Meeting disinfection byproduct regulations
Construction was almost finished when the city learned it was being placed under a consent order for exceeding maximum contaminant levels for trihalomethanes (THM) and HAA5s (the haloacetic acid family) in the drinking water.
Initial engineering evaluations identified capital-intensive filtration options including enhanced coagulation/ filtration, activated carbon, and reverse osmosis. A city of 10,000 isn't in a position to quickly restructure rates and obtain the necessary bonding to fund such systems, all of which exceeded $2 million.
That narrowed the options to a chemical solution.
Ozonation was eliminated in part because of capital requirements, but also because we weren't convinced it would succeed as a sole solution to the problem.
Chloramination accomplishes disinfection through the addition of ammonia and is thought to adversely affect the taste and odor of treated water. However, studies and feedback from utilities that already had these issues — as did Inverness, where water supplies have very high levels of iron and manganese — indicate that chloramination can actually improve water quality aesthetics.
While less costly in terms of construction, operating a chloramination system requires additional operations expertise. Inverness had an existing relationship with one of Florida's largest chlorine suppliers, Odyssey Manufacturing Co. in Tampa, which has extensive experience with the process. President Pat Allman described several case studies in detail and outlined the fundamental needs, activities, goals, and expectations to give us the confidence we needed to move forward.
That effort kicked off with cleaning and rehabilitating the existing 500,000-gallon storage tank using existing earmarked capital improvement funds and installing a 2,200-gpm aerator. The tank's exterior was painted to match the water plant and branded with the city's logo. The rehab was completed over a 12-day period for $125,000.
Converting to chloramination involved adding a Foxcroft FX1000-Pon-line total chlorine residual meter, an ammonia skid with two feed pumps, a day tank with a digital scale, and a new feed line to the storage tank. Additional activities included:increased flushing at critical points of the systemrewinding motors and replacing bearings in high-service pumpsreplacing the treatment facility's control systemrenovating the chlorine feed system to improve monitoring and analysismanaging the replacement of the fluoride feed system.
“Chloramination can create its own set of problems if dead end lines aren't eliminated or flushed regularly,” says Woodard & Curran's overall utilities Project Manager Brian Heath. “You need to think through a lot of permutations involving flows, water chemistry, equipment dosage controls, and how you can best use staff to effectively flush and monitor the system each day for the first two weeks of operation. You have to plan on committing a lot of attention to the front end of this kind of process.”
As we enter our fourth year with this client, the experience has been one of the most rewarding in my 35-year career. Former city employees who'd been indifferent to pursuing certification seem renewed by the prospect of expanding their career path. Our management team is directly involved in planning and implementing capital improvements. The relationship proves public and private workforces can effectively collaborate to tackle and resolve multiple problems at once, understanding what can go wrong and preparing for those contingencies.
Public Works Director Katie Cottrell recently told me, “The team worked so well together and the added technical support was essential to all that we were able to accomplish.”
—Cherniak (firstname.lastname@example.org) is a senior vice president with Woodard & Curran and serves as senior area manager for facilities the firm contract-operates in Florida.WEB EXTRA
To read how one town explained the switch from chlorination to chloramination to disinfect drinking water, click here.