Xaxaxa xaiaaD x a d xb xbxb xbitaabo xyxbAb o

Completely mixed, continuous culture with one limiting nutrient (S), two competing species (a, b), and bionsass recycle us .lag a selective separator which favors the slower growing species "a". V - volume of reactor; F «

volumetric inflow rate; D » dilution rate 5 F/Y; S « influent concentration

of limiting substrate; S = concentration of limiting substrate in reactor; x\ X^, X^ « concentration of species i in reactor, recycle stream and second outflow, and first outflow respectively; u " specific growth rate of species i • V S/K^ + S; a - ratio of recycle flow to inflow; 6 ® ratio m i i _± i of second outflow("product" stream) to inflow; 3 = 3L/T"; a B / CI + a) - ratio of cell mass recycled to cell mass coming out of reactor (0 <a 0 /(1 + a) < 1)

A^ = 1 + a - a 8i> 0; » yield constant for species i. Since the separator s b &

favors species a, 8 > 3 and g > 1. A, dot over a symbol indicates its

Figure III.A. 1. Selection process through biomass recycle.

A theoretical model of selective cell harvesting and recycling resulting in dominance of the slower-growing over the faster-growing species. (Source: Benemann et al.

Figure III. A.2. Initial experiment demonstrating the maintenance of Oscillatoria in outdoor ponds.

Maintenance of a culture of Napa Oscillatoria using selective recycle. Bars indicate the relative volume, concentration and filament length distribution of Oscillatoria (while bat height indicates filaments shorter than 150 ^m; vertical stripes indicate filaments between 150 and 375 ^m; slashes indicate filaments longer than 375 ^m). Volumes of single algal cells were calculated on an equivalent concentration basis and are shown as triangles (shaded area, top). Vertical arrows marked R indicate when the culture was harvested with a microstrainer (30-^m opening fabric) and the captured algae (almost all Oscillatoria) returned to the pond. Experiments were carried out in a

3-m circular pond mixed continuously at 3 cm/s. Settled raw sewage, supplemented with 100 ppm of bicarbonate was used as substrate. (Source: Benemann et al. 1977).

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