Effects of nutrient loading on Anabaena flos-aquae biofilm: biofilm growth and nutrient removals

Abstract

Effects of three different nutrient loadings (low nutrient loading, medium nutrient loading and high nutrient loading, denoted as LNS, MNS and HNS, respectively) on the structure and functions of algal biofilm using Anabaena flos-aquae were investigated using synthetic wastewater. Nutrients removal efficiencies, biofilm thickness, microalgae dehydrogenase activity (DHA) and exopolysaccharide (EPS) productions were examined. Results showed that the changes of nutrient concentration were insignificant after 4 days of experiment for the case of HNS condition; 9 days for the case of MNS condition, and 6 days for the case of LNS condition, respectively. The biofilm thickness, nutrient removal efficiencies, algae DHA and EPS productions increased with the increase of nutrient loadings in synthetic wastewater. For the case of HNS condition, the microalgal biofilm exhibited the best performance in terms of C, N and P removal efficiencies, reaching the removal rates of 68.45, 3.56 and 1.61 mg·L(-1)·d(-1) for C, N, P, respectively. This was likely because, fact with the high nutrient loading, the high biological activity could be achieved, thus resulting in high nutrient removals. The thickness of the biofilm in HNS condition was 75 μm, which was closely related to EPS production. DHA and EPS concentrations were 7.24 and 1.8 × 10(-2) mg·mm(-2), respectively. It was also shown that apart from the nutrient loading, the structure and functions of microalgal biofilm were also influenced by other factors, such as illumination and temperature.

A new easy method for determination of surface adhesion of phototrophic biofilms

“…In the first stages of the biofilm, EPS is increasingly formed to enable cells to adhere more strongly to the surface, which Carniello et al (2018) and Tolker‐Nielsen et al (2015) described in detail. There is also the possibility that, when biomass is transferred to a new system, EPS is first increasingly used to store nutrients, which are afterwards metabolized (Flemming, 2011; Li et al, 2016). However, since not only the amount of EPS but above all their composition is crucial for adhesion, an analysis of the EPS components would be necessary for a more precise assessment.…”