When measuring the quality of water, pH is among the most important indicators. It tells you how acidic or alkaline the water is, which makes it easier to determine which contaminants are in the water.
If you discover that the water is acidic, you can take steps to filter contaminants and increase the pH level. While alkaline water isn’t typically as harmful as an acidic solution, there are many industrial processes that require more neutral pH ranges. In this scenario, there are several treatments that can help you reduce the water’s pH.
This type of testing is necessary for many applications. For example, bottled water manufacturers and municipalities must maintain specific pH ranges to ensure the quality of the water isn’t poor. It’s also common for pH testing to frequently occur in aquaculture and environmental monitoring. The following is the ultimate guide to pH testing, including relevant methods and best practices.
Understanding the pH Scale
To understand how pH works, you must first learn about the pH Scale. This scale goes from 0-14. At 7.0, the pH is neutral, which means that it’s clean and free of nearly all contaminants.
When the pH scale drops below 7.0, the solution will be acidic. Water can become more acidic in the environment when rock formations, tree roots, and soil microbes seep into the solution. Depending on the pH, acidic water is often considered to be dirty and unsafe to drink.
If the pH of a water sample is above 7.0, the solution is alkaline. There are numerous substances that can lead to an increase in the alkalinity of water, which include magnesium and calcium. The pH within blood and human cells can be anywhere from 6.8-7.4. The pH levels of some common substances are:
- Filtered water – 7.0
- Borax – 9.0
- Bananas – 4.0
- Apples – 3.0
- Lime water – 12.0
- Baking soda – 9.0
- Black coffee – 5.0
- Eggs – 8.0
- Rice – 6.0
- Carrots – 6.0
- Mangoes – 6.0
- Sugar – 7.0
There are many reasons why companies and scientists test pH levels in water. For drinking water, the pH range must be between 6.5-8.5. If the water is too acidic, it will likely taste and smell bad. It can also cause illness depending on the types of contaminants that are found in the water.
The main issue with drinking alkaline water is that it can have a bitter taste. However, consuming too much alkaline water can cause digestive problems like vomiting, stomach pain, and nausea.
Methods of pH Testing in Water
There are several types of testing you can use to measure the pH of water, which include everything from pH test strips to digital pH meters.
pH Test Strips
These test strips are available in the form of pH paper or a liquid-based solution. When you dip pH paper into water, it will change to a different color based on the current pH level. If you buy pH paper, you should receive a color-coded scale that allows you to determine if the water is acidic or alkaline.
In most cases, a color that’s closer to orange or red is more acidic. If the color of the water takes on a bluish or greenish hue, it’s likely alkaline. You can also buy liquid pH strips that involve placing a few drops of a pH solution into the water. Once you do this, the water will change color, which you can match to your pH strip.
The paper that’s used for pH testing is coated with Flavin, a soluble chemical that can change color depending on the types of substances that are present in the water. If the solution has a neutral pH, the paper should turn light green.
The color of the pH paper changes depending on how many hydroxide or hydrogen ions are in the water. If the water contains high levels of hydrogen ions, the solution will be acidic. A higher concentration of hydroxide ions indicates a more alkaline or basic solution.
Digital pH Meters
A digital pH meter is a relatively modern instrument that you can use to identify the alkalinity or acidity of a solution. When you place the meter in water, it should provide a precise pH reading. Many industrial facilities use these meters to perform comparisons.
For example, a wastewater treatment facility will measure the pH of contaminated water before adding treatments and other solutions that should increase the pH. The water’s pH will then be tested to identify the effectiveness of the treatments. Treated wastewater is safe to discharge into the environment.
There are numerous types of digital pH meters, which include combination, differential, laboratory, and process meters. Most digital pH meters are combination sensors that consist of a reference electrode and a measuring electrode. The measuring electrode checks for any changes in the water’s pH value. In comparison, the reference electrode offers a stable signal that the measuring electrode can be compared against.
These meters also come with a high input impedance component, which effectively amplifies the signal to ensure an accurate reading. The accuracy of a digital pH meter depends on the type and brand you choose for your facility or home. Normally, the pH meter electrode has a high internal resistance, which means that the voltage change in the water is difficult to properly measure. The meter’s input impedance ensures that even the smallest of changes to electrode voltages will be correctly measured and displayed.
The electrodes within a pH meter are often made with high-quality glass that senses the concentration of hydrogen ions in the water. In most cases, the glass that the measuring electrode is made with consists of alkali metal ions that produce an ion exchange reaction with the hydrogen ones, which shows a possible difference between the two.
