10Submerged aerated filters (SAFs) treat wastewater to achieve stringent organic carbon and ammonium (NH 4 + ) effluent consents. Currently SAF design follows a black box approach, where inlet and outlet contaminant concentrations are monitored, with little consideration for internal hydrodynamic conditions. Although tracer tests have been used on bioreactors, integrated monitoring of internal fluid velocities, mixing characteristics and process 15 performance has not been established for SAFs. Tracer tests were performed on a 7.74 m 3 SAF, with internal recirculation at 100, 75, 50, 25 and 0% media fill ratios with and without biofilm on the media surface. Results suggested that, SAF internal hydrodynamic conditions directly influenced process performance and media fill ratios could be manipulated to provide optimum conditions for removal of biochemical oxygen demand (BOD 5 ) and NH 4 + . A 50% 20 media fill ratio showed optimum hydrodynamic conditions for BOD 5 removal, with a removal efficiency of 70% (mass removal of 1.59 kg.m -3 .d -1 ). A 100% media fill ratio showed optimum hydrodynamic conditions for NH 4 + removal, with a removal efficiency of 60% (mass removal of 0.14 kg.m -3 .d -1 ). Therefore optimisation of internal hydrodynamic conditions is key for selective contaminant removal and achieving high effluent quality. 25

Although not-well-understood, process stress could provide a novel approach to resilience analyses in wastewater treatment processes by identifying the influence of a stressor on wastewater processes. This paper identifies how industry and academia view the concept of process stress in wastewater treatment processes. It also investigates how individuals, their role and education influence their decision bias and their propensity to use decision support tools. Survey results from 255 respondents showed that many wastewater professionals still have a preference to use personal or company-specific spreadsheets (33%), with a similar proportion of respondents using simulation and decision support tools (29%). The concept of process stress in wastewater treatment was well understood by industry and 2 academic professionals as a variance from benchmarked conditions. This analogy of process stress means that it can be either, a positive or negative magnitude of variation from a benchmarked state, which expands on the approach taken in current resilience and benchmark simulation models. Therefore, the concept of process stress was a well understood by a vast majority of respondents, with 82% of respondents agreeing that an analytical tool that considers process stress would be a useful contribution to developing the understanding and management of process resilience. The study also highlights the requirement for a process stress analysis methodology, which builds on current resilience methods and separates the stressor (cause) from process stress (effect). Overall, this research has identified the requirement to measure and analyse stresses in wastewater treatment processes and recommends a strategy to develop this methodology.

No abstract

No abstract

No abstract