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Biosolids land application information/summary
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Biosolids land application information/summary
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INTRODUCTION
The Lucas County Commissioners own and operate the Maumee River Wastewater Treatment Plant (MRWWTP) located at 5758 North River Road in Waterville, Ohio. The facility is a 22.5 million gallon per day activated sludge treatment plant that currently serves a major portion of the County’s population west of the City of Toledo including the City of Maumee, the City of Sylvania, the Village of Holland, the Village of Waterville, the Village of Whitehouse, and several surrounding Townships, as well as a small portion of Wood County.
The MRWWTP currently produces approximately 50,000 gallons sewage sludge per day. The facility uses anaerobic digestion to condition the sludge to meet Class B pathogen and vector attraction reduction requirements. After anaerobic digestion, the sludge is dewatered in a belt filter press to remove water and thus reduce volume.
PROCESS
Wastewater entering the MRWWTP undergoes screening and grit removal to separate floatable and heavy settleable solids from the influent. After this preliminary treatment, the screened and de-gritted wastewater is pumped to the primary clarification tanks. In primary clarification, the influent wastewater mixes with wasted activated sludge from the secondary treatment process where the combined solids are allowed to settle to the bottom of the tanks and floatable materials are allowed to accumulate on their surface. These primary settling tanks remove approximately 95% of the settleable solids and 50% of the organic pollutant loading entering them. The settled solids are pumped from the primary settling tanks to the anaerobic digesters for further treatment. Floatable sludge and scum are skimmed off of the top of the primary tank and then are pumped to the anaerobic digesters for further treatment.
The anaerobic digesters consist of 3.3 million gallons of heated (35oC) and mixed storage, which provides primary digestion, with an additional 1.0 million gallons of unheated, unmixed secondary digestion treatment. The digesters provide in excess of 50 days of primary digestion with an additional 20 days of secondary digestion.
Following the digestion process, the resulting biological sludge is dewatered in a belt filter press to increase the dry solids content from approximately 3% to a range of 16-19%. This dewatered sludge cake is stockpiled at the MRWWTP on uncovered concrete storage pads until conditions are favorable for land application. Leachate and runoff from these storage pads is collected and returned to the influent of the plant for treatment.
LAND APPLICATION
The MRWWTP utilizes an independent contractor for the transport and land application of its biosolids product. Synagro Central LLC is the current contractor under agreement with Lucas County Commissioners for biosolids management. The MRWWTP’s biosolids contractor is responsible for securing the necessary application sites and for executing any written biosolids spreading agreement with the landowner. Presently, the MRWWTP is permitted by the Ohio EPA to land apply its biosolids in Fulton, Henry, Lucas Ottawa, Sandusky, Williams and Wood Counties.
As a Class B biosolids material, sites that receive MRWWTP biosolids are subject to several restrictions designed to reduce the likelihood of pathogen transfer from the biosolids to any type of corporeal being – either through direct contact or indirect association.
At the land application sites, the biosolids must be spread within 24-hours of being deposited at the site. A self-propelled or tractor pulled slinger type spreader is used to provide uniform distribution of the sludge. Application activities are conducted only during daylight hours. Regulations require that the biosolids are not applied within 300 feet of wells or springs, 100 feet of occupied buildings, or 33 feet of surface waters.
MONITORING & REPORTING
In addition to measuring the biosolids percent dry weight and percent volatile solids, the MRWWTP also measures the nutrient and metals concentrations of biosolids on a monthly basis. These results are electronically reported to the Ohio EPA with the MRWWTP’s Monthly Operating Report (MOR). The facility also sends an annual report to the Ohio EPA detailing the total quantity of biosolids produced at the plant, the monthly nutrient and metals sample analyses, and the results of the annual organics, metals, and pesticides sampling results.
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