Laboratory pH meters are ideal for light applications. Process pH sensors are built with sturdier bodies that can more effectively withstand solutions with extreme pH ranges. Keep in mind that electrodes are mainly designed to measure aqueous media. You shouldn’t place them in solvents that don’t contain free hydrogen ions.
When you buy a digital pH meter for your facility, make sure it’s stored properly. The electrodes must remain moist at all times. Hydration is necessary to accommodate the ion exchange process. If the sensor becomes dry, you’ll need to put it in tap water for 30-60 minutes to prepare the glass.
If you use a digital pH meter, make sure you inspect it regularly for electrode damage. You’ll notice that the electrode is no longer providing accurate results if it produces a reading that never changes, a sluggish response, or erratic measurements. In any of these situations, the electrode can no longer be properly calibrated. While electrodes are highly beneficial for precise pH measurement, they are also fragile. The amount of time an electrode lasts depends on how well you maintain your digital pH meter.
Smart pH Sensors
Smart pH sensors are equipped with better and more accurate technology than traditional ones. These sensors are suitable for heavy-duty industrial processes that require constant monitoring. The main difference between smart pH sensors and standard ones is software.
When you buy a smart pH sensor for your facility, you can connect it to software, which ensures that you’ll receive the readings immediately after they’re taken. This data should be displayed on your computer and collected in a program that makes it easier for you to analyze it and identify what, if any, changes need to be made to the chemical balance of the water. With smart pH sensors, you won’t be as dependent on manual operators. The only downside is that these sensors can be expensive and might not be suitable for smaller facilities or residential homes.
Best Practices for Accurate pH Testing
If you need to collect field samples for pH testing, there are specific protocols and procedures you must adhere to. First, make sure you prepare the sample containers and glassware that you’ll be using during testing. These containers need to be rinsed and cleaned before you take your first measurements.
When collecting water samples, there are a few things you should take with you, which include the pH meter of your choice, a wash bottle that contains deionized water for rinsing the electrode, and a data sheet that you can use to record pH results.
Make sure you calibrate the meter before you go to the sampling site. The frequency at which you calibrate the meter depends on the type of solution you’re placing it in. It’s a good idea to calibrate your meter every 25 samples. The calibration process depends on the type of meter you have. If you’re using a laboratory sensor, you’ll need two buffer solutions that are set to 4.01 and 7.0.
The buffer solutions you use should be kept at room temperature when calibrating your sensor. Never use a buffer once you get past the expiration date. When storing a buffer, place a cap over it to prevent contamination. Since the pH value of a buffer solution changes depending on the temperature, your meter should be equipped with a temperature sensor that standardizes the pH during calibration. Make sure that you never reuse these solutions.
During the calibration process, begin with the 7.0 buffer, which is the “zero point” of the scale. While a 7.0 pH reading is equivalent to an mV value of 0, a 4.0 reading leads to 180 mV. A single pH change results in plus or minus 60 mV to your readings. Before calibrating your meter, clean the electrode. Once you calibrate the meter with the initial buffer solution, rinse the electrode with deionized or distilled water. The electrode can then be placed into the 4.0 buffer. Make sure you adjust the meter to show the correct value.
Even if you have experience with pH meters, there are numerous mistakes that you’ll need to avoid, which include everything from poor electrode maintenance to inaccurate calibration. If you don’t maintain the pH meter’s electrode, it can become dirty, which will lead to incorrect readings. These electrodes are susceptible to dust and dirt, which you can rinse off with deionized water or a gentle detergent.
It’s also crucial that the sensor is properly calibrated if you want to maintain accuracy. Your pH meter will likely accommodate a two-point calibration. In the U.S., you can use a 7.0 pH solution and a 4.01 solution. Some facilities use a 10.01 buffer. The NIST standard involves 0.1, 6.86, and 9.18 buffer solutions.
You must also avoid using a dried electrode, which can result in a sluggish and inaccurate response. If the bulb completely dries out, soak it in tap water or another solution for at least 30 minutes. To obtain accurate readings, you’ll need to analyze samples within two hours after you collect them.
pH Levels and Water Quality
The smallest of pH changes can lead to significant water quality and safety issues. Keep in mind that the water’s existing pH can also change the chemical state of different pollutants. These alterations can impact the transportation, bioavailability, and solubility of a contaminant.
