Microbial biomass recovery using a synthetic cationic polymer

A synthetic cationic polymer (Praestol) for biomass recovery by flocculation of Tetraselmis suecica, Spirulina platensis and Rhodopseudomonas palustris was tested both in the laboratory and outdoors. The flocculating efficiency of Praestol increased with the dose used up to 1 mg litre-i for all microorganisms tested. With this flocculant dose, the percentage of biomass separated was 86% for Rhodopseudomonas and 70% for Tetraselmis and Spirulina. The maximum flocculation efficiency was observed when the flocculant : biomass ratio was 1:1000 (by weighO. Moreover, satisfactory flocculation efficiency was maintained when Praestol was used on cultures grown in sea- or brackish-water media. No inhibitory effect on the growth of the cultures was noted when the medium was recycled in the pond afier flocculation.