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CHEMICAL AUTOMATION

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Chemical Automation is the main component of Automated Water Treatment.

Chemical Automation refers to the automatic monitoring and control of the sanitizer and pH levels in water to maintain clean and safe water in order to prevent corrosion, scaling, growth of germs and bacteria (such as E.coli and Pseudomonas) and ... closure by the Health Department !

It also results in significant savings in the cost of chemicals, maintenance and repairs.  It is now recognized as a must for all commercial and public pools and spas, as well as for quality residential installations.

In addition to Chemical Automation, CHEMTROL® controllers offer Integrated Automation for control of filtration, heating and conductivity.

SANITIZER CONTROL

The activity of the sanitizer is measured with a special electrode called an ORP or Redox electrode. Both of these terms stand for Oxidation-Reduction Potential. ORP does not measure directly the amount of sanitizer in the water but rather its activity, which makes it more valuable to proper water sanitation.

ORP readings are used to monitor the activity of the sanitizer: chlorine, bromine and or ozone. ORP - which is measured in millivolts (mV).  They provide a superior index of bacteriological water quality because it monitors the activity of the sanitizer rather than just its quantity as with conventional PPM (parts per million) test kits.

The website (2006) of the WORLD HEALTH ORGANIZATION (WHO) at: http://www.who.int/water_sanitation_health/ states:

The oxidation–reduction potential (also known as ORP or redox) can also be used in the operational monitoring of disinfection efficacy. In general terms for swimming pools and similar environments, levels in excess of 720 mV (measured using a silver/ silver chloride electrode) or 680 mV (using a calomel electrode) suggest that the water is in good microbial condition, although it is suggested that appropriate values should be determined on a case-by-case basis.

In 1971, the third edition of the "International Standards for Drinking Water Quality" of the WORLD HEALTH ORGANIZATION (WHO) stated:

"A redox potential of 650 mV (measured between platinum and calomel electrodes) will cause almost instantaneous inactivation of even high concentrations of virus. Such a potential can be obtained with even a low concentration of free chlorine but only with an extremely high concentration of combined chlorine."

In 1985, a study of thirty commercial spas by the OREGON DEPARTMENT OF HEALTH also confirmed 650 mV to be the minimum value required to prevent the growth of germs and bacteria. Public pools and spas in many European countries are now required by law to maintain an ORP level of 750 mV or more.

In the US, the 1988 revision of the Standards for Public Spas published by the NATIONAL SPA AND POOL INSTITUTE (NSPI) states:

"When chlorine or bromine is used as a primary disinfectant, ORP can be used as a supplemental measurement of proper sanitizer activity. The recommended minimum is 650 mV with no ideal and no maximum. The use of ORP testing does not eliminate the need for testing the sanitizer level with standard test kits".

pH CONTROL

pH represents the acidity or basicity of the water on a logarithmic scale that represent the concentration of hydrogen ions H+ in the water. pH is very important to water chemistry because the hydrogen ions are small and very active and therefore affect most chemical reactions in water.

pH values range from 0 to 14, with 7 being neutral.  For instance a neutral pH of 7 represents a H+ ion concentration of 10(-7) or 1/10,000,000, while a basic pH of 8 represents a concentration of only 10(-8) or 1/100,000,000.

The pH scale is logarithmic. When the pH value increases by one unit, i.e. from 7 to 8, the acidity of the water decreases tenfold.  Small changes in pH therefore have large effects and this is why close pH control is critical to water maintenance.

The ideal pH range for water treatment is 7.4 to 7.6. Below 7.4, the water is too acidic. This causes eye irritation and corrosion of the equipment (pump, filter, plaster, etc). Above 7.6, the water is too alkaline. This causes eye irritation plus cloudiness, scaling and stains.

Most important, pH affects the dissociation, and therefore the effectiveness, of Hypochlorous Acid HOCl, the most active sanitizer form of Free Chlorine, as shown in the curve below.

At a pH of 7.5, Free Chlorine is about 50% HOCl . At higher pH values, HOCl dissociates into the ionic form OCL- which is a less active sanitizer.

The pH of the water can increase due to the addition of alkaline (basic) chemicals such as liquid chlorine (Sodium Hypochlorite NaOCl), dry chlorine (Calcium Hypochlorite Ca[OCl]2) or make-up water.  It can decrease with the addition of Chlorine Gas (Cl2), body perspiration, acid rain or make-up water.

