Decision will likely be made in January
The Hannibal Board of Public Works Board finds itself at a crossroads regarding the city’s next water filtration system. Board members have three options from which to choose, any one of which could do an adequate job, according to the engineering firm Black & Veatch, which presented its draft report during Tuesday’s HBPW Board meeting.
The three options are granular activated carbon (GAC), reverse osmosis (RO) and a hybrid system consisting of three elements – preozone, enhanced coagulation and aeration (PECA).
Each option has its advantages and disadvantages, according to information presented by Black & Veatch, which has been working to come up with treatment options since May when it began its chloramine replacement study.
Regarding GAC, there is “high confidence” it will meet treatment objectives. It also is a “relatively simple” system to operate.
Identified as a “potential roadblock” to the RO system is if waste water could not be discharged to the river.
As for the PECA option, Black & Veatch reported that more testing would be required to ensure its feasibility. The hybrid system, which would be the easiest of the options to implement, would require close monitoring to ensure total organic carbon (TOC) and disinfection byproducts (DBP) goals are met.
Another significant factor is the cost of building the new system and then the annual expense of operating it.
GAC is expected to have the highest operating and maintenance costs due to periodic carbon replacement. Black & Veatch suggested there is the potential to lower those costs if regenerated carbon can be utilized.
As for RO, it would be the most costly system to install and operate.
PECA claims both the lowest initial costs and lowest operational costs.
According to a memo written by Stevenson, of the three options Black & Veatch recommends GAC.
“The RO option which has a higher capital cost but a lower annual operating cost is still too expensive in a 20-year present worth analysis,” he said. “Another system using enhanced coagulation coupled with ozone oxidation has lower capital costs and lower operating costs but is fairly complicated to operate and has a higher probability of operator error or equipment failures leading to future water quality violations.”
As for members of the HBPW staff, there was not a consensus Tuesday on which system to recommend. Citing its simplicity, Stevenson endorsed the GAC option. Heath Hall, director of operations for the HBPW, also supports the GAC.
However, George Hausdorf, the Water and Wastewater Plant supervisor, said he believes RO is the “correct option.”
None of the four board members hinted at their personal preference.
Board President Lennie Rosenkrans was not willing to commit to an option until January.
“It’s worth thinking about,” he said.
The BPW is changing water treatment systems following an April measure approved by voters that prohibited the use of ammonia as a water disinfectant, which was the BPW’s primary method of disinfection.
Reach reporter Danny Henley at firstname.lastname@example.org .