- Quality control is essential for the raw water used in the treatment of drinking water.
- Yet many municipalities often do not have generous budgets for drinking water treatment. This is why system operators are faced with the challenge of implementing safe processes for the production of clean water while adhering to rigorous cost calculations.
- Online measurement of pH value and oxidation-reduction potential (ORP) enables drinking water treatment plant operators to assess the quality of the raw water they use and implement measures to protect the system.
Importance of pH and ORP Measurement in the Treatment of Drinking Water
Before the raw water from lakes, rivers or wells can be fed into supply lines as drinking water, a variety of analyses and filtration processes ensure its harmlessness. Although the concentrations of certain germs and pollutants can only be documented in continuously implemented, complex offline analysis procedures, online pH and ORP measurement of incoming raw water provides technicians with important information about the water quality and the steps that must be taken, if any.
Recording raw water values plays a key role in the overall process of drinking water treatment. Measures for neutralizing extreme pH values or oxidation-reduction potentials are not only taken in the spirit of health compatibility, but also to protect treatment plants and filters against premature wear. Acidic water is not just unhealthy, it corrodes water lines as well. On the other hand, ORP describes the concentration ratio of reduced and oxidized substances in the water. These include nitrate, sulfate, and manganese oxide. A low ORP also means that the risk of microbial contamination is considerably high. To raise ORP and thereby disrupt germ cell metabolism, oxidant chemicals such as chlorine are added to the water. Their dosing is based on ORP measurement, and the values must be recorded reliably to avoid under- and overdosing. Underdosing would not thoroughly kill the germs. Overdosing would accelerate system component wear, necessitating extra treatment steps to reduce chlorine concentration to maintain health safety compatibility and lead to excessive, inefficient chemical consumption.
Sensor Contamination in Online Monitoring: Reducing the Risk of Blocked Junctions
As a rule, groundwater features a low level of contamination but depending on the regional circumstances, raw water can also contain surface water and the precipitation that collects in wastewater channels. To avoid abbreviated service lives and maintenance intervals, which would require frequent process interruption, the pH and ORP sensors used for online raw water measurement must be resistant to high levels of contamination. They must also be designed such that junction blockage is avoided, even at high levels of impurity.
The SE 554 Memosens sensor was developed for pH measurement in contaminated, alkaline or acidic media. As a particularly economical solution, SE 554 is also available in a version for simultaneous pH and ORP measurement with platinum electrodes. Two open junctions reduce the risk of blockage or contamination to a minimum.
Measurement interference that may arise as a result of diffusion potential at the junction is reduced by a high level of potassium chloride and its special distribution in the polymer of the reference electrode. Due to their high stability and accuracy and very low maintenance requirements (it is not necessary to refill electrolyte), using SE 554 sensors contributes to a significant reduction in total operating costs.
The SE 564 ORP sensor was also designed for use in highly contaminated media in which deposits tend to form. As is the case with SE 554, the modern temperature- and pressure-resistant polymer electrolyte in the SE 564 ensures long-term stable measurement and eliminates the need to use conventional ceramic junctions. Instead, a double open junction establishes contact between the reference system and process medium, reliably preventing blockage in the measurement of wastewater containing solid impurities.
Memosens Enables Quick Sensor Replacement and Easy On-Site Troubleshooting
Sensor exchange within minutes, using pre-calibrated Memosens replacement sensors, is also possible under harsh ambient conditions. After they are connected, the replacement sensors automatically transfer the calibration and sensor data saved in their electronics to the transmitter and measurement can continue without significant interruption.
If there are measuring point problems, the mobile process analyzers in the Portavo series enable quick and easy sensor diagnostics on site. Often, simple problems can be solved by cleaning the sensor or recalibrating it with Portavo. In many cases, this solution avoids prophylactic sensor replacement and subsequent troubleshooting in the laboratory.
Reliable Measured Value Transmission in Wet Environments
Due to the inductive transmission of sensor values and supply voltage in connectors, using Memosens sensors prevents interference with measured value transmission in wet environments as well. Even with sensor cables that are up to 100 m long, the measured values are accurately transmitted because they are digitized and not subject to the attenuation that affects analog signals. As a result, transmitters can be installed in protected environments far from the measuring point.
Return on Investment
- The design features of the SE 554 and SE 564 pH or ORP sensors ensure long service lives – even in highly contaminated media. As a result of minimized maintenance effort and extended replacement cycles, using Memosens sensors lowers measuring point costs.
- Quick sensor replacement with pre-calibrated Memosens sensors reduces downtime and avoids complicated on-site calibration, reliably preventing measured value distortion and subsequent errors.
- The Portavo 908 Multi mobile analyzer enables calibration and sensor data to be easily recorded at remote measuring points.