Acids are used to decrease the pH of the water, usually liquid muriatic acid (Hypochloric Acid HCl), dry acid (Sodium Bisulfate NaHSO4) or Carbon Dioxide CO2 gas.  Bases like caustic soda (Sodium Hydroxide NaOH) or dry soda are used to raise the pH.

The addition of pH correction chemicals used to be done manually or with a chemical feeder.  It is now done on demand with automatic controllers.

A chemical controller monitors the pH of the water with an electronic sensor consisting of a glass pH electrode.

The pH sensor readings vary from 0 mV for a neutral pH of 7 to about -60 mV for a pH of 8. For the recommended pH of 7.4, the reading is about -25 mV. It should be recognized however that the pH readings vary slightly from electrode to electrode. This is why pH testers and controllers always include a pH calibration adjustment. Calibration can be made with a Phenol Red test kit.

As shown on the Selection Chart, CHEMTROL® offers the most complete line of electronic controllers for monitoring and control of water chemistry.

INTEGRATED CONTROLLERS

  • The CHEMTROL® 7000 Integrated Controller features the new PPM Sensor for Free Chlorine and duplex operation by remote computer. It is the most advanced and most complete command center for automated water treatment in swimming pools, spas, cooling towers and industrial water treatment. It monitors and controls the chlorine concentration in in PPM (parts per million), an oxidizer in mV of ORP and the pH of the water. It includes water balance control, heater control and remote operation by computer or telephone. It also includes pump and filter programming capability with automated sequential filter backwash cycles.
  • The CHEMTROL® 6000 Integrated Controller monitors and controls the sanitizer concentration either in ORP or in PPM (parts per million) and the pH of the water.  It includes water balance control, heater control and remote operation by computer or telephone. It also includes pump and filter programming capability with automated sequential filter backwash cycles.

PROGRAMMABLE CONTROLLERS

  • The CHEMTROL® 5000 Programmable Controller features the new PPM Sensor for Free Chlorine. It monitors and controls the chlorine concentration in in PPM (parts per million), an oxidizer in mV of ORP and the pH of the water. It includes optional water balance control, heater control and remote operation by computer or telephone.
  • The CHEMTROL® 4000 Filter Controller includes pump and filter programming capability with automated sequential filter backwash cycles. Also included is heater control with fireman safety and energy saver program and remote computer operation with true duplex Windows software.
  • The CHEMTROL® 3000 Programmable Controller monitors and controls the sanitizer concentration either in ORP or in PPM (parts per million) and the pH of the water. It includes optional water balance control, heater control and remote operation by computer or telephone
  • The CHEMTROL® 2100 Programmable Controller features aan 8-line display for easy monitoring and control of sanitizer ORP and the pH of water.  It includes optional Free Chlorine control, optional heater control and remote operation by computer or telephone.
  • The CHEMTROL® 2000 Programmable Controller monitors and controls the sanitizer concentration in ORP and the pH of the water.  It includes optional control of PPM (parts per million), heater control and remote operation by computer or telephone.

DIGITAL CONTROLLERS

  • The CHEMTROL® 265 PPM/pH Digital Controller features the proprietary new PPM Sensor for Free Chlorine. It monitors and controls Free Chlorine and pH with proportional feed control and adjustable overfeed and out-of-range alarms. It includes 4-20 mA outputs for control of municipal and industrial water.
  • The CHEMTROL® 255 PPM/pH Digital Controller features the proprietary new PPM Sensor for Free Chlorine. It monitors and controls Free Chlorine and pH with proportional feed control and adjustable overfeed and out-of-range alarms.
  • The CHEMTROL® 250 ORP/pH Digital Controller monitors and controls the ORP of the sanitizer and the pH of the water with proportional feed control and adjustable overfeed and out-of-range alarms.
  • The CHEMTROL® 240 pH Digital Controller monitors and controls the pH of the water. It includes proportional feed control and adjustable overfeed and out-of-range alarms.
  • The CHEMTROL® 230 ORP Digital Controller monitors and controls the ORP of the sanitizer for use with neutral-type sanitizers. It includes proportional feed control and adjustable overfeed and out-of-range alarms.

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