Conserving Cooling Tower Water Many Times Over

Electronic devices have changed the way that people work and live by simplifying complex tasks. The iPhone is said to have combined more than 15 separate devices that Radio Shack offered, and reduced the cost of ownership while decreasing complexity. Electronics has benefitted the water market in many ways with sensors, analytics and data management; delivering remarkable improvements while reducing costs.

Electronic water conditioning is a relatively new application that controls scale and biofilm in water systems while reducing chemistry and labor.  Consider the role that chemicals have historically played for managing water quality, and the millions of gallons of hazardous chemicals that are used each day. These electronic devices are able to reduce water consumption and chemical use by over 50%.

Cooling towers in the U.S. use trillions of gallons of water per year to keep building temperatures comfortable.  They require 3 or more separate chemicals to maintain efficient operations by controlling mineral scaling, biological activity, and corrosion. Traditional control measures require chemicals specific to each problem, many of which are hazardous. Chemically treated water cannot easily be reused, so it is discarded into a sanitary sewer after brief use, based on cycles of concentration, or the levels of concentrated calcium in the circulating water.

Innovations of electronic devices have reduced requirements for chemical additives for achieving water quality objectives, while reducing costs, reducing chemical use significantly, and allowing billions of gallons of water to be repurposed for irrigation or other applications. This delivers significant conservation of potable water resources.

Saving more than half of a cooling tower’s water use with non-chemical devices is a significant breakthrough for cost savings as well as conservation, and offers these benefits:

  • Conserve makeup water volume
  • Reduce chemical additives and costs
  • Avoid sanitary sewer disposal and associated costs
  • Provide water for irrigation of landscape while avoiding historic water expense

Saving water twice has significant benefits for conservation of water as well as cost savings

Some Water Use Details

Communities have begun to recognize the importance of conserving water used by residences, businesses and government. The U.S. Geological Survey (USGS) estimated in 2010 that 355 billion gallons of water was used each day in the U.S. 

Office buildings have a large water use “footprint” that accounts for approximately 9% of the total use of water in the United States, which equals about 31 Billion gallons per day.

Approximately half of this total is dedicated to Cooling & Heating (28%) and Landscaping (22%) of buildings, or approximately 16 Billion gallons of water.  

16 billion gallons of daily water use presents is a big opportunity to develop conservation strategies. An obvious objective that is not frequently practiced is to repurpose discharged cooling tower water to be used for irrigation.

Making better use of this water use is the purpose of this article.

Water Costs Today

The cost of water and wastewater vary by region and city. Houston, TX charges a commercial building $4.10 per 1,000 gallons for fresh water and $6.35 per 1,000 gallons for discharge into a sanitary sewer. An average 1,000 ton cooling tower uses 15 million gallons of water per year, with water costs of nearly $100,000 on average. 

Costs for water have increased steadily and will continue to climb as cities use pricing to encourage conservation. The challenge we face is to use water longer without compromising operating efficiencies.

Cycles of Concentration are the Key to Water Conservation

Cycles of concentration (COC) is the measure of the number of times (or cycles) that dissolved solids in a water system concentrate due to evaporation. In cooling towers or other heat transfer systems, evaporative condensers and fluid coolers remove heat from water by evaporating a portion of the recirculating water. The evaporated water is pure H2, that leaves dissolved solids such as calcium behind, resulting in an increase in concentration levels.

If the cycles of concentration are allowed to continue, the dissolved solids become saturated and begin to form as scale, particularly in areas where heat and pressure undergo change, like chiller units and fill screens.

To prevent this, anti-scaling chemicals are added, and the conductivity of the water is measured to determine the total dissolved mineral content of the water. (Higher conductivity levels indicate higher dissolved minerals in solution).  

A cooling system can operate at higher cycles of concentration when scale inhibitors are added, though most automated chemical systems will purge a significant volume of water when 3 cycles of concentration are achieved.

