Water, the primary building block of life. We all need it and we all use it. Once we use it where does it go? What happens to the waste water?
The city's waste water treatment plant is the final stop for all of the sewage from the city, as well as septage from the county. Allen overseas the entire waste water treatment plant to make sure the plant operates effectively and efficiently. With nearly 18,000 city residents, and counting, all creating waste water every day, that adds up to a lot of water to treat.
Water Treatment Plant
This plant was built in 1984. At that time, it was designed for 2.88 million gallons per day. As of October last year, we expanded to 4.32 million gallons per day. Right now, we are treating approximately 2.55 million gallons a day. Waste water treatment is an important process, simply because it removes most of the pathogenic bacteria in water, basically acts like a giant water filter pitcher. Makes it clean to put back into the river, so that we can have water reused downstream. Downstream of us, I believe, the first place they would draw water out would be possibly in Grand Junction. Further down, we have Lake Powell, where they, where a lot of water recreation. It is important for us to clean the water.
Waste water entering into the plant is called influent. The head works building is the first stop for the incoming influent. First, the water enters the bar screen room. This chamber houses a giant screen, which screens out all of the trash from the influent. Although the bacteria and bio-solids in waste water will be digested and broken down during the treatment process, trash will not decay. It could serve as a safe haven for harmful bacteria to hide. All trash must be removed early in the process. This is the bar screen room, part of the head works building. A bar screen does run 24/7. We have that large plastic bag for the trash. The trash goes in there. It's de-watered and goes in there. A bag is to contain the odors. Once it is full, we seal it off. It is taken to the landfill.
After removing the large trash, the influent goes through grit removal. Grit is considered to be inorganic compounds, like sand, coffee grounds, eggshells and other things, which are not caught in the bar screen. These materials also disrupt the treatment process. This is the grit removal. What it is, is we have an aerated grit chamber. We aerate the grit, sorry the influence coming in. The grit settles and the organics flow on by. The grit is pumped up to here, into the grit classifier where it's de-watered and dumped into the garbage. We also haul that to the landfill.
After grit removal, the water is almost ready to leave the head works building. This right here is the end of the head works building. This is where we measure the influence load coming into the plant. Measuring the flow of the waste water helps the crews stay on top of the treatment process. For efficiency, the plant is running with only a portion of the machinery working. If the waste water flow rises above the normal capacity, the crew can activate more machinery, in order to accommodate the increase in influent.
Waste water came from the head works building. Comes into here, to the screw pump. These screw pumps are large augers. They lift the waste water from down here, drop it up there. From there it sits and goes to any of the 3 oxidation ditches. The screw pumps are the central processing hub of the treatment plant. Many liquids and bio-solids will return here again and again, in order to be fully processed and treated. From the screw pumps, the waste water goes into the oxidation ditches. We have 3 of them. Currently, we have 2 operating. In the oxidation ditches, we have 3 rotors. Rotors aerate the water, makes it into an aerobic process. What we use is aerobic bacteria. All we're really doing is creating an environment for them, to make them happy. They feed on the incoming pathogen bacteria.
The oxidation ditches are the first step in the chemical and biological breakdown of the bacteria in the bio-solids and the water. From here, the influent is sent to giant tanks, called clarifiers.These are the clarifiers. We have 3 of them. The clarifiers, the over flow from the oxidation ditches go into the clarifier. They go into the center trough. They are, the water is spread out and hits the baffles. The sludge settles to the bottom. The bottom of the clarifier is roughly 15 feet. It's a conical shaped bottom. We have scrapers along the bottom that continually scrape the settled sludge into a hopper. The clarifier is a pivotal point in the process. The suspended bio-solids, called liquid sludge, begin separating from the clarified water. At this point, the water is ready for final treatment. The sludge must be retreated over and over again, in order to fully oxidize the solids, and remove as many harmful microbes as possible.
From the clarifier, the sludge will most likely end up back in the screw pumps, to be redistributed into the oxidation ditches again, only to wind up back in the clarifier. This cycle is called the activated sludge process, and is often repeated many times, over the course of several days. Who says when the sludge is ready to move on? These are the settle-ometers. I do them twice a week. They tell us how fast our sludge is settling in the ditch.
The results will determine where the sludge will go next, depending on how well the sludge separates from the water. Once the sludge thickens enough, like the beaker on the right, the crew will know that it's time to pull the sludge out of this activated sludge cycle, and send it to the digester building. This is the next step in its treatment. This process is called wasting. Behind me is our digester building. Behind the concrete, we have 4 cells. The cells are aerated by 3 100 horsepower blowers. Only 1 of which is running. It usually runs 24 hours a day. She helps with the nitrogen cycle. It also helps raise the PH a little bit, back up to 7. In the digester process, the PH does drop sometimes, to right around 6. Anyone can test water in your home. You can buy a water test kit. Check out some reviews online before purchasing a kit. We personally recommend http://www.bestconsumerreviews.com.
The digester literally digests and breaks down as much of the remaining pathogenic bacteria as possible, in order to prepare the sludge for its final treatment, the centrifuge. In the centrifuge room, powerful machines spin the liquid sludge. With the aid of chemical polymers, much of the remaining water is removed from the bio-solids. This creates a dry sludge, as well as a liquid by-product called centrate. The newly dried sludge then travels up a conveyor, into a truck to be shipped to a composting facility in Delta. The centrate is returned back to the screw pumps, to go through the whole process again, so that the water can be treated and released. What happens to the actual water in this process?
To answer that, we have to revisit the clarifiers. Because the sludge settles to the bottom of the clarifiers, the water on top is clear of any suspended solids. That means there's no where for the surviving bacteria to hide. The water must undergo one final purification process, before it is ready to be released into the Uncompahgre River. That process is the UV chamber. Inside this building is our ultra-violet disinfection. We have 2 channels. We have 4 banks in each channel. It is flow paced, so that when the flow comes up, more banks of lights do come on. When a flow drops down, they do go off. UV light kills bacteria by destroying its DNA. By doing that, the bacteria cannot reproduce and so, it cannot do any further harm. The purified water, called effluent, is then released into the outflow pond.
In this effluent pond, when the river was higher years ago, and against this bank, we used to have come up into this pond and live. They lived here year round. One final sample is taken from this outflow pond, to insure the water quality of the effluent going into the river. This test compares this water, to the influent, coming into the plant, at the very beginning of the process. We have about 99% removal, which means, when you look at the influent coming in, and how dirty it was, compared to the effluent, and what's going out. We've removed 99% of everything that was in that water. From the outflow pond, the purified water is released into the Uncompahgre River, so that other people, plants and animals can use it downstream. The waste water treatment plant offers tours to anyone who is interested.