Reclaiming Biologically Pretreated Greywater for Reuse by Photocatalytic Oxidation: Qualitative Study on the Removal of Trace Organics

This study was carried out for gathering qualitative information about the potential of photocatalytic oxidation for the removal of trace organics (analysed by gas chromatography coupled to mass spectrometry, GC/MS) from biologically pretreated greywater to make it suitable for high quality reuse applications like groundwater recharge. Additionally, fractions of bulk organics (humic substances, building blocks, and low molecular weight organic acids) were quantified by liquid chromatography with organic carbon detection. Biologically pretreated greywater was subjected to photocatalytic oxidation in open stirred vessel reactors with UV lamps positioned over the reactors. UV doses of 0, 5, and 15 Wh·L-1 and TiO2 P25 photocatalyst concentrations of 1, 5, 10, and 20 g·L-1 were investigated. Photocatalysis experiments with a 15 Wh·L-1 UV dose were also conducted in the presence of 1 g·L-1 powdered activated carbon. Subsequent to mere contact of the photocatalyst to biologically pretreated greywater without UV, GC/MS did not indicate a substantial removal of trace organics, while humic substances were increasingly adsorbed by increasing photocatalyst concentration. A UV dose of 15 Wh·L-1 and TiO2 concentrations > 5 g·L-1 were favorable conditions for photocatalytic oxidation resulting in the removal of most of the trace organics, especially chlorinated phosphate flame retardants. Also humic substances were efficiently removed under these conditions. Photocatalytic oxidation is thus a promising process for advanced greywater treatment prior to groundwater recharge. Addition of powdered activated carbon did not improve trace and bulk organics removal by photocatalysis with a UV dose of 15 Wh·L-1 and with photocatalyst concentrations > 5 g·L-1.

Occurrence of micropollutants in the wastewater streams of cruise ships

Nowadays the protection of the marine environment raises increasing academic and public attention.The issue of organic micropollutants is of equally high importance for the marine ecosystems.Maritime vessels are considered to significant sources of micropollutants especially if the ship carries many passengers,which is often true for cruise ships which frequent attractive and sensitive sea areas.The emission pathways for micropollutants include wastewater discharges and sewage sludge disposal.The findings of the German research and development project NAUTEK contribute to bridging the knowledge gap about micropollutant emissions from cruise ships.As expected,micropollutants were detected in both the blackwater and greywater on board,emitted from either the passengers or certain ship operations.In total,16 out of 21 target substances were detected.Peak concentrations of pharmaceuticals could be found mainly in blackwater(peak conc.Carbamazepine 3.9 mg/L,Ibuprofen 29 mg/L,Diclofenac 0.04 mg/L),while greywater is mainly characterized by substances such as ointment residues,UV-filters and flame retardants(peak conc.Diclofenac 0.65 mg/L,Bisphenol A 8 mg/L,Tris(1-chloro-2-propyl)phosphate 136 mg/L).Further analyses suggest a gradual removal of the micropollutants by the onboard MBR plant(MBR effluent peak conc.Carbamazepine 0.47 mg/L,Ibuprofen 6.8 mg/L,Diclofenac 0.3 mg/L).Findings of this research provide a critical stepstone for shaping technical solutions for onboard micropollutants removal and water resource recycling.