KWR researcher @MarthedeGraaff's second report from 12th IWA International Congress on Anaerobic Digestion
Day 2 started with a plenary session by Professor Foresti (University of Sao Paulo, Brazil), who gave an overview of anaerobic digestion (AD) in Latin America. UASB reactors have been applied widely for treatment of wastewater. Little effort is being done for recovery of P, N or S; the focus of the research in Latin America is more on energy and biohydrogen production. Some research is focusing on nitrogen removal by using electron donors such as methane and sulfur compounds, or applying anammox. As widely known, anaerobic digestion does not remove nutrients, so if they have to be removed, a post treatment step always is necessary.
During the second day I attended several presentations, switching between sessions. Subjects varied from AD of household garbage in Europe to the importance of trace metals during AD. There were a few presentations about micro-aerobic treatment, combining methane production with oxidation at very low oxygen concentrations, such that the methanogenesis is not inhibited. This improves the effluent quality because COD concentrations are lower and sulfide is oxidized improving the biogas quality. This is being
researched in Czech Republic by Pavel Jenicek. Another interesting presentation was by professor Willy Verstraete about the AD of microalgae. As always, his presentation was very inspiring. Advantage of using microalgae is that there is no competition for food. However, costs are high and only at optimal conditions it can be compatible with respect to costs. Best biofuel is biogas according to Verstraete, so there is no need to produce other biofuels from the algae; that is too complex.
Day 2 ended with workshops. I attended the workshop about nutrient recovery by professor Jules van Lier. This was very interesting and gave me some new input for the Exploratory team of WERF. There are still so many challenges for the recovery of nutrients and other resources.
Day 3 started with a plenary session by professor Herbert Fang, University of Hong Kong, presenting an overview of AD in East Asia. In Japan night soil used to be treated by AD, but now aerobic treatment followed membrane separation is the core technology. In China central government is sponsoring biogas projects; resulting in more than 40 million projects. These are mostly in small households with about 20-30 pigs and the biogas is used for cooking. Prefab digesters are for sale.
Day 3 ended with a ‘technical’ tour to a Tequila factory, Herradura, in the town of Tequila. It was impressive to see such a large factory in the middle of Mexico. The wastewater is treated in a digester and the biogas produced is covering the energy demand of the factory. Mexicans are really good in organizing parties; we had diner at the Tequila factory and there was no shortage of Tequila.
The last day started with my presentation (see conclusions below). Fortunately I did not have to present first, because it took some time before the rooms were full… My presentation went well and I received quite some positive reactions afterwards. Other presentations I attended were about anaerobic MBR and solving the fouling problem. An interesting presentation was by Marta Carballa (Spain). She explained that AD of kitchen waste is not so straight forward. She showed results of several pretreatments to improve the hydrolysis.
The congress ended with a plenary session by professor Bruce Rittman, Arizona State University. He is famous for his research in Microbial Electrochemical Cells (MXCs). Although AD is at the moment more feasible, he believes that MXCs have more advantages, e.g. producing hydrogen. But his main message, and I agree with him, is that we should make use of the BOD in anaerobic processes and not oxidize as is currently being done in many wastewater treatments. His group is also researching the pre-treatment technologies for sludge to make it more readily bioavailable. He showed results of the OpenCel process, developed at his group, which uses pulsed electrical fields of high voltage to open flocs and cells. Last subject was about photosynthetic microorganisms; they can help us to produce biomass so that we can produce energy out of it.
In the closing ceremony the winner of the Leaf award was presented. This year it was the group of Jurg Keller, AMWC, UQ, Australia. They showed that you could use the MXCs not in competition with methanogenesis, but to upgrade the biogas by producing NaOH in the MXCs.
Marthe de Graaff
