Aerobic granule technology combined with selected microbial agents for the degradation of toxic wastewater pollutants

Growing water scarcity urges for reuse of wastewater and for energy and cost efficient, lower footprint treatment systems. Wastewater treatment using aerobic granular sludge sequential batch reactors (AGS-SBR) is a recently introduced and very promising technology economically outcompeting the conventional activated sludge, as simple and compact systems where all treatment steps are accomplished in a single tank. It has been successfully applied for the treatment of domestic and industrial wastewaters. Portugal is one of the first countries to adopt the technology with Netherlands and South Africa. High biomass concentration and biosorption capacity are two highly attractive AGS properties. AGS holds a promise for biodegradation of pollutants. One of such class of compounds are fluoroorganics, used in pharmaceutical, agricultural and industrial applications. The potential of AGS, via bioaugmentation with specialized bacteria, for the treatment of such compounds will be explored, following studies by the proponents. Polysaccharides are claimed to be the major gel-forming constituents of the granular Extracellular Polymeric Substances (EPS), which can be recovered from AGS, converting organic compounds in wastewater into a resource. The diversity of such EPS in different systems will be tackled by comparing EPS from lab- and full-scale reactors. As microorganisms present in the native sludge not always harbour the capacity to degrade pollutants, bioaugmentation will be explored, however, several constraints may limit its efficiency. Previous work of the research group reports a successful case of bioaugmentation of AGS to remove pollutants. We will investigate if the degrading bacteria can establish as granules producing their own immobilisation material, and/or whether we can use the EPS derived from AGS as an immobilisation matrix. One other aspect that deserves exploitation in AGS systems is whether horizontal gene transfer (HGT) is promoted. Bioaugmentation with degrading bacterial strain harbouring a catabolic gene for 2-fluorophenol degradation, gave indications of HGT. This project will address this question to open the way for its future exploitation as bioaugmentation strategy.
This project will thus address the following research questions:
i) are EPS unique to particular treatment systems or are they similar in diverse granular sludge processes?;
ii) can degrading bacteria produce their immobilization material to form granules or can they be immobilised in granular sludge EPS?;
iii) does HGT transfer occurs within AGS opening the possibility to contribute to the success of bioaugmentation?;
iv) how robust is the AGS towards the transient appearance of toxic pollutants in the wastewater and how successful is bioaugmentation?

This novel biotechnological approach will benefit the environment, economy and the society, as it represents a more sustainable and efficient water treatment.