title: Long term diurnal variations in contaminant removal in high rate ponds treating urban wastewater.
abstract: In this investigation, diurnal variations in contaminant removal in high rate ponds (HRP) treating urban wastewater were evaluated. Two experimental HRPs (surface area 1.54 m2 and depth 0.3 m), each with a clarifier in series (surface area 0.025 m2), were operated in parallel with different hydraulic retention times (3-10 days) but with the same environmental conditions over a period of one year. The operating strategies adopted only yielded a significant overall difference in removal between the two HRPs for nutrients. Effluent total suspended solids and chemical oxygen demand were slightly higher at midday than at dawn, while for total nitrogen and total phosphorous the concentrations were slightly higher at dawn. All these differences were related to the diurnal changes of DO and pH. The main conclusion of this work is that the diurnal variations of the contaminant concentrations in HRPs do not seriously affect their reliability in treating wastewater.
authors.affiliation: Environmental Engineering Division, Department of Hydraulics, Coastal and Environmental Engineering, Civil Engineering School, Technical University of Catalonia, c/Jordi Girona 1-3, 08034 Barcelona, Spain. joan.garcia@upc.edu
authors.forename: J
authors.initials: J
authors.lastname: García
authors.forename: B F
authors.initials: BF
authors.lastname: Green
authors.forename: T
authors.initials: T
authors.lastname: Lundquist
authors.forename: R
authors.initials: R
authors.lastname: Mujeriego
authors.forename: M
authors.initials: M
authors.lastname: Hernández-Mariné
authors.forename: W J
authors.initials: WJ
authors.lastname: Oswald
mesh_terms: D018533:Biomass; D002940:Circadian Rhythm; D002947:Cities; D056890:Eukaryota / Q000235:genetics / Q000378:metabolism*; D005160:Facility Design and Construction; D014644:Genetic Variation; D006863:Hydrogen-Ion Concentration; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism; D010100:Oxygen / Q000032:analysis / Q000378:metabolism; D010788:Photosynthesis; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods*; D014876:Water Pollution / Q000517:prevention & control; D018508:Water Purification / Q000379:methods*
chemical_list: D009584:Nitrogen; D010100:Oxygen