Freshwater, barely enough for a world population of 7.9 billion people, is distributed unevenly, frequently wasted, polluted, and unsustainably managed. The availability of safe and sufficient water supplies is inextricably linked to how wastewater is managed. There is thus a need to develop, understand and optimise efficient and effective wastewater treatment (WWT) technologies to enhance water quality and facilitate resource recovery and water recycling. The adoption of modern biofilm technology has accelerated in recent decades as WWT in large urban centres were required to upgrade their treatment to meet more stringent standards and to expand to deal with higher inflows. Biofilm technology is the choice when process intensification is required in a WWT plant and to provide capacity to deal with stringent treatment standards for nutrients. Biofilm technology is often considered as an upgrade of the conventional activated sludge process to meet a higher effluent quality and treatment capacity without requiring expansion in the footprint of the WWT plant. However, the deployed operational efficiency of these processes is significantly below what is theoretically possible due to (a) a design process that, while using some mathematical modelling, uses rules-of-thumb, and (b) a significant knowledge gap in the understanding of several complex physio-chemical and biological mechanisms, the subject of this project.
Biofilms, the key catalysts in biofilm-based WWT processes, are structurally complex, integrated multi- cellular communities of surface-adhering microorganisms embedded within an extracellular polymeric (EPS) matrix. In the WWT context they provide a higher volumetric productivity and enhanced nutrient removal capacity compared to the Activated Sludge process. Municipal wastewater comprises soluble organic and nitrogenous matter but also a significant fraction of suspended organic particles and dissolved polymeric material/colloidal matter and some inorganic particulates. The fraction of the particulate organic matter including colloidal/polymeric matter in pre- settled municipal wastewaters is typically 40–60% of the total organic matter. Current mathematical models for biofilm processes are heavily focused on the soluble components. It is now widely accepted that one of the major limitations of biofilm models is that, while they handle soluble components reasonably well “…a general lack of basic research …has led to a severe deficiency in the ability of existing…biofilm models to describe the fate of particulate components in biofilm reactors..”. These limitations can only be addressed by developing a fundamental understanding of biofilm-particulate interactions, the focus of this project.
Objectives:
Specific Objective 1: Employing a sophisticated platform based on advanced imaging/particle tracking and fluorescent labelling techniques integrated with a continuous flow biofilm cultivation system, we will develop fundamental insights into biofilm-particulate interactions focusing on research questions that have not been previously elucidated because of the limitations of conventional approaches.
Specific Objective 2: Investigate (a) spatial profile of the reaction rates in terms of the breakdown of particulate organic matter in the biofilm (b) quantify the effect of particulate organic matter loading and spatial profile on the reaction rates of soluble components within the biofilm and translate this in quantitative terms to mathematical relationships.
Specific Objective 3: Using a combined experimental-modelling approach, develop further the IWA multispecies biofilm model framework and refine and validate the model using data from a pilot plant wastewater process.
