Abstract
Photosynthetic performance of algal-bacterial biofilms from an Italian wastewater treatment plant was studied in a flow-lane photobioreactor at different irradiances, temperatures, and flow regime to evaluate the effects of these environmental parameters on biofilms’ functioning, in view of application of these communities in wastewater biological treatment. Pulse amplitude modulated fluorescence was used to estimate the effective quantum yield of PSII (ΔF/Fm’) of the light-acclimated biofilms and to perform rapid light curves (RLCs) for the determination of the photosynthetic parameters (rel.ETRmax, α, Ik). Chl a, ash free dry weight (AFDW), and dry weight (DW) were measured to assess phototrophic and whole biofilm biomass development over time. From the analysis of photosynthetic parameter variation with light intensity, temperature and flow rate, it was possible to identify the set of experimental values favoring biofilm photosynthetic activity. Biomass increased over time, especially at the highest irradiances, where substrata were fastly colonized and mature biofilms developed at all temperatures and flow conditions tested.
Highlights
Biological treatment is an important and integral part of wastewater treatment (WWT) procedures
Microalgal-bacterial combinations have been employed for treating secondary wastewater effluents in the form of suspensions in the enhanced pond and wetland (EPW) system, a multiple step process including high-rate algal ponds (HRAPs) [6], and gravity algal harvesters (AHs) [7]
This study provided new insights into photosynthetic activity of light-acclimated cultures, contributing to the knowledge of wastewater biofilm ecophysiology, in light of their exploitation in water bioremediation
Summary
Biological treatment is an important and integral part of wastewater treatment (WWT) procedures. Thanks to the synergistic relationship between photosynthetic and heterotrophic microorganisms, the use of microalgal-bacterial consortia in WWT is considered a cost-effective, efficient, and sustainable alternative to conventional activated sludge treatment, especially for municipal wastewaters, due to the potential for cost-free oxygenation, efficient nutrient removal, and carbon dioxide sequestration provided by microalgae metabolism [4,5]. In this way, microalgal-bacterial combinations have been employed for treating secondary wastewater effluents in the form of suspensions in the enhanced pond and wetland (EPW) system, a multiple step process including high-rate algal ponds (HRAPs) [6], and gravity algal harvesters (AHs) [7]. Biofilm was collected without regard of light absorption and labelled as last sampling (ls)
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