Some BOD is removed in the septic tank by anaerobic digestion and by solids which settle to the bottom of the septic tank, but much of the BOD present in sewage (especially detergents and oils) flows to the leaching field.,
For Soluble BOD, an industrial user needs to remove the suspended solids, oil and grease and metals prior to discharge. Discharging BOD typically results in a user fee or surcharge. A post filtration system, like a bio-reactor or ozone treatment system, is needed to reduce Soluble BOD if a surcharge is not an option.
So, coming into the plant is 245 mg per liter of BOD and leaving there's 22 mg per liter. We have a formula that says efficiency or removal efficiency equals what's coming in minus what's coming out then you divide that by what's coming in and then we multiply by a 100 to convert the decimal to a percent.Jun 22, 2018
BOD is fairly easy to remove from sewage by providing a supply of oxygen during the treatment process; the oxygen supports bacterial growth which breaks down the organic BOD. Most enhanced treatment units described incorporate some type of unit which actively oxygenates the sewage to reduce BOD.
Primary treatment removes about 60 percent of total suspended solids and about 35 percent of BOD; dissolved impurities are not removed. It is usually used as a first step before secondary treatment.
A sewage treatment plant providing both primary and secondary treatment is expected to remove at least 85 percent of the BOD and suspended solids from domestic sewage.
Explanation: The main function of Primary treatment is to carry out the removal of suspended solids present in the sewage. Heavy suspended solids are removed by screens and fine suspended solids are removed in the grit chamber and in the primary sedimentation tank.