Part two of Mike Barhorst’s recent column: In the secondary treatment process, the primary effluent enters an aeration basin. The aeration basins are responsible for the removal of the dissolved solids, suspended solids, and ammonia.
The flow then enters the secondary clarifiers where additional separation processes take place. The clean treated water flows through weirs near the surface of the final clarifier to the disinfection process.
The newly added disinfection process is referred to as ultraviolet (UV) disinfection. Unlike chemical approaches to water disinfection, UV provides rapid, effective inactivation of microorganisms through a physical process. When bacteria, viruses and protozoa are exposed to the germicidal wavelengths of UV light, they are rendered incapable of reproducing and infecting. UV light has demonstrated efficacy against pathogenic organisms, including those responsible for cholera, polio, typhoid, hepatitis and other bacterial, viral and parasitic diseases.
After the effluent passes through the UV process, it is called final effluent. The final effluent flows through a pipe where samples are periodically collected by the automatic sampler and where on-line monitors provide continuous monitoring of the pH, temperature and dissolved oxygen concentration within the effluent. When the final effluent surpasses OEPA standards for clean water, it is discharged into the Great Miami River.
The solids handling process is designed to provide treatment to the sludge that is generated in the treatment of sewage. The sludge that is removed from the primary clarifier is pumped to the anaerobic digester. The sludge is held in the digester for approximately 15 days for treatment to occur.
After the sludge has undergone treatment in the anaerobic digester it flows by gravity into the secondary digesters. The secondary digesters provide storage. The sludge that has undergone treatment and is now in storage is called biosolids. The biosolids are held in storage until it is dewatered in a centrifuge. The centrifuge removes the water and concentrates the solids.
Biosolids contain nitrogen, phosphorous, and material that makes it an excellent fertilizer. The city of Sidney’s Wastewater Treatment Plant operates a Biosolids Recycling Program that includes the land application of biosolids on area farm fields in some cases, eliminating the need for chemical fertilizers for crop growth.
The city of Sidney is fortunate to have a large and diverse industrial base. Because of the substantial amount of industry, the Ohio Environmental Protection Agency (OEPA) required the city of Sidney to develop and implement an Industrial Pretreatment Program in 1989. The purpose of the Industrial Pretreatment Program (IPP) is to protect the city’s sanitary sewer system, the Wastewater Treatment Plant’s processes and equipment, and the Great Miami River from potential harmful discharges of pollutants from industrial and commercial sources. This is accomplished by regulating and monitoring the discharges from industrial and commercial sources to ensure that it meets the limits established by the OEPA.
To ensure the city is properly treating the wastewater, the city has a laboratory at its treatment facility. The lab is staffed by a full-time chemist who analyzes samples from the system 600-800 times each month.
The staff at the Wastewater Treatment Plant is also responsible for monitoring stormwater. Stormwater is water that flows into the storm sewers following any precipitation event. As water moves over yards, streets, homes, driveways, etc., it picks up pollutants and carries them with it. Most runoff is directed to a storm drain that drains directly to the river or a stream.
Any pollutants, including chemicals applied to lawns, road salt, motor oil spilled on driveways, gasoline spilled when filling a gas tank, etc., will be carried to the river potentially harming wildlife and possible drinking water sources. In 1987, Congress amended the Clean Water Act to require the USEPA to establish requirements for storm water discharges.
The city’s Stormwater Management Plan outlines the measures taken to improve the water quality entering the receiving water bodies, such as the Great Miami River. Fortunately, the steps taken must be working as OEPA has designated the river below the Wastewater Treatment Plant and “exceptional warm water habitat.”
Disinfection of wastewater to prevent waterborne disease is considered to be one of the great modern engineering achievements. Should you ever have questions about your wastewater system, don’t hesitate to contact Utilities Director Larry Broughton 937-498-8152 or Wastewater Plant Superintendent Barry Zerkle 937-498-8720.
The writer is the mayor of Sidney.