title: Effect of different salt adaptation strategies on the microbial diversity, activity, and settling of nitrifying sludge in sequencing batch reactors.
abstract: The effect of salinity on the activity of nitrifying bacteria, floc characteristics, and microbial community structure accessed by fluorescent in situ hybridization and polymerase chain reaction-denaturing gradient gel electrophoresis techniques was investigated. Two sequencing batch reactors (SRB₁ and SBR₂) treating synthetic wastewater were subjected to increasing salt concentrations. In SBR₁, four salt concentrations (5, 10, 15, and 20 g NaCl/L) were tested, while in SBR₂, only two salt concentrations (10 and 20 g NaCl/L) were applied in a more shock-wise manner. The two different salt adaptation strategies caused different changes in microbial community structure, but did not change the nitrification performance, suggesting that regardless of the different nitrifying bacterial community present in the reactor, the nitrification process can be maintained stable within the salt range tested. Specific ammonium oxidation rates were more affected when salt increase was performed more rapidly and dropped 50% and 60% at 20 g NaCl/L for SBR₁ and SBR₂, respectively. A gradual increase in NaCl concentration had a positive effect on the settling properties (i.e., reduction of sludge volume index), although it caused a higher amount of suspended solids in the effluent. Higher organisms (e.g., protozoa, nematodes, and rotifers) as well as filamentous bacteria could not withstand the high salt concentrations.
authors: Department of Biotechnology, Delft University of Technology, Julianalaan 67, Delft 2628 BC, The Netherlands. j.p.bassin@tudelft.nl
authors: João Paulo
authors: JP
authors: Bassin
authors: Robbert
authors: R
authors: Kleerebezem
authors: Gerard
authors: G
authors: Muyzer
authors: Alexandre Soares
authors: AS
authors: Rosado
authors: Mark C M
authors: MC
authors: van Loosdrecht
authors: Marcia
authors: M
authors: Dezotti
mesh_terms: D000222:Adaptation, Physiological; D000641:Ammonia / Q000378:metabolism; D001419:Bacteria / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D019149:Bioreactors / Q000382:microbiology*; D004587:Electrophoresis, Agar Gel / Q000379:methods; D017404:In Situ Hybridization, Fluorescence; D058465:Nitrification / Q000187:drug effects*; D016133:Polymerase Chain Reaction / Q000379:methods; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D012722:Sewage / Q000737:chemistry / Q000382:microbiology*; D012965:Sodium Chloride / Q000737:chemistry / Q000494:pharmacology*; D014865:Waste Disposal, Fluid
chemical_list: D012336:RNA, Ribosomal, 16S; D012722:Sewage; D012965:Sodium Chloride; D000641:Ammonia