Modelling anaerobic wastewater treatment

Abstract

There is a real need for dynamic models in the design and operation of treatment processes given that design theory and control strategy are directly linked to process modelling. The core objective of this study was to develop both a computer simulator and a physical model of an avant-garde second generation anaerobic wastewater treatment technology, then use one to validate the other, and vice versa. An extensive literature review of anaerobic wastewater treatment technologies is presented with focus given to granular sludge and the granulation process, these being the underlying factors behind the emergence and success of many anaerobic technologies. A database of dynamical mathematical descriptions for anaerobic digestion processes has been compiled, ranging from Andrew's model of 1969 to the most recent and comprehensive descriptions as presented by the IWA Anaerobic Digestion Model No. 1 (ADM1) and its extensions. This study centres on: (a) the expanded granular sludge bed (EGSB) reactor; it being the most versatile technology current in operation, and (b) the IWA ADM1, it being constructed by world leaders in the field of dynamic anaerobic digestion modelling and who view it as the most comprehensive and flexible description to date. A stand-alone Windows based computer simulator, 'SimEGSB', was developed using Microsoft Visual Basic Version 6.0 as the programming language. The simulator was verified in terms of its computational procedures and implementation of the conceptual model. A physical model was designed, constructed and operated under different control strategies using a synthetic wastewater feed. Data was collected for several months, but due to circumstances and factors beyond control, this was rendered useless for its intended purpose in the calibration and validation of the computer simulator. While the physical model was shown to be capable of performing a stable treatment, its representation of the technology at full-scale goes undetermined. The application of 'SimEGSB' for simulation of the same is also constrained, in that, it has the status of an untested prototype.