New London council reviews costs, options
By John Faucher
On Monday, Aug. 3, the New London Board of Public Works Committee approved two options for consideration in the 2015 Wastewater Treatment Plant Master Plan.
The board needed to approve one or more options for budgeting purposes in anticipation of a future WWTP rate study.
Plant Operator Ben Gruel provided a brief overview of issues they commonly deal with at the plant.
He said many of the structures in the plant are approaching the 30 year-old mark and there are numerous problems resulting from age.
Over the past several months, Gruel has informed board members of the plant’s under-utilized capacity and decreased flows.
“This creates problems with loading, and results in poor treatment efficiencies and higher maintenance costs,” said Gruel.
Other WWTP priorities taken into account in the master plan include addressing future energy needs and savings, digester upgrades, and use of biological phosphorus removal instead of chemical addition.
Eric Lynne from Donohue and Associates said now is the ideal time to consider beneficial changes to the WWTP unit processes.
Lynne presented four alternate options for a plant upgrade. He gave the total cost estimates for each option and highlighted the advantages and disadvantages.
The first option would keep things as status quo, with replacement of equipment in-kind. Lynne said the positives with this alternative would be lower construction costs, and maintaining excess capacity for growth. Negatives include higher costs for maintenance with 20 plus year-old technology and processes, with higher operating costs and limited flexibility for future nutrient limits.
Factoring in the capital cost, Lynne estimated the cost of is option at $8,780,000.
The second option would maintain optimal capacity, abandon the rock trickling filter and improve other units to optimize the plant.
Positives include low cost construction, retention of a robust system and some excess capacity for growth, with some reduction in operations and maintenance costs. The negatives of mixing 20 year-old technology and some modern technology in this option included still having a limited turndown and higher operating costs, and limited flexibility for future nutrient limits.
The estimated cost of this option is $8.71 million.
The third option would minimize annual costs with nitrification. It would abandon trickling filters, construct additional activated sludge and bio-phosphorus and improve other units to optimize.
Lynne said positives include that the plant would be sized more appropriately to fit the city’s needs, lower operating costs, exceed permit requirements and is amendable to total phosphorus and total nitrate permit limits.
The cost of this option is $10.62 million.
The fourth option would minimize annual costs without nitrification, abandon trickling filters, add bio-phosphorus to existing activated sludge and improve other units to optimize.
Lynne said positives include that the plant would be sized to fit the city’s needs, lower operating costs and made it amenable to future total phosphorus permit limits.
Negatives include higher cost construction, and it could require expansion to comply with a possible permit change for future ammonia removal.
The cost of this option is estimated at $9.06 million
In considering the four alternatives, Lynne encouraged the board look into the future.
“You want to get to the solution that takes you into the next 20 years,” he said.
Board members discussed the pros and cons of each option. They asked Gruel which plant he thought best suited the city in the long term.
He told them the third option would be the preferred system or plant of choice.
Committee members further discussed that the need to choose an alternative at this time was simply for future budget purposes involving the rate study.
Alderman Denis Herter made a motion that they approve the third option, with the fourth option as a possible substitute. The motion carried unanimously.