Biokinetic and biotransformation of nitrogen during photosynthetic bacteria wastewater treatment

Comparative study of the removal of sulfate by UASB in light and dark environment

At present, the application of sewage treatment technologies is restricted by high sulfate concentrations. In the present work, the sulfate removal was biologically treated using an upflow anaerobic sludge blanket (UASB) in the absence/presence of light. First, the start-up of UASB for the sulfate removal was studied in terms of COD degradation, sulfate removal, and effluent pH. Second, the impacts of different operation parameters (i.e., COD/SO42- ratio, temperature and illumination time) on the UASB performance were explored. Third, the properties of sludge derived from the UASB at different time were analyzed. Results show that after 28 days of start-up, the COD removal efficiencies in both the photoreactor and non-photoreactor could reach a range of 85-90% while such reactors could achieve > 90% of sulfate being removed. Besides, higher illumination time could facilitate the removal of pollutants in the photoreactor. To sum up, the present study can provide technical support for the clean removal of sulfate from wastewater using photoreactors.

Mineral pollutants removal through immobilized microalgae-bacterial flocs in a multitrophic microreactor

Microalgae-bacterial flocs (MaB-flocs) immobilization technique using polyvinyl alcohol (PVA) crosslinked with sodium alginate represent a novel approach for sustainable pollutants removal. The present work was performed to evaluate the performance of a multitrophic batch reactor at microscale for treating two synthetic wastewater solutions prepared with two different initial Chemical Oxygen Demand (COD): 200 mg.L^-1 and 450 mg.L^-1, respectively. Three MaB-flocs concentrations were entrapped into PVA-alginate beads: C₁ (2%, v/v), C₂ (5%, v/v) and C₃ (10%, v/v), without O₂ supply, during three periods 2, 4 and 6 days of batch incubation. PVA-alginate beads containing the highest concentration C₃ of MaB-flocs improved the performance of the microreactor to remove significantly NH₄⁺ and PO₄^3- of about 61% and 82%, respectively, from wastewater more than two other concentrations used. This result confirms that C₃ of MaB-flocs displays not only a good potential for nutrients removals but also the highest MaB-flocs morphological progression after 6 days of treatment with the highest COD of 450 mg.L^-1. The feasibility of the PVA-alginate for cells immobilization, investigated through microscopy analysis, reveals that the evolution of multicellularity in MaB-flocs, for all experiments.