Design of batch algal cultivation systems and ranking of the design parameters

Abstract

In this article, we developed a process to design batch algal cultivation systems consisting of outdoor ponds, indoor photobioreactors (PBRs), outdoor PBRs, and indoor ponds for both freshwater and industrial wastes (wastewater and flue gas). We considered pH, temperature, light conditions, carbon, nutrients, inhibitors, mixing, and O2 degassing as design parameters and sequentially ranked them according to the necessity of cultivation conditions. Although each set of conditions warrants a unique design according to the requirements, some scenarios were common for every system, i.e., microalgae species, temperature, pH, light, size, shape, and material were always ranked before nutrients, and mixing technique and inhibitors were consistently ranked after nutrients. Light and temperature for outdoor conditions, pH for ponds, and nitrogen and phosphorus were deemed noncontrollable. Ponds do not require material for construction; O2 degassing and the selection of microalgae were always ranked first; and SOx and NOx were considered only for industrial flue gas. We constructed cultivation models of Chlorella vulgaris (C. vulgaris) for Bangkok based on the developed designs of algal cultivation systems. Monod’s model (mathematical model) and simulations by SuperPro Designer software using the optimum parameter values predicted a maximum algal productivity of 0.0114–0.0381 and 0.11–0.7 g/l/day (open pond and PBR, respectively), bioremediation of 52–70% and 81–90% (open pond and PBR; only wastewater), and CO2 biofixation of < 1% (only PBR). A comparison between the results found in this study and the literature on C. vulgaris suggests that both Monod’s model and simulation software can predict algal productivity and bioremediation, but they are not recommended for CO2 biofixation.