Visit to Franklin Wastewater Treatment Plant

Gunnar Solberg
AP Environmental Science
Alan McIntyre

Franklin Wastewater Treatment Plant

On Thursday, December 6, 2012 we traveled as a class to the Franklin Wastewater Treatment Plant. The treatment plant, located in Franklin, New Hampshire, is located beside the Winnipesaukee River and cleans the water that runs in the river to keep the river safe from human waste. We have been learning in class about the effects of humans on freshwater and how we deal with it. The Wastewater Treatment Plant is extremely helpful in keeping the rivers clean and free of human wastes.

Alan explained how pumping stations all throughout New Hampshire move sewage and waste to the treatment plant, keeping the waste out of the river, where the waste is removed and the water is put back into the river.

Nashua River before Water Treatment Plants and after

Ken Noyes was our tour guide around the plant. He explained all the workings of the plant and how it keeps chemicals and waste from entering the river. We started by learning about the effects of humans on rivers before there was any cleaning going on. The Nashua River was a great example of how awful people treated the river. A textile company would dump their waste into the Nashua River leaving it whatever color they used that day. After Wastewater Treatment Plants the river was always clean and was rid of most pollutants.

In order to ensure that everything at the plant is running smoothly there is a computer program that constantly runs. This computer program known as the SCADA system monitors water levels, pH, and other things in the water as well as alerts the workers when something goes wrong or is going to go wrong. This system of having computers is extremely helpful to the workers at the plant because it reduces the time they have to be out checking the pumps and making sure nothing has gone wrong. "The plant receives about 6 million gallons a day, it is designed to handle 11.5 million gallons a day" said Artie. In the spring when the snow on the mountains melt the plant does receive its maximum capacity very often.

Primary Treatment

Primary Clarifier water very brown

According to Ken Noyes, "Primary treatment removes 30-75% of waste in the water." Water waste includes, suspendable solids, floating solids, and dissolvable solids. The primary clarifiers remove floating and suspendable solids in the water, as well as greases and other things that may be present. This is a main step in cleaning the water because the removal of these solids prevents eutrophication. Eutrophication is bad because it increases turbidity, lowering the amount of sunlight and oxygen at lower depths. Eutrophication kills many species because they cannot survive with lower oxygen and sunlight levels. This area is very important because it removes much of the substances that cause eutrophication. The way this area works is there is  an extremely large metal fan that sweeps the bottom of this million gallon basin. All the solids that have floated down are pushed by this fan into a hole in the center of the basin, removing the solids from the water. At the top of the basin there is another fan-like piece of equipment that travels along the surface of the water. This removes the greases that sit on top of the water.

Secondary Treatment

Secondary Treatment

 Secondary Treatment is when the water travels to smaller basins and is cleaned using microorganisms. This process is called "Activated Sludge."  The water is moved to a smaller basin where microorganisms are put in it to eat the remaining waste in the water. Ecoli is a main organism used to clean the dissolved solids from the water. The process of using these organisms is very helpful because they get rid of all the things you cannot see in the water or feel in the water. The dissolved solids pose a large problem but with the help of these microorganisms they are cleaned up very quickly.  The bubbles you see in the picture is oxygen being pumped into the water where the organisms are. This keeps them alive and thriving so they can eat as much as possible.  The problem posed by having microorganisms in the water is that there cannot be to few, because then they would not get rid of as much dissolved waste as they should, and there cannot be too many, this would cause eutrophication. This problem is know as the "Mass to Food Ratio." The workers know how many microorganisms are needed to clean certain levels of waste in the water, so they use this Mass to Food Ratio to determine if there are too many organisms or not enough. Keeping a stable ratio keeps the water as clean as possible and the microorganisms satisfied.

Secondary Clarifier

Secondary Clarifier

The Secondary clarifier is the same thing as the primary clarifier, the difference is that the secondary comes after the secondary treatment. This process pumps 3000-3300 gallons per minute. The secondary clarifier is an insurance that all of the harmful solids are out of the water. Notice how clean the water already looks compared to past photographs. This process uses the same fan at the bottom of the basin to collect solids and the skimmer on top to remove greases. The water in it all comes from the secondary treatment where it was cleaned with micro organisms. These organisms are still present in the water making it unsafe to drink or interact with. The water is much cleaner when it comes to dissolvable, suspendable, and floating solids. These are not the problem anymore. The amount of microorganisms in the water is very high and if released back into the environment they would pose a large problem to the ecosystem. This makes it necessary for the water to go through one last stage before re-entering the river.


Disinfection

The disinfection process is extremely important. When the water passes through the final stage of clarifying it is free of 95% of solids but is riddled with microorganisms. To fix this problem the water runs through a shaft that has UV lights which kill microorganisms in .03 seconds of exposure making it the most efficient way of getting rid of them. This process ensures that the harmful organisms do not go into the waterway and hurt the surrounding environment. At times these aeration tanks will have too much water running through them, this leads to the excess water being moved through an alternate pipe to a basin where the water is disinfected using chlorine tablets. This process is less efficient and is only used when there is too much water for the UV aeration area to handle.

Solid Disposal
After the solids are taken from the primary and secondary clarifiers, they are transported to a tank roughly 29 feet deep. In this tank there are "acid farmers." These microorganisms eat the solid waste and reduce solids by 55-70%. The remaining water is moved to a centrifuge where the remaining solids are separated and taken away.

Lab Analysis
Inside there is a lab that runs tests on the water that leaves the plant. In the lab they test for things that were in the water when it came to the plant, as well as things it may have left with that was introduced by the plant. The main tests run are for Ecoli, Chlorine, and pH. Other tests are also run but these three things are the main parts of the water the plant is worried about.

Conclusion
This trip was extremely fun, although it smelled awful at the plant. It was cold but the material was interesting and the tour guides engaging. I was especially surprised by the thought of everything that goes down a drain ends up at one of these plants. That means that every shower, flush, brushed teeth, dishes, and much more all travel to get cleaned at a place like this. The amount of water that goes through each day is insane. It really puts into perspective my water usage on a daily basis. I am now extremely aware of how I use water throughout the day.