Long-term operation of high rate algal ponds for the bioremediation of piggery wastewaters at high loading rates.
The performance of two 464-L high rate algal ponds (HRAPs) treating 20- and 10-folds diluted swine manure at 10 days of hydraulic residence time was evaluated under continental climatic conditions in Castilla y Leon (Spain) from January to October. Under optimum environmental conditions (from July to September), both HRAPs supported a stable and efficient carbon and nitrogen oxidation performance, with average COD and TKN removal efficiencies of 76+/-11% and 88+/-6%, respectively, and biomass productivities ranging from 21 to 28 g/m(2)d. Nitrification was identified as the main TKN removal mechanism at dissolved oxygen concentrations higher than 2mg/L (accounting for 80-86% of the TKN removed from January to May and for 54% from July to September). On the other hand, empirical evidences of a simultaneous nitrification-denitrification process were found at dissolved oxygen concentrations lower than 0.5mg/L (high organic loading rates). However, despite the achievement of excellent COD and nitrogen oxidation performance, phosphorous removal efficiencies lower than 10% were recorded in both HRAPs probably due to the high buffer capacity of the piggery wastewater treated (absence of abiotic pH-mediated PO(4)(3-) precipitation). Finally, a detailed monitorization of the dynamics of microalgae population revealed that the combination of moderate temperatures/solar irradiances and high organic loading rates, prevailing during late spring and summer, supported higher microalgae diversities than those found during winter conditions.
Godos
Ignacio de
Id
Department of Biodiversity and Environmental Management, University of León, León, Spain.
Blanco
Saúl
S
García-Encina
Pedro A
PA
Becares
Eloy
E
Muñoz
Raúl
R
D000822:Animal Husbandry; D000818:Animals; D001673:Biodegradation, Environmental; D002244:Carbon / Q000032:analysis; D004777:Environment; D056890:Eukaryota / Q000166:cytology / Q000378:metabolism*; D009584:Nitrogen / Q000032:analysis; D010100:Oxygen / Q000378:metabolism; D013472:Sunlight; D013552:Swine; D013696:Temperature; D013997:Time Factors; D014835:Volatilization; D014865:Waste Disposal, Fluid
D002244:Carbon; D009584:Nitrogen; D010100:Oxygen