The current facility was constructed in 1986, and upgraded in 1998 to provide biological phosphorous removal, and in 1999 to construct auto-thermal aerobic digesters, and revise the preliminary treatment building. The upgrade was completed in January 2000. The facility is designed to clean 1.8 million gallons of wastewater per day, and remove 7,950 pounds of Biochemical Oxygen Demand (BOD) per day, 9,820 pounds of suspended solids per day, and 120 pounds of phosphorus per day.
The wastewater entering the treatment facility is a grayish brown mixture of the original clean water, and all the pollutants picked up from various sources. The wastewater has a slightly musty, stale odor, which is not strong or overpowering. This picture shows a sample of the wastewater entering the facility.
Wastewater flows through the 36-inch interceptor sewer to the Facility. Septage haulers discharge septage into a manhole located about 500 feet upstream of the preliminary treatment building. Septage is mixed with the incoming wastewater and carried into the facility. Leachate from the Portage County and other surrounding permitted county landfills, is accepted at the Facility in a 15,000 gallons receiving tank. Septage, holding tank waste, and other commercial hauled in wastes are also accepted after first analyzing and undergoing necessary discharge permitting. The receiving station has telemetry to monitor discharge volumes of hauled in wastes and automatically discharges it into the 36-inch sewer about 50 feet upstream of the preliminary treatment building.
The first step of the cleaning process takes place when the wastewater enters the preliminary treatment building and flows through a fine screen. The fine screen removes all the large debris from the wastewater stream. The screenings are cleaned, compacted, and placed in a dumpster, and disposed at the landfill.
The wastewater flows through a grit removal system. Sand and other heavy inorganic materials are removed, cleaned, drained, and deposited in a dumpster. The wastewater then flows through a 12 inch parshall flume with an ultrasonic measuring device for flow measurement. The wastewater falls into a wet well and is pumped to the oxidation ditch by a combination of five submersible influent pumps. A composite sampler collects samples of the influent.
The heart of the treatment facility is the oxidation ditch. The organic and suspended materials are removed from the water by a process as simple as nature itself. Bacteria common to and river, lake, or pond, are the tools that clean up the water. The treatment facility is essentially a large reactor designed to maintain the proper conditions for the bacteria to live and work.
The bacteria use organic material as a food source. The oxidation ditch provides oxygen to keep then alive, and continually mixes the bacterial and the wastewater so the bacteria can find and absorb the food they need. Nutrients, such as phosphorus and nitrogen, are also removed when proper conditions are present in the process.
This whole process is completed in a matter of several hours. At the end of the process, the organic and suspended matter has become part of the bacteria cells. The next step is to separate the bacteria and the water. Separation occurs in the clarifiers.
Conditions in oxidation ditch are controlled by a sophisticated computerized monitoring and control system to provide the proper environment for biological phosphorus removal to take place. A chemical feed system was constructed during the 2000 upgrade, to provide chemical phosphorus removal capability as a backup to the biological system.
Clarifiers are large tanks that provide quiescent conditions. The bacteria are slightly heavier than water, and will settle to the bottom, given enough time and quiet conditions. A concentrated bacteria/water mixture is pump from the bottom of the clarifiers, and returned to the oxidation ditch, and the cycle starts all over again.
Cleaned water from both clarifiers is mixed in the effluent collection well. Samples of the effluent are taken from this well by 24 hour composite sampler. Water flows from the collection well to the disinfection system.
The disinfection system is operated from May 1 to September 30. During this period the water enters a specifically designed chamber that houses 48 UV emitting bulbs that radiate a specific wavelength of UV light that disinfects the majority of the effluent that flows in between them. The disinfected effluent then flows over a weir at the end of the treatment tank and through about 1,300 feet of underground piping to the river outfall. Treated effluent is discharged to the Wisconsin River.
The process provides optimum growth conditions for the bacteria, and there is an ample food source in the wastewater. The bacteria grow and reproduce in the system. The most efficient removal is obtained at a certain balance between the bacteria in the system and the amount of food entering the process. As the bacteria grow and reproduce, a portion of the bacteria must be removed on a regular basis. Excess bacterial solids or
biosolids generated by the process are diverted from the RAS piping into an aerated storage tank. The biosolids from the storage tank is fed to a gravity belt thickener where 94% to 96% of the water is removed. Thickened biosolids is discharged into the auto-thermal aerobic digesters.
The biosolids entering the digesters is quite active, viable, and have a high proportion of organic material incorporated into its cell mass. The biosolids in this state are unstable and could create strong odors, attract flies, and be generally undesirable. The biosolids are treated further to reduce their organic content in digesters. The digesters stabilize the biosolids by blowing air through the mixture, and raising the temperature to about 110 degrees Fahrenheit. The biosolids are held under these conditions for 30 to 70 days. At the end of this process, the biosolids have a relatively low organic content and will not cause odors, attract flies, and etc.
These digesters consist of three tanks, each having floor mounted fine bubble aeration diffusers and a propeller mixer. The blowers, pictured here pump air through the mixture. Biosolids flow through the digesters in a plug flow mode. Biosolids exit the auto-thermal digesters and flows to a pre-existing aerobic digester.
Digested biosolids are pumped to a dewatering Screw Press. This machine drains and squeezes additional water from the biosolids. Polymer and ferric chloride is injected into the biosolids to help release additional water. The biosolids is discharged in cake form at about 17% solids content. The cake solids are transported by a conveyor to a covered storage pad and stored until the biosolids are applied to agricultural land in spring and fall.
While the biosolids are organically stable, they do supply generous amounts of nitrogen and phosphorus. These, of course, are two of the main constituents of commercial fertilizer. The treated biosolids are applied to agricultural land, and serve as a fertilizer and soil conditioner. The high amounts of organic matter in the biosolids are especially attractive in areas with sandy soils, to help build the soil organic levels.
Samples of the wastewater coming into and leaving the treatment facility are taken and tested daily. The data is used to monitor the amount of pollutants coming into the treatment facility, the conditions and performance of the processes, and the quality of the water leaving the facility. Some of this data is reported monthly to DNR to verify compliance with requirements. The rest is used in the day to day operation of the facility.
The Wastewater Utility operates 24 hours per day, 365 days per year. Wastewater never takes a holiday.
The staff of 6 is responsible for operation, maintenance, lab work, record keeping, and administration, as well as, operation and maintenance of the collection system, industrial monitoring, working with new industrial dischargers, meeting regulatory requirements, answering alarms, marking locate requests, monitoring construction, and other associated duties.
Cleaning the water, the Village is a major undertaking, not only in the effort, but also the cost. As higher and higher levels of clean water are demanded, the efforts and cost will increase. The Plover Wastewater Utility is well situated to meet those demands.
Challenges that the Wastewater Utility faces, that the public can assist in as preventative maintenance in the collection system:
- Be mindful of what gets sent down drains, toilets, or other means of entry to the sanitary sewer system. Rags, personal hygiene products, or other hard and solid objects pose the risk to plug or bind up in pumps that serve the residential areas. If the pumping rate is compromised or stopped, there is the potential of sewage backing up into neighborhoods, not just individual residences. Educating the households is one of the best way to help in preventative measures of such backups.
- Needles and other sharps should be disposed of properly in collection containers and never into the Sanitary sewer system. Not only do they add to the potential plugging of pumping equipment, they also pose a hazard the Wastewater Utility employees as wastewater contains a wide array of potentially infectious materials.
If you want more information on the Plover Wastewater Utility, please call the Manager at 715-345-5259. Tours are available, but arrangements must be made in advance.