MicroAlgal Biofilm Reactor (MABR) - Evaluation of Biomass Support Materials and Nitrate Removal Performance

Microalgal biofilms have attracted a good deal of attention as highly beneficial systems capable of reducing the cost of dewatering operations, the costliest component of suspended-growth systems. The support material is a key factor for algal biofilms generating high solids biomass slurries. This study presents results from screening experiments for algae biofilm support materials in a stationary flood-and-drain system (FDS) and a rotating biological contactor (RBC). Areal biomass productivity served as the selection criterion for attachment while nutrient removal performance was also monitored. Batch experiments tested the attachment capability of Scenedesmus obliquus ATCC (R) 11,477 on the surface of several materials, (e.g., cotton duck, PVC foam, ceramic et.) with BG11 as growth medium. The highest average biomass productivity of 3.4 +/- 0.7 g center dot m(- 2)center dot d(- 1) was recorded in the FDS using cotton duck as a support material. Comparable total nitrogen (TN) uptake rates of 3.51 and 3.14 mg L(- 1)d(- 1)were obtained under low P conditions (N:P = 35:1) in the FDS and RBC, respectively. Under high P conditions (N:P = 5:1), the TN uptake rate and removal efficiency increased to 16.04 mg L(- 1)d(- 1) and 99.8%, respectively. In addition, nitrate removal experiments were carried out in a continuous flow microalgal biofilm reactor (MABR) with cotton duck support material operating at steady state and high effluent recirculation rates. The reactor was modeled using first order nitrate uptake kinetics in a completely mixed regime. The applied model fitted the experimental data adequately and allowed for determination of the nitrate uptake rate constant (K = 58.1 d(- 1)) via linear regression (R-2 = 0.967).

Automated summary

Microalgal biofilms are highly beneficial systems that can reduce the cost of dewatering operations. The choice of support material is crucial for generating high solids biomass slurries. This study screened different materials to find the best support material for algal biofilms, and evaluated their attachment capability and nutrient removal performance. The results showed that cotton duck as a support material had the highest average biomass productivity in a stationary flood-and-drain system.