| Introduction | | | | because these samples rarely have nitrate in them |
| On August 27, 2009 the State-EPA Nutrient | | | | anyway. Recall the nitrogen reactions. An influent to a |
| Innovations Task Group issued an urgent call to | | | | POTW will contain particulate nitrogen, dissolved |
| action to EPA Administrator Lisa Jackson. The task | | | | organic nitrogen, and ammonia. The particulate |
| group studied documented levels of excess nutrients | | | | nitrogen mostly settles as sludge removing it from |
| in our nations waterways. Current, and past, efforts | | | | the equation. Organic nitrogen and ammonia are |
| to control these pollutants have been inadequate on | | | | oxidized to nitrate during the treatment process. The |
| the national and statewide scale. Efforts to date | | | | TKN digestion boils the sample in concentrated |
| have been predominantly "regulation at the pipe" and | | | | sulfuric acid in the presence of a metallic catalyst to |
| have not addressed the non point sources that are | | | | speed the reaction. Potassium sulfate is added to |
| the root cause of elevated concentrations of | | | | raise the boiling point to about 380 C. The digestion |
| nutrients in ground and surface waters. Nutrient | | | | will not completely recover all organic nitrogen |
| pollution significantly impacts all of us. It impacts our | | | | compounds making the TKN result actually less than |
| drinking water, our recreational water, such as | | | | or equal to the TN determined by alkaline persulfate |
| beaches and rivers and lakes, and it affects, and | | | | oxidation. |
| even kills, aquatic life. None of us want a bunch of | | | | According to the EPA definition, Total Nitrogen equals |
| dead rivers, but what can we do? | | | | TKN plus nitrate plus nitrite. |
| What are Nutrients? | | | | Phosphorus |
| Nutrients are elements that are essential to life. Being | | | | Phosphorus is an essential nutrient found in living |
| essential to life they are also essential components of | | | | organisms as part of DNA among other important |
| the molecules that make up living tissue. Decaying | | | | molecules. Phosphorus is always found in nature |
| organic matter and human and animal waste are | | | | bound to other atoms and usually as the inorganic |
| significant sources of nutrient pollution in ground and | | | | phosphate. It is phosphate that is available to plants |
| surface water. The chemicals we manufacture and | | | | and used as a fertilizer. It is phosphate that is |
| use in day-to-day life may also contain nutrients, as | | | | consumed by algae and has the potential to cause |
| well as the fertilizers that we spread on our yards | | | | algal blooms. Measurement of total phosphorus is |
| and farms. It is the broad application of fertilizers, the | | | | important because it can, with time, convert to |
| animal feeding lots, the widespread use of septic | | | | bioavailable soluble phosphate. |
| tanks, and runoff water from rainfall to school kid | | | | Dishwashing, laundry, and many hand detergents and |
| carwashes that are responsible for the immeasurable | | | | or soap contain phosphorus. The phosphorus content |
| amounts of nutrients that find their way into the | | | | in detergent can be as high as 8.7%. Phosphate is a |
| watershed. These are the non-point sources that | | | | very effective way to improve soap quality, |
| cannot be easily regulated. | | | | especially in waters that contain high amounts of |
| For 30 years the Clean Water Act has regulated | | | | calcium and magnesium. Unfortunately, the |
| industrial and municipal effluents. Limits are getting | | | | phosphates in these detergents find their way into |
| lower and lower. It is easy to take a sample at the | | | | the environment. In the 1970's green rivers and lakes |
| end of a pipe. It's easy to know where the sample | | | | were becoming common and phosphate usage in |
| comes from, and who is responsible if pollutants are | | | | soaps began its eventual reduction. Although there is |
| too high. Unfortunately, 30 years of regulation of | | | | not a federal ban on phosphate is soap many states |
| industry has not significantly reduced the problem. | | | | are taking action. For example, Washington State has |
| Obviously, there are other sources. | | | | limited the amount of phosphate in dishwasher |
| And the sources are us. Our everyday activities of | | | | detergent to 0.5% |
| washing our cars, fertilizing and watering our lawns, | | | | Chemical Analysis of Phosphorus |
| irrigating farms, and even desiring green golf courses. | | | | Phosphorus can exist in water in different forms. The |
| The essential nutrients that are in the fertilizers and | | | | standard method for phosphorus is meant to |
| detergents are entering the groundwater, not by an | | | | measure only phosphate, also called reactive |
| industrial effluent but down the gutter and into the | | | | phosphate. This is because what is actually measured |
| storm drain. Rainfall is washing nutrients into creeks | | | | is defined by the molybdate reaction itself. |
| and rivers and carrying them into basins such as the | | | | Phosphorus species are distinguished from each other |
| Gulf of Mexico or Chesapeake Bay. Hypoxic zones, | | | | empirically by filtration, and then a series of digestions |
| also known as dead zones, are forming where | | | | that selectively convert phosphorus to phosphate. |
| excess nutrients are deposited. | | | | After the digestion phosphate is measured. Thus, to |
| The excess nutrients cause a rapid growth of algae. | | | | analyze organic phosphorus only, one digests for total |
