title: Reclaimed wastewater quality enhancement by oxygen injection during transportation.
abstract: In-sewer treatments have been studied in sewer systems, but few have been carried out on reclaimed wastewater systems. A study of oxygen injection has been performed in a completely filled gravity pipe, 0.6 m in diameter and 62 km long, in cast iron with concrete inside coating, which is part of the reclaimed wastewater reuse scheme of Tenerife (Spain). A high pressure oxygen injection system was installed at 16.0 km from pipe inlet and a constant dosage of 30 mg/L O(2) has been injected during six months, under three different operational modes (low COD, 63 mg/L; high COD, 91 mg/L; and partially nitrified water). Oxygen has been consumed in nitrification and organic matter reduction. Generally, nitrification is clearly favored instead of the organic matter oxidation. Nitrification occurs, in general, with nitrite accumulation due to the presence of free ammonia above 1 mg/L. Denitrification is in all cases incomplete due to a limitation of easily biodegradable organic matter content, inhibiting the appearance of anaerobic conditions and sulfide generation. A notable reduction of organic matter parameters is achieved (TSS below 10 mg/L), which is significantly higher than that observed under the ordinary transport conditions without oxygen. This leads to a final cost reduction, and the oxygen injection system helps water reuse managers to maintain a final good water quality in the case of a treatment plant malfunction.
authors.affiliation: Dpt. Chemical Engineering, University of La Laguna, Av. Astrof. Fco. Sánchez S/N. 38200 La Laguna, Spain. luerguez@ull.es
authors.forename: L E
authors.initials: LE
authors.lastname: Rodríguez-Gómez
authors.forename: M
authors.initials: M
authors.lastname: Alvarez
authors.forename: J
authors.initials: J
authors.lastname: Rodríguez-Sevilla
authors.forename: M C
authors.initials: MC
authors.lastname: Marrero
authors.forename: A
authors.initials: A
authors.lastname: Hernández
mesh_terms: D007267:Injections; D058465:Nitrification; D009930:Organic Chemicals / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry*; D011786:Quality Control; D014867:Water / Q000737:chemistry; D018508:Water Purification / Q000379:methods*
chemical_list: D009930:Organic Chemicals; D014867:Water; D010100:Oxygen