Real-Time Determination of Total Solids in UASB Reactors Using a Single Emitter Ultrasonic Sensor

The lack of proper sludge withdrawal routines has been one of the main causes of solids washout and consequent deterioration of effluent quality from up-flow anaerobic sludge blanket (UASB) reactors treating sewage in developing countries. The establishment of an adequate sludge withdrawal routine depends on the knowledge of the sludge mass inside the reactor, but for this, it is necessary to continuously monitor the solid’s profile along the height of the digestion compartment of such reactors. Knowing the sludge concentration at the highest point of this compartment, immediately before the passage of the liquid to the settling compartment, allows the definition of more robust strategies for sludge discharge, in order to not exceed the retention capacity (storage) of solids in the reactor. To couple with that, a low-cost ultrasound sensor was developed and tested with the aim of monitoring total solids concentration inside UASB reactors. Bench and demo-scale tests were performed to validate the developed technology. Results have shown that the sensor can provide real-time values of total solids inside the reactor with 0.1% accuracy up to 1% total solids content.