WASTEWATER TREATMENT FACILITY
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 lb. of BOD(Biochemical Oxygen Demand) per day,
9,820 lb. of suspended solids per day, and 120 lb. of phosphorus
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
Wastewater flows through
the 36-inch interceptor sewer to the Facility. Septage haulers
discharge septage into a manhole located about 500 ft. 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.
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.
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.
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 1300 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 F. 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.
There are a few of the 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.