Modeling and Evaluation of CO₂ Supply and Utilization in Algal Ponds

Abstract

A mathematical model was constructed to simulate the behaviour of an open algal pond particularly with respect to CO 2 supply and utilisation. The algal pond considered takes wastewater as feed, which provides substrate for aerobic bacteria and also nutrients for the algal-bacterial consortium. CO 2 -containing gas such as flue gas or biogas is considered as additional source of CO 2 to support the growth of algae which at the same time also serves the purpose of CO 2 abatement. A number of simulation studies were carried out to evaluate the performance of the system in terms of the production of algae, treatment of wastewater, and CO 2 fixation and removal. Important design and operating parameters were considered, including pond depth, hydraulic retention time, composition of the feed wastewater, flowrate and CO 2 fraction of the supplied gas flow, and the area utilised for gas flow induction. Several useful observations were made based on the simulation results, with the potential to provide guidance to the future practical development of multi-functional algal ponds.

Hydration status and diurnal trophic interactions shape microbial community function in desert biocrusts

“…Even when the soil is nearly saturated, the rate is ∼ 1-10 s −1 ( → 1, θ ≈ θ s ). For comparison, studies on waste water treatment used the rate of ≈ 6.9 × 10 −5 s −1 (Buhr and Miller, 1983;Yang, 2011). Thus, mass transfer between gas and liquid in unsaturated soils is assumed to be rapid, and the concentration at each phase is always at equilibrium following Henry's law:…”

“…Some mathematical models have introduced pH estimation for systems with phototrophs under light-dark cycles, such as algal ponds (Buhr and Miller, 1983;Yang, 2011;Gomez et al, 2014) and phototrophic biofilms (Wolf et al, 2007). The algal pond models invoke solution equilibrium and charge neutrality and employ differential algebraic equations to estimate pH, while the phototrophic biofilm models consider acid-base reactions with rate equations by proposing near-equilibrium kinetics.…”

Microalgae production in a biofilm photobioreactor

“…Although this study was the first to optimize CO 2 utilization for biofilm cultivations, the results are in the high range of results with suspension cultivations. Two studies demonstrated CO 2 utilization efficiencies around 70% without significant productivity penalties (Valiorgue et al 2014;Yang 2011). Other studies report CO 2 utilization efficiencies up to 95%, however, the implications for biomass productivity were not quantified (Doucha and Lívanský 2006;Rubio et al 1999).…”

“…For microalgae grown in suspended cultures, processes with minimal CO 2 loss have been developed by employing experimentally validated models (Doucha and Lívanský 2006;Rubio et al 1999;Valiorgue et al 2014;Yang 2011). Their primary conclusion is that CO 2 utilization can be improved by increasing the mass transfer from the gas to the liquid (Doucha and Lívanský 2006;Rubio et al 1999;Valiorgue et al 2014;Yang 2011).…”

“…Their primary conclusion is that CO 2 utilization can be improved by increasing the mass transfer from the gas to the liquid (Doucha and Lívanský 2006;Rubio et al 1999;Valiorgue et al 2014;Yang 2011). For microalgal biofilm cultivation, however, processes with minimal CO 2 loss have not been developed, though it has been demonstrated that elevated CO 2 levels are required for maximal productivity Ji et al 2013a;Schultze et al 2015).…”