BIODEGRADATION KINETIC PARAMETERS OF A DAIRY WASTEWATER MODEL SYSTEM (CHEESE WHEY)

CONTRERAS E.; BERTOLA N.; BEVILACQUA A.

Campeche, Mexico

Simposio; Fifth Latin American Biodegradation and Biodeterioration Symposium (LABS5); 2004

Abstract   Dairy wastewater composition varies according to the products being manufactured, but they are generally characterized by high content of organic matter, nutrients and varying pH. This wastewater requires substantial treatment in order to avoid environmental impacts. Respirometry is a frequently used tool for the characterization of wastewater and activated sludge kinetics. In this paper an open respirometry technique was used to study the biodegradation of dairy wastewater model system. The synthetic wastewater composition was the following: dehydrated cheese whey 1.5 g/l, (NH4)2SO4 0.94g/l, NaHCO3 1.03g/l. Activated sludge was obtained from a lab-scale (4.5 L) completely mixed, continuous-flow activated sludge reactor. Hydraulic retention time was 54 h, a solids retention time of 45 days was maintained by direct wastage. After 5 months of operation the activated sludge reactor reached a steady state. Since nitrate was absent in the feeding wastewater, the presence of nitrate in the outlet stream was due to the activity of the nitrifying population. Respirometric results showed that the aerobic biodegradation of cheese whey and ammonia respectively were independent. In addition, the observed OURex responce to the injection of N (autotrophic activity) was in accordance with the presence of nitrate in the outlet stream of the activated sludge reactor. Although nitrifiers were present in the tested activated sludge, cheese whey organic nitrogen was not oxidized; therefore, cheese whey respirograms only reflected carbonaceous compounds oxidation. A value of 0.28 ± 0.01 mgO2/mgCOD was determined for the cheese whey oxidation coefficient.