Comparison and evaluation of four physical-chemical methods for wastewater COD characterization
废水COD 4种物化表征方法的比较与评估

In order to determine a suitable physical-chemical method for wastewater COD characterization,four methods of flocculation,flocculation+0.45 μm membrane and direct filtration using 0.1 μm membrane and 0.45 μm membrane were compared and evaluated experimentally.The results showed that some kinds of membrane could affect the measurements due to significant "COD release".The reproducibility of the four methods filtrating wastewater is satisfied and comparable.The treatment of physical-chemical separation has no effects on the analysis of readily biodegradable COD fraction(SS).However,the biodegradable COD(BCOD) in their filtrates contains COD fractions with different biodegradation rates,in which the percentage of SS is only 35%～45%.It is concluded that physical-chemical methods could not characterize SS appropriately.In terms of the soluble inert COD(SI),flocculation+0.45 μm membrane could be more advantageous because of its speediness,less interference and similar separation mechanism to activated sludge system.