How partial nitrification could improve reclaimed wastewater transport in long pipes.
Reclaimed wastewater transport is studied in a concrete-lined cast iron pipe, where a nitrification-denitrification process occurs. The pipe is part of the Reuse System of Reclaimed Wastewater of South Tenerife (Spain), 0.6 m in diameter and 61 km long. In order to improve wastewater quality, at 10 km from the inlet there is injection of fresh water saturated in dissolved oxygen (DO), after which a fast nitrification process usually appears (less than two hours of space time). The amount of oxidized nitrogen compounds produced varies between 0.8 and 4.4 mg/l NOx(-)-N. When DO has disappeared, a denitrification process begins. The removal of nitrite is complete at the end of the pipe, whereas the nitrate does not disappear completely, leaving a concentration of about 0.4-0.5 mg/l. For a COD/NOx(-)-N ratio higher than 5, a first order nitrification rate in NOx(-)-N has resulted, with the constant k20 = 0.079 h-1, for a NOx(-)-N concentration range of 0.8-4.4 mg/l. Finally the following temperature dependency for the first order denitrification rate constant has been found: k = k20 x 1 x 15T-20. Although nitrogen could be used as nutrient in the agricultural reuse, its removal from reclaimed wastewater could be useful in order to diminish the chlorine needs for reclaimed wastewater disinfection.
Delgado
S
S
Department Chemical Engineering, University of La Laguna, Av. Astrof. Fco. Sánchez, S/N 38200 La Laguna, Spain.
Alvarez
M
M
Rodríguez-Gómez
L E
LE
Elmaleh
S
S
Aguiar
E
E
D000383:Agriculture / Q000379:methods; D018441:Biofilms; D003247:Conservation of Natural Resources; D004203:Disinfection / Q000379:methods; D005618:Fresh Water / Q000737:chemistry* / Q000382:microbiology; D006801:Humans; D006862:Hydrogen Sulfide / Q000378:metabolism; D007700:Kinetics; D009584:Nitrogen / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D012722:Sewage / Q000737:chemistry; D013030:Spain; D013696:Temperature; D018505:Waste Management / Q000295:instrumentation* / Q000379:methods*; D018508:Water Purification / Q000295:instrumentation / Q000379:methods; D014881:Water Supply / Q000592:standards
D012722:Sewage; D009584:Nitrogen; D010100:Oxygen; D006862:Hydrogen Sulfide