Abstract
Impact of marginal availability and severe deficiency of nitrogen on the growth of glycogen accumulating organisms (GAOs) and performance of anaerobic/aerobic activated sludge systems treating nutrient deficient wastewater was investigated at marginal availability and severe deficiency of phosphorus. Two continuous-flow lab-scale systems were operated simultaneously fed by model winery wastewater, one with marginal availability and the other one at severe deficiency of nitrogen. In the second experimental stage, marginal availability of P was converted into severe deficiency by interrupting external dosing.Common practice of dosing N- and P-sources to marginal availability caused enhanced proliferation of filamentous bacteria leading to poor biomass settling and instable operation. At marginal N-availability accumulation of GAOs started when conditions became deficient for phosphorus. In severe lack of nitrogen GAOs overgrew filaments, and outcompeted phosphorous accumulating organisms (PAOs) initially present in the seed. Stable and good performance could be maintained even after withdrawal of phosphorous dosing.
Highlights
Several kinds of basically food-industrial wastewater, included the one discharged from wine production are in lack of nitrogen and phosphorus
Diluted Sludge Volume Index (DSVI) values remained in the range of 300-600 cm3/g, and unambiguous tendency for reaching the really low starting point could just be observed after P-dosing had been interrupted
Comparing the ~12 mgN/l ammonia consumed in the selector and the ~35 mgN/l ammonia consumed in the reactor, to the appropriate amounts of Chemical Oxygen Demand (COD) removed, ratios of 100 readily biodegradable COD (rbCOD) to ~4.8 NH4N in the selector and 100 rbCOD to ~6.14 NH4N in the reactor can be calculated
Summary
Several kinds of basically food-industrial wastewater, included the one discharged from wine production are in lack of nitrogen and phosphorus. Winery wastewater having been used in this study as a model for nutrient deficient influent may derive from a number of technological steps including cleaning of the basins, equipment and floor; rinsing the transfer lines, washing the barrels, bottling facilities and filtration units, etc Both the volume and the pollution load of winery effluents vary greatly in relation to the operational period (i.e. vintage, racking and bottling) and the kind of wine produced. Several different processes are currently available for treating winery wastewater, such as physicochemical methods (coagulation, flocculation, electrocoagulation, etc.), membrane filtration and separation (nanofiltration and reverse osmosis) as well as advanced oxidation processes (ozonation, Fenton oxidation, etc.,) [2] It is still the biological treatment being most commonly used in full-scale as it is considered to be the most environmental-friendly and cost-effective solution, its control needs adequate engineering expertise
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