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Water & Wastewater
Wastewater Treatment Process
The Wastewater Treatment Plant (WWTP) is designed to treat an average daily flow of 6 million gallons per day and a peak flow of 12 million gallons per day.
Preliminary treatment consists of metering and physical means. If these materials are not removed, they can interfere with downstream processes. Influent metering is used for process control and monitoring. Preliminary treatment process:
A screen removes coarse materials such as paper, tree roots, plastics, and stringy material.
Flow then travels to the aerated grit and grease-removal chamber, where grit settles to the bottom and grease rises to the top to be removed.
The screenings, grit, and grease are further de-watered and sent to a landfill for environmentally-safe disposal.
The added air helps to separate grit from organic materials and freshens the raw wastewater for treatment in the secondary treatment process.
This stage uses microbes to consume wastes remaining in the water:
Air is added to the aeration tanks to support the growth of the microbes and mix them in with the wastes.
Flow then enters the clarifiers, where gravity separates the solid material containing the microbes from the treated water.
The settled solids are collected and pumped back to the beginning of the secondary process and mixed with raw sewage leaving the grit-removal chamber to start the process over again.
Clear water is sent to the disinfection process. At this point, 98% or more of pollutants have been removed from the wastewater.
Ultraviolet (UV) light is used to destroy pathogenic organisms. UV is safer for the environment and plant personnel than chemical means of disinfection. Flow is measured once again before running over a cascade that adds oxygen to the water before final discharge to the Little Miami River.
Some of the solids that settle in the clarifier are separated from the secondary process to maintain a viable population of microbes in the system. Solid-handling process:
These solids are pumped to aerobic digesters, where microbes continue to reduce the wastes and thicken the solids.
The thickened solids are then de-watered on the belt filter press.
The de-watered solids are disposed of in a landfill.
Treatment Effectiveness Testing
To measure treatment effectiveness, the National Pollution Discharge Elimination System (NPDES) requires regular testing of the wastewater as it enters and leaves the WWTP and in the river upstream and downstream of the discharge point.
Tests & Samples
The laboratory staff provide high-quality, legally-defensible, and timely environmental laboratory data. More than 2,100 samples are analyzed each year to determine compliance with the NPDES. In addition, 3,500 tests are performed each year to monitor and control the unit processes.
To ensure high quality, the Ohio Environmental Protection Agency (OEPA) requires an annual blind test. The OEPA knows the results of samples sent to the laboratory, but the lab employees do not. The samples are tested according to established methods, and the results are sent back to OEPA. OEPA then compares our results to the actual concentration in the sample. If the results of the lab are within a prescribed range, they are accepted by the OEPA, and the lab standards and methods are in accordance with professional practices.
The Lebanon WWTP laboratory has demonstrated full compliance with quality control / quality assurance by receiving Certification of Recognition in each of the 11 years that the blind tests have been required. Required testing includes wet testing, metals, organics, and microbiological. Due to cost of equipment and time required to perform some tests, they are sent to a contract lab. These include the metals and organics.
50 South Broadway Lebanon, OH 45036