Increasing COC to 6 or more would reduce water use by half, but chemical programs are not able to control scaling at these concentrations.

The purged water is usually discharged into a sanitary sewer since the chemicals (anti-scaling, biocides, anti-corrosion, others) prevent reuse of the water. The loss of water is expensive due to cost of new water, as well as the expense of sanitary discharge, and the lost chemistry that needs to be replenished.

Electronic water conditioning has changed this process.

Electronic Water Conditioning Increases Cycles of Concentration

Purging water at 3 cycles of concentration is a standard procedure in systems that cannot prevent the formation of scale above this level. Chemicals can only go so far, but this limitation is with chemistry, and new approaches are available.

Let’s think differently and consider what happens when a new process causes scale to form in the water as crystals that cannot attach to piping and equipment. With Electronic Water Conditioning, the water can be increased to 7 cycles of concentration without concern for of scale formation on assets. The chart shows the cost savings when COC is increased to 7 cycles.

The third row of data shows the cost savings associated with using the purged water for irrigation, which saves both the sanitary disposal charges and the costs for irrigation water.

About Electronic Water Conditioning

Innovations in electronics have improved processes and quality of life at home, work, and the community. Electronic water conditioning provides a chemical-free solution for the harmful effects of limescale, corrosion, bacteria, and algae in water systems. This results in significant water savings, up to 75% reduction of chemical use, and increased performance of assets with lower maintenance costs.

HydroFLOW differs from magnetic and wire-wrap solutions, and is 30,000 times more powerful than other electronic water conditioners. The HydroFLOW has an induced signal that continuously conditions water throughout an entire system. HydroFLOW water conditioning induce an electric signal of ±150kHz into any water pipe on which they are installed (metal or PVC).

The oscillating sine waves of the induced AC signal cause the positively and negatively-charged ions to form suspended clusters in the water, preventing them from attaching to piping and equipment.

HydroFLOW causes scale to form in water as crystals that are not able to attach, so cycles of concentration can be doubled which saves a significant volume of water. When Irrigation is incorporated into the water management process, there are cost savings from avoiding sanitary sewer discharge, plus the cost avoidance of purchasing water for irrigation.

HydroFLOW provides numerous benefits for water conservation and use:

  • Reduces 20-50% of Make Up Water demand
  • Reduces Disposal volumes by 50-100%
  • Reduces Chemical Use by Approximately 75%
  • Controls Biofouling and Algae
  • Improves filtration by flocculating particulates
  • Conserves approximately 12% kWh per month
  • Reduces Maintenance and Extends Asset Life
  • Simple to Install and has No Moving Parts

Sustainable Water Management from Process Integration

The pie chart above shows that of the 9% of daily water consumption in the U.S. is attributed to commercial building operations, 28% of the water is used for heating and cooling, while 22% is allocated for irrigation.

Daily water consumption by commercial buildings can be reduced by nearly 50% when electronic water conditioning is applied, since cycles of concentration can be increased while chemicals are decreased. The water quality is then suitable for irrigation, which eliminates a significant portion of water costs to maintain the landscape.

HydroFLOW enables reuse of cooling tower discharge while saving costs of purchase and disposal, while significantly reducing the water footprint of commercial building operations. By enabling purged water to be used for irrigation, water conservation is unlocked by converting a waste stream to become a resource.

Cost Savings Example for a 1,000 ton Cooling Tower 

The figures presented in the table above are illustrated below showing cost savings of $53,874 using HydroFLOW and repurposing purged water for landscaping, which saves more than half of current costs. When HydroFLOW is installed on the cooling system without redirecting the water to irrigation, cost savings are $36,298; reducing annual costs from $96,456 to $60,158.

Corporate sustainability goals can be advanced significantly using electronic water conditioning for saving water, reducing chemicals and saving energy.

By unlocking the dependence on chemistry, while preventing scale formation and biological fouling, significant quantities of water can be reused for irrigation, which replaces the demand for fresh water for a second time.

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