The pH of water can affect aquatic life, human health, and industrial processes. For example, when the water’s pH is too low or too high, aquatic organisms will die off. Each aquatic species prefers a different pH range. Since the temperature of water can change the pH level, each creature requires a different temperature. Most aquatic lifeforms can survive in waters that range from 6.5-9.0 pH.
High and low pH levels can also damage your health. If the water’s pH is low, it will be considered acidic. Drinking too much acidic water can lead to heartburn and acid reflux. When the water’s pH gets lower than 3.0, it might start to corrode metals.
You should also be cautious about drinking alkaline water. While many companies sell alkaline water with high pH levels, drinking excessive amounts of this water can cause tingling in your hands and face. Vomiting can also occur. High pH levels often lead to worse water heater efficiency and slower plumbing.
Industrial facilities typically find alkalinity to be even more damaging than acidity. Alkalinity is often caused by elevated levels of magnesium and calcium. These chemicals can increase the hardness of the water, which will eventually lead to scale deposits growing on piping and other metal surfaces.
Troubleshooting pH Imbalances in Water
The pH of water can change for any reason. However, there are things you can do to identify the cause of pH imbalances. If you wish to maintain a balanced pH of 7.0, everything from pollutants and soil to chemicals and minerals can create a pH imbalance. Environmental factors contribute to most of these changes.
Let’s say that you have an in-ground well on your property. The pH of your well water can increase or decrease if surface runoff contaminates it. The contaminants that are found in soil include hydroxide, carbonate, and bicarbonate compounds. These are mineral deposits, which means that they will cause the alkalinity to increase. If your water’s pH changes considerably in a short period, this indicates that it has been contaminated, which means that you may need to treat it. Keep in mind that highly acidic or alkaline water tastes and smells bad.
If you want to increase or decrease pH levels in your water sample, there are different solutions available to you. For example, acidic water with a low pH can be treated with a neutralizing filter. You can raise the pH by using a filter that contains magnesium oxide, calcite, or calcium carbonate. Make sure you backwash these filters regularly to remove sediment buildup. The neutralizing material in the filter bed will also need to be replenished often.
After you install a neutralizing filter, it’s highly recommended that you test your water regularly to determine its hardness. Keep hardness levels below 120 milligrams per liter. If the magnesium and calcium in your water approach 180 milligrams per liter, you may want to soften the water.
If you need to increase pH in a high-yield process, you can do so by adding soda ash to the water via a chemical feed pump. This substance can increase your water’s pH level to at least 8.0. You can also use potassium to achieve the same result. However, drinking too much potassium might lead to side effects like muscle weakness, nausea, diarrhea, and cardiac arrest.
When you’re trying to find the ideal treatment method, you must consider the upfront cost as well as the ongoing operating expenses. The costs associated with regularly treating water include repairs, maintenance, filters, and consumable supplies.
You can also reduce the pH of your water by using a reducer chemical. These chemicals include sodium bisulfate or muriatic acid. They are often sold at home improvement centers and pool supply stores. Muriatic acid is a highly potent chemical that can be dangerous if it splashes around or spills.
When you purchase a container of muriatic acid, make sure you read the manufacturer’s instructions to safely handle it. You can prevent major changes to the pH of your water by treating the solution whenever you notice minor alterations.
pH Testing in Different Water Sources
The pH testing process can vary depending on the water source. For example, pH testing in tap water can be completed in seconds. Since tap water typically ranges from 6.5-8.5 pH, it shouldn’t be too difficult to calibrate your meter and maintain accurate readings. When you conduct pH testing in natural water bodies, such as lakes, rivers, and oceans, you can expect the pH to have a broader range that can be as low as 5.0 and as high as 9.0.
In industrial and agricultural water applications, pH testing is often continuous. Plant operators or managers need to treat water before discharging it, which means that readings need to be taken before and after the treatment process. If you’re attempting to maintain water quality in an aquarium or pool, consider doing so twice every week to determine if you need to adjust the pH. When you add substances to the water to alter the pH, you must know how many gallons are being treated.
Conclusion
By testing the pH of water, you can determine if it’s ready to drink or needs to be treated. This water quality measurement is a key indicator that tells you if the liquid is contaminated or too alkaline. While it’s possible to use pH test strips and liquids, your best bet is to regularly monitor pH levels in your water sources with digital or smart sensors. When using a pH sensor, make sure you calibrate it regularly and store the electrodes in a liquid solution. To ensure water quality in your facility, use advanced pH testing methods that allow you to capture precise readings.
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