Phosphorus What is Phosphorus? Phosphorus (P) is a chemical element with an atomic number of 15 and an atomic mass of 31. Due to its high reactivity, phosphorus does not naturally exist as a free element. Phosphorus generally occurs as phosphate in minerals. Phosphate is typically found in the Earth’s crust at a concentration of about 1 gram per kilogram. The two types of elemental phosphorus are white phosphorus and red phosphorus. When exposed to oxygen, white phosphorus emits a faint glow caused by oxidation (also known as chemiluminescence). Phosphorus belongs to the pnictogen group of elements which consists of nitrogen, phosphorus, arsenic, antimony, bismuth and ununpentium (recently assigned the name moscovium). These elements are grouped because of their similar atomic structure, which lends them the ability to form stable compounds due to their tendency to form double and triple covalent bonds. Except for nitrogen (which remains a gas), the other pnictogens are solids at room temperature. Complex organisms such as plants and animals need phosphorus because phosphates are a component of DNA, RNA, ATP and phospholipids. Phosphorus is mined for use in detergents, pesticides, nerve agents and predominantly fertilizers. Phosphates/Orthophosphate In orthophosphate (one of the most common phosphates), one phosphorus atom is bonded to four oxygen atoms. Orthophosphate is sometimes called “reactive phosphorus” because it bonds easily with other electron-deficient elements and compounds since the three “extra” electrons on the oxygen atoms strongly want to bond with protons alike. Condensed Phosphates Condensed phosphates are multiple orthophosphate molecules “condensed” together and sharing a covalent bond between adjoining phosphorus (P) and oxygen (O) atoms. This group includes metaphosphate, pyrophosphate and polyphosphate — which are often used for corrosion control in drinking water distribution systems. Total Phosphorus/Organic Phosphorus Total phosphorus is a sum of all the phosphorus present: orthophosphate/phosphates, condensed phosphates and organic phosphorus. Organic phosphorus is usually present in the form of phosphates contained inside or bonded to an organic compound. Quick Links Why Measure Phosphorus? Featured Products Related Processes Methods for Monitoring FAQs Shop Now Why Measure Phosphorus? While phosphates don’t contribute to taste and odor issues, and, therefore, may not be a target in drinking water, high phosphate levels in wastewater discharge can have a significant impact on the surrounding ecosystem. High levels of phosphates in source water can accelerate types of algae and plant growth; this can lead to eutrophication and algae blooms. When this occurs, fish and aquatic life are robbed of oxygen, resulting in large fish kills and destroyed habitats. Measuring Phosphate in Wastewater is Critical for a Healthy Ecosystem Measuring phosphate in wastewater effluents is critical to maintaining a healthy ecosystem and protecting wildlife. Many areas have strict discharge limits for phosphates to protect the ecosystem that receives this water. Besides protecting the ecosystem, failing to monitor and control your phosphate levels can also lead to violations and fines. Drinking water plants that use phosphates for corrosion control may need to monitor phosphates in finished water, distribution system and other stages of the treatment process. Hach ® solutions are designed to keep you in compliance and give your operators the knowledge they need to make treatment decisions. At Hach, find the testing equipment, resources, training and software you need to successfully monitor and manage phosphorus levels in your specific process application. Featured Products to Measure Phosphorus Phosphate Analyzers Hach's Phosphax Analyzers are designed for rugged, outdoor installations and provide easy access to reagents and serviceable parts. Shop Now EZ Series Total Phosphorus Analyzers The EZ Series Online Analyzers offer multiple options to monitor total phosphorus in water. Shop Now EZ Series Phosphate Analyzers The EZ Series Online Analyzers offer multiple options to monitor phosphate in water. Shop Now 5500sc Phosphate Analyzer The 5500 sc Phosphate Analyzer requires only 2 liters of reagent for the analyzer to perform unattended for up to 90 days; twice as long as the predecessor Series 5000 instruments. Shop Now Spectrophotometers Hach is an innovator in spectrophotometry and offers many of the leading spectrophotometric instruments in the water analysis market. Shop Now Colorimeters Whether you are looking for a single parameter testing device such as the DR300, or a more sophisticated hassle-free instrument like the DR900 that can measure many parameters with up to 90 methods, we have a solution. Shop Now Total Phosphorus Reagents Hach is dedicated to providing high-quality