pH is one of the key metrics associated with the water and wastewater treatment process. The measurement and analysis of pH value plays a vital role in many industrial processes.
Alteration of pH value has significant effect on the water quality, process efficiency and consumers’ safety. A small change can alter the behaviors of chemicals, flavour, colour, shelf-life, stability and acidity of measured medium.
Industrial Applications
Installation
Connection
Maintenance / Cleaning
Industrial Applications
- Water treatment: Inadequate of pH in water can cause corrosion, degrading the pipes and taps on distribution system. Corrosion can cause harmful heavy metals to seep into water supply. If pH level is too high, it can cause an unpleasant taste safety issues.
- Wastewater treatment: pH value must be controlled for optimal chemical or microbial reactions, to ensure the treatment process runs efficiently.
- Food and beverages: pH level is important in creating the right physical and chemical reactions to ensure that the taste of products is palatable and consistent in production. pH alterations can also provide protection against bacterial growth and preserve the quality and shelf life of some food.
- Paper and pulp / textile: pH values can affect the colour and fading of quality of dyes in the production process. pH measurement is also used in the biological treatment process of the highly polluted effluents produced during the manufacturing process.
- Agriculture: pH value in soil can be influenced by weather, fertilizer, amount of irrigation, nutrient availability, etc. Therefore, consistent pH measurement is important to cultivate healthy plants and livestock.
- Oil and gas: pH measurements are used to ensure that the separation process used in desalting is optimised. Salt and other unwanted contaminants need to be removed before refining process.
Installation
Proper installation of pH sensor is crucial to getting accurate and reliable results. Below are some best practices for pH sensor mounting:
Inline
- Inline tees can be installed directly on process piping or in slip streams
- Low flow cells are suitable for sidestream applications for diversion of small samples of process liquid
Submersion (Tank, container)
- To prevent leakage, wrap the sensor threads with pipe tape before inserting into its mounting
- Do not over tighten the sensor
- Electrodes must be submerged completely in the process liquid
- Accumulation of air bubble around the sensors will cause inaccuracy or inconsistency in readings
- Apply a small amount of back pressure to the flow cell or pipe to prevent air bubble formation
- Run the sensor cables through a conduit to prevent moisture intrusion/signal distortion
- Do not leave the sensor cable dangling into the tank, pond or basin
Connection
- Long cable distance:Long cable distances may degrade the signal. For best performance, install long cable runs in a noise-free environment. Please refer to datasheet for the maximum length and manufacturer’s recommended distance from the meter.
- Shortening of connection cable: Sensor connection cable consist of a layer of special layer of graphite for screening. Cutting of the surplus may decrease the isolation resistance between the core and the screen of the cable.
- Entry of moisture: Moisture caused by improper protection or broken cable may reduce the insulation resistance of the cable connections causing a partial short circuit. Immersion fittings may be subject to condensation when fitted in low temperatures processes.
Maintenance / Cleaning
Periodic maintenance and cleaning will ensure accurate pH measurement and prolong the lifespan of pH sensors. Below are some best practices for pH sensor cleaning and maintenance:
- Never store electrode dry:
Ensure that the storage cap is filled with KCL storage solution and remain on the pH sensor to prevent electrode from drying during long-term storage - Storing electrode in distilled or deionized water:
This can deplete salts from the electrode filling solution, resulting in poor electrode performance. - Formation of salt crystals:
Formation of salt crystals by the protective cap, diaphragm, or inside the electrode are common. External salt crystals can be removed by rinsing with water. Any salt crystals inside the electrode can be dissolved by immersing the electrode in warm (45 °C) water. - Cleaning method:
Ensure that the electrode is clean and free from contamination. Never wipe the electrode with a cloth or any other type of material. Any static formed will harm the electrode. Always rinse the probe with distilled water to clean of contaminants before, during and after use. - Formation of air bubbles:
Any air bubbles in the pH bulb or by the junction need to be removed. Gently swing the pH electrode in circular motion to displace the air bubble. Gel filled electrodes may need to be replaced if a hole/air bubble is formed near to or around the diaphragm. - Operating temperature:
Do not expose to high temperatures (>65 °C) unless the electrode is designed for it. - Periodical calibration:
A calibration of the pH meter will help identify a problem with the electrode and ensure that the pH measurement is accurate. Buffer solutions are used during calibration. Always check the expiration date and how long it has been open for. Carbon dioxide will dissolve into the buffer over time, causing carbonic acid to accumulate and lowering the pH of the buffer.
