Pasco County Uses Total Life Cycle Costing to Select Chloramination Analyzers

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Courtesy of ASA Analytics

Pasco County, Florida Water Utilities serves its customers with water from its 58 permitted wells blended with the water supplied by its large regional supplier, Tampa Bay Water. In 2002 Tampa Bay Water converted to monochloramine disinfection because of its advantages over free residual chlorine. Monochloramine is more stable and better extends the disinfectant residual throughout the distribution system. It also has been shown to reduce the formation of trihalomethanes and halogenic acetic acids while reducing taste and odor problems associated with chlorine. It is also relatively inexpensive to produce.

When Tampa Bay Water adopted monochloramine, Pasco County also converted its entire system to monochloramine so the water from all of its sources would be compatible. In addition to its many pumping stations Pasco has two re-pump stations. Water purchased from Tampa Bay Water is stored until high demand hours and then pumped to the distribution system. It's possible for the water to sit in storage for up to two days and operators must accurately determine the levels of monochloramine, ammonia and chlorine before water is pumped to their customers. Sometimes they have to adjust their chemicals, usually by adding sodium hypochlorite.

Producing monochloramine requires precise control of the process, which necessitated Pasco to upgrade its monitoring and control system with what it thought at the time was the only proven ammonia and monochloramine online analyzer available. The newly installed analyzers used reagents supplied by the manufacturer to measure free ammonia, total ammonia and monochloramine. However, the additional expense of the reagents dramatically increased the county's operating budget.

'There was little we could do to control our increased operating costs,' said Jim Kaplan, Water Operations Supervisor. 'Because the manufacturer of our analyzers was our only source for the reagents, we could not seek competitive bids. Our costs had increased to over $1200 a month, and we recognized this was not a sustainable solution.'

Soon after installing the first analyzer Pasco Water Operations management began investigating other alternatives including the ChemScan UV-2150/S manufactured by ASA Analytics. At the time very few ChemScans were installed in Florida and even fewer municipalities knew much about them.

'Hillsborough County, our neighbor to the south was using ChemScan. We were able to see their analyzers perform and their operators gave us a very positive reference. Until then, about the only thing we knew about the ChemScans was they were priced $5,000 higher than the analyzers we had already purchased.'

But Pasco's Water Operations management saw a couple of significant advantages with the ChemScan that would potentially improve their operating budgets and justify replacing the analyzers they had recently installed. First, the ChemScan analyzers use reagents that can be produced with common chemicals purchased from any of a number of local distributors. Water Operations management projected the savings would dramatically reduce their monthly chemical expenditures.

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