University of Bath

Manipulation and modelling of microalgae for enhanced wastewater phosphorus removal

This project aims to improve and inform the way in which ponds are operated while simultaneously improving pond operation and resilience.

High rate algal ponds are a promising alternative for the removal of excess nutrients from secondary effluent, providing both the potential for recovery of phosphorus and a renewable process; neither of which are provided by the current standard of iron dosing. However, HRAPs come with their own set of challenges. Low growth rates compared to other wastewater technologies and the requirement for light penetration require a higher retention time and low pond depth, in turn leading to very large surface area requirements. Additionally, the process requires separation of biomass for the effluent, which incurs further running costs. To improve the viability of HRAPs, it is necessary to develop methodologies and tools for improving HRAP function. Through literature review, polyphosphates and “luxury uptake” were identified as good targets for the manipulation of phosphorus uptake. The project initially focused on learning and developing tools for detection of polyphosphate and investigation into the link between Psr1 and polyphosphates. Through the dual-pronged approach of bioinformatics and molecular investigation the project will improve and inform the way in which ponds are operated while simultaneously improving pond operation and resilience.

High Level Research Objectives

  1. Improve viability of Raceway ponds for wastewater treatment

  2. Improve reliability of microalgal species for wastewater treatment

  3. Develop modelling tools for bioreactor operation.

Science

To explore algal storage and uptake mechanism, we are working on understanding the Psr1 gene. Psr1 is a gene which affects many aspects of starvation responses in C. reinhardtii. A literature review has identified a putative link between Psr1 mutants and polyphosphate metabolism.

We are confirming this link, and have identified a shortlist of candidate genes via analysis of RNAseq data. These genes will be assayed for polyphosphate-associated activity followed by further characterisation and potential overexpression/knockout studies in Chlamydomonas. We then aim to further develop these constructs with the aim manipulating microalgae to to improve P content of biomass and aim to transfer these findings in model organism to candidate species AV-12.

Given time constraints we will also investigate Polyphosphate metabolism through cell sorting. We are currently developing methods for qualitatively and quantitatively assessing polyphosphate content as a selection criterion via FACS, which will enable cell cycle and expression analysis.

Impact

The project aims to understand and then enhance the update of phosphorus / phosphate by micro-algae, in order to develop a means to recover / recycle phosphate from waste water in a sustainable manner. We aim to exploit algal genetics to enhance phosphorus uptake, both amount and rate, and to find an acceptable end use for the algal biomass, such as fertiliser substitute or animal feed. Bioinformatics studies will shine further light on the understudied subject of phosphorus metabolism in Chlorophytes.