K. Kujawa-Roeleveld

Anaerobic biodegradation of estrogens-hard to digest

Although many publications are available on the fate of estrone (E1), 17beta-estradiol (E2) and 17alpha-ethynylestradiol (EE2) during aerobic wastewater treatment, little is published on their fate under strictly anaerobic conditions. Present research investigated the digestibility of E1 and EE2, using digested pig manure, granular UASB sludge, UASB-septic tank sludge and activated sludge as inocula. Besides, actual concentrations were measured in a UASB septic tank treating black water. Under anaerobic conditions E1 is reduced to E2 but the extent of this reduction depends on type of inoculum. No significant loss of the sum of E1 and E2 and of EE2 was observed. Adsorption was responsible for a 32-35% loss of E1 and E2 from the liquid phase in the UASB septic tank and the effluent still contained considerable concentrations of respectively 4.02 microg/l and 18.79 microg/l for E1 and E2 with a large fraction present in conjugated form. No EE2 was detected in the UASB effluent.

Resource recovery from source separated domestic waste(water) streams; Full scale results

A major fraction of nutrients emitted from households are originally present in only 1% of total wastewater volume. New sanitation concepts enable the recovery and reuse of these nutrients from feces and urine. Two possible sanitation concepts are presented, with varying degree of source separation leading to various recovery products. Separate vacuum collection and transport followed by anaerobic treatment of concentrated black water (BW) demonstrated on a scale of 32 houses preserve 7.6 g/N/p/d and 0.63 gP/p/d amounting to respectively 69 and 48% of the theoretically produced N and P in the household, and 95% of the retained P was shown to be recoverable via struvite precipitation. Reuse of the anaerobic sludge in agriculture can substantially increase the P recovery. Energy recovery in the form of biogas from anaerobic digestion of concentrated BW, fits well in new concepts of sustainable, zero energy buildings. Nutrient recovery from separately collected urine lowers the percentage of nutrient recovery in comparison with BW but can, on the other hand, often be implemented in existing sanitation concepts. Theoretically 11gN/p/d and 1.0 g P/p/d are produced with urine, of which 38-63 and 34-61% were recovered in practice on a scale of 8-160 inhabitants in Sweden. New sanitation concepts with resource recovery and reuse are being demonstrated worldwide and more and more experience is being gained.

A downflow hanging sponge (DHS) reactor for faecal coliform removal from an upflow anaerobic sludge blanket (UASB) effluent

This research was conducted to study the faecal coliforms removal capacity of downflow hanging sponge (DHS) reactors as a post-treatment for an upflow anaerobic sludge blanket (UASB) reactor. Three long-term continuous laboratory-scale DHS reactors, i.e. a reactor with cube type sponges without recirculation, a similar one with recirculation and a reactor with curtain type sponges, were studied. The porosities of the applied medium were 91%, 87% and 47% respectively. The organic loading rates were 0.86 kgCOD m(-3) d(-1), 0.53 kgCOD m(-3) d(-1) and 0.24 kgCOD m(-3) d(-1) correspondingly at hydraulic loading rates of 1.92 m3 m(-2) d(-1), 2.97 m3 m(-2) d(-1) and 1.32 m3 m(-2) d(-1), respectively (COD: chemical oxygen demand). The corresponding averages for faecal coliform removal were 99.997%, 99.919% and 92.121% respectively. The 1989 WHO guidelines standards, in terms of faecal coliform content for unrestricted irrigation (category A), was achieved with the effluent of the cube type DHS (G1) without recirculation. Restricted irrigation, category B and C, is assigned to the effluent of the cube type with recirculation and the curtain type, respectively. Particularly for organic compounds, the effluent of evaluated DHS reactors complies with USEPA standards for irrigation of so called non-food crops like pasture for milking animals, fodder, fibre, and seed crops.