How much COD can be removed by using ferrous sulfate and alkaline sodium aluminate for flocculation and precipitation?
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This post was last edited by Gorō Bagua Stick on 2015-7-8 at 10:23. I use ferrous sulfate together with sodium aluminate in an alkaline environment to carry out flocculation and precipitation treatment for chemical wastewater (COD). After precipitation, the wastewater is intended to be sent directly to the anaerobic tank; I’m not sure how much COD can be removed in this way
The last edit to this post was made by Gorou’s Eight Trigrams Staff on 2015-7-8 at 10:30. The extent of COD removal depends on the SS and TDS levels in the raw water, as well as on the effectiveness of coagulation; moreover, different wastewater types and different chemicals used result in varying levels of COD removal； Generally, the optimal combination of chemicals and the dosage levels need to be determined through experiments ； For some waters, coagulation results in little reduction of COD, or even no effect at all; whereas for other waters, coagulation is very effective, achieving a reduction of 50–60%.
I used ferrous sulfate along with sodium aluminate in an alkaline environment; after precipitation, the color was light tea-colored. Due to insufficient conditions, it is unknown what the COD will be after precipitation (the raw water value is 20,000). I plan to add bentonite inside to remove the color once again until it becomes colorless.
The pH value has a significant impact on the coagulation effect, and it is generally kept at a slightly alkaline level； Ferrous sulfate and aluminum salts are coagulants; in addition, the coagulant aid PAM must be added to facilitate bridge formation and aggregation, thereby increasing the size of sludge particles and making it easier to separate them from the water ； It is advisable to keep the reaction time at around 30 minutes. The stirring in the PAM mixing tank should not be too intense, in order to prevent the formed sludge particles from being broken apart.
My process is the same; I just don’t know how much COD can actually be removed
It’s impossible to determine this; it’s likely to be over 20%. An accurate figure can only be obtained through laboratory testing, so please conduct a test as soon as possible.
After settling, I saw that the color changed from dark green to light brown. I had added an electrolysis process, but the client said it was too costly.
It is because ferrous iron is oxidized to ferric iron.
I wonder if increasing the flocculant dosage can reduce COD If the COD is too high, it cannot enter the anaerobic tank.
It’s hard to say exactly; it’s probably around 20-30%. Pilot tests need to be conducted
It’s just that there are no conditions to conduct experiments; I’ve done it before. But 15,000 dropped to 11,000