Critical evaluation and modeling of algal harvesting using dissolved air flotation. DAF Algal Harvesting Modeling

Journal Article · Mon Jul 14 00:00:00 EDT 2014 · Biotechnology and Bioengineering

DOI: https://doi.org/10.1002/bit.25300 · OSTI ID:1141043

Zhang, Xuezhi ^[1]; Hewson, John C. ^[2]; Amendola, Pasquale ^[1]; Reynoso, Monica ^[1]; Sommerfeld, Milton ^[1]; Chen, Yongsheng ^[3]; Hu, Qiang ^[4]

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1. Arizona State Univ., Mesa, AZ (United States)
2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
3. Georgia Inst. of Technology, Atlanta, GA (United States)
4. Chinese Academy of Sciences (CAS), Hubei (China)

In our study, Chlorella zofingiensis harvesting by dissolved air flotation (DAF) was critically evaluated with regard to algal concentration, culture conditions, type and dosage of coagulants, and recycle ratio. Harvesting efficiency increased with coagulant dosage and leveled off at 81%, 86%, 91%, and 87% when chitosan, Al³⁺, Fe³⁺, and cetyl trimethylammonium bromide (CTAB) were used at dosages of 70, 180, 250, and 500 mg g^-1, respectively. The DAF efficiency-coagulant dosage relationship changed with algal culture conditions. In evaluating the influence of the initial algal concentration and recycle ratio revealed that, under conditions typical for algal harvesting, we found that it is possible that the number of bubbles is insufficient. A DAF algal harvesting model was developed to explain this observation by introducing mass-based floc size distributions and a bubble limitation into the white water blanket model. Moreover, the model revealed the importance of coagulation to increase floc-bubble collision and attachment, and the preferential interaction of bubbles with larger flocs, which limited the availability of bubbles to the smaller sized flocs. The harvesting efficiencies predicted by the model agree reasonably with experimental data obtained at different Al³⁺ dosages, algal concentrations, and recycle ratios. Based on this modeling, critical parameters for efficient algal harvesting were identified.

• Research Organization: Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC04-94AL85000
• OSTI ID: 1141043
• Report Number(s): SAND--2014-1616J; 505032
• Journal Information: Biotechnology and Bioengineering, Journal Name: Biotechnology and Bioengineering Journal Issue: 12 Vol. 111; ISSN 0006-3592
• Publisher: WileyCopyright Statement
• Country of Publication: United States
• Language: English