| The algae grow so rapidly that they cut off their | | | | phosphorus in one sample aliquot, and hydrolysable |
| own light and die. This is a normal, geologic process, | | | | phosphorus in another aliquot. Reactive phosphate is |
| occurring more rapidly than normal. As the algae dies | | | | then determined in each digest and Organic |
| it decays and the decay process consumes oxygen. | | | | Phosphorus is calculated by difference. |
| Without oxygen aquatic life cannot breathe. | | | | Total Phosphate is water-soluble. Instrumental |
| What is Nutrient Pollution? | | | | methods require that samples be filtered, or the |
| Nitrogen and Phosphorus are the principal elements | | | | turbidity and/or solids will interfere. Therefore to |
| referred to when discussing nutrient pollution. Other | | | | accurately measure total phosphate you must filter |
| essential elements, such as carbon, silica, and sulfur | | | | the sample. Since total reactive phosphorus is equal |
| are not included in this discussion. Organic nitrogen | | | | to filterable reactive phosphorus the results are the |
| and organic phosphorus are associated with the | | | | same. Remember though, that for best results, |
| organic matter we measure and report as TOC. | | | | filtration should be in the field. The portion for the |
| Nitrogen and phosphorus are essential elements in | | | | total analysis is not filtered. If the particulates (TSS |
| DNA, RNA, and nitrogen is a major component of | | | | or SS) are high, then continuous flow methods should |
| protein and urine. Nitrogen and phosphorus occur as | | | | not be used for the analysis of Total Phosphorus. |
| both water-soluble and water insoluble species. | | | | Total phosphorus is batch digested that converts all |
| Unfortunately, both soluble and insoluble become | | | | phosphorus compounds to phosphate. The digest is |
| bioavailable. Looking at this table, we see that | | | | filtered and phosphate is then measured, usually by |
| Nitrogen and Phosphorus are somewhat similar | | | | molybdenum blue. |
| chemically, for instance, the plus 5 ions known as | | | | The continuous flow method for TDP utilizes 254 nm |
| nitrate and phosphate are very stable and highly | | | | UV irradiation to assist in the digestion of organic |
| water-soluble. | | | | material. Since continuous flow methods cannot be |
| Nitrogen | | | | used to adequately digest samples containing high |
| Nitrogen is an essential nutrient for plant growth | | | | amounts of solids and continuous digestion should not |
| ranking only behind carbon, hydrogen and oxygen in | | | | be used unless the total phosphorus is essentially |
| total quantity needed. The nitrogen gas making up | | | | equal to the dissolved phosphorus. |
| about 80% of the atmosphere is largely inert and | | | | TKN is the classical digestion for total organic |
| unavailable to life directly. Lightning will convert small | | | | nitrogen. The TKN digest can also be used to analyze |
| amounts of nitrogen to nitrate. Nitrogen in fertilizers | | | | for total phosphorus. The advantage in this is not |
| largely comes from the chemical reaction between | | | | added recovery, for the acid persulfate quantitatively |
| nitrogen and hydrogen gas to form ammonia. The | | | | recovers all of the total phosphorus. The only |
| ammonia can then be oxidized to form nitrate. | | | | advantage in the TKP is the ability for the laboratory |
| Fertilizers will often contain ammonia, nitrate, and/or | | | | to test for TKN and TP in a single digest. The |
| urea as the sources of nitrogen. Organic matter, | | | | perceived benefit is time and labor savings. Because |
| referred to as humic matter, manure, mulch, etcetera | | | | of the higher acid and salt concentration of the |
| contains about 5% Nitrogen. This nitrogen is slowly | | | | resulting TKP digest compared to persulfate digests, |
| converted to ammonia by bacteria and is eventually | | | | TKP detection limits are usually higher that limits |
| oxidized to nitrite then nitrate. During a storm event, | | | | found by persulfate. The other advantage to TKP is, |
| or during irrigation the nitrate in soil is easily leached | | | | of course, that it is EPA approved. |
| into the runoff. | | | | All of the colorimetric methods used for the |
| Dissolved inorganic nitrogen includes nitrate, nitrite, | | | | determination of phosphate by molybdenum blue are |
| and ammonia. Dissolved organic nitrogen includes | | | | highly dependent upon final acid concentration and |
| water-soluble proteins, amines, amides, and so forth. | | | | the amount of molybdate. Attempts made at |
| Basically decayed organic life and some man made | | | | analyzing total phosphorus digests without careful |
| chemicals that are dissolved in water. Total Organic | | | | attention to acid concentration are often not |
| nitrogen is the sum of dissolved organic nitrogen and | | | | successful. After the digestion is complete, you are |
| particulate organic nitrogen. Particulate organic | | | | measuring orthophosphate. Any method used to |
| nitrogen is, well obviously, the insoluble organic | | | | measure phosphate can be used. The problem with |
| compounds, or organic matter, in the water. Total | | | | extending a total P determination to Ion |
| Dissolved Nitrogen is the dissolved organic nitrogen | | | | Chromatography, for instance, comes from the |
| plus the dissolved inorganic nitrogen, and Total | | | | excessive sulfate ion introduced in the digestion. |
| nitrogen includes all of the above. Notice, there is | | | | Earlier methods utilizing persulfate in sulfuric acid |
