Potential impact of biofouling on the photobioreactors of the Offshore Membrane Enclosures for Growing Algae (OMEGA) system

Abstract

The influence of PBR composition [clear polyurethane (PolyU) vs. clear linear low-density polyethylene (LLDPE) (top) and black opaque high-density polyethylene (bottom)] and shape (rectangular vs. tubular) on biofouling and the influence of biofouling on algae productivity were investigated. In 9-week experiments, PBR biofouling was dominated by pennate diatoms and clear plastics developed macroalgae. LLDPE exhibited lower photosynthetic-active-radiation (PAR) light transmittance than PolyU before biofouling, but higher transmittance afterwards. Both rectangular and tubular LLDPE PBRs accumulated biofouling predominantly along their wetted edges. For a tubular LLDPE PBR after 12 weeks of biofouling, the correlation between biomass, percent surface coverage, and PAR transmittance was complex, but in general biomass inversely correlated with transmittance. Wrapping segments of this biofouled LLDPE around an algae culture reduced CO2 and NH3-N utilization, indicating that external biofouling must be controlled.

Biofilm Formation by Chlorella vulgaris is Affected by Light Quality

“…A major group of inhabitants in the initial biofilm formed under conditions where light is present, phototrophic biofilms, are cyanobacteria and microalgae [12,14]. There are many practical issues arising from phototrophic biofilm formation, including problems with biofouling on technical surfaces such as ship hulls and lowered light transmittance in photobioreactors [7,14]. Recent research shows that bacteria, both phototrophs and chemotrophs, can use the quality of the light available to make important lifestyle decisions such as persistence in a single cell state or as a surface-attached biofilm [5].…”

Interactions of marine mammals and birds with offshore membrane enclosures for growing algae (OMEGA)

“…Gulls and coots are omnivores that are known to be well adapted to urbanized environments [44,45] which may explain their opportunistic foraging behavior on the biofouling that developed on the PBRs. The PBR biofouling community in Moss Landing harbor was characterized [46] and found to included diatom films, seaweeds, crustaceans, and bryozoans—known food resources for gulls and coots [28,44]. The observed spikes in the number of coots associated with PBRs may be related to their behavioral tendency to aggregate during foraging [47].…”

“…It has been shown that the submerged surfaces of OMEGA PBRs provide substrate, refugia, and habitat for sessile and associated organisms [46], thereby increasing local productivity and diversity and potentially improving coastal water quality [20,21,56]. …”

Global Agriculture: Industrial Feedstocks for Energy and Materials

“…Interest in algae is also driven by perceived high productivities and the potential for carbon uptake and sequestration in mitigating carbon dioxide emissions from power plants. Sea-based floating membrane bioreactors have also been proposed to enable large-scale off-shore farming of algal biomass using municipal wastewaters as nutrient sources (Howell, 2009;Harris et al, 2013). Commercial yields are unlikely to exceed approximately 80 metric tons dry matter per hectare per year (Scott et al, 2010) although more optimistic estimates are frequently made.…”