Start-up of a nutrient removal system using Scenedesmus vacuolatus and Chlorella vulgaris biofilms

Jairo Hernán Moreno Osorio,Gabriele Pinto,Antoninio Pollio,Giovanni Esposito,Luigi Frunzo,Piet Nicolaas Luc Lens

doi:10.1186/s40643-019-0259-3

Jairo Hernán Moreno Osorio, Gabriele Pinto + Show 4 more

Open Access

https://doi.org/10.1186/s40643-019-0259-3

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Abstract

Microalgal biofilm-based technologies are of strong interest due to their high biomass concentrations and ability to remove nutrients from wastewater, utilize CO2 and produce secondary valuable products. This study investigated the biomass production and nutrient removal efficiency of the microalgae Scenedesmus vacuolatus ACUF_053 and Chlorella vulgaris ACUF_809 from a synthetic wastewater, describing a start-up process in a new biofilm photobioreactor (PBR) configuration. Two sets of experiments were performed. The first one compared the performance of a suspended and attached cell system under batch conditions. The second set of experiments was addressed under semi-batch conditions to study the microalgae biofilm development in the PBR. Five stages in the development of the biofilm were identified for S. vacuolatus: attachment, biofilm formation, maturation I, adaptation and maturation II. The biofilm development phases had a different nutrient removal efficiency. S. vacuolatus biofilm showed a higher phosphate demand during the first attachment and formation phases, while it had a higher nitrate demand during the subsequent phases. C. vulgaris biofilm formation was affected by the pH increase (up to 10.6). The biofilm PBR design using both S. vacuolatus and C. vulgaris showed potential for wastewater treatment due the higher nutrient removal rates.

Highlights

In the last decades, the application of suspended microalgal technology for wastewater treatment has received considerable attention (Li et al 2010; Abdel-Raouf et al 2012; Bernstein et al 2014; Han et al 2017)
S. vacuolatus ACUF_053 performance Evaluation of PBR system performance under batch operation Suspended and attached S. vacuolatus ACUF_053 cells cultivated under the same conditions in synthetic wastewater as described above were able to grow in both culture conditions
The results suggest a different EPS production between S. vacuolatus ACUF_053 and C. vulgaris ACUF_809; this should be demonstrated quantitatively to propose the application of biofilm technologies of these strains for different biotechnological processes, e.g. treatment of different types of wastewater

Summary

Introduction

The application of suspended microalgal technology for wastewater treatment has received considerable attention (Li et al 2010; Abdel-Raouf et al 2012; Bernstein et al 2014; Han et al 2017). Microalgal culture systems have low biomass concentrations and problems with biomass/liquid separation which constitute the main drawbacks in the scale-up and industrial application of microalgal processes (Gupta et al 2016). Biofilm photobioreactors (PBR) can be grouped into three categories: permanently submerged systems, intermittently submerged systems and perfused systems (Berner et al 2015). The latter uses a porous substrate that supplies nutrients and moisture to the microalgae which grow on the outside of the membrane, exposed to the surrounding gas phase (Shi et al 2007). Attached algal culture systems such as the Algal Turf Scrubber (ATS) have been used successfully for growing filamentous

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