Current studies have shown that microalgae growth and phosphorus
removal in cold region wastewater systems are inconsistent
and not well understood (Ragush et al., 2015; Schmidt et al., 2016).
Therefore, the objective of this study is to determine microalgae
growth rates and phosphorus uptake under simulated cold
regions conditions. A lab scale factorial experiment was used to
evaluate multiple conditions and their associated interactions. The
conditions studied were temperature, photosynthetically active
radiation (PAR) and phosphorus concentration. Luxury uptake was
quantified in order to determine predominate removal mechanisms.
Chlorella vulgaris and Chlamydomonas reinhardtii were used,
as they were previously identified as two prominent microalgae
species in facultative WSPs operated in cold climates.
2. Materials and methods
2.1. Algae cultivation
Chlorella vulgaris and Chlamydomonas reinhardtii strains were
obtained from the National Research Council of Canada. Strains
were cultivated in 250 mL erlenmeyer flasks under constant illumination
using a modified Bold 3 N medium developed by UTEX.
These cultures were used to seed a 10 L chemostat receiving simulated
raw wastewater as growth medium. A chemostat was used in
order to maintain a consistent inoculant for experiments. The simulated
wastewater recipe is shown in Table 1. No organic carbon
was added in order to minimize bacterial growth. Sodium EDTA
was added as a chelating agent to prevent metal precipitation. The
chemostat was under constantillumination using fluorescentlights
resulting in a PAR of approximately 150 mol/m2/s on the immediate
surface.
2.2. Experimental approach
Temperature, initial phosphorus concentration and PAR were
tested to determine their influence on microalgae growth rates and
phosphorus uptake. A summary of the levels used for each factor
is shown in Table 2. PAR and temperature levels were representa-