The productivity of the thin-layer microalgal cultures was also strongly influenced by the surface/volume ratio (S/V). This could be documented by comparing the growth of the Chlorella cultures in the experimental and production units, which differed significantly in S/V ratio. A 17-day experiment showed that growth of Chlorella was much faster in the experimental unit with S/V ratio of 133 m⁻¹ than in the production unit with S/V ratio of 102 m⁻¹, despite the same starting biomass concentration (Fig. 9). The mean net productivity of both cultivation units was calculated from five cultivation cycles. We found values of 18.7 ± 5.14 and 14.3 ± 4.11 g dry biomass m⁻² day⁻¹ for the experimental and production units, respectively (Table 3). Thus, the experimental unit with higher S/V ratio was more productive by about 30% on average during a 4-month cultivation period from June to September 2007 in comparison with the production at lower S/V ratio.