Sebastian, 

You can recycle it, however care must be taken for the buildup of undesirable contaminants (both solutes and microrganisms). Mass cultures are rarely axenic, and recycling water can have undesirable microorganisms which will compete with the microalga. If you use flocculating agents, again care must be taken - the microalga can be tolerant, but several agents are polyamines with mild toxicity. Natural flocculants, at the other side, may be a substrate for contaminating bacteria.

Recycling is effectively done in Spirulina cultivation (actually, part of the biomass is separated and extra salts are added to the solution). There is a limit to the amount of biomass that can be produced with the same water, because of the increasing concentration of e.g. sodium.

Another concern is the evaporation - it can be estimated by experimentation or guessed using relative humidity values from the region where you will cultivate. In closed systems there also is evaporation, and that is easier to calculate because the air leaves the system saturated. This is important, because a loss of only 2% of the water each day (for a system aerated with 1VVM) may represent significant loss of water for long cultures.

Your question is important, and alternatives for recycling and pretreating the recycled water must be considered and evaluated environmentally and economically.

If you have a more specific system in mind, I´d be glad to further discuss implications.

Best regards, 

Júlio

Sebastian, 

You can recycle it, however care must be taken for the buildup of undesirable contaminants (both solutes and microrganisms). Mass cultures are rarely axenic, and recycling water can have undesirable microorganisms which will compete with the microalga. If you use flocculating agents, again care must be taken - the microalga can be tolerant, but several agents are polyamines with mild toxicity. Natural flocculants, at the other side, may be a substrate for contaminating bacteria.

Recycling is effectively done in Spirulina cultivation (actually, part of the biomass is separated and extra salts are added to the solution). There is a limit to the amount of biomass that can be produced with the same water, because of the increasing concentration of e.g. sodium.

Another concern is the evaporation - it can be estimated by experimentation or guessed using relative humidity values from the region where you will cultivate. In closed systems there also is evaporation, and that is easier to calculate because the air leaves the system saturated. This is important, because a loss of only 2% of the water each day (for a system aerated with 1VVM) may represent significant loss of water for long cultures.

Your question is important, and alternatives for recycling and pretreating the recycled water must be considered and evaluated environmentally and economically.

If you have a more specific system in mind, I´d be glad to further discuss implications.

Best regards, 

Júlio

If I understood well you are interested in separation methods for algae and water. According to my knowledge the best way is centrifugation.

Best regards

Vit

 good answer Júlio Cesar De Carvalho

Dear Vit

Centrifugation could be possible for small mount.

Bit for huge biomass hod could you centrifuge it?

Regards

Sorry. I can´t contribute to your investigation. I don´t investigate this issue.