Radar technology has long had the reputation of being the best method of level measurement available - but does this also apply to the wastewater market? Based on its physical characteristics, radar technology certainly offers great flexibility and high performance. However, from an objective standpoint, non-contact level measurement using ultrasound is often the first choice and also the right choice due to its cost-effectiveness and application-specific benefits!
Level measurement in the wastewater industry
From a process engineering, water management and safety perspective, level information and limit detection data constitute important parameters in the operation of wastewater treatment plants (WWTP) and drainage systems. For example, level monitoring and control in a WWTP are key factor in ensuring optimum interaction between the subareas of influent (e.g. in a lift station), preclarification and sludge treatment. In this regard, calls from planners and operators for a universal method of level measurement are well founded. A universal method would, for example, lead to a reduction in the amount of training required and a decrease in the number of errors during commissioning. It would also result in cost savings, for example in the context of spare parts inventory. However, in terms of measurement technology, the tasks and requirements facing level measuring devices in the wastewater industry are as wide-ranging and varied as the measuring principles available on the market.
Each method of measurement has its pros and cons based on physical and/or device-related characteristics that become evident under different process and environmental conditions. The mounting location can also have an impact on measurement reliability or the ‘handling’ of the measuring point.
To support users and planners in choosing the right device, the pros and cons of the different methods of measurement based on application are outlined as follows. The information presented concentrates on non-contact time-of-flight methods, namely ultrasound and radar. Note: As one of the leading manufacturers of level measurement technology, the objective assessment of safety, reliability and cost is a key priority for Endress+Hauser. If a level transmitter is selected solely because it is a modern method of measurement, the planner or operator may in some cases miss out on the benefits afforded by a different measuring principle at a lower price.
Overview of measurement methods
For level measurement and point level detection in the wastewater industry, Endress+Hauser offers eight different measurement methods: ultrasonic, guided radar, free-space radar, radiometric, vibronic, capacitance, conductivity, hydrostatic and float. Each of these methods of measurement is valid and facilitates the important decision of choosing the right method for the application in question. Endress+Hauser’s capacitive measurement technology is a very cost-effective solution for continuous level measurement or level detection in conductive liquids or foam. Capacitive probes are guaranteed to work reliably, particularly within small measuring ranges and where there are rapid changes in level, but also in aggressive media that forms build-up, e.g. in chemical tanks.