With sufficient time, high wastewater temperature a characteristic of desalter effluent and low oxygen conditions anywhere in the wastewater system will result in the uneven conversion of organic nitrogen compounds to ammonia through hydrolysis and ammonification as illustrated in Figure 2. Figure 2: Nitrogen Conversion. The Total Kjeldahl Nitrogen TKN test combines the measurement of the organic nitrogen and the ammonia nitrogen concentrations into a single value.
Therefore, you must run a separate ammonia test, the value of which is subtracted from the TKN value, to obtain the organic nitrogen concentration. For refinery biological treatment systems that experience highly variable ammonia loadings it may appear that ammonia oxidation nitrification has decreased when the effluent ammonia concentration increases, while this is may not actually be true.
The effective oxidation of ammonia is, in a sense, hidden, due to amines and other organic nitrogen compounds being converted to ammonia after the influent sample point. Knowing the influent and effluent concentrations of TKN and ammonia will provide a much better understanding of how the biological system is handling nitrifying the applied ammonia load.
What is nitrification efficiency and how can it be measured? The easiest way I know of is to calculate the nitrification rate NR each day as shown in Equation 1. In truth though, I have never once come across a wastewater plant that calculates the NR. The "ammonia in" value is the influent ammonia concentration measured before the bioreactor.
The "ammonia out" value would typically be obtained from the secondary clarifier effluent. Equation 1: Nitrification Rate. Several months of nitrification rate values using refinery data are shown below in Figure 3. There is a lot of variability in the data and there a several days where the nitrification rate dropped to zero, none of which is surprising in an industrial wastewater treatment facility.
The analysis starts with an acid digestion of the sample organics, converting organic nitrogen to ammonia. This requires boiling the sample in concentrated sulfuric acid, potassium sulfate, and a copper catalyst to convert the organic nitrogen to ammonia. Therefore, this digestion procedure must be contained within a fume hood. The second part of the method is a repeat of the distillation describe above, however, the acidic digestion sample pH, must be raised to 9.
Once again nitrogen concentrations within the receiving solution can then be determined using classical titrimetic, colorimetric or specific ion electrode determination methods. Once the total nitrogen is determined the inorganic nitrogen fraction value can be subtracted to resolve just the organic nitrogen fraction. Sources of nitrogen from azide, azo, hydrozones, nitrile, semicarbozones, and oximes are not recovered in the TKN procedure as outlined above.
It is important to note that there are three sizes of Kjeldahl nitrogen digestion and distillation determination equipment available. Each enables the operator to perform the same digestion and distillation chemical procedures for nitrogen analysis. However, as the size of the Kjeldahl equipment decreases, so does the digestion and distillation sample vessels. An undigested sample aliquot reacts with an indicator to determine the oxidized nitrogen photometrically. The chemistry vials require no preparation or glassware no cleanup!
No blank is required, further reducing expense. The new s-TKN system:. Performing a low-cost, safer TKN gives operators an improved tool for process control. Real-time results also eliminate the delay of outsourcing, giving a more effective tool for making necessary process adjustments. Additionally, with a nominal cost per test, the possibility of increased testing gives more optimal results. Order Status Contact Us Login.
Additionally, our lab only measures TKN at or above 0. Thus, the results shown here reflect that our analyses do not detect TKN below 0. Use our interactive graph to check out all the data we have collected since Hover over a data point to see more information or try clicking on the name of a month to see all the data for just one month!
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