Experimental validation of hindered settling models and flux theory applied in continuous flow process for harvesting Acutodesmus obliquus

Abstract

Batch settling and flux theory were used to predict the best working conditions in a continuous flow process for havesting Acutodesmus obliquus using a tannin‐basis flocculant. From batch tests, a settling velocity model was proposed. Three different models were tested: two exponential functions; and one power‐law function. The power‐law function presented a lower variance (1.356 × 10−9) and R2 equal to 0.995. This suggested model was applied in flux theory, and the system performance was predicted by feed flowrate and initial microalgae concentration in continuous flow process. In experimental tests, a pilot settler (0.045 m3) was used to validate the proposed model. Nine different experimental conditions of feed flowrate and initial microalgae concentrations were used to evaluate the settling behaviour of the unit. The flux theory predicted better results when the applied solids flux was near limiting the solids flux. Experimental results showed that in the proposed working condition of 10−5 m3 s−1 feed flowrate and 58 kg · m−3 initial microalgae concentration, the highest biomass removal was 98.3 %, and sludge concentration profiles could stabilize over time. Overall, these results demonstrate a potential application of the batch tests and theory flux to predict a continuous flow process, considering biomass purification.

Entropy solutions and flux identification of a scalar conservation law modelling centrifugal sedimentation

“…Lerche and Frömer use Kynch's assumption, which is valid when the critical volume fraction is large or compression can be neglected for the suspension at hand. Further experimental support for using only the Kynch assumption for different materials can be found in other works …”

“…The system (49) has unique solutions h, h , h ∈ C 1 (t i , t s ), and the proof is analogous to that of Lemma 14. We recall that ′ ( h ) − ′ ( h ) > 0 by (30). Since h (t), h (t) >â nd S(0, h ) = v( h (t)) > 0, Equations (49b) and (49c) imply that also h is increasing.…”

“…Since ′ ( h ) − ′ ( h ) > 0 by (30) and v( h ) > 0 for h < max , the sign of h ′′ equals the sign of the right-hand side of (50). Grouping terms, we get that the right-hand side of (50) can be written as…”

“…Further experimental support for using only the Kynch assumption for different materials can be found in other works. 1,[25][26][27][28][29][30][31][32][33] Although Baron and Wajs 34 mentioned the method of characteristics to solve (1) (for = 1), it was Anestis 35 (see also Anestis and Schneider 5 ) who presented the basic characteristic equations, jump conditions, and plots of qualitatively different types of solution in the case of the Richardson-Zaki function (cf. RZ defined by (5)) cut off at a maximum volume fraction less than one, such that the function is not continuous there (discontinuous or multi-valued); see Martin et al 32 for experimental verification.…”

Cellular feasibility study of Acutodesmus obliquus

“…Microalgae biomass can be effectively preserved through storage, however, there are few studies that show cell viability techniques when the biomass is refrigerated, or even frozen for long periods of time. The freezing method becomes unfeasible mainly due to the formation of ice crystals, being responsible for cell expansion, causing cell wall disruption (Hanashiro et al 2019;Kapoore et al 2019;Tessarolli, Day, Vieira 2017;Umamaheswari e Shanthakumar, 2016).…”