title: Dosing free nitrous acid for sulfide control in sewers: results of field trials in Australia.
abstract: Intermittent dosing of free nitrous acid (FNA), with or without the simultaneous dosing of hydrogen peroxide, is a new strategy developed recently for the control of sulfide production in sewers. Six-month field trials have been carried out in a rising main sewer in Australia (150 mm in diameter and 1080 m in length) to evaluate the performance of the strategy that was previously demonstrated in laboratory studies. In each trial, FNA was dosed at a pumping station for a period of 8 or 24 h, some with simultaneous hydrogen peroxide dosing. The sulfide control effectiveness was monitored by measuring, on-line, the dissolved sulfide concentration at a downstream location of the pipeline (828 m from the pumping station) and the gaseous H2S concentration at the discharge manhole. Effective sulfide control was achieved in all nine consecutive trials, with sulfide production reduced by more than 80% in 10 days following each dose. Later trials achieved better control efficiency than the first few trials possibly due to the disrupting effects of FNA on sewer biofilms. This suggests that an initial strong dose (more chemical consumption) followed by maintenance dosing (less chemical consumption) could be a very cost-effective way to achieve consistent control efficiency. It was also found that heavy rainfall slowed the recovery of sulfide production after dosing, likely due to the dilution effects and reduced retention time. Overall, intermittent dose of FNA or FNA in combination with H2O2 was successfully demonstrated to be a cost-effective method for sulfide control in rising main sewers.
authors.affiliation: Advanced Water Management Centre, The University of Queensland, QLD, Australia. g.jiang@awmc.uq.edu.au
authors.forename: Guangming
authors.initials: G
authors.lastname: Jiang
authors.forename: Anthony
authors.initials: A
authors.lastname: Keating
authors.forename: Shaun
authors.initials: S
authors.lastname: Corrie
authors.forename: Kelly
authors.initials: K
authors.lastname: O'halloran
authors.forename: Lam
authors.initials: L
authors.lastname: Nguyen
authors.forename: Zhiguo
authors.initials: Z
authors.lastname: Yuan
mesh_terms: D001315:Australia; D004777:Environment; D005843:Geography; D006862:Hydrogen Sulfide / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D009608:Nitrous Acid / Q000032:analysis*; D009862:Online Systems; D011891:Rain; D012722:Sewage / Q000737:chemistry*; D012995:Solubility; D013440:Sulfides / Q000302:isolation & purification*; D013997:Time Factors; D062065:Wastewater / Q000737:chemistry / Q000191:economics; D018508:Water Purification / Q000191:economics
chemical_list: D006862:Hydrogen Sulfide; D009608:Nitrous Acid; D012722:Sewage; D013440:Sulfides; D062065:Wastewater
keywords: ADWF; Average dry-weather flow; Biofilm; COD; Chemical oxygen demand; FNA; Free nitrous acid; H(2)O(2); HRT; Hydraulic retention time; Hydrogen peroxide; Odour; SRB; Sewer; Sulfide; Sulphate-reducing bacteria; WWTP; Wastewater treatment plant