Freshwater is an essential resource for everyday life. Although water covers 71% of the earth’s surface, only 3% is freshwater, and just 1% of this freshwater is usable. With the growing demand for water, sustainable water management is more important than ever. This means using freshwater in a way that meets current environmental and economic needs without compromising the ability to meet those needs in the future.
Whether located in hospitals, office buildings, or manufacturing plants, the industrial water systems used for heating, cooling, and process applications can present high-value opportunities for water conservation and increased sustainability.
Water Quality and Cost
Water quality is an important determining factor for water conservation. The impurities contained in the freshwater used to operate industrial water systems can vary widely from place to place and throughout the year. This is important because these impurities determine the potential for water related problems including corrosion, mineral deposits, and microbiological fouling. As the chart shows, there are geographies where the freshwater is low in impurities (e.g., Seattle, WA) and other areas where it’s high in impurities (e.g., San Angelo, TX). Water cost is also an important component of the sustainability equation that can vary widely from place to place.
Maximizing Cycles to Minimize Water Usage
Cycles of concentration (cycles) measures the degree to which dissolved impurities of the makeup water are concentrated in a cooling tower or steam boiler system. Maximizing the cycles is important for sustainability because this can also minimize water, energy, and chemical consumption.
The charts below show the calculated water usage and costs in a cooling tower system operating at 500 tons of load at varying cycles of concentration. As cycles increase, the water blown down from the system decreases. When the cycles get higher, water usage is reduced, but there is also increased risk of system damage and inefficencies. Often increasing cycles above 6 may provide minimal return versus the risk taken. A water treatment professional will be able to determine the maximum cycles of concentration for a particular system and its water quality. Other options can be explored to further reduce freshwater usage and increase cycles of concentration. Common methods are shown in Table 2:
|Methods to Reduce Water Usage in Cooling and Boiler Systems
||Lower pH and alkalinity
|Reverse Osmosis (RO)
||Reduce all salts
|Alternative Water Sources*
|Eliminate uncontrolled water losses/leaks
*Air handler condensate, groundwater, rainwater, municipal, site-specific recycled water
An example of a boiler water savings project is the installation of an RO system on a 4000 HP steam boiler system where the makeup cycles of concentration were increased from 4 to 20. Changing the makeup water quality led to greater than $94,000 savings in both energy and water.
Depending upon the water quality and its availability, it may be possible to use water that is currently being sent to drain to supplement the freshwater requirements for heating, cooling, and other water systems. Reusing this water could potentially save water, wastewater, and energy costs.
An example of a cooling tower savings project using an alternative water source is an air handling unit producing over 1.1 million gallons of condensate annually. This high-quality water source could be used in a cooling tower system to displace fresh water makeup requirements. For a 1,000-ton cooling tower system operating at 50% load, this could result in greater than $12,000 of annual water savings.
Alternative water sources do have pros and cons in regard to their use and this is summarized below. These should be considered before its use.
Leaks and Other Water Losses
Finally, leaks and uncontrolled water losses are one of the most overlooked causes of increased freshwater usage. All types of systems can experience this, and some common examples include:
- Cooling tower basin/sump overflowing
- Leaking recirculating pumps
- Blowdown/bleed valves that get stuck open
- Filtration equipment backwashing too frequently
- Online testing equipment water sampling
While water losses in these locations may appear to be small, they can add up quickly. For example, over the course of a year, a 2 GPM cooling tower overflow can lead to over a million-gallon increase in use which can equate to $10,500 in excess water cost. It is important to identify and minimize these losses.
With there being many opportunities/projects for water savings in cooling towers, steam boilers, and other water systems, Chem-Aqua can provide sustainable water solutions for many industrial, manufacturing, and process applications. As a global leader in custom-designed water treatment programs, Chem-Aqua has the experience, knowledge, and technology to effectively optimize your water use and identify savings opportunities. Contact Chem-Aqua for assistance today!