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

Das, P., Quadir, M. A., Thaher, M. I., Alghasal, G. S. H. S., Aljabri, H. M. S. J.
International journal of environmental science and technology 2019 v.16 no.7 pp. 3355-3364
Chlorella, NPK fertilizers, Scenedesmus, Triticum, algae culture, biofertilizers, biomass production, carbon dioxide, flue gas, leaves, microalgae, municipal wastewater, nitrogen, nutrients, organic carbon, phosphorus, trace elements, wheat
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.