Pure drinking water ranks among our top, global priorities. Emerson’s Ryo Hashimoto, describes the importance of analytical measurements in assuring purity in a Control Engineering Asia article, Pure by Analysis.
Ryo highlights the challenges with drinking water in Asia:
Regionally, Asia faces severe stress on water availability, primarily due to high population density, agriculture and industrial uses. The quality of drinking water is a health concern as water is a medium for disease transmission. In Southeast Asia, as in other developed regions, there can be significant water quality issues. Of these, contamination of drinking water sources by disease causing microorganisms remains the most important.
Based on these needs, mobile water treatment technology has emerged:
Mobile systems can offer a range of treatment options, including clarification, filtration, demineralization, reverse osmosis, membrane separation and/or induced air/ gas flotation. Systems are skid-mounted and may be installed on-site or trailer-mounted. Trailers contain instrumentation and equipment for a fully automatic and monitored operation.
Analytical measurements can be applied across many processes found in water treatment to improve quality, reduce treatment time, and reduce costs:
Commonly used processes include pretreatment, coagulation, flocculation, sedimentation, filtration, and disinfection. Other treatment methods could include ion exchange, reverse osmosis, and adsorption.
In the pretreatment phase, measuring attributes of the incoming water is important:
Influent monitoring measurements could include pH, conductivity, temperature, turbidity, and dissolved oxygen. Some plants also keep a permanent record of each of these measurements for future reference or for detecting seasonal changes in the source water.
Past the pretreatment phase, primary disinfection comes next to address pathogens such as bacteria, viruses, and parasitic protozoa. Chlorine and ozone are two methods used in disinfection. Ryo notes that ozone sensor for monitoring ozone dosage and residuals during the primary disinfection stage.
The clarification process comes next and:
…is usually a multi-step process for reducing turbidity and suspended solids, and comprises the stages of coagulation, flocculation and sedimentation.
pH measurement for the chemical additions to reduce water mineral content and to reduce turbidity. After clarification, the filtration process comes next:
Larger particles become trapped first and smaller particles such as clay, iron, manganese, microorganisms, organic matter, precipitates from other treatment processes, and silt are also removed resulting in crystal clear water.
The filters used in this process must be periodically backwashed to remove the particles trapped in the filters. An important measurement is turbidity as a measure of the filters’ performance:
Turbidity is the clarity of the sample, and the cloudy appearance is caused by tiny particles in the water. Turbidity measurements also help monitor and improve plant efficiency. High turbidity levels are an indication that the filter is not operating properly, and backwashing is necessary.
The final process steps include secondary disinfection and final treatment. Analytical measurements often included are chlorine measuring systems for the secondary disinfection process.
Even if you’re not in the water treatment industry, the article provides a great overview of the processes and important measurement to help assure pure, safe drinking water.