title: Nitrous oxide emissions for early warning of biological nitrification failure in activated sludge.
abstract: Experiments were carried out to establish whether nitrous oxide (N2O) could be used as a non-invasive early warning indicator for nitrification failure. Eight experiments were undertaken; duplicate shocks DO depletion, influent ammonia increases, allylthiourea (ATU) shocks and sodium azide (NaN3) shocks were conducted on a pilot-scale activated sludge plant which consisted of a 315 L completely mixed aeration tank and 100 L clarifier. The process performed well during pre-shock stable operation; ammonia removals were up to 97.8% and N2O emissions were of low variability (<0.5 ppm). However, toxic shock loads produced an N2O response of a rise in off-gas concentrations ranging from 16.5 to 186.3 ppm, followed by a lag-time ranging from 3 to 5 h ((0.43-0.71) x HRT) of increased NH3-N and/or NO2(-) in the effluent ranging from 3.4 to 41.2 mg L(-1). It is this lag-time that provides the early warning for process failure, thus mitigating action can be taken to avoid nitrogen contamination of receiving waters.
authors.affiliation: Southern Water, Captstone Road, Chatham, Kent, ME57QA, UK. mark.butler@southernwater.co.uk
authors.forename: M D
authors.initials: MD
authors.lastname: Butler
authors.forename: Y Y
authors.initials: YY
authors.lastname: Wang
authors.forename: E
authors.initials: E
authors.lastname: Cartmell
authors.forename: T
authors.initials: T
authors.lastname: Stephenson
mesh_terms: D000641:Ammonia / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D009609:Nitrous Oxide / Q000032:analysis*; D010100:Oxygen / Q000378:metabolism; D010865:Pilot Projects; D012722:Sewage; D013997:Time Factors
chemical_list: D012722:Sewage; D000641:Ammonia; D009609:Nitrous Oxide; D009584:Nitrogen; D010100:Oxygen