Microalgal nutrients recycling from the primary effluent of municipal wastewater and use of the produced biomass as bio-fertilizer

Availability of N, P and other trace metals in municipal wastewater (MWW) makes it very attractive to produce microalgae biomass using MWW. Although limited organic carbon is available in MWW, supplementing flue gas as CO2 sources may enhance both the biomass production and recycling of nutrients. Five microalgae strains were grown in the primary effluent of MWW, in a small-scale indoor experiment, to compare their nitrogen and phosphorus recovery abilities. From this study, two potential strains (Chlorella sp., and Scenedesmus sp.) were selected for the large-scale (i.e., 200 L) outdoor experiment. Each of these strains was grown in four different conditions: (1) MWW without any CO2 source, (2) MWW with pure CO2, (3) MWW with simulated flue gas (SFG), and (4) modified BG-11 medium with pure CO2. For both strains, injection of either CO2 or SFG in the MWW cultures resulted in faster growth rates, and higher biomass productivities compared to cultures that did not receive CO2 or SFG. Furthermore, recovery of TN from the MWW was ≥ 95% for the microalgae cultures that received either CO2 or SFG; however, in all cases, phosphorus recovery was less than 15% of the initial concentration. Both the MWW grown microalgae biomass (MWGMB) were used as bio-fertilizer to grow the wheat plant. Both the Number of leaves and the average size of the leaves of the plants were higher for both the MWGMB compared to conventional NPK fertilizer.Acknowledgements This work was supported by Qatar Science andScopu

Potential application of microalgae in produced water treatment

The current study examines pollutant removal efficiency from the produced water of a local petroleum industry by five different local microalgae species. The five microalgae strains Monoraphidium, Chlorella, Neochloris, Scenedesmus, Dictyosphaerium, Chlorella and Dictyosphaerium species showed a significant amount of biomass generation within all different concentrations of produced water. Although the biomass yield of Neochloris strain was low, it was able to remove a higher amount of organic carbon than the other microalgae strains. Although biomass yield varied significantly among the microalgae strains, nitrogen removal efficiency was similar for all strains. Similar results were also obtained for most of the BTEX components. On an average, Dictyosphaerium sp. produced 0.5 g/L biomass density on different strength of produced water. Total nitrogen removal efficiency reached up to 63.76% when Scenedesmus sp. was grown in produced water. Only in case of phosphorus and various metals, removal efficiencies were better by Dictyosphaerium specie; reached up to 88.83%. Despite low biomass generation, Neochloris sp. removed 41.61% of total organic carbon from the different concentrations of produced water. Although benzene and ethylbenzene removal efficiency was 100% for all the different produced water, small amount of toluene and xylene remained in the produced water. Thus, the results indicate that microalgae strains can be used to remediate produced water effluents-derived from petroleum industries.Scopu