How is organic content estimated in wastewater?
Supplying clean and fresh water is a major barrier to global sustainable development. In this scenario the re-use or recycling of industrial or municipal wastewater after treatment is critical to meeting the growing demand for water.
At the same time, rising population and production have increased water demand, resulting in an increase in wastewater volume. Because of the increased consumption of water and the formation of process wastewater, more efficient removal of by-products and contaminants is required, allowing effluent discharge within specified environmental regulatory limitations.Organic content in wastewater can cause low coagulation efficiency, disinfection byproduct generation, membrane fouling, oxidant demand, and biomass growth, all of which can make treatment of wastewater more difficult.
Why organic content needs to be estimated?
Although the majority of waste characteristics are simple and uncomplicated to assess, the organic content requires specific attention. The BOD, COD (chemical oxygen demand), TOC (total organic carbon), and TOD (total organic demand) can all be used to assess the waste's organic content. When interpreting these findings, extreme caution is advised.
Tests used to estimate organic content in wastewater?
BOD (or CBOD), COD, TOC, and Oil & Grease are the four most popular tests used to evaluate organic contamination in wastewater.
What is BOD?
Under aerobic conditions, the BOD is defined as the amount of oxygen necessary for biochemical oxidation of organic matter present in the water. This test is based on the assumption that microbes using molecular oxygen will oxidize all biodegradable organic materials in a water sample to CO2 and H2O. The BOD-5 test determines the amount of biodegradable organic carbon and, in some cases, oxidizable nitrogen in the waste. Today's standard technique is to restrict nitrification, leaving just carbonaceous oxidation as CBOD-5.
What is COD?
For determining the concentration of organic matter in wastewater samples, COD is the most commonly used alternative test to BOD. The COD test is much faster than the 5-day BOD test, taking only a few hours to complete. It can be used as a near-real-time operational adjustment parameter by wastewater treatment system employees.
COD can be used to test wastewater that is too toxic to be tested by BOD. With the exception of certain aromatics, such as benzene, which are not entirely oxidized in the reaction, the COD test detects the total organic carbon. Other reduced compounds, such as sulphides, sulfites, and ferrous iron, will also be oxidized and recorded as COD in an oxidation-reduction test.
What is O&G?
Due to the unique physical features and highly concentrated energy content of O&G, these are a set of related elements, of particular significance in wastewater treatment. Although both words relate to the same wastewater ingredients, the term O&G (oil and grease) has replaced the term FOG (fat, oil, and grease).
Plants and animals (e.g., lard, butter, vegetable oils and fats) as well as petroleum sources can contribute to O&G constituents in wastewater (e.g., kerosene, lubricating oils).
What is TOC?
Total Organic Carbon (TOC) is a non-specific indicator of water quality that measures the quantity of carbon atoms bound up in organic molecules in a water sample (because pure water contains no carbon). It simply detects the presence of undesirable organic chemicals in pure water, not specific carbon-containing substances.
Unlike BOD and COD, TOC is a very sensitive indicator of the amount of organic carbon in a sample. The test's sensitivity makes it useful for assessing water that could be used in the production of medications or food for human consumption, as well as for determining the purity of water that will be used in sensitive manufacturing processes such as the production of semi-conductors.
Once a stable ratio of TOC to BOD has been established at a particular location, TOC can be utilized in the wastewater treatment industry as a rapid technique to assess the Biochemical Oxygen Demand (BOD) of effluent water.
Conclusion
Remember to use extreme caution when interpreting test results and comparing them to the results of other tests. To avoid the disproportionate association of volatile suspended solids in the corresponding tests, BOD and COD or TOC correlations should normally be done with filtered samples (soluble organics).
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