
at Columbia University and funded by the National Science Foundation.
He investigates new, more efficient ways to treat wastewater.
Wastewater contains elements such as phosphorous,
organic carbon and nitrogen,
which are often removed during the treatment process.
Let's start with nitrogen.
When we want to remove nitrogen from wastewater in addition
to the organic carbon, the energy footprint
of a wastewater treatment plant essentially doubles.
At the Newtown Wastewater Treatment Plant in Brooklyn, New York,
treating wastewater involves several steps.
First, the system separates floating matter and solids from the water.
The remaining sewage then enters an aeration tank.
What we do in aeration tanks is we supply oxygen to microorganisms
that actually treat the sewage.
Typical microbes for wastewater treatment require oxygen
to degrade organic pollutants.
The resulting sludge is further treated, and, in its final step,
the water is disinfected.
Chandran is trying to reduce the amount
of energy used in this process.
He uses a type of bacteria found in wastewater called anammox.
These organisms don't need oxygen to remove nitrogen from wastewater.
While traditional wastewater treatment often releases greenhouse
gases, such as nitrous oxide and carbon dioxide,
using anammox bacteria does not.
They allow us to remove nitrogen
at far lower energy costs and chemical costs.
Not just that, you would save sixty percent in terms of aeration costs
if we use the anammox model for removing nitrogen.
Chandran and his team are also looking at ways
to use wastewater's abundant chemicals,
nutrients and other resources to produce energy.
CHANDRAN: We have been able to convert the organic carbon
and food waste in sewage sludge, in fecal sludge to biodiesel
which is a liquid fuel, easily transported and easily used,
directly used in diesel engines.
The Newtown Wastewater Treatment Plant is already producing energy
from organic material.
The digesters are heated to about 95 degrees Fahrenheit.
They act like the human body.
They break down the organic material.
And we provide no oxygen.
And one of the products of the digestion process is methane gas.
Methane gas is a common energy source.
We are right now using a good portion of our digester gas
to heat our boilers at our locations.
The boilers are used for heating the environmental areas,
the personnel areas, and they're also used to reheat the digesters.
Chandran and his team are also finding additional uses
for wastewater products.
For example, they are using the organic carbon found in wastewater
to develop bioplastics, and taking the phosphorous and nitrogen
from wastewater for use in irrigation.
By linking the water sector, the energy sector, the food sector
and a few other sectors, we are now able to address these challenges,
not just one by one, individually in isolation,
but together in conjunction.
That's a very sustainable model.
As Chandran and his team help make the human water cycle more
energy-efficient, they are also helping us see wastewater not
as waste, but as a precious resource.