The influences of the recycle process on the bacterial community in a pilot scale microalgae raceway pond

• Bacteria were present over the whole harvest/recycle process at large scale.
• Electroflocculation had little effect over the bacterial community.
• Bacteria found within this study are a symbiotic partner to Tetraselmis sp.

The use of recycled media has been shown to be a necessary step within the lifecycle of microalgal biofuels for economic sustainability and reducing the water footprint. However the impact of the harvesting of microalgae on the bacterial load of the recycled water has yet to be investigated. Within this study PCR–DGGE and real-time PCR was used to evaluate the bacterial community dynamics within the recycled water following harvest and concentration steps for a pilot scale open pond system (120,000 L), which was developed for the production of green crude oil from Tetraselmis sp. in hyper saline water. Two stages were used in the harvesting; Stage 1 electroflocculation, and Stage 2 centrifugation. Electroflocculation was shown to have little effect on the bacterial cell concentration. In contrast bacterial diversity and cell concentration within the centrifugation step was greatly reduced.