NITROGEN SOURCES AND CONSUMPTION IN BREWERY WASTEWATER TREATMENT

The goal of this work was to improve understanding of nitrogen sources in beer waste and the utilization of nitrogen by the biomass in the activated sludge process in order to develop a means of adjusting nitrogen feed based on upstream, rather than downstream, parameters. The methods described may be generally applicable to other types of food or industrial waste that must be supplemented with nutrients in an activated sludge process. Brewery wastewater is generally known to contain insufficient available nitrogen for growth of healthy biomass with good settling properties. (CSU, 2003b) To provide the necessary nitrogen, NH3-N is supplemented upstream of the aeration trains. This feed process is controlled by testing grab samples for NH3-N several times per shift, upstream and downstream of the aeration system. One problem with this is that the results of ammonia feed adjustments are not known for several hours after the adjustment is made, and ammonia levels may be higher or lower than expected in the effluent. Nitrogen mass balances based on NH3-N indicate that the biomass is generally nitrogen deficient, with TOC (total organic carbon):N (nitrogen) ratios ranging from 16:1 to 103:1, significantly higher than the optimum 10:1 needed for healthy biomass. At the same time, TKN (total Kjeldahl nitrogen) analyses on the sludge show an average of about 10% nitrogen by weight, which indicates that nitrogen levels are adequate for healthy metabolism. TKN and SKN (soluble Kjeldahl nitrogen) analyses on the brewery wastewater indicate significant levels of organic nitrogen, which appears to be metabolized by the biomass. Plant operations data, including flow rates, basin sizes and stream concentrations, were applied to the “Simulation of Single Sludge Processes” (SSSP) model, (Bidstrup, 1987) which simulates nutrient removal, to develop system and kinetic parameters. These parameters were then used to model the effects of different operating strategies, such as step feed, adjustment of nitrogen feed and various sludge ages, on final effluent quality. Brewery wastewater streams from different sources, including malting, packaging, brewing, fermenting, and yeast drying, were thoroughly characterized and applied to the model to determine differences in supplemental nitrogen needs for different feed streams.