title: Ammonia-based intermittent aeration control optimized for efficient nitrogen removal.
abstract: This work describes the development of an intermittently aerated pilot-scale process (V = 0.45 m(3) ) operated for optimized efficient nitrogen removal in terms of volume, supplemental carbon and alkalinity requirements. The intermittent aeration pattern was controlled using a strategy based on effluent ammonia concentration set-points. The unique feature of the ammonia-based aeration control was that a fixed dissolved oxygen (DO) set-point was used and the length of the aerobic and anoxic time (anoxic time ≥25% of total cycle time) were changed based on the effluent ammonia concentration. Unlike continuously aerated ammonia-based aeration control strategies, this approach offered control over the aerobic solids retention time (SRT) to deal with fluctuating ammonia loading without solely relying on changes to the total SRT. This approach allowed the system to be operated at a total SRT with a small safety factor. The benefits of operating at an aggressive SRT were reduced hydraulic retention time (HRT) for nitrogen removal. As a result of such an operation, nitrite oxidizing bacteria (NOB) out-selection was also obtained (ammonia oxidizing bacteria [AOB] maximum activity: 400 ± 79 mgN/L/d, NOB maximum activity: 257 ± 133 mgN/L/d, P < 0.001) expanding opportunities for short-cut nitrogen removal. The pilot demonstrated a total inorganic nitrogen (TIN) removal rate of 95 ± 30 mgN/L/d at an influent chemical oxygen demand: ammonia (COD/NH4 (+) -N) ratio of 10.2 ± 2.2 at 25°C within the hydraulic retention time (HRT) of 4 h and within a total SRT of 5-10 days. The TIN removal efficiency up to 91% was observed during the study, while effluent TIN was 9.6 ± 4.4 mgN/L. Therefore, this pilot-scale study demonstrates that application of the proposed on-line aeration control is capable of relatively high nitrogen removal without supplemental carbon and alkalinity addition at a low HRT.
authors.affiliation: Brown and Caldwell, 1600 Duke Street, Suite 310, Alexandria, Virginia, 22314. pregm001@gmail.com.
authors.forename: Pusker
authors.initials: P
authors.lastname: Regmi
authors.affiliation: Hazen and Sawyer, P.C.
authors.forename: Ryder
authors.initials: R
authors.lastname: Bunce
authors.affiliation: Civil and Environment Engineering Department, Virginia Tech, Blacksburg, Virginia.
authors.forename: Mark W
authors.initials: MW
authors.lastname: Miller
authors.affiliation: Department of Earth and Environmental Engineering, Columbia University, New York City, New York.
authors.forename: Hongkeun
authors.initials: H
authors.lastname: Park
authors.affiliation: Department of Earth and Environmental Engineering, Columbia University, New York City, New York.
authors.forename: Kartik
authors.initials: K
authors.lastname: Chandran
authors.affiliation: ARA Consult, Innsbruck, Austria.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Wett
authors.affiliation: DC Water Authority, Washington DC.
authors.forename: Sudhir
authors.initials: S
authors.lastname: Murthy
authors.affiliation: Hampton Roads Sanitation District, Virginia Beach, Virginia.
authors.forename: Charles B
authors.initials: CB
authors.lastname: Bott
mesh_terms: D000332:Aerobiosis; D000468:Alkalies / Q000378:metabolism; D000641:Ammonia / Q000378:metabolism*; D002244:Carbon / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry; D009584:Nitrogen / Q000378:metabolism*; D010100:Oxygen / Q000032:analysis; D013696:Temperature; D018508:Water Purification / Q000379:methods
chemical_list: D000468:Alkalies; D003470:Culture Media; D002244:Carbon; D000641:Ammonia; D009584:Nitrogen; D010100:Oxygen
keywords: NOB out-selection; ammonia-based aeration control; nitritation-denitritation