Extensive research has led to the development and increased use of membrane bioreactors in wastewater treatment. Going with the current global trends, future demands are expected to escalate due to the numerous advantages including small footprint, high-quality effluent and flexible design that allows for upgrading. Generally, wastewater treatment constitutes depth filtration, physicochemical treatment, and disinfection. On the other hand, dissolved solids and organic contaminants require additional reverse osmosis to eliminate. However, membrane bioreactors, which were chosen to replace direct membrane filtration, are limited to specific cases. Consequently, their expensive operational costs and high energy requirements, determined by the types of fouling control, are significant disadvantages in their applications.
In a recently published literature, several methods including dynamic control systems have been developed to reduce energy consumption in membrane bioreactors. Alternatively, fouling control through automatic backwashing have been used to improve process productivity. Therefore, researchers have identified controlling the backlash frequency as an efficient way of controlling the residual fouling in membrane bioreactors.
To this end, University of La Laguna researchers: Dr. Enrique González, Dr. Oliver Díaz, Elisabet Segredo-Morales, Dr. Luis Rodríguez-Gómez, and Dr. Luisa Vera recently developed a backwashing control system for effective control of the peak flow capacities in submerged membrane bioreactors. In particular, they investigated the possibility of monitoring the conditions of the peak flux using the developed membrane bioreactors. Their work is currently published in the research journal, Industrial and Engineering Chemistry Research.
Briefly, the research team initiated their experimental work by cross-examining the influence of transmembrane setpoint value on residual and reversible fouling. Consequently, the experimental tests were carried out in different unit sizes and peak conditions. To actualize their study, a case study was performed to compare the results of the developed backwash mode to its conventional counterparts. Eventually, the new control system was validated by testing the optimal conditions and comparing to the long-term in a pilot-scale membrane bioreactor.
The authors observed that the alternative operation mode demonstrated the feasibility of its efficiency in controlling the fouling as compared to the conventional methods. This further resulted in higher process productivity ranging from 14-16%. In addition, from the long-term tests, it was worth noting that the controlled mode was capable of achieving sustainable operation at high peak flux and peak periods which were recorded as 70 L/h m2 and 6 hours respectively. However, during the short-term tests, low transmembrane set-point values resulted in insignificant effects on process performance.
In summary, the study successfully presented an efficient automatic backwashing control system for enhancing the process performed in a membrane bioreactor. It enables determination of the degree of the membrane fouling by adjusting the filtration length in relation to the transmembrane setpoint value. Altogether, the proposed framework offers immense promises in advancing the design and operation of membrane bioreactor for efficient and effective treatment of wastewater.
González, E., Díaz, O., Segredo-Morales, E., Rodríguez-Gómez, L., & Vera, L. (2018). Enhancement of Peak Flux Capacity in Membrane Bioreactors for Wastewater Reuse by Controlling the Backwashing Strategy. Industrial & Engineering Chemistry Research, 58(3), 1373-1381.Go To Industrial & Engineering Chemistry Research