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Wastewater treatment: sulfide and oil & grease


I'm an undergraduate University student doing an assignment about wastewater treatment. The analysis report shows that the sulfide content in the wastewater is 7.760 mg/l and there is 1 mg/l of oil and grease. BOD is 780 mg/l and the COD is 1900 mg/l. I wish someone could help me as I do not know what is the cause of that, and give some opinions on how to reduce the BOD and COD. Thank you in advance.

Phing Voon Chung
student - Malaysia

"Natural Wastewater Treatment Systems"
from Abe Books

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Are these real numbers from an actual physical installation where you are interning or are they a hypothetical example, Phing?. If it's a real installation, you must not speculate in lieu of determining the actual situation! But if sheerly a hypothetical as a learning experience, sulfide could come organic installations like egg processing or from industrial use of sulfide chemicals. Oil and grease should be rather obvious: processing of oily, greasy parts. Hopefully you know what BOD and COD areand domestic treatments plants with trickling filters or activated sludge are designed to reduce BOD and COD. Best of luck.

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey


Oil and grease is an organic compound, so, by adding oxidation reagent such as ozone, hydrogen peroxide, chlorine dioxide, potassium permanganate into the wastewater could reduce the BOD and COD. However, physical method such as adsorption with activated carbon also could reduce the BOD and COD. Ozone and hydrogen peroxide are the most environmental friendly reagent because after being reduced, it converts to carbon dioxide and water. While chlorine dioxide would produce a by product, called chlorite that has to be removed by adding ferrous ion salts or reduced sulfur compounds. Potassium permanganate would produce black insoluble manganese dioxide after the treatment. It could be removed by conventional filtration. Activated carbon that had been used to adsorb the oil and grease has to be reactivated by heating or burning. Apart from these methods, biological method is one of the cheaper methods. Bacteria seed or yeast is adding into the wastewater and leave the bacteria to degrade the oil and grease using their secreted enzyme. Beside, oil and grease could also be decomposed using titanium dioxide when irradiated under UV light. By using hydrogen peroxide, ion sulfide will be oxidized to ion sulfate.

Alexander Chong
PhD student in USM - Penang, Malaysia


Pollution prevention priorities, discuss the constraint factors that contribute to selectivity of pollution prevention method. Give pros and cons of selected method.
more specified towards water recycles.

- Kuantan, Pahang

Ed. note: You lost us, Nagentheran. Is this advise for the original inquirer about what to include in his work, or are you asking someone to write your essay assignment for you? :-)

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