Influence of Inoculum and Initial pH on Dairy Effluent Biodegradation and Mineralization

P. Álvarez-Mateos, J. Pereda-Marín, F. Carta-Escobar, M. M. Durán-Barrantes and E. Guillén-Jiménez

Abstract
Dairy effluents are constituted mainly by milk, alkaline washing wastes, and water. In accordance too the characteristics of this type of industrial wastewater, a biological treatment was applied in a batch reactor. The process chosen was nitrification to reduce the nutrient content. In order to enhance ammonium oxidation, the medium was inoculated with municipal wastewater from a secondary clarification tank of the Ranilla treatment plant (Seville, Spain). Municipal wastewater of temperature at about 26 °C during the warmer season (September) showed higher concentrations of nitrite and nitrate. Different initial pH values (8.5, 10.5, 11.0, 11.5 and 12.0) were tested, and the organic matter content, expressed as Chemical Oxygen Demand (COD), was maintained constant at 1000 mg. The municipal wastewater was taken in two different seasons, winter (February) and summer (September), to know the effect of season on the nitrification. The results indicate a difference in the rate of the process but not in the behaviour. The reduction in COD is nearly the same in both cases, and the difference depends on the initial pH value rather than on the season of the inoculum.

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Keywords
dairy industry, nitrification, biological treatment, aerobic treatment, Batch reactor