COD problems? Organoclay (OILSORB) to the rescue.
It is a fact that many plant engineers fail to understand the significance of COD (chemical oxygen demand) measurements.
As one example, the discharge limit may be 50 ppm for COD and 100 ppm for oil. If an engineer is asked if he has a problem with oil content, he might say “no, it is only 30 ppm; however, my COD is too high, at 70 ppm.” He does not know what to do about it; he does not understand that if the oil content is reduced, he will be in compliance. He does not realize that COD includes oil and grease.
In another example, someone purchases OILSORB to assist in cleaning up his wastewater. OILSORB is used to remove oil, grease, and large organic hydrocarbons of low solubility, such as PCB, PNAH, BTEX, and phenolic compounds, but the customer calls complaining that OILSORB didn’t work for him. Upon questioning, it is revealed that he tried to remove isopropyl alcohol, to lower the COD. Isopropynol, a low molecular weight organic solvent, is not removed by OILSORB.
It is critical that the enduser understand what contaminants can and can’t be removed by adsorbents such as OILSORB and activated carbon.
It is important that it is understood that. COD represents any chemical compound which can be oxidized. COD is defined as the amount of oxygen (expressed in ppm of oxygen) consumed under specific conditions during the oxidation of organic and inorganic matter in water. Examples include hydrocarbons, heavy metals and many anions. The exceptions are generally compounds containing nitrogen and chlorine. The ultimate oxidation products are carbon dioxide and water.
TOC (total organic carbon) is also a measurement for organic compounds, but specifically quantifies the carbon dioxide produced in an analytical combustion chamber. TOC is expressed in ppm of carbon.
The BOD (biochemical oxygen demand) is defined as the amount of oxygen required by bacteria to digest organic matter under aerobic conditions, usually measured after a 5-day incubation period. Because the structure of the organic compound will affect its oxygen demand, BOD is very imprecise and considered only an indicator rather than an absolute measurement tool. The BOD test is widely used to indicate the “biodegradation strength” of domestic and industrial wastes in terms of oxygen that they will require if discharged into natural watercourses in which aerobic conditions and bacteria exist.
It is often advantageous to measure the 3 criteria, TOC, COD and BOD, to calculate the COD/TOC and COD/BOD, ratios that can be indicative of particular types of pollution, particularly in industrial wastewaters.
A treatment train of OILSORB organoclay and activated carbon, perhaps preceded by a DAF (dissolved air flotation) technology or oil/water separation unit (in the event of high free oil/grease content), are often required to bring a discharge into compliance with the regulations.
