Hi everyone: I am doing my Chemistry group project right now, it is something about the water quality. And I am in charge of the COD (Chemical oxygen demand) part. The teacher told me that COD contains two parts: concentration (mg/L)and light absorbance rate (A)...something like that (I translated it from Chinese). But I didnt found any related information about the "light absorbance rate" on the internet. Can anyone give me some information about COD? Also, can someone tell me how can I get the international standards (or standards of other countries, or organizations such as UN or EU) of water quality (COD, BOD, DO...etc)? Thanks a lot!