What happens to the stuff that goes down our sinks and toilets? Where does the water from our dishwashers and washing machines go? How do you recycle or clean waste water in Antarctica?
50 years ago, waste water as well as glycol and formaldehyde was simply drained into the streets or collected in buckets and dumped in the ocean in front of McMurdo. Things have changed. Now we have the Waste Water Treatment Plant.
The McMurdo Waste Water Treatment Plant – where brown water goes in and cakes come out.
The 5 year old Waste Water Treatment Plant is nestled halfway up a hill, between the sea ice and the buildings of McMurdo. Inside is a complex system of tanks and pipes, machines and bacteria, that work together to make "cakes" out the stuff that goes down our toilets.
Diagram of the McMurdo Waste Water Treatment Plant – what happens here?
Bec, Dale, and Kirt run the place and they gave me a tour complete with explanations of each step of the process – from the gray water beginning to the brown cake ending.
Bec, Dale, and Kirt in front of The McMurdo Waste Water Treatment Plant. How do they convert this dirty water into cakes?
McMurdo has an intricate plumbing system. Everything that is dumped down a sink or toilet or dumped into the system via a pipe ends up at the Waste Water Treatment Plant. In the end, 2% of what ends up at the Waste Water Treatment Plant is solid and 98% is water. The aim of the treatment plant is to separate out the solid waste from the clean water. The Muffin Monster Masticator starts the process by grinding up all the big hard pieces into little ones. Once through this first step, water is measured by a flow meter so Bec and her crew can see how much waste water is going in the system. Like spies, they can see in the charts the peaks when the masses of McMurdoites shower, do their laundry, or use the restroom and the lulls when people are hard at work. With more people than ever on base, Bec and her crew hope that the plant will be able to handle the increased water flow.
Bec, Dale, and Kirt in front of The McMurdo Waste Water Treatment Plant. How do they convert this dirty water into cakes?
Once the water has been measured, a simple screen filters out big particles that don't belong in the system. Stickers from apples and oranges somehow seem to sneak through. Grease balls also accumulate as McMurdo does not yet have a grease trap. Lastly, oddly enough, we don't seem to chew our corn enough! The filter catches so many kernels of corn that Bec and her crew have given the trash can next to the screen filter, the name "Corn Bucket".
Now that the grey waste is really just grey water without big chunks, it gets interesting. This is where the Water Bears get to work. What bears am I talking about? We all know that polar bears don't live in Antarctica so what is this business with water bears?
Water Bears are actually just one of the many kinds of microscopic bacteria that "clean" the water. Just like in our seafloors or forests, there are communities of creatures living in these slurry waste water tanks.
Bec looking for water bears and other creatures.
These creatures, however, are microscopic and each of the different kinds of bacteria, ciliates, bristle worms, carnivorous free swimmers, amoebas, and bacteria has a different function in the cycle of waste water treatment. I saw a few of them dancing through my microscope! Bec and her team use microscopes to carefully monitor the critters. They look for diversity in terms of what critters they find. They want microorganisms that show up early and ones that show up later in the succession of the waste water treatment – just like the ferns that show up quickly and trees that take longer to grow in forests. If they were to find just Water Bears and bacteria called Bristle Worms then their wastewater would be too old and the crew would need to open valves to move the waste water to the next step. If they were to find the "newer" microorganisms, like free swimming ciliates, then they should continue to circulate the water, not opening the valve to allow it to continue to the next phase.
The home of all kinds of creatures. What is floating in here today?
This stage of the treatment is actually three tanks through which the water continually cycles. In the first tank, called the Anoxic Basin, the bacteria work on urine or ammonia. Starved of oxygen, the microorganisms remove the nitrogen, releasing it into the air. In the second tank, the Aeration basin, the wastewater gets aerated by steady streams of air. This helps the microorganisms process the waste very efficiently. The third tank, called the clarified water tank, actually separates the solid waste from the water. Gravity makes solid waste sink to the bottom while most of the water stays above it. While this water is pretty clean, it still goes through a UV chamber to be further disinfected before it exits through more pipes into the ocean.
The UV chambers. Water gets disinfected here before it goes out into the sound.
As the solid waste accumulates in the clarified water tank, it is pumped back into the system entering at the Anoxic Basin for more cycles of cleaning and treatment until it gets "wasted". Once the microscopic community has reached a satisfactory balance of diversity and the accumulating sludge in the clarified water tank has reached a specified consistency, it go through the final stages of becoming a cake. This happens about once a day though less in the winter when there aren't as many people in McMurdo. In wasting, the waste from the clarified water tank is first moved to a machine called a digester. This machine continues to mix the sludge up with air until it is ready to press even more water out of. With very little water remaining, this sludge then makes its way to the last machine, a belt filter press, which literally squeezes water out with the help of man-made polymers and two belts that squeeze together.
The digester. Sludge goes in and cakes come out.
In the end, Bec and her team are left with "cakes", thin, towel-like layers of "biosolids". These cakes can now be dropped into large containers called triwalls and be prepared for shipping back.
Triwalls of cakes. What can we do with them now?
Not disturbing anyone's sense of smell, the cakes sit in their boxes in refrigerated mill vans for many months as they make their long way back to the US. They must pass through New Zealand as they have different laws for processing waste water. In the US, they cannot be used for cover crops like other "cakes" from waste water treatment plants because of tomato seeds! Tomato seeds are so hardy that they survive not only Waste Water Treatment plans but also our own bodies' digestive systems. Most of the fresh food that we eat in Antarctica is grown in New Zealand. If we were to use the cakes from the plant here in Antarctica with crops in the United States, then inevitably New Zealand tomato plants would start to grow. Since we don't want to potentially contaminate our tomato plants, we use the cakes as filler for landfills.
Bec and a cake. Where will this go?
Thus the process is complete. The filters removed the big particles, the bacteria took out the harmful ammonia and other chemicals, and the various tanks and machines with the help of gravity and polymers removed most of the water! The critters that our team is studying out on the seafloor by the sewage outfall are much happier as they now have cleaned, disinfected water instead of untreated sludge or waste water. Next steps include adjustments to enable the plant to handle the growing population of McMurdo personnel and building a system for both Palmer and the South Pole. At Palmer they do a little bit of cleaning and at the Pole they simply freeze their waste water and store it in the ice, hundreds of miles from our sea floor critters and seals.