title: A new photo-activated sludge system for nitrification by an algal-bacterial consortium in a photo-bioreactor with biomass recycle.
abstract: Wastewater treatment technologies requiring large areas may be less feasible in urbanizing regions of developing countries. Therefore, a new technology, named photo-activated sludge (PAS), was investigated to combine the advantages of regular activated sludge systems with those of algae ponds for the removal of ammonium. The PAS consisted of a mixed photo-bioreactor, continuously fed with BG-11 medium, adjusted to 66 mgN-NH4⁺/l. The reactor volume was 2 l, hydraulic retention time was 24 hours, with a depth of 8 cm, and continuous illumination at the water surface was 66 μmol PAR/m²/s (photosynthetically active radiation). Reactor effluent passed through a settler and settled biomass was returned to the reactor. A well settling biomass developed, that contained both algae and nitrifiers. Effluent contained 10 mgN-NH4⁺/L and 51 mgN-NOx⁻/L. Using a simplified model, the specific algae growth rate was estimated at about 0.62 day⁻¹, which was within the expected range. For nitrifiers (ammonia oxidizers), the specific growth rate was 0.11 day⁻¹, which was lower than reported for regular activated sludge. The in-situ photo-oxygenation process by algae contributed 82% of the oxygen input, whereas oxygen diffusion through the mixed surface provided the remaining 18%. The foreseen energy savings that a PAS system could achieve warrant further investigations with real wastewater.
authors.affiliation: Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education, PO Box 3015, 2601 DA, Delft, The Netherlands E-mail: p.vandersteen@unesco-ihe.org.
authors.forename: Peter
authors.initials: P
authors.lastname: van der Steen
authors.affiliation: Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education, PO Box 3015, 2601 DA, Delft, The Netherlands E-mail: p.vandersteen@unesco-ihe.org.
authors.forename: Kuntarini
authors.initials: K
authors.lastname: Rahsilawati
authors.affiliation: Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education, PO Box 3015, 2601 DA, Delft, The Netherlands E-mail: p.vandersteen@unesco-ihe.org.
authors.forename: Angélica M
authors.initials: AM
authors.lastname: Rada-Ariza
authors.affiliation: Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education, PO Box 3015, 2601 DA, Delft, The Netherlands E-mail: p.vandersteen@unesco-ihe.org.
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Lopez-Vazquez
authors.affiliation: Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education, PO Box 3015, 2601 DA, Delft, The Netherlands E-mail: p.vandersteen@unesco-ihe.org.
authors.forename: Piet N L
authors.initials: PN
authors.lastname: Lens
mesh_terms: D018533:Biomass; D019149:Bioreactors; D008027:Light; D058465:Nitrification; D061005:Ponds; D059027:Recycling; D012722:Sewage / Q000382:microbiology*; D014865:Waste Disposal, Fluid; D062065:Wastewater; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000378:metabolism
chemical_list: D012722:Sewage; D062065:Wastewater; D014874:Water Pollutants, Chemical