| REALLY no such thing as total inorganic nitrogen. This | | | | neutralized the sample and then analyzed |
| is because inorganic nitrogen compounds are all | | | | orthophosphate. Some continuous flow methods |
| water-soluble. | | | | measure the phosphate in the acid solution adjusting |
| Chemical Analysis of Nitrogen Compounds | | | | the acid in the reagent accordingly. The TKP |
| Total dissolved nitrogen, or the result you get when | | | | digestions have really only been tested using a |
| analyzing total nitrogen on a filtered sample consists | | | | mercury catalyst, and excess chloride must be added |
| of dissolved organic nitrogen, nitrate, nitrite and | | | | to prevent interference from the mercury. Like TKN, |
| ammonia. Methods used to determine TDN usually | | | | the blue color of a copper catalyst may interfere |
| rely on an alkaline persulfate digestion that converts | | | | with the method. The auto dialysis method helps to |
| all of the nitrogen present to nitrate and then the | | | | control the final acid concentration and some of the |
| nitrate is determined colorimetrically. Analyzing | | | | residual color introduced by the copper. Dialysis is |
| inorganic nitrogen alone will only recover about 30 - | | | | essentially an online dilution leading to a higher |
| 40 % of the total dissolved nitrogen in the natural | | | | detection limit than the cleaner persulfate digest. To |
| environment. Sewage treatment and industrial plant | | | | sum up, for lower total phosphorus numbers (say |
| effluents, on the other hand, are predominantly | | | | below 0.1 ppm) it is recommended to use the acid |
| inorganic nitrogen (nitrate) since the treatment | | | | persulfate digestion because the matrix will be easier |
| process is designed to completely oxidize dissolved | | | | to control and work with. For concentrations above |
| organic nitrogen and ammonia to nitrate. | | | | 0.1 ppm, the TKP digestion is adequate. |
| Total nitrogen, or the result you get when analyzing | | | | Conclusion |
| total nitrogen on a non-filtered sample consists of | | | | The clean water act was signed amid stories of |
| dissolved organic nitrogen, nitrate, nitrite and ammonia | | | | massive fish kills and rivers catching on fire. We all |
| plus particulate nitrogen. Since all inorganic nitrogen | | | | know that these things rarely happen in the US |
| compounds are soluble, particulate nitrogen is almost | | | | anymore. We have monitored sewage treatment |
| entirely organic nitrogen, or PON. Methods used to | | | | effluents and in many cases applied numerical |
| determine TN can rely on the same alkaline persulfate | | | | maximums on the amount of nutrients that can be |
| digestion used to determine TDN with the exception | | | | discharged. We still have a ways to go. |
| that samples are not filtered. Since samples are not | | | | Our chemical analysis methods were written for |
| filtered, the automated version is not applicable if | | | | highly polluted water. The methods we use were not |
| there is a significant amount of sediment (or solids) in | | | | validated at the lower concentration levels we need |
| the sample. In other words, the automated inline | | | | to measure today. Many of the conditions of these |
| digestion methods measure TDN and are only | | | | methods assume higher concentrations will be |
| applicable if TDN and TN are essentially equal (there | | | | present, and the former rigid nature of the Clean |
| is no particulate organic nitrogen). | | | | Water Act rules did not let us change anything. |
| The DIN fraction, measured to calculate the Total | | | | Fortunately, in 2007 the EPA added Part 136.6 to the |
| Organic Nitrogen content can be, and should be, | | | | CFR allowing us to make modifications to our nutrient |
| analyzed on a filtered sample. Remember that there | | | | methods providing the modifications improve method |
| is no such thing as Total Inorganic Nitrogen since it is | | | | performance. These modifications are going to allow |
| equal to Dissolved Inorganic Nitrogen. Another | | | | us to monitor more water, with better accuracy and |
| infamous parameter in the total nitrogen world is, of | | | | detection limits. |
| course, TKN (Total Kjeldahl Nitrogen). TKN, as | | | | We have more to go, because regulation of point |
| routinely used, does not measure nitrate or nitrite. It | | | | sources has not solved the problem. Much of the |
| is essentially a measure of organic nitrogen plus | | | | problem is the non point sources we call storm water |
| ammonia nitrogen. | | | | run off and irrigation water. We need to watch what |
| TKN is the classical, if you will, analysis for total | | | | we do when we apply fertilizers and watch what |
| organic nitrogen. TKN has its roots in food and feed | | | | goes down our storm drains. But more importantly, |
| analysis as a way to quantify the amount of protein. | | | | what we need is increased monitoring of our rivers |
| TKN has been extrapolated to environmental analysis | | | | and streams. The only way we can begin to solve |
| and is the regulated parameter for Total Nitrogen. | | | | our problems is to know exactly what they are. To |
| Unless steps are taken to include nitrate and nitrite | | | | understand this problem we need more data, and the |
| the regular TKN method does not measure it. TKN | | | | data we need is accurate, low level quantitative |
| essentially measures organic nitrogen and ammonia. | | | | analysis of nutrients. |
| TKN is sufficient in POTW or municipal influents | | | | |