THE EFFECT OF ORGANIC LOADING RATE ON THE PERFORMANCE OF FULL-SCALE WASTE STABILIZATION PONDS IN TEMPERATE CLIMATE: A STUDY IN THE ARGENTINE PATAGONIA

FALESCHINI, MAURICIO; ESTEVES, JOSÉ LUIS; CAMARGO VALERO, MILLER

Sevilla

Congreso; SmallWat11; 2011

CENTA (Fundación Centro de las Nuevas Tecnologías del Agua)

This work focuses on the performance of a primary facultative pond, in a full-scale waste stabilization pond (WSP) system, located in a temperate climate region in the Argentine Patagonia (42º 45´S; 65º 05´W).  Seven sampling points were selected to monitor water quality and removal efficiencies regarding organic matter and inorganic forms of nitrogen.  Samples were collected fortnightly for 38 months and processed for temperature, dissolved oxygen, pH, total and filtered BOD5, Nitrite, Nitrate, Ammonium, Chlorophyll a and Suspended Solids. Weather conditions clearly determined three water temperature intervals with average figures of 7.7ºC in winter, 14.0ºC in spring and autumn, and 20.0ºC in summer.  During the experimental timeframe, the influent flow rate increased from 12,051 m3/day to 14,846 m3/day; consequently, the surface organic loading supported for the primary facultative pond ranged from 55 kg BOD/ha to 68 kg BOD/ ha day, and the theoretical retention time decreased from 31 to 24 days. Generally speaking, a better pond performance was reported when surface organic loading was lower than 60 kg/ha day (i.e., soluble BOD5 removal > 70%); while ammonium removal was clearly seasonal, with higher ammonium concentrations in the pond effluent during the colder months.  Nitrification was reported during the warmer months of the year and partially responsible for ammonium removal as nitrate concentrations up to 14 mg N-NO3-/L were found in the pond effluent; however, nitrification was restrained to few months a year when organic loading was higher than 60 kg/ha day.