Goal: Evaluate bacterial and chemical contamination in algal biomass cultures
One major concern in using waste for algae production is the presence of pathogens and chemical contaminants that could hamper the growth of algae or disqualify algal biomass as a certified fish feed.
Monitoring of the bacterial contamination Validated enzyme specific test kits (figure on the right) were used to determine the levels of total coliforms, E. coli, Enterococcus, and Pseudomonasaeruginosa in algal cultures grown in primary and secondary wastewater effluents spiked with 5% AD effluent (IDEXX Labs, Westbrook, Maine). Our preliminary results showed that 3Log and 4Log removal of total coliforms and E. coli, respectively and 2Log removal of Enterococcus and Pseudomonasaeruginosa can be expected during a 10 day cultivation process. These promising results show that significant pathogen reduction is attained during growth and pathogens did not hinder the growth of C. sorokiniana.
Monitoring of the heavy metals contamination Results achieved in our lab and other studies reported in the literature show that heavy metals and organic pollutants have the potential to bioaccumulate in algae and subsequently in fish during use as aquaculture feed. As for metals, we know that Cr, Ni, Cu, Pb, Cd, Zn are common in domestic sewage water and sludge. While major fractions are distributed between precipitates (by sulfide, carbonate, or phosphate) or assimilated in anaerobic microbes during AD, a minor fraction is still bioavailable as soluble complexes with natural chelating compounds.
The Bouwer Lab maintains an inductively coupled plasma mass spectroscopy (ICP-MS) instrument (see the figure). The ICP-MS is ideal for heavy metal analysis that allows multi-element analysis with detection limit 1-100 ppt. It will be used to assess both AD effluent and algal biomass product.
The maximum concentration is regulated in animal and fish feed including As , Cd, Hg, and Pb. Our group examined the levels of these toxic metals in the wastewater, AD effluent, and algal biomass. We found that the algal biomass cultivated in wastewater meets this requirement for Cd and Pb content, but As and Hg must be examined additionally.