Jesup sewer plant options are detailedThe Jesup City Council is scheduled to decide to move forward on one of four options for revamping the city’s sewer plant. The decision may be made as early as next Monday, July 6, or it could wait until the council’s second July meeting on July 20. Council members are planning to tour facilities similar to some of the proposed options prior to making their decision.
Cost of the options will vary from around $9 million to more than $11 million, including both construction and operating costs for 20 years. The project must be completed by October 1, 2023 according to the schedule required by the Iowa Department of Natural Resources (IDNR).
The sewer plant upgrade is required by new rules and regulations through the IDNR.
Information detailing the four options was presented to the council at a special meeting June 18 by Alex Potter of McClure Engineering.
The current sewer system is an “aerated lagoon treatment system.” Required improvements include complete ammonia removal; E. coli bacterial removal and an Iowa Nutrient Reduction Strategy plan for total nitrogen and total phosphorous removal.
Option 1 is most similar to the current aerated lagoon system; it will include an aerated lagoon plus moving bed biofilm reactor with UV. It will use all four currently in-place lagoons plus a headworks building, two Parshall flumes, control building, blower building, MBBR treatment units, UV disinfection, chemical feed structure and an outfall structure.
Although option 1 is far and away the cheapest to construct – estimated at $6.18 million – it is also the most expensive to operate and maintain. 20-year operation and maintenance costs would be $5.16 million, making this option the most expensive of all with a total 20-year cost of $11.34 million.
The cost of each option is not the only factor brought into consideration by Potter during his presentation. He listed “pros” for option 1 as: lowest initial project cost; smallest footprint; maintains aerated lagoon treatment infrastructure; and requires a grade II operator. “Cons” were listed as: highest 20-year total cost; most expensive system to operate; requires heating to meet current effluent limits; and requires chemical addition to meet nutrient removal requirements.
This option is the most expensive to construct at $9.37 million; but its 20-year operations and maintenance costs are in-line with options 3 and 4 at $1.64 million. Total cost of this option over 20 years would be $11.01 million. This is an AeroMod Sequox, which is a continuous flow activated sludge system with UV. It would use 3 of the current 4 lagoons plus a headworks building, flow control structure, two Parshall flumes, a pump station, aeromod treatment system, blower building/control building/lab; UV disinfection and outfall structure. Two of the lagoons would be used for flow equalization; the third would be used to store up to ten years accumulation of sludge.
“Pros” for option 2 included: “package” activated sludge treatment sysem; aerated lagoons are repurposed; enhancing operator flexibility and control; proven process; biological nutrient removal. “Cons” included: highest project cost; highest cost of activated sludge options; produces sludge byproduct; limited expandability; and requires a grade III operator.
This option, a Fluidyne ISAM Sequencing Batch Reactor with UV, is slightly less costly to construct than option 2 at $8.86 million. Operation and maintenance cost is also slightly less at $1.59 million over 20 years, making the total 20-year cost of this option $10.44 million. This option would use all four lagoons, two for flow equalization, one for sludge storage, and the smallest lagoon for post-sequencing batch reactor equalization. It would require a headworks building, flow control structure, two Parshall flumes, a pump station, Sequencing Batch Reactor facility, blower/control/lab building, UV disinfection and an outfall structure.
“Pros” were listed as: enhanced operator flexibility and control; aerated lagoons are repurposed; proven, stable process; modular design; treatment occurs in a single reactor; biological nutrient removal. “Cons” included: higher project cost compared to MBBR and Biolac options; sophisticated control scheme; produces sludge byproduct; requires a Grade III operator.
This option would also use all four lagoons as part of a Violac WaveOx system. This is an activated sludge in an earthen basin with UV system. Construction cost would be $7.41 million and 20-year maintenance and operations cost would be $1.65 million, for a total cost of $9.06 million, making this the least costly option. It would require use of a headworks building, flow control structure, two Parshall flumes, blower building, pre-anaerobic selector zone, biolac treatment system, clarifier, UV disinfection and an outfall structure. Two lagoons would be used for flow equalization, one for sludge storage, and the fourth as a quiescent cell.
“Pros” included: lowest project cost and operations cost of the activated sludge alternatives; some operator flexibility and control; reuse of aerated lagoons. “Cons” included: produces sludge by-product; few installations in Iowa; may require chemical addition to meet nutrient removal requirements; limited expandability; and requires a Grade III operator.
Three other treatment options were discarded during the planning process: covered aerated lagoon treatment system; submerged attached growth reactor (SAGR); and sidestream treatment.
The next regular council meeting will be Monday, July 6 at 7 p.m. in the council chambers of city hall. The public may attend in person or via zoom. In-person attendance may be limited to provide for social distancing during the COVID-19 pandemic emergency still in effect.
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