Growth and value of Chlorella salina grown on highly saline sewage effluent

Chlorella salina was successfully cultivated in secondarily treated domestic sewage effluent of salinity (14%) in an outdoor cultivation tank. Removal efficiencies of NH₄⁺ -N, NO₃⁻ -N, and PO₄³⁻ -P by this alga from secondarily treated sewage effluent were 89–100%, 35–66% and 100%, respectively. The high removal efficiencies of inorganic N and P means that this process can be used as a tertiary sewage treatment. The yield of the sewage-grown algae was 5.1 g m⁻² day⁻¹ for a retention time of 6 days. The high protein content (46.8%), relatively good amino-acid profile and low metal content enabled the use of algal biomass as feed supplement for the silver carp (Hypophthalmichthys molitrix). The food conversion ratios (FCR) of 5% and 10% sewage-grown algae supplemented fish food were better than on the control diet (i.e. artificial fish food alone), while the FCR of 20% sewage-grown algae supplemented fish food and live sewage-grown algae alone were inferior to that on the control diet. These results indicate that cultivation of C. salina in secondarily treated sewage effluent of high salinity can be used as a tertiary sewage treatment to remove inorganic N and P from secondarily treated sewage effluent to reduce pollution problems, and to produce algal protein suitable as a supplement for fish feed in aquaculture.  

Growth and value of Chlorella salina grown on highly saline sewage effluent

Chlorella salina was successfully cultivated in secondarily treated domestic sewage effluent of salinity (14%) in an outdoor cultivation tank. Removal efficiencies of NH₄⁺ -N, NO₃⁻ -N, and PO₄³⁻ -P by this alga from secondarily treated sewage effluent were 89–100%, 35–66% and 100%, respectively. The high removal efficiencies of inorganic N and P means that this process can be used as a tertiary sewage treatment. The yield of the sewage-grown algae was 5.1 g m⁻² day⁻¹ for a retention time of 6 days. The high protein content (46.8%), relatively good amino-acid profile and low metal content enabled the use of algal biomass as feed supplement for the silver carp (Hypophthalmichthys molitrix). The food conversion ratios (FCR) of 5% and 10% sewage-grown algae supplemented fish food were better than on the control diet (i.e. artificial fish food alone), while the FCR of 20% sewage-grown algae supplemented fish food and live sewage-grown algae alone were inferior to that on the control diet. These results indicate that cultivation of C. salina in secondarily treated sewage effluent of high salinity can be used as a tertiary sewage treatment to remove inorganic N and P from secondarily treated sewage effluent to reduce pollution problems, and to produce algal protein suitable as a supplement for fish feed in aquaculture.