WMSR Radio has been receiving complaints recently about a terrible odor and wondering if anything was wrong at the Manchester wastewater treatment plant.
Paul Coston, chief operator at the Wastewater Treatment Plant says that the cause of odor is the lack of dissolved oxygen in the wastewater. Wastewater entering the plant only has an average of 2 to 3 parts per million. Oxygen is added in the biological reactor (oxidation ditch) as well as in the bio-solids digesters to support microscopic biological life. The water leaving the treatment plant (effluent) must have minimum dissolved oxygen reading 6 parts per million in order to support aquatic life in the receiving stream.
Left over ammonia from the treatment process is removed in the bio-solids to the digesters where it becomes concentrated. When the ammonia loading levels rise in the digesters above the treatment capability of the microscopic organism, odor occurs.
There are only a couple treatment methods to help combat odor. The odor can be treated chemically with the addition of costly chemicals and chemical feed systems to the bio-solids digesters or by spraying some type of re-odorant. Also, odor can be treated biologically with the right combination of dissolved oxygen and mixing. Manchester has been utilizing the second method for years with minimal odors being produced and it wasn’t until recently while trying new operating methods that the odor became more noticeable. Coston says they have changed their oxygen feed rate timing to help combat the odor and the plant has become much less odorous within the last two weeks.
The U. S. E.P.A. through the State of Tennessee Department of Environment and Conservation regulates all aspects of Sewage Treatment and Bio-solids disposal. The City of Manchester Sewage Treatment Plant currently is in compliance with the National Pollution Discharge Elimination Permit and State of Tennessee Bio-Solids Permit.