Aerial view of the Warren, Maine lagoon system. Photo courtesy of Woodard and Curran.

Lagoon Systems In Maine 

Systems In Maine

An Informational Resource for
Operators of Lagoon Systems

Mars Hill Wastewater Lagoon System - Mars Hill  Maine. Photo Courtesy of Wright-Pierce Engineers.
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2003 Maine Wastewater Salary Survey as conducted by the Maine Wastewater Control Association

2003 Maine Wastewater Rate Survey conducted by the Maine Rural Water Association

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Penobscot Watershed and Development of a TMDL 

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Biosolids Technology

Sludge Removal 
and Biosolids Utilization

   The Millinocket Wastewater Treatment Facility utilizes 3 aerated lagoons for the treatment of the Town's wastewater. As biomass accumulates, the mass settles to the bottom of the lagoon creating a layer of sludge. This layer of sludge is monitored periodically for depth. While this layer is accumulating, the solids are undergoing aerobic and anaerobic digestion to the point where only inert solids remain. This sludge is digested continuously for a period of 3 to 7 years depending on the rate of accumulation.

    The sludge and water are then removed from the lagoon by vacuuming and / or pumping it to the onsite sand drying bed. The sludge remains on the drying bed for a period of 2 to 3 years. This sludge dries to a solids content of between 60 to 80 percent.

aerated lagoons

    click graph for larger size

Sludge removal at the Millinocket Wastewater Treatment Facility has occurred 7 times in the plant's 22-year history. Most recently, Lagoon #2 was dewatered in the summer of 1999 and removal operations commenced. The determination was made to remove the accumulated biomass in Lagoon #2 in 1999 after the three-facultative lagoons had been sampled for blanket depth.

Sludge Removal From Lagoon #2
Summer of 1999

aerated lagoons

    The lagoon was taken out of the normal sequence of operation on April 26th. Influent flow was routed from Lagoon #1 to Lagoon #3. Several airlines remained on to allow the bacteria to utilize any organics, which may have been left in the lagoon as well as to continue the aerobic process. Dissolved Oxygen residuals were monitored and used as an indicator to ensure the remaining organics were consumed.

aerated lagoons

    The dewatering process of Lagoon #2 began on July 12th. A Gorman Rupp gasoline Ford pump with a 6 inch suction and discharge was utilized to pump the wastewater back into Lagoon #1. This also provided for further treatment of the water. The pump was operated between 10 to 12 hours per day. It was noticed that the sludge was being drawn out of the lagoon so pumping was halted on July 25th with approximately 1 foot of water left in the lagoon. Costs for fuel for the pump was approximately $700.00 for 897 gallons.

aerated lagoons

aerated lagoons
On August 2nd Walker Industrial Services arrived on site to begin the sludge removal process. A two-man crew, pump operator and small tractor operator, worked removing the material from the 625 foot long by 325 wide lagoon from sun up to sun down, approximately 14 hours per day. The sludge was pumped (6 inch discharge piping) at an average of 1,100 gallons per minute to the on site sand drying bed. The pump has the capability of 2,000 gpm on shorter discharge runs.

aerated lagoons

On August 6th, the project was 95% complete and the sludge pumping process was halted. Sludge remained behind the effluent baffle chamber of the lagoon at this time. The pumping distance at this end of the lagoon was in excess of 750 feet and the efficiency of the hydraulically powered pump was drastically reduced at this distance.

     The material left was removed several days later by utilizing a high powered vacuum truck provided by the contractor. The truck, with an 8-inch suction line capability, drew the sludge out then transported the material to the sand drying bed for off loading. This particular truck, manufactured by Guzzler and sold at a cost of around $200,000, can vacuum sludges from as far as 1,000 feet away. Thirteen loads of sludge were removed from behind this area.

aerated lagoons

     The sludge resides on the beds for a period of 2 to 3 years in which the air-drying process, a Class B pathogen reduction process, occurs.

aerated lagoons     After drying and the appropriate analysis performed to comply with state and federal regulations, the sludge is removed from the surface of the drying bed and piled into one spot, thus still remaining on the bed. After calculating the agronomic rate, the applicable amounts of sludge is loaded onto a dump truck with a G.I. sander body. The sludge is then transported to the Municipal Airport (approximately 1/2 mile away) for spreading on the safety strips of the east-west runway.

     Once the agronomic rate is met on the 21-acre land spread site, spreading is halted. The remaining unspread sludge remains on the drying bed, continually undergoing the air drying treatment process, until it can be utilized during the next spreading season. Allowing the sludge to remain on the drying bed eliminates the need for storage accommodations.

     The treated biosolids are used as a soil and fertilizer amendment on the safety strips of the east-west runway. The limiting factor for biosolids spreading is nitrogen content. Grasses, lichens, and some mosses grow naturally on the safety strips.

     Because the site is regulated by the municipal airport, access to the spread area can easily be restricted to public contact for 30 days after the application of stabilized biosolids.




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