The chemical oxygen demand (COD) is an important parameter for the determination of organic load in water. It is based on the almost complete oxidation of organic content to CO2 and H2O, and the results are given as oxygen needed for this reaction in mg/L. In particular, for operating wastewater treatment plants (WWTP) and taxation of the wastewater polluters, COD is used worldwide in national and EU directives. Since the end of 1970s, the standard method for COD determination is oxidation of wastewater samples with potassium dichromate (K2Cr2O7) and masking chloride ions with mercury sulfate (HgSO4), since otherwise chloride ions lead to an elevated COD value through co-oxidation with K2Cr2O7. This reaction, regulated through DIN/EN/ISO norms worldwide, produces huge volumes of environmental pollutants while measuring an environmental parameter. Replacing the COD through e.g. total organic carbon (TOC) does not work due to missing reproducible correlations of the two parameters with each other, since the organic carbon in wastewater may occur in different oxidation stages (e.g. in ethane versus in oxalate) leading to much different correlation factors. In the meantime, Hg is classified as a priority pollutant and should be “phased out” soon, and Cr (VI) is a strong carcinogen and should be forbidden from 2017 after REACH. Therefore, there is a high demand for the development of an alternative method for COD determination without polluting the environment. In the frame of a research project granted by the Federal German Environmental Foundation (DBU), we have developed a new method using Mn (III) as oxidant and AgNO3 for the removal of chloride ions for preventing them from co-oxidation. The excess amount of Mn(III) applied for oxidation is titrated back with iron(II)sulfate as it is also done in the current COD standard method with Hg and Cr(VI). This method was tested with different types of aqueous samples including domestic and industrial wastewaters, containing low and high concentrations of chloride, and differently persistent organic compounds. The results obtained were compared with the standard method using Hg and Cr (VI). Most importantly, the new wet-chemical method developed makes use of the same COD equipment as for the standard method that is currently in use. With this, the laboratories worldwide do not need to purchase new equipment and new detectors for end point determination. Other oxidants tested for COD determination were less satisfactory. The new method was also tested in several laboratories in Germany and in Turkey giving similar and reproducible results (interlaboratory comparison). This novel COD determination method is environmentally benign and does not pollute the environment with neuro-toxic Hg and carcinogenic Cr (VI) compounds. Therefore, this method will be further developed to German DIN and international ISO procedure for COD analysis.