title: Automatic control of external carbon source addition for nitrogen removal in sewage with low C/N ratios.
abstract: For cost-effective nitrogen removal from sewage with low C/N ratios, an automatic control system for the addition of external carbon based on oxidation-reduction potential (ORP) data in an anoxic reactor has been developed. In this study, it was carried out with a pilot-scale modified Bardenpho process. This consisted of anoxic1, aerobic1, anoxic2 and aerobic2 stages with an external recycle ratio of 150% (Q/Qinf), and a media packing ratio of 2.4%-2.9% (v/v) in the aerobic reactor. As a result of applying the automatic control system for the minimization of the external carbon source dosage, the dosage was decreased by about 20%. This estimate was based on ORP compared with a stable dosage of 75 mg/L based on the C/NOx-N ratio of the anoxic influent. It was necessary that the ORP set-value be regulated from -120 mV to -80 mV because influent NH4+-N concentration varied from 12 to 15 mg/L due to rainfall. Correspondingly, the demanded dosages were decreased. Drift of the the real-time value in control system was more stable after changing the ORP set-value from -120 mV to -80 mV.
authors.affiliation: Department of Environmental Engineering, Pusan National University, Busan, 609-735, Korea. hai@pusan.ac.kr
authors.forename: H U
authors.initials: HU
authors.lastname: Nam
authors.forename: Y O
authors.initials: YO
authors.lastname: Kim
authors.forename: J H
authors.initials: JH
authors.lastname: Lee
authors.forename: S H
authors.initials: SH
authors.lastname: Hur
authors.forename: T J
authors.initials: TJ
authors.lastname: Park
mesh_terms: D001331:Automation; D019149:Bioreactors; D002244:Carbon / Q000032:analysis; D003362:Cost-Benefit Analysis; D009584:Nitrogen / Q000032:analysis / Q000302:isolation & purification*; D010084:Oxidation-Reduction; D012722:Sewage / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000191:economics / Q000379:methods*
chemical_list: D012722:Sewage; D002244:Carbon; D009584:Nitrogen