Cationic polyacrylamide induced flocculation and turbulent dewatering of microalgae on a Britt Dynamic Drainage Jar

• Published in: Separation and purification technology 2020-02, Vol.233, p.116004, Article 116004
• Main Authors: Musa, Mutah, Wolf, Juliane, Stephens, Evan, Hankamer, Ben, Brown, Richard, Rainey, Thomas J.
• Format: Article
• Language: English
• Subjects: Biofuels; Britt dynamic drainage jar; Desirability function; Dewatering; Microalgae; Response surface methodology (RSM)
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2019.116004

•Microalgae dewatering using papermaking technique was assessed on a Britt jar.•Effects of stirrer speed, flocculant dosage and pH on retention was investigated.•Response surface methodology (RSM) was used to analyse and optimize the process.•The formation of shear-stable flocs using a cationic polyacrylamide was achieved.•Microalgae dewatering on a paper machine wet-end is feasible and will be efficient. Dewatering is one of the major constraints to the large scale production of microalgae biofuels, with many drawbacks in currently deployed technologies. Using an approach similar to papermaking, cationic polyacrylamide (CPAM) based flocculants can stabilize flocs of microalgae under turbulent conditions to achieve effective dewatering of dilute suspensions in high speed filtration systems. The effects of flocculant dosage, stirrer speed (i.e. turbulence) and pH on filtration retention was investigated using a Britt Dynamic Drainage Jar (BDDJ) which simulates a commercial paper machine. The development of a stable floc system that withstood turbulence was achieved through the flocculant’s dual effects of charge neutralization and bridging of the microalgae cells. Retention of microalgae on a 76 µm screen improved from 7% when no flocculant was used to 94% at a flocculant dosage of 10 mg/L of CPAM, stirrer speed of 1200 rpm and pH of 6.5 as optimum conditions. The most significant effects on microalgae retention were that of flocculant dosage; followed by the combined interaction between stirrer speed and flocculant dosage; and that of pH. A key finding is that high retention was obtained under moderately turbulent conditions. This study shows that the paper dewatering technique will be potentially applicable for microalgae preconcentration in the production of biofuels, and further pilot scale studies are recommended.