Harvesting of chitosan coagulated Chlorella vulgaris using cyclic membrane filtration-cleaning

Membrane filtration is an efficient harvesting technique for microalgae. This work experimentally evaluated the performances of cyclic filtration and cleaning tests on Chlorella vulgaris, which has excellent potential for CO₂ capture and lipid production. The algal cells were coagulated using chitosan and were filtered at 1bar using a surface-modified hydrophilic polytetrafluoroethylene (PTFE) membrane. Direct filtration of the original algal suspension led to severe irreversible fouling on the PTFE membrane. Coagulation using 50mg/L chitosan can mitigate pore blocking but cannot enhance filtration flux. With 100mg/L chitosan, most fines were incorporated into large flocs to build up cakes of low resistance and protect membrane pores from severe blocking. Flux recovery ratios after cleaning all exceeded 95% at greater than 50mg/L chitosan dosage. The chitosan-coagulation and surface modified PFTE membrane are feasible to dewater the C. vulgaris ESP-6 isolate using cyclic filtration-cleaning process. © 2012 Taiwan Institute of Chemical Engineers.