Search for: [Abstract = "The paper presents the results of studies concerning the designation of COD fraction in raw wastewater. The research was conducted in four municipal mechanical\-biological sewage treatment plants and one industrial sewage treatment plant. The following fractions of COD were determined\: non\-biodegradable \(inert\) soluble SI, biodegradable soluble fraction SS, particulate slowly degradable XS and particulate non\-biodegradable XI."]