Combination of foam fractionation and photo-Fenton like processes for greywater treatment

In this work, the combination of physical foam fractionation and photo-driven advanced oxidation (P-AOP) was investigated to develop a compact unit for greywater (GW) treatment. The treatment efficiency was assessed in terms of different parameters including chemical oxygen demand (COD), 5 days biochemical oxygen demand (BOD5), electrical conductivity and turbidity. To the best of our knowledge, this is the first time that foam fractionation has been used for the treatment of GW. The effect of air flow 1.5 (FF1), 3 (FF2) and 6 (FF3) L/min and treatment time (up to 3 h) were evaluated. A removal of 66.5, 79.7 and 82.5% in terms of COD for FF1, FF2 and FF3 respectively was achieved after 3 h treatment by foam fractionation. The COD removal through P-AOPs, namely H2O2/UV-C (control) and photo-Fenton like with IDS (Iminodisuccinate) as chelating agent (i.e., H2O2:900 mg/L and Fe-IDS 2 mg/L), were 30.2% and 63.8%, respectively. When the process of foam fractionation was tested in combination with the best condition of H2O2/Fe-IDS/UV-C, a removal of 95.3% of COD was achieved. The possibility to make the unit more sustainable was also evaluated by replacing UV-C light source with sunlight and the COD removal decreased slightly from 95.3% to 89.5%. Both combinations are effective but, whenever local conditions are suitable (flowrate, land availability and cost, average annual solar irradiation), solar light option is the most sustainable and attractive option for GW treatment also due to the significant lower operation cost (1.99 €/m3 Vs 15.33 €/m3).