Quantitative and qualitative greywater characterization in Greek households and investigation of their treatment using physicochemical methods

Abstract

Data for the quantity of greywater produced in Greek households was collected from two different cities, while samples from different residences were taken for greywater's quality characterization. Laboratory experiments were also performed to investigate the use of coagulation on COD and TSS removal from two different types of greywater, while a combined treatment consisting of coagulation, sand filtration and adsorption on granular activated carbon (GAC) was applied to achieve adequate quality for greywater reuse. According to the results, average greywater production in Greek residences was 82.6 ± 49.3 L per inhabitant and day, while the major sources were shower/bathtub and laundry, contributing to 41% and 26%, respectively. On the other hand, blackwater production was estimated at 59.4 ± 29.6L per inhabitant and day. Greywater produced in shower/bathtub and hand basin had similar quality characteristics, while kitchen sink's greywater were more contaminated, presenting lower pH values and higher concentrations of TSS and total COD. Coagulation experiments with FeCl3 and Al2(SO4)3 showed that process efficiency was differentiated significantly according to the type of greywater and the coagulant used. The highest removal efficiency (COD: 81%; TSS: 79%) was achieved for greywater that did not contain wastewater from the laundry and for Al2(SO4)3×14 H2O dosage of 800 mg L(-1). The application of coagulation, sand filtration and GAC adsorption resulted to average concentrations of COD and TSS equal to 28 ± 11 and 11 ± 3 mg L(-1), respectively, in treated greywater.