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Some of the unanswered questions are:

1. Does the coagulant precipitate and, if so, is the major form an oxide or phosphate solid? 
2. Do these solids transform to more crystalline entities over time?
3. If, rather, the coagulant initially forms dissolved complexes with the organic matter present, how stable are these complexes?
4. If Fe(III) salts are added to the anoxic chamber, is iron reduced to Fe(II) species?
5. On transport to the aerated chambers, does Fe(II) oxidise and, if so, what are the oxidation products?

The objective of this project is to improve nutrient removal, minimise membrane fouling and aid the dewatering of excess sludge in hybrid coagulation/submerged membrane bioreactor (MBR) treatment of wastewater by:

1. Experimental examination of the impact of coagulant addition on SMBR performance and
2. Kinetic modelling of key coagulant transformation processes within the SMBR.

Judicious use of both laboratory-based and pilot-scale experimentation using both synthetic and real wastewaters coupled with advanced mineral characterisation techniques (EXAFS, SAED, HRTEM) combined with systems-based kinetic modelling will assist greatly in elucidating the key processes operating in hybrid coagulation/submerged membrane bioreactor (C/SMBR) systems.

The project commenced in July 2010. A wide range of coagulant dosing 

conditions were tested using three small scale membrane bioreactors located at UCMST and one pilot scale MBR at Sydney Water’s Bondi Sewage Treatment Plant.  

Upon the completion in 2014, the project succesfuly derived operating protocols for membrane bioreactors that allow the development of cost effective operating methods. Novel cleaning strategies that are far more effective than traditional cleaning protocols used in MBR plants have also developed. Superior performance of membranes modified with the in-house developed antimicrobial additives was maintained during long-term pilot plant studies using brackish river water. The number of required backwashes for the modified membrane was an order of magnitude less than the control. Additionally trans-membrane pressure for the modified membrane was significantly lower. Membrane performance was also tested when the feed was spiked with bacteria and modified membrane performed significantly better than control. We found insignificant depletion of antimicrobial active component from modified membrane during long-term pilot plan studies.