title: Influence of iron precipitated condition and light intensity on microalgae activated sludge based wastewater remediation.
abstract: The indigenous microalgae-activated sludge (MAAS) process during remediation of municipal wastewater was investigated by studying the influence of iron flocculation step and light intensity. In addition, availability of total phosphorous (P) and photosynthetic activity was examined in fed-batch and batch mode under northern climatic conditions and limited lighting. This was followed by a semi-continuous operation with 4 d of hydraulic retention time and mean cell residence time of 6.75 d in a photo-bioreactor (PBR) with varying P availability. The fed-batch condition showed that P concentrations of 3-4 mg L-1were effective for photosynthetic chl. a development in iron flocculated conditions. In the PBR, the oxygen evolution rate increased with increase in the concentration of MAAS (from 258 to 573 mg TSS L-1) at higher surface photosynthetic active radiation (250 and 500 μmol m-2s-1). Additionally, the rate approached a saturation phase at low MAAS (110 mg L-1) with higher light intensities. Semi-continuous operation with luxury P uptake and effective P condition showed stable average total nitrogen removal of 88 and 92% respectively, with residual concentrations of 3.77 and 2.21 mg L-1. The corresponding average P removal was 68 and 59% with residual concentrations of 2.32 and 1.75 mg L-1. The semi-continuous operation produced a rapidly settleable MAAS under iron flocculated condition with a settling velocity of 92-106 m h-1and sludge volume index of 31-43 ml g-1in the studied cases.
authors.affiliation: Department of Energy, Building and Environment, Mälardalen University, SE-721 23, Västerås, Sweden. Electronic address: anbarasan.anbalagan@live.com.
authors.forename: Anbarasan
authors.initials: A
authors.lastname: Anbalagan
authors.affiliation: Department of Energy, Building and Environment, Mälardalen University, SE-721 23, Västerås, Sweden.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Schwede
authors.affiliation: Department of Energy, Building and Environment, Mälardalen University, SE-721 23, Västerås, Sweden; ABB AB, Corporate Research, SE-721 28, Västerås, Sweden.
authors.forename: Carl-Fredrik
authors.initials: CF
authors.lastname: Lindberg
authors.affiliation: Department of Energy, Building and Environment, Mälardalen University, SE-721 23, Västerås, Sweden.
authors.forename: Emma
authors.initials: E
authors.lastname: Nehrenheim
mesh_terms: D019149:Bioreactors; D011232:Chemical Precipitation; D005427:Flocculation; D007501:Iron / Q000737:chemistry / Q000378:metabolism; D008027:Light; D058086:Microalgae / Q000378:metabolism* / Q000528:radiation effects; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism; D012722:Sewage / Q000737:chemistry*; D062065:Wastewater / Q000737:chemistry; D018508:Water Purification / Q000379:methods*
chemical_list: D007501:Iron; D009584:Nitrogen; D012722:Sewage; D062065:Wastewater
keywords: Iron flocculation; Microalgae-activated sludge flocs; Nitrogen; Phosphorous; Photosynthetic active radiation; Settling velocity