Mount Katahdin as viewed from Daicey Pond in Baxter State Park

Maine Wastewater Control Association 
60 Community Drive, Augusta, ME 04330 
 

Wastewater Treatment Plant Profile

Milo Water District
Milo, Maine

Background

   It became apparent in the early 1990's that the town of Milo could no longer dispose of its untreated sewerage by allowing it to flow into the Piscataquis River. The Trustees of the Milo Water District began to seek alternative methods for disposal and acquired the engineering firm of A.E. Hodson to help seek out a feasible solution.

    It was determined that an aerated lagoon system would best serve the community’s needs and financial constraints. Also influencing the decision for the lagoon system was the availability of a parcel of land to accommodate the space requirements in the construction of a lagoon system.

  
   The Milo Pollution Control Facility is a 0.39 MGD aerated facultative lagoon system. It serves 661 residential, 49 commercial and 1 industrial user. The largest user is the Bangor and Aroostook Railroad which contributes an average of 14,000 cubic feet per month. This secondary treatment facility consists of  (1) 2.4 acre and (2) 1.2 acre lagoons with a total volume of 12 million gallons and a retention time of approximately 30 days. Average daily flow to the facility is 0.10 mgd with peak flow coming in occasionally at 0.9 mgd. The system was designed to meet EPA design criteria with BOD loading rates designed to be near the upper boundary of EPA rates in order to maximize solids deposition with an anaerobic decomposition of solids in lagoon #1. This allows lagoons #2 and #3 to act as a polishing step to obtain a quality effluent.

Treatment Features

   The treatment facility has a manually cleaned bar rack which intercepts influent before the lagoons. The surface aspirating aerators are manufactured by Eimco and the Propulsar models deliver 1.5 lbs. of oxygen per 1 horsepower per hour. Lagoon #1 has 8 surface aspirating aerators. Lagoon #2 and #3 each have 2 surface aspirating aerators.

    Operators monitored and experimented with different angles and pitches of the floating aerators.  The most effective angle was found to be at 45 degrees. This effectively forced the air and motion pattern from 3 feet  ( 33 degree pitch ) to 7 feet below the lagoons surface. Better mixing conditions were achieved throughout the lagoons. The facility’s aeration system is automated whereby the use of dissolved oxygen sensors and timers provide optimum dissolved oxygen levels.

   
   Some key operation features used by plant staff include 2 natural phenomenon’s – duckweed and daphnia. Duckweed nearly covers lagoon #2 and #3 to keep sunlight from entering thereby reducing algae blooms. Daphnia present in these lagoons consume the algae that does proliferate.

    Beneficial algae growth in Lagoon #1 is encouraged. The algae produces energy-free pure DO, up to 250 lbs. of O2 per day. Carbon is usually algae’s growth limiting nutrient in municipal ponds. Carbonic acid is created as a result of aerobic biomass respiration. High algae growth strips the CO2 from the carbonic acid, and then drains down the entire carbonate alkalinity buffering pool, ultimately raising pH and causing a shortage of carbon. As a result of the higher pH, large reductions in the ammonia nitrogen, and phosphorous take place.

    Effluent from lagoon #3 flows into the chlorine contact tank where it is disinfected with sodium hypochlorite and dechlorinated with sodium bisulfite. The finished effluent then flows to the Piscatiquis River.

Solids Treatment

    The proper utilization and disposal of sludge is one of the most critical issues facing wastewater treatment plants today. Soaring budgets, difficulties in site location, and the ever-changing nature of regulation combine to create new problems for our treatment plants. As with any lagoon system, the ponds will eventually need the sludge removed from them. Recognizing this fact, the district began seeking options for sludge treatment in the spring of 2001. One solution slowly gaining acceptance in Maine is the utilization of sludge reed beds. After reviewing several options, it was determined that a reed bed would best suit the facility given the availability of land buffering the treatment ponds. With Dirigo Engineering preparing the plans, in-house treatment plant staff constructed a 54’ x 80’ phragmite reed bed complete with an 80 mil pvc liner. A depth of 6 feet was maintained with 3:1 side slopes. The bed has 3 separately piped inlets so that the sludge can be flowed to different areas of the bed. Neighboring Guilford-Sangerville Sanitary District donated reeds from their reed bed to help get the Milo bed established. Once transplanted into the Milo bed, these reeds started out in size from between 8 to 18 inches high. With 30,000 gallons of sludge added during the summer, the reeds were 7 feet tall by fall! Total construction costs for the reed bed - $20,000.

Collection System

     The wastewater collection system for Milo consists of 11 miles of gravity sewer, 10,000 liner feet of forcemain, 200 manholes and ten pump stations. The collection system experiences high inflow and infiltration. The district undertakes a construction project annually to decrease I & I sources within the collection system. The district purchased a UEMSI predator Advantage mini mainline camera and has been proactive in seeking out and repairing various sources of I & I within the collection system.

      All of the pump stations are fitted with non-clog submersible pumps. The Main Pump Station on Riverside St pumps the sewerage down to Ferry Road where it flows to the plant via gravity. Standby generators (175 kw) provide emergency power at the Ferry Road and Riverside Street pump stations in the event of an emergency.

  
   The Riverside Street pump station, often referred to as the Main Pump Station, is a 12’ square by 24’ cast in place pump station. The station was originally equipped with ( 3 ) 60 horsepower submersible pumps capable of pumping 520 gpm each. District employees retrofitted the station by replacing one of the Peabody Barnes pumps with a 48 horsepower Flyght submersible. This actually increased pumping capacity to 800 gpm for the Flyght unit.

   The Ferry Road pump station is a 12’ square by 22’ cast in place pump station. It is equipped with ( 2 ) 25 horsepower pumps capable of pumping 880 gpm. The generator at this pump station also supplies stand by power for the treatment plant.

   The remaining small precast pump stations are provided emergency power utilizing a 30 kw trailer mounted generator.

Staff

The hard working and dedicated staff of the Milo Water District are the heart and soul of the municipality’s water and wastewater operations.

   District employees are encouraged to acquire the maximum amount of operator certifications possible and are financially compensated for each certification they earn.

Recognition

            The Maine Municipal Association honored the Milo Water District and its employees in December of 2000. The district was awarded the MMA’s leadership award for superior efforts in workplace safety during the year 2000 as demonstrated through the MMA Leader Program.

    The Maine Rural Water Association recognized the Milo Water District for Outstanding Operations in 1997.

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