Case study: characterization of source-separated blackwater and greywater in the ecological housing estate Lübeck “Flintenbreite” (Germany)

The objective of this paper is the characterization of grey- and blackwater from the housing estate “Flintenbreite” in Lübeck, Germany. The housing area “Flintenbreite” was selected for the investigation since its wastewater system has separate flows for grey- and blackwater. Although the knowledge on the characteristics of blackwater and greywater is essential for the design of treatment units, the data basis is still weak and design values are not available. In general greywater wastewater contains lower levels of organic matter and nutrients compared to domestic wastewater. The greywater loads for COD_t, TN_t and TP_t found in Lübeck Flintenbreite were 45 g per capita and day (gpcd), 0.84 and 0.4 gpcd. The liquid greywater phase contained the majority of the daily loads. Around 5, 7 and 2.5% of the inhabitant-specific daily loads were found in the greywater solid phase. The mean concentrations of the organic blackwater parameters TOC, DOC and DIC were 15.06, 6.16 and 5.51 gcpd are much higher compared to municipal wastewater. Due to the fact that the TOC is about two times higher than the DOC, a direct correlation between dry residues and total organic carbon was proved. The TP content of 0.44 gcpd in blackwater is quite low. A high variability of the nutrient amounts during the yearly seasons is assumed, because the amount of phosphorous in blackwater was 1/3 higher in the summer season compared to the winter season. For the parameter TN, a high average concentration of 8.47 gpcd was found. High TN concentrations of more than 1 g/l are usually declared as critical for the anaerobic treatment process, but during 2 years of anaerobic digestion experiments no adverse effects of the anaerobic digestion were detected.