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Treatment System Description

In 1997 it was decided to begin preliminary design preparations for the replacement of a Waldoboro wastewater treatment plant that was 50 years old and had outgrown its usefulness. The aging plant located below Friendship Street in Waldoboro was expensive to operate and presented serious environmental concerns to the Medomak River. Because the River had a very high value as a shellfish producing area, the best way was to enlarge and protect the shellfish harvest was to eliminate the discharge from the plant. Land application of Waldoboro’s effluent, similar to the Thomaston Pollution Control Facility which benefited the St. George River, was an acceptable alternative to the Maine Department Of Environmental Protection and a good long term solution for Waldoboro, Maine

Trustees of the Waldoboro Utility District convinced voters of what had been apparent to them for years. The treatment plant needed to be replaced with a modern aerated lagoon system which was to be located on 2 parcels of land off of Route 235.

For years downtown residents had complained about odors from the existing plant which had chemically treated and discharged its effluent to the Medomak River.

Normally the treatment facility had handled the average 100,000 gallons of sewage generated in the town daily and had safely treated it before discharge to the river. The plant was labor intensive and requires constant management to biologically digest and chemically balance the effluent returned to the Medomak River.

One of the major differences of the lagoon system and the old plant was detention time. The old facility only had the capacity to hold sewage for 8 hours as compared to the new lagoon system which has holding times as long as 4 to 6 months before its effluent needs to be land applied.

Savings realized from the new facility showed chemical costs go from $8,000 annually to zero, labor requirements from $60,000 to $20,000 and sludge removal costs from $36,000 to $6,000.

Funds Available for the Construction of the New Lagoon Facility

The Waldoboro Utility District received Grants and Loans totaling $5.2 million dollars to build the new treatment facility at a location away from the Medomak River. A grant of 3.2 million dollars was available thru the Maine Department of Environmental Protection came thru an $8.0 million dollar bond issue in 1996. Waldoboro’s share was high because its median household income is low at only $17,083 per year. It is a DEP policy that sewer users pay no more than 2% of the median household income in sewer rates.

An additional 2.0 million dollars came from the US Department of Agriculture, Rural Development Program in the form of a 1.0 million dollar grant and a $1.0 million dollar loan.
 

There were no tax monies involved in the financing and all costs will be paid back by the users of the sewer system.
 

New Treatment Plant Design

A sewer collector system covers most of the village area transports the wastewater to the Main Pump Station just off Main Street near the river. This station provides screening prior to pumping it to the Railroad Pump Station located between Route 220 and Route One next to the railroad. From here the wastewater is pumped thru a force main to the treatment facility. The Waldoboro Wastewater Treatment Facility provides secondary treatment thru aerated facultative lagoons. Treated effluent may be spray irrigated from April 15th to November 15th and is stored during the remaining periods of the year (November 16th to April 14th.

The treatment facility consists of two aerated lagoons, a storage lagoon, inlet and outlet structures, mechanical building and spray fields.

Process Description

The wastewater received at the treatment facility is pumped from the Railroad and Main Pump Stations after passing through the mechanical bar screen and into the wet wells. The volume is measured as it is and then pumped to the lagoons for aeration, biological oxidation and sedimentation. The wastewater enters Lagoon No. 1 through a diffuser pipe that distributes the flow across the lagoon.

Lagoon aeration is through a diffused air system that is tapered to match the oxygen demand. Most of the aeration capacity is provided in Lagoon No. 1 with most of the aeration at the inlet end because of the high organic loads of the wastewater.

Aeration tapering is accomplished through the use of larger aeration tubes at the inlet end of Lagoon No. 1 and by changing the spacing between the air laterals and aerators. The aerators are close together at the inlet end of the Lagoon No. 2.

Following treatment, the wastewater passes from Lagoon No. 2 to the storage lagoon where it can be land applied in season or it can be stored. During the period of land application the treated wastewater is pumped from the storage lagoon and spray irrigated with a line shaft centrifugal pump and fixed sprinkler system. During non-discharge periods the effluent is stored in the storage lagoon.

An effluent magnetic flow meter, with readout and totalizer are located inside the mechanical building. The flow meter measures the discharge to the spray fields. The spray irrigation rate is recorded to maintain discharge records. The discharge rate will vary depending on which field is being used. The pumping rate should be determined for each field anytime conditions change. Under normal conditions one filed is sprayed at a time.

Irrigation System Pumps

Lagoon Specifications


 

System Information

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