Ammonia–nitrogen and orthophosphate removal by immobilized Scenedesmus sp. isolated from municipal wastewater for potential use in tertiary treatment

Scendesmus   sp. isolated from municipal wastewater, entrapped in calcium alginate as algal sheets was employed to remove inorganic nutrients (N and P) from artificial and real domestic secondary effluents in parallel-plate bioreactor after starvation. The key factors affecting the removal efficiency (NH4+–N and PO43-–P), system stability and reuse efficiency of screens were studied and discussed. It has been shown that cell density in the mixture of algal gel was the key factor compared with the thickness of the gel and the cell density of the reactor. A complete removal of NH4+–N and PO43-–P was achieved within 4 h of treatment in parallel bioreactors with the optimal cell density in the mixture of algal (2 × 108 algae mL−1) and 3 mm gel sheets after second cycle. Nine cycles of wastewater treatment in 21 days were accomplished, holding higher removal efficiency. NH4+–N removal efficiency was 99.1% after 105 min, 100% after 135 min, PO43-–P removal efficiency was 100% after 15 min in domestic secondary effluents. Immobilized Scendesmus sp. is shown to have great potentialities for removal of inorganic nitrogen and phosphorus from treated effluents.