title: Post-denitrification using alginate beads containing organic carbon and activated sludge microorganisms.
abstract: Nitrate concentration in the final effluent is a key issue in pre-denitrification biological treatment systems. This study investigated post-denitrification with alginate beads containing immobilized activated sludge microorganisms and organic carbon source. A batch study was first performed to identify suitable carbon sources among acetate, glucose, calcium tartrate, starch and canola oil on the basis of nitrate removal and bead stability. Canola oil and starch beads exhibited significantly higher denitrification rates, greater bead stability and lower nitrite accumulation (6 mg/L and 10 mg/L, respectively). Glucose and acetate beads showed longer acclimation phases and degraded faster whereas tartrate beads had higher nitrite build-up (39 mg/L) and degraded due to brittleness. Post-denitrification with canola oil and starch beads was investigated in the final clarifier of a coupled upflow bioreactor and aerobic system treating synthetic dairy farm wastewater, and showed a denitrification efficiency of >90%. Beads faded in 12 days due to alginate degradation. Therefore, enhancement in bead strength or use of more stable nontoxic gel would be required to further prolong the treatment. Moreover, this study was conducted at laboratory scale and further research is needed for application in real systems.
authors.affiliation: Department of Civil and Environmental Engineering, The University of Auckland, Auckland 1142, New Zealand E-mail: drfarhan@awkum.edu.pk; Present address: Department of Environmental Sciences, Abdul Wali Khan University, Mardan 23200, Pakistan.
authors.forename: Dilawar Farhan
authors.initials: DF
authors.lastname: Shams
authors.affiliation: UR 114 BioWooEB-CIRAD, Montpellier, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Rubio
authors.affiliation: Department of Civil and Environmental Engineering, The University of Auckland, Auckland 1142, New Zealand E-mail: drfarhan@awkum.edu.pk.
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Elefsiniotis
authors.affiliation: Department of Civil and Environmental Engineering, The University of Auckland, Auckland 1142, New Zealand E-mail: drfarhan@awkum.edu.pk.
authors.forename: Naresh
authors.initials: N
authors.lastname: Singhal
mesh_terms: D000464:Alginates / Q000737:chemistry*; D019149:Bioreactors; D002244:Carbon; D058440:Denitrification; D020723:Glucuronic Acid / Q000737:chemistry; D006603:Hexuronic Acids / Q000737:chemistry; D009566:Nitrates; D009573:Nitrites / Q000378:metabolism; D012722:Sewage / Q000382:microbiology*; D014865:Waste Disposal, Fluid / Q000379:methods; D062065:Wastewater
chemical_list: D000464:Alginates; D002244:Carbon; D020723:Glucuronic Acid; D006603:Hexuronic Acids; D009566:Nitrates; D009573:Nitrites; D012722:Sewage; D062065:Wastewater