MODELING AMMONIA REMOVAL FROM AMMONIA SUPPLEMENTED BREWERY WASTEWATER By Julie E. Smith 1 and Linda A. Figeuroa 2 1 – Coors Brewing Company, 2 – Colorado School of Mines PROBLEM Control of effluent ammonia in brewery wastewater while still meeting the nutritional requirements of the treatment organisms is a challenge. Because brewery wastewater is limited in nitrogen, ammonia is added to ensure adequate nitrogen is provided to the biomass for optimum metabolism. Ammonia feed is controlled based on ammonia analyses on grab samples upstream and downstream of aeration basins, conducted several times per day. The relative amount of ammonia in the upstream or downstream samples determines whether ammonia feed is increased or decreased. While this strategy is effective part of the time, there are times when effluent ammonia is higher or lower than expected. One hypothesis is that ammonia represents only a fraction of the total available nitrogen and the fraction is not constant because of variations in the wastewater organic nitrogen content to the treatment process. A better understanding of nitrogen availability and utilization is needed because nutrient deficiencies are a suspected cause of sludge settling problems. APPROACH Perform analyses of all nitrogen sources in composite samples upstream and downstream of aeration basins, including:  Ammonia (NH 3 -N)  Total Kjeldahl Nitrogen (TKN)  Soluble Kjeldahl Nitrogen (SKN)  Particulate Organic Nitrogen (TKN – SKN)  Soluble Organic Nitrogen (SKN – NH 3 -N) Perform mass balances of nitrogen across aeration basins Model ammonia removal with SSSP 3 using actual plant data 3 – SSSP Simulation Model, V1, Steven M. Bidstrup, Clemson University, © 1987 NITROGEN SOURCES In addition to NH 3 -N, which is fed as either anhydrous ammonia or ammonium hydroxide, brewery wastewater contains significant nitrogen as protein from the following sources. NITROGEN CONSUMPTION AND STOICHOMETRY The following table shows a comparison of theoretical ammonia consumption and cell yield during cell synthesis and metabolism of substrates present in brewery waste. MASS BALANCING Biomass requires about 1 part nitrogen (N) to 10 parts carbon (C) for healthy metabolism. 4 For the month of April, 2004, the average C:N ratio was 48:1 in the primary effluent was observed, with a high of 103:1 and a low of 16:1, based on measurements of NH 3 -N. The month of April was a typical month in terms of C:N ratio, and suggests that the biomass should be nitrogen deficient. However, regular TKN analyses performed on biomass shows the N content of the sludge to average about 10%, well within the normal range. On April 24, 2004, TKN (Total Kjeldahl Nitrogen) and SKN (Soluble Kjeldahl Nitrogen) analyses were performed on the primary effluent in addition to NH 3 -N. The NH 3 -N was 17 mg/L and the SKN was 31.9 mg/L; therefore, the soluble N that was available to the biomass was almost twice as much as measured NH 3 -N. The total organic carbon (TOC) concentration that day was 309 mg/L. The C:N ratio based on NH 3 -N would be calculated as 18:1, suggesting a nitrogen deficient condition. However, when soluble organic nitrogen is included, the C:N ratio was actually 10:1, suggesting sufficient nitrogen for healthy cell metabolism. The nitrogen in the effluent on April 24 was 4.2 mg/L, and was all in the form of NH 3 -N, suggesting the soluble organic nitrogen was utilized by the biomass stoichiometrically. PWTP System Parameters AERATION BASIN SYSTEM CONFIGURATION Feed Composition – From PWTP Data on 4/24/4 COMPARISON OF MODEL AND PLANT PERFORMANCE The kinetic parameters developed from tuning the model using the 4/24/04 data were used to model plant performance on other selected days. The additional days were selected based on available data. 4/24/04 was the only day which had a full set of data, including SKN. Model parameters for the other days were estimated based on derived relationships between TOC, Soluble TOC, TSS, VSS, TKN and SKN. CONCLUSIONS 1.Brewery waste contains significant amounts of organically bound nitrogen, which may amount to two or more times the ammonia nitrogen. 2.If a brewery waste stream is high in protein, more ammonia may be released in metabolism than is consumed. 3.Soluble organic nitrogen from brewery waste appears to be metabolized by the biomass. 4.When organic nitrogen is accounted for, the waste stream may not be deficient in nitrogen. 5.The SSSP model provides reasonable estimates of nitrogen and solids in brewery effluent. ACKNOWLEDGEMENTS We would like to thank Coors Brewing Company for their support of this work, and the operators and operator-analysts at the Coors PWTP for their helpful input. SourceProtein, % Wt. Grain Hops Yeast Trub Wort, Extract0.4 – 1.2 Beer!0.2 – 0.6 Substrate Yield g Cells/g COD NH-N Cons. g N/g cells TOC:N Cons. Ratio g TOC/g N Glucose :1 Ethanol :1 VFA (Acetate) :1 C 8 H 17 O 3 N (general organic matter) :1 C 16 H 24 O 5 N 4 (general protein) – Rittman and McCarty, 2001 Feed Effluent 50% 25% 50%25% Feed Effluent Actual PWTP Model Component Value EnglishModel Inert Particulates112 mg/L FSS158 g COD/m 3 Particulate Organics220 mg/L VSS310 g COD/m 3 Soluble Organics309 mg/L TOC746 g COD/m 3 Soluble Ammonia-N17 mg/L17 g N/m 3 Soluble Organic N14.9 mg/L14.9 g N/m 3 Biodegradable Particulate Organic N 24.6 mg/L24.6 g N/m 3 Alkalinity250 mg/L as CaCO mole/m 3 SSSP MODEL - TUNING Component Value EnglishModel Number of Reactors33 Reactor 1 Volume1 MG3,785 m 3 Reactor 2 Volume0.5 MG1,893 m 3 Reactor 3 Volume0.5 MG1,893 m 3 Solids Retention Time2.4 days Average Flow Rate4.750 MGD17,979 m 3 /day Recycle Flow Rate1.494 MGD5,655 m 3 /day Date MLVSS, mg/LEffluent NH3-N, mg/L Actual mg/L Model mg/L Error %Actual mg/L Model mg/L Error % 4/24/ /11/ /26/ /16/ /1/ Given the limitations in the plant data, the model does a fairly good job of predicting MLVSS and NH 3 -N exiting the trains. This is particularly true given that the same kinetic parameters were used for all five days, and in reality the kinetics probably vary somewhat. In general, the model did a decent job of differentiating extremely high ammonia from average or low values. Also, the model did a very good job at estimating both MLVSS and NH 3 -N on 2/1/04, which is an example of a day when the effluent NH 3 -N of 14 mg/L was significantly higher than the influent NH 3 -N, at 5.2 mg/L. Feed 50% 25% Effluent