Efficient Water Management Blog

How to Double Cooling Tower Water Conservation

 

Electronic devices have changed the way that people work and live by simplifying complex tasks. Think of how a microwave simplifies the heating of water at less cost and time than using a stove. The iPhone combined more than 15 separate devices and reduced the cost of ownership, while decreasing complexity of completing tasks. Electronic innovations have benefited the water market in many ways with sensors, analytics and data management; delivering remarkable improvements while reducing costs.

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The control of limescale and biological fouling in water systems has traditionally depended on chemicals. However, advances in electronics achieve the intended results while reducing chemistry by 75% in many cases.

Smart buildings enable green buildings to achieve objectives in water conservation while reducing operating 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. Electronic water conditioning reduces cooling tower water consumption by over 50% and chemical use by 75% in many cooling tower applications.

Cooling Tower Water Conservation 

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. Smart building technologies are changing best practices for cooling water system management at commercial and industrial facilities.

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Innovative electronic devices reduce 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 that benefit the broader community with significant conservation of potable water resources. 

Green Buildings and Smart Buildings are converging with the use of technologies that include physical water conditioning and sensors with data analytics that help to improve efficiencies of equipment maintaining operating specifications and extending useful life of components, while reducing water, energy and chemical use.

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

Reusing cooling tower water 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, Texas 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; nearly $10.50 per thousand gallons. Austin, Texas charges $6.57 and $9.48 for fresh and sewer volumes respectively, or $16.05 per thousand gallons used.

An average 1,000 ton cooling tower uses 15 million gallons of water per year, with water costs of nearly $50,000 on average. 

Quote.pngCosts for water are expected to increase 3-6% per year in Texas and will continue to climb as cities use pricing to encourage conservation. A critical challenge that communities face is to use high quality water for the most beneficial purposes and reusing it on applications that don't depend on potable water quality to accomplish intended results.  

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 H2O, that leaves dissolved solids such as calcium behind, resulting in an increase in concentration levels.

Cycles of Concentration increase as water evaporates and increase scale potentialIf 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 have limited effectiveness as CoCs increase, which limit water conservation.

Let’s think differently and consider what happens when instead of scale formation being suppressed, precipitation of scale is facilitated so that calcium crystals form in the water and cannot attach to piping and equipment. Electronic Water Conditioning safely allows circulating water to be at 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.

Cycles of concentration cost savings for cooling towers

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. Think about how efficiently a microwave oven heats water, and consider the use of a frequency that prevents limescale from forming on surfaces by causing it for form in the water instead as microscopic crystals.

HydroFLOW physical water conditioner for cooling tower scale preventionPhysical 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.

Why HydroFLOW Performs Better than Other Water Conditioners

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

HydroFLOW causes scale to form in water as crystals that are not able to attach to piping and equipment, 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

Over 9% of the total daily water consumption in the U.S. is attributed to commercial building operations, or 31 Billion gallons/ day. Of that figure 28% of the water is used for heating and cooling, while 22% is allocated for irrigation. 50% of water that is consumed each day by commercial buildings is rarely combined because the chemicals used to treat cooling tower water prevent repurposing for irrigation, so both water uses remain separated. Conserving the volume of cooling tower water and reducing irrigation water demand in commercial buildings are key sustainability objectives since they both draw from drinking water supplies.

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 use (and cost) to maintain the landscape.

Reuse of cooling tower discharge saves costs for 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 enabled 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 below are illustrated below showing annual cost savings of $53,874 using electronic water conditioning and repurposing "blowdown" water for landscaping, which saves more than half of current water costs.

Electronic water conditioning without reusing water for irrigation provides cost savings of $36,298 by reducing annual costs from $96,456 to $60,158.

When the water that would have been discharged into the sanitary sewer is repurposed for irrigation, the additional conservation and cost savings amount to more than $15,000 per year. $53,000 is considerable operating cost savings, but also reflects significant water savings.

HydroFLOW water savings for cooling tower with irrigation discharge
 
By reducing dependence on chemistry for preventing scale formation and biological fouling, more than half of the water that is currently being sent offsite to a wastewater treatment plant can be reused for irrigation. You save half the water in a cooling tower operation and also reusing the water for landscaping or greywater use which reduces the demand for fresh water for a second time.

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

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