title: [Hydroxylamine conversion by anammox enrichment].
abstract: OBJECTIVE
  Hydroxylamine is an important intermediate product of anammox. This study was focused on the characteristics of hydroxylamine and nitrite conversions by anammox enrichment.
  
  
  METHODS
  The changes of nitrogenous substrates and related products with time were measured using batch tests with anammox enrichment as inoculum.
  
  
  RESULTS
  Since hydroxylamine didn't react with nitrite in uninoculated control culture, these two compounds were chemically stable. Both of them decreased with time in anammox enrichment inoculated cultures, in which ammonia as intermediate product would be produced and converted with the maximum concentration being 0.338 mg/L. The total nitrogen concentration decreased from 4.694 mmol/L to 0.812 mmol/L with conversion rate 82.7% in the end. When hydroxylamine and nitrite concentrations were about 2.5 mmol/L respectively, the maximum specific sludge conversion rates of hydroxylamine was 0.535 mmol/(gVSS.h), which was 1.81 times bigger than that of ammonia in ammonia reaction system; the maximum specific sludge rate of total nitrogen was slightly higher than that in ammonia reaction system. When hydroxylamine concentration increased to 5.0 mmol/L, the hydroxylamine and nitrite conversion rates promoted by 26.7% and 120.7% respectively; and the maximum ammonia accumulated was 1.810 mmol/L. When nitrite concentration increased to 5.0 mmol/L, the hydroxylamine and nitrite conversion rates promoted by 6.9% and 9.0% respectively; and the maximum ammonia accumulated was 0.795 mmol/L.
  
  
  CONCLUSIONS
  Anammox enrichment was capable of converting hydroxylamine and nitrite simultaneously and had the higher conversion rate of hydroxylamine than ammonia conversion rate. Hydroxylamine and nitrite conversion rates were less affected by increase in nitrite concentration, but more significantly influenced by increase in hydroxylamine. The maximum ammonia concentration accumulated would rise as the result of increasing both hydroxylamine and nitrite. The result of experiment was consistent with pathway model presented by van de Graaf AA.
authors.affiliation: Department of Environmental Engineering, Zhejiang University, Hangzhou 310029, China. hu_anhui@126.com
authors.forename: Anhui
authors.initials: A
authors.lastname: Hu
authors.forename: Ping
authors.initials: P
authors.lastname: Zheng
authors.forename: Huifeng
authors.initials: H
authors.lastname: Lu
authors.forename: Shuang
authors.initials: S
authors.lastname: Ding
authors.forename: Caihua
authors.initials: C
authors.lastname: Wang
mesh_terms: D000641:Ammonia / Q000737:chemistry*; D019149:Bioreactors / Q000382:microbiology; D019811:Hydroxylamine / Q000737:chemistry*; D009573:Nitrites / Q000737:chemistry*; D012722:Sewage / Q000737:chemistry; D014865:Waste Disposal, Fluid
chemical_list: D009573:Nitrites; D012722:Sewage; D019811:Hydroxylamine; D000641:Ammonia