TURBidity Ultrasound Sensor

Over the last decade the focus on water quality have increased tremendously in both the EU and the US. Pollution of the drinkable water supply network can occur on a short time scale and traditionally the periodic control currently used does not detect leaks until several weeks later. The current turbidity measurement methods really on expensive equipment requiring regular maintenance at least every 2-3 months.

For these reasons there is a huge potential for a cheap, reliable sensor which could be used as an early warning system and provide real time feedback to the water supplier. Figure 1 illustrates how such a sensor could be integrated in the water distribution system and eventual pipe leaks (or other sources of pollutant like accidental mixing with wastewater, abnormal concentrations of bacteria or even acts of terrorism) to be identified almost instantaneously and the location of the leak would be known to great precision depending on the density of sensors.

The TURBUS (TURBidity Ultrasound Sensor) project aims to develop such a sensor.

The sensor is based on ultrasound instead of the light used by conventional turbidity sensors. This allows for several advantages, of particular importance is the low maintenance requirement. The design is heavily based on a tested and proved Kamstrup flowmeter design, and the sensor is expected to be completely maintenance free for more than 7 years. Combined with the low expected cost of 200€ and the ability for the sensor to run off a single battery for upwards of 12 years should make the sensor network illustrated in figure 1 feasible.

The TURBUS design is illustrated in figure 2. Two piezo ultrasonic transducers (Tx1 and Tx2) produce an ultrasonic wave in the water pipe. This wave will scatter off of particles in the water and the scattered signal is recorded by the ultrasonic receiver (Rx).  Due to the Doppler effect the frequency of the scattered light is shifted compared to the fundamental ultrasound frequency, which allows the scattered signal to be separated from the original signal. The amplitude of the signal is proportional to the amounts of particles and hence the turbidity can be measured.