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A change in the pH level of water can alter the behavior of chemicals in the water.
pH affects product quality and consumer safety. Changes in pH can alter flavor, color, shelf-life, product stability and acid content.
Inadequate pH of tap water can cause corrosion in the distribution system and can allow harmful heavy metals to leach out.
Managing industrial water pH environments helps prevent corrosion and damage to equipment.
In natural environments, pH can affect plants and animals.
Hach offers the testing equipment, resources, training and software to successfully monitor and maintain pH in a wide array of process applications.
pH is a measure of the hydrogen ion activity in a solution. Pure water that contains an equal balance of positive hydrogen ions (H+) and negative hydroxide ions (OH-) has a neutral pH.
Hach calibration pH buffers are available in a variety of color-coded or colourless solutions, in different packaging types and sizes from 15 mL up to 20 L. pH buffers are also available in convenient single-use pouches (Singlet) and unit-dose powder pillows for on-site and field analyses ensuring freshness, eliminating the possibility of contamination.Shop Now
pH of drinking water is measured at multiple stages in a drinking water plant.
Optimum tap water pH level is 6.5-8.5.
Drinking water pH level must be monitored to minimize corrosion, contamination and adverse effects on taste/odor/color/appearance.
pH adjustment is necessary for the precipitation of heavy metals in wastewater plants.
In biological treatment processes, pH can affect the microorganism metabolizing waste. If the pH is too high or low in aeration basins, the microorganisms lose the ability to convert waste to energy and raw materials. In nitrification basins, if the pH drops too low the nitrifying bacteria begin to inhibit the nitrifying process.
Anerobic digesters must maintain a balance between several microbial populations. If the pH increases outside of acceptable limits, methane production stops and the digester system will fail.
To comply with regulation pH must be measured in effluent. (Facilities must abide by the National Pollutant Discharge Elimination System.)
Proper pH balance is critical to overall boiler chemistry at nearly every stage and to maintaining high purity water.
pH is an important factor in monitoring the corrosive properties of water which can damage equipment.
This method uses a pH sensing system (including a pH meter, a pH sensing electrode & a pH reference electrode) to take an electrochemical measurement to precisely determine where the tested fluid falls on the pH scale.
Our online technology course provides more information on the importance of monitoring and measuring pH.
Advantages: This is the most accurate method for pH measurement. Portable, lab or process/online options are available for this method. This method can be EPA approved for monitoring pH.
Disadvantages of this Method: This method requires proper handling, care and maintenance of the pH probe and involves higher instrument costs.
Like the visual method, an indicator solution is used to create a color change in the solution being tested. However, with this method the color change is not assessed by the human eye, it is measured by a colorimeter or spectrophotometer to produce a more precise pH reading.
Advantages: This method removes the subjectivity of the human eye, it is portable, it does not require complex pH meter calibration.
Disadvantages of this Method: Solutions being tested with this method must be colorless. No online/process options exist for this method, there are costs associated with instruments. This method is not an EPA-approved method for monitoring pH.
An indicator solution changes color when added to the solution being tested. That color change is then visually compared against a color chart to determine pH.
Liquid dyes are added directly to the solution to produce a color change that indicates pH.
Dye-infused paper strips are dipped into a solution and then change color to indicate pH. This method is not affected by color or turbidity in a sample.
Advantages: This method is simple, inexpensive and portable.
Disadvantages of this Method: Solutions being tested with this method must be free of color and have no turbidity. Solutions being tested with this method must not have a secondary reaction with the indicator solution. No online or process options exist for this method. This method does not produce exact measurements.
When testing the pH of soil-based samples it is advisable to use a pH probe with a strong glass tip and high electrolyte outflow. Mix 5 g of the soil sample with 25 g of deionized water while stirring carefully. Let the mixture stand without stirring for 10 minutes to separate the particles from the liquid. Insert the pH probe in such a way that the glass bulb is totally covered by particles, but the diaphragm is not. Wait for a stable reading.
A pH meter and electrode such as an HQD meter/Intellical probe must be used if your results need to be reported to an agency such as the USEPA. You can review the Hach USEPA pH electrode method 8156 for additional information.
pH meters will give the best accuracy and sensitivity, measure across the full pH range, and can be used with most water samples, compared to colorimetric or test strip measurements. However, they require regular calibration with pH buffer solutions. Hach has several different kits available, complete with calibration buffers, for simplified measurement solutions.
pH is a critical water quality indicator. There are several common techniques available for measuring pH: titrimetric, colorimetric, litmus paper, and electrochemical. The most common and accurate pH technique is by electrochemical combination electrode. A combination pH electrode responds to the hydrogen ion (H+) concentration (activity) by developing an electrical potential across the electrode bulb/water interface. This potential difference is measured with a voltmeter. Electrodes are designed for optimal performance in various matrices. Hach HQd meters and a versatile assortment of IntelliCAL probes bring simplicity and consistency to pH measurements in any matrix. See this document for more information.
Hach has a complete portfolio of instruments and chemistries with support and services to help you get the right results.