Winery wastewater treatment plants generally face severe nutrient deficiency, and therefore conventional technologies and supplementary nutrient dosing strategies may fail. The purpose of the paper is to show how traditional way of dosing N-source for marginal availability to nutrient deficient influents results in poorly settling activated sludge regardless of the application of aerated or non-aerated selectors. External N-source calculated for marginal availability resulted in nutrient deficiency due to the relatively high yield experienced (0.7 g biomass COD/g substrate COD). In the fully aerated system with overall N-deficiency, rapidly increasing overproduction of extracellular polysaccharide was experienced, leading to SVI (Sludge Volume Index) values up to 600 cm3 g−1. In the system with the non-aerated selector, initial nutrient deficiency could only be detected in the second reactor. Since neither overgrowth of floc-forming GAOs (Glycogen Accumulating Organisms) nor denitrification could be experienced, the non-aerated reactor operated as low-DO (Dissolved Oxygen) basin, attributing to the drastic overgrowth of filamentous bacteria leading to SVI values >1000 cm3 g−1. Since dosing external N-source for marginal availability is likely to cause severe biomass separability problems in activated sludge winery wastewater treatment, either pronounced N-overdosing and pre-denitrification or severe nutrient deficiency and GAO cultivation can rather be recommended.
Authors:A. Jobbágy, B. Kiss, V. Bakos, and G. Tardy
In order to decrease the organic load on the downstream domestic wastewater treatment plant, a three stage, fully aerated activated sludge system was established for the pretreatment of a vegetable processing wastewater. The results of the research verified that this design was inappropriate at the given, highly fluctuating wastewater quality. Nitrate formed through nitrification of the pea processing wastewater could not be denitrified, thus rising sludge occurred in the secondary clarifiers. On the other hand, during the corn campaign, severe deterioration of the COD (Chemical Oxygen Demand) removal efficiency, as well as the overproduction of extracellular polysaccharides leading to viscous bulking, were caused by the extremely high C/N ratio. In order to efficiently treat the wastewater of the vegetable processing industry, establishment of highly flexible systems with unaerated first stage proves to be necessary.