reagents for routine and challenging water analyses. Shop Now DRB200 The DRB200 is designed to save time and ensure accuracy during testing requiring sample digestion. Shop Now SL1000 - PPA Portable Parallel AnalyzerⓇ- Portable Colorimeter with USB The Hach SL1000 Portable Parallel Analyzer (PPA) performs the same tests with less than half the manual steps. Get highly accurate results, with less opportunity for errors, in a fraction of the time. Shop Now TOC The Hach TOC analyzer completes a full breakdown of process samples to deliver trusted results. The self-cleaning oxidation technology enables the B7000 TOC TN TP analyzer to easily handle difficult samples which can contain salts, particulates, fats, oils, and greases. Shop Now Which Processes Require Phosphorus Monitoring? Drinking Water Source water may contain elevated concentrations of phosphates due to agricultural runoff, which may cause eutrophication of surface water with algae growth and release of cyanotoxins. Condensed phosphates are often used for corrosion control in drinking water distribution systems, therefore drinking water treatment processes may require monitoring for phosphate in both raw and distributed finished water. Wastewater Treatment How is Phosphorus Monitored? Colormetric Methods (Orthophosphate) Orthophosphate (reactive phosphorus) is combined with molybdate in an acidic medium to produce either a blue or yellow color. Be aware that no analytical test is perfect and some condensed phosphates may be measured with these tests too. Due to the acidic chemistry, some suspended orthophosphate may be detected if the sample was not first filtered to 0.45 micron. To measure all phosphorus including the particulate phosphates, it is necessary to use a total phosphorus test, which incorporates rigorous digestion to convert most of the particulate phosphate to dissolved format. Benchtop/Portable: TNT843 ULR Method 10209 (Reactive and Total) TNT843 LR Method 10209 (Reactive and Total) TNT844 HR Method 10209 (Reactive and Total) TNT845 UHR Method 10210 (Reactive and Total) TNT846 HR Molybdovanadate Method 10214 (Reactive) PhosVer 3 Method 8048 PhosVer 3 TNT Method 8048 Molybdovanadate TNT HR Method 8114 HPT487 ULR Method 10307 Reactive Phosphorus LR Chemkey (PPA) Reactive Phosphorus HR Chemkey (PPA) Online: 5500sc Phosphate Analyzer Phosphax sc LR Phosphate Analyzer Phosphax sc Phosphate Analyzer EZ Series Phosphate Analyzers Acid Hydrolyzable Phosphate/Condensed Phosphate To measure condensed phosphates, it is first necessary to transform them into orthophosphate using sulfuric acid and heat, digesting the sample at 150°C for 30 minutes. This is called “acid hydrolyzable phosphate” since the condensed phosphates are hydrolyzed into orthophosphate. After the digestion, either the ascorbic acid or molybdovanadate methods are used to measure the orthophosphate. Some organic phosphate will be hydrolyzed into orthophosphate as well, so the results are not “pure” condensed phosphate. Of course, just performing the digestion and colorimetric test will tell you the concentration of both the original orthophosphate and condensed phosphates. If you want just the condensed phosphate concentration, then simply run the orthophosphate test on the same sample without a digestion and subtract those results from the first concentration value. Acid Hydrolyzable Phosphorus TNT LR Method 8180 (PhosVer 3) Total Phosphorus/Organic Phosphate Organic phosphates are stubborn compounds that do not like to break down easily. To test for them, it is necessary to not only digest the sample first with sulfuric acid and heat, but also add a strong oxidant such as potassium persulfate to break the orthophosphates free from the organic bonds. After digestion, the same ascorbic acid or molybdovanadate methods can be used to measure the phosphate concentration. The described test will convert all the different forms of phosphate into orthophosphate, which means the results are total phosphorus. If you want to know only the organically bound phosphate concentration, it is necessary to perform the acid hydrolyzable test and subtract those results from the total phosphorus concentration (total phosphorus concentrations will always be larger than the orthophosphate concentration). Benchtop: TNT843 ULR Method 10209 (Reactive and Total) TNT843 LR Method 10209 (Reactive and Total) TNT844 HR Method 10209 (Reactive and Total) TNT845 UHR Method 10210 (Reactive and Total) Total Phosphorus TNT LR Method 8190 (PhosVer 3) Total Phosphorus TNT HR Method 10127 (Molybdovanadate) Online: EZ Series Total Phosphorus Analyzers B7000 BioTector ® TOC/TN/TP Analyzer Frequently Asked Questions Can the Phosphax sc Analyzer be used in seawater applications? What is the difference between reactive, acid hydrolyzable, and total phosphorus? 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