How to estimate organic content of the waste?
Conventional calculations for assessing pollution levels in water and wastewater are laboratory-based devices that measure the oxygen demand required to oxidise pollutants.
The organic strength of waste water may be assessed in three ways:
1) BOD (3 or 5 days): biochemical oxygen demand for 3 or 5 days.
2) COD stands for chemical oxygen demand.
3) TOC stands for total organic carbon.
What is BOD?
BOD stands for biochemical oxygen demand. BOD is a measure of the proportion of organic matter that can be decomposed by microbes and is commonly represented as the quantity of oxygen used (mg/L) over five days at 20°C or three days at 27®C. BOD is composed of rapidly biodegradable organic carbon (carbonaceous or BOD) and, in rare occasions, ammonia (nitrogenous or BOD). BOD is the principal driver and consists of organic carbon molecules that are soluble, particulate, or colloidal.
In some applications, like as industrial wastewaters, which typically contain heavy metal ions, cyanides, and other microorganism-toxic chemicals, the BOD-5 test has limits. When toxic compounds poison microorganisms, they lose their capacity to oxidise waste, rendering the BOD-5 test worthless as a measure of organic pollution.
What is COD?
COD stands for chemical oxygen demand.The quantity of oxygen required for the chemical oxidation of substances in water is referred to as COD. This need is calculated using a strong oxidant, most often dichromate and, to a lesser degree, permanganate.
What is TOC?
TOCstands for total organic carbon.The total organic carbon (TOC) in a sample is a direct measure of all organic carbon. The oxidation of organic carbon molecules determines it. TOC analysers can be designed to measure a variety of organic carbon fractions, including TOC, Purgeable Organic Carbon (POC), Non-purgeable Organic Carbon (NPOC), and Dissolved Organic Carbon (DOC).Inorganic Carbon (IC) is eliminated or quantified depending on the organic carbon approach used. Total Carbon may be calculated by measuring both inorganic and organic carbon (TC).
Calculating organic content:
Although the interpretation of the majority of waste characteristics is clear and unambiguous, the organic content requires specific study. The organic content of trash can be evaluated using the BOD, COD (chemical oxygen demand), TOC (total organic carbon), or TOD (total organic decomposition) (total oxygen demand). These findings should be interpreted with extreme care.
1. The BOD-5 examination calculates the quantity of biodegradable organic carbon and, under specific conditions, oxidizable nitrogen in waste.
2. The COD test analyses all organic carbon, with the exception of aromatics such as benzene, which are not totally oxidised in the process. Because the COD test is based on oxidation-reduction, additional reduced compounds such as sulphides, sulphites, and ferrous iron will be oxidised and recorded as COD. The COD test will not oxidise NH3-N.
3. Because the TOC test assesses all carbon as CO2, inorganic carbon (CO2, HCO3-, and so on) present in wastewater must be eliminated prior to analysis or adjusted for in the computation.
Ensure to use extreme caution when interpreting test findings and comparing them to those of other tests. To minimise the disproportionate association of volatile suspended solids in the respective tests, correlations between BOD and COD or TOC should normally be done with filtered samples (soluble organics).
For more information, contact Netsol Water.
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