Beginning in October 2016, AS Filtration, LLC conducted a year-long study to document the effectiveness of a non-oxidizing biocide within a side stream filter on the cooling tower system of a four-story office building in Chattanooga, Tennessee. AS Filtration installed an Aqua-Stream™ side stream filter, utilizing their unique Pathex® antimicrobial filter media, on the 400-ton cooling tower system in operation at the office building (Image 1). The goal of this study was to analyze the effects of the Aqua-Stream™ and Pathex® on bacteria, energy use, water use, and overall equipment/maintenance costs.
Water is a fundamental component of any cooling tower system, as it is the medium through which heat exchange is achieved. Cooling tower operation, with side stream filter placement options, is depicted in Figure 1, below. The Aqua-Stream™ filter at the Chattanooga site is located between the pump and heat exchanger (Option 2, below). As water passes through the heat exchanger, waste process heat is transferred to the cooler water, allowing equipment to operate without overheating. A portion of this hot water is then evaporated in the cooling tower, with the remaining water being cooled for reuse through the heat exchanger.
Cooling towers consume water in two ways: evaporation and blowdown. Evaporation, as seen above, occurs as part of normal cooling tower operation. Because of this, the remaining water retains a constantly growing concentration of dissolved solids. Blowdown manages this issue by purging the water with high concentrations of solids or minerals, often to the sewer system, and refilling the system with clean (usually municipal) water. The longer water can recirculate through the system before blowdown is required, the less water the cooling tower consumes. Side stream filtration helps manage water usage by constantly filtering and removing the suspended and dissolved particles that lead to blowdown. Logically, this translates into water savings, as less make up water is required to operate the cooling tower.
The next entry will examine the maintenance requirements and equipment costs associated with cooling systems and their operation.