Abstract
The ability of microalgae to remove nitrogen and phosphorus from wastewater has been used in recent years as an alternative treatment for discharges from livestock slurry, which generate a negative environmental impact on vulnerable ecosystems. With this background and the feasibility of using microalgae, we have evaluated the effect of Chlorella sp. and Synechocystis sp., in removing contaminants from the pig manure collected from El Prado ESPE. Slurry samples were collected, filtered and autoclaved, and the supernatant was further dilluted to three different concentrations of 40%, 60% and 80%. The microalgal growth and pollutants removal property was evaluated up to 15 days in batch culture. The cell density was determined by counting in a Neubauer hemocytometer, and the pollutants removal was analyzed by standard colorimetric methods. The microalgae Chlorella sp. showed a maximum cell growth of 1.70 ± 0.09 x107 cells/mL at 60% effluent concentration on day 6. While Synechocystis sp. showed a maximum growth of 1.04 ± 0.05 x107 cells/mL, at 60% concentration on day 9. On the other hand, there exists a competition when microalgae used as a consortium. The cell growth of Chlorella sp. was higher at all concentrations compared to Synechocystis sp.. Overall, efficiency of pollutant removal were between 40% and 90%, which demonstrate the feasibility of using microalgae in tertiary swine wastewater treatment.
Highlights
The pollution resulting from wastewater of animal origin which contains high loads of nitrogen and phosphorus has created serious threats to the aquatic environment, the main problems are eutrophication of waters, air pollution by volatilization of ammonia and land degradation (Godos et al, 2010)
With this background and the feasibility of using microalgae, we have evaluated the effect of Chlorella sp. and Synechocystis sp., in removing contaminants from the pig manure collected from El Prado ESPE
This study evaluated the optimal conditions for the growth of microalgae, the efficiency of NH4+ and PO4+ removal, the reduction of Chemical Oxygen Demand (COD) and Biodegradable Oxygen Demand (BOD), using pig effluent as a wastewater
Summary
The pollution resulting from wastewater of animal origin which contains high loads of nitrogen and phosphorus has created serious threats to the aquatic environment, the main problems are eutrophication of waters, air pollution by volatilization of ammonia and land degradation (Godos et al, 2010). The ability of microalgae to remove nitrogen and phosphorus from wastewater has allowed the use of microalgae cultures as tertiary treatment, presenting great advantages over physical and chemical conventional systems, because they do not generate secondary pollutants and presents an efficient recycling of nutrients (De la Node and De Pauw 1988). The use of microalgae in the wastewater treatment reduces costs by not adding chemicals, and at the same time recovering nutrients as biomass that could be used as fertilizer, animal nutritional supplement, and bio fuels (Kim and Park 2007). Wastewater from the pig production units at El Prado farm contains a high concentration of inorganic nutrients, proving to be a suitable medium for the growth of microalgae. The concentration of nitrogen and phosphorus in wastewater has a direct influence on the growth kinetics and is closely related to efficient nutrient removal (Goldberg and Cohen 2006)
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