TS, VS, TSS and VSS were measured according to the standard
methods (APHA, 1998). The tCOD and sCOD were determined by
spectrophotometry (DR6000, HACH Company, Germany) and
sCOD was measured after filtration (0.45 l m). The total COD of fer-mentation products marked as tCODp was calculated by the sum of
COD of individual fermentation product.