The Evolution of Biological Anaerobic Wastewater Treatment over Time

Invited speaker: Prof David Stuckey

David Stuckey is currently Emeritus Professor of Biochemical Engineering in the Department of Chemical Engineering at Imperial College London, and a Visiting Professor at Nanyang Technological University (NTU) in Singapore for the last 10 years. He obtained his Batchelors in Chemical Engineering, and a Masters in Biochemical Engineering from the University of Melbourne, Australia. He then did his Ph.D in Environmental Engineering at Stanford with Perry McCarty. Prof Stuckey has worked in Australia, the U.S., Norway (at NTH/SINTEF in Trondheim), Switzerland (ETH/EAWAG in Zurich), and the U.K. (Uni of Sussex, and I.C.). His current research interests are in Downstream Separations of high value added products using novel techniques such as Colloidal Liquid Aphrons (CLAs), reverse micelles and surfactant precipitation, and reactor design using membrane separation/delivery of substrates.

Biological anaerobic treatment (anaerobic digestion-AD) has been used for close to a century for stabilising sewage sludge generated by aerobic biological treatment (activated sludge) initially, and lately some industrial wastewaters. Its advantages are many compared to aerobic treatment; it is a net producer of energy (in the form of methane, since it does not need oxygen pumped into it), and produces considerably less sludge than aerobic treatment(due to the lower Gibbs Free energy available since methane is a final product). However, there is one major drawback to AD, the cells grow slowly compared to aerobic treatment due to the lower energy yields, and hence the reactor (hydraulic) retention time (HRT) has to be of the order of days rather than hours (Activated sludge 6-8 hours, AD 20-30 days due to pathogen depletion). This led to very large and expensive Anaerobic reactors, with large footprints. In order to “optimise” the anaerobic reactor we needed to develop reactor designs that enabled the cells to be kept in the reactor for long periods of time (Solids Retention Time-SRT), while managing a very short hydraulic retention time (HRT) to minimise the reactor size and cost.