Microflotation performance for algal separation

Abstract

The performance of microflotation, dispersed air flotation with microbubble clouds with bubble size about 50 µm, for algae separation using fluidic oscillation for microbubble generation is investigated. This fluidic oscillator converts continuous air supply into oscillatory flow with a regular frequency to generate bubbles of the scale of the exit pore. Bubble characterization results showed that average bubble size generated under oscillatory air flow state was 86 µm, approximately twice the size of the diffuser pore size of 38 µm. In contrast, continuous air flow at the same rate through the same diffusers yielded an average bubble size of 1,059 µm, 28 times larger than the pore size. Following microbubble generation, the separation of algal cells under fluidic oscillator generated microbubbles was investigated by varying metallic coagulant types, concentration and pH. Best performances were recorded at the highest coagulant dose (150 mg/L) applied under acidic conditions (pH 5). Amongst the three metallic coagulants studied, ferric chloride yielded the overall best result of 99.2% under the optimum conditions followed closely by ferric sulfate (98.1%) and aluminum sulfate with 95.2%. This compares well with conventional dissolved air flotation (DAF) benchmarks, but has a highly turbulent flow, whereas microflotation is laminar with several orders of magnitude lower energy density. Biotechnol. Bioeng. 2012; 109:1663–1673. © 2012 Wiley Periodicals, Inc.

Intensification of yeast production with microbubbles

“…The method applied here is similar to the microflotation method previously reported in Hanotu et al, (2012Hanotu et al, ( , 2013Hanotu et al, ( and 2014. After culture, the medium pH was adjusted to 5 and 7 respectively followed by the addition of chitosan for cell agglomeration at varying concentrations: (0, 0.2, 0.4, 0.6, 0.8, 1, 1.2 %v/v).…”

“…The fundamental problems relating to yeast harvesting after propagation are equally challenging but not insurmountable as tuning the bubble size to match the size range for particle harvesting can mitigate both the capital and operating costs , whilst ensuring high recovery efficiency (Hanotu et al, 2012). With microbubble production by fluidic oscillation, this is achievable by either using an appropriate sparger or better yet, adjusting the oscillation frequency.…”

In-situ disinfection and a new downstream processing scheme from algal harvesting to lipid extraction using ozone-rich microbubbles for biofuel production

“…Recovery by flotation is the industry's most effective 68 technique for colloidal particle recovery. The process entails generating bubbles that attach to 69 the cells and results in the rise of the consortium to the surface of the column, where 70 skimming is performed [9] [10]. 71…”

“…After accumulation, the D. salina biomass was harvested via microflotation [9]. A 208 litre of the D. salina culture was obtained (diluted to 1.00 OD 682 ) and pretreatment was 209 performed using aluminium sulphate as a coagulant.…”

“…After this step, the sample was 213 transferred to the one litre microflotation column. According to Hanotu et al [9] 214 microflotation is a fluidic oscillator-driven system of flotation. The microflotation rig is fitted 215 with a steel mesh diffuser with 50 m-sized pores.…”