Jay Wetherbee works for Veolia Water, which provides wastewater services for public authorities and industrial companies. Mr. Wetherbee is the assistant project manager at the Smithfield Wastewater Treatment Plant. He was initially at school studying a degree in business, but gained interest in wastewater treatment by a friend suggesting him to take one of the classes that deal with that field. Since then, he received several licenses and has been working at this specific plant for 20 years. Mr. Wetherbee is a plant operator, which works with the equipment that the engineers design.
Mr. Wetherbee started his lecture by handing out a piece of paper to each of the students that contain a flow diagram of a typical plant treatment process. There are three major stages: pretreatment, primary treatment, and secondary treatment. At every wastewater treatment plant, the influent flows into the plant with debris, raw sewage, and whatever else that has found its way into the pipe. The screening process is the first stage of pretreatment, which removes the large debris, like branches, soda cans, and trash. This step is very simple, but it is also extremely important, because what is left is small particles and water, which is a lot easier to clean and disinfect. The grit removal is the next step, and this will remove the sand, dirt, and gravel found in the influent. Every wastewater treatment plant needs to have a grit removal because without it, it can put a lot of stress on the remaining mechanical processes, thus creating a large financial investment for maintenance. Ironically, the plant that Mr. Wetherbee works for does not have a grit removal because the township tried to cut cost to save them money during the design/build of the wastewater treatment plant. Unfortunately, it is costing the town a low of money to maintain and fix the remaining machines that operate the plant, so cutting a corner actually has put a bigger burden on the town because the total cost has exceeded the total cost if the grit removal was implanted in the design/build at the very beginning.
Now the flow has reached the primary treatment stage, which settles out the sludge. The sludge is either sent to a landfill or burn in an incinerator. Secondary treatment is when the water goes into the aeration basins. This is where microorganisms thrive and need oxygen to live and feed of the bacteria that exist in the water. Activated sludge is the next step in secondary treatment, which removes suspended and dissolved solids. Once the water leaves the activated sludge tanks, it is disinfected, to kill pathogenic organisms that might still exist in the influent. There are two types of disinfection: sodium hypochlorite (cheaper) and ultra violet (more expensive but it is also better for disinfection). Once the water is disinfected, it can leave the plant to either be discharged into a local water source or enter another treatment process stage for further treatment. It is also important that the concentration of chlorine in the water is extremely low, because when it is discharged into the environment, the fish and other aquatic life will die if the concentration is higher than desired.