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Results are presented of a systematic experimental investigation aiming to eliminate refractory organics from industrial effluents, of high and non-biodegradable organic load, by two Advanced Oxidation Processes (AOPs). Bench scale experiments were performed with real wastewater samples collected from a pesticides manufacturing plant, of varying TOC content (800-1820 mg/L), to investigate the effectiveness of boron-doped diamond (BDD) anodic oxidation (AO), of H2O2 photolysis with UV-C irradiation (H2O2/UV-C), and their combination (i.e. AO/H2O2/UV-C) on the total organic carbon (TOC) removal. The effect of main operating conditions was investigated for both processes, separately and in combination. In the case of AO, TOC and COD were removed at a rate of 36.4 mgC/h and 89.5 mgO2/L, by applying a current density of 100 mA/cm2 and a recirculation flow rate of 1400 mL/min. The H2O2/UV-C process achieved a TOC removal rate of 369 mgC/h and over 98% color removal after 4 h of treatment, when a single dose of 6 g/L H2O2 and 11.8 W/L of UVC irradiation dose were applied. Finally, the combined process (AO/H2O2/UV-C) led to a faster TOC abatement (534 mgC/h) and a higher color removal, after treating the wastewater with 77 mA/cm2 current density, 5.9 W/L UVC irradiation dose and ‘on-line’ dosing 15.7 g/L H2O2.

Results are presented from an ongoing R&D project, aiming at full utilization of dairy-industry effluents. Development of a membrane-based method is pursued, for treatment of digestate (after fermentation yielding bio-gas) to recover nutrients (N-NH4, P-PO4) and water for reuse/recycling or safe disposal. The performance is investigated herein of four commercial nanofiltration/ultra-low-pressure reverse osmosis membranes, employed in dead-end filtration mode, for nutrients recovery from solutions simulating the liquid digestate/effluent of an anaerobic membrane-bioreactor (AnMBR). Best-performing membranes, regarding nutrients’ rejection, were assessed within a sufficiently broad range of all key process parameters, including trans-membrane pressure and feed-composition. Further testing took place in a cross-flow set-up, simulating real operating conditions. For ~80% permeate recovery, the concentrate was significantly enriched in nutrients; i.e. compared to feed-solution, N-NH4 was concentrated twice, whereas P-PO4 was concentrated by 3- to 4-times. Research with real AnMBR effluent is on-going, for process improvements/optimization, mainly focusing on composition of concentrate/nutrients (for use in liquid fertilizers), membrane-fouling mitigation and quality of permeate/water for possible reuse.

Treated municipal wastewater is considered a valuable non-conventional water resource. However, a substantial number of wastewater treatment plants installed in the Mediterranean region have proven to be unsuccessful copies of systems operating in technolo-gically advanced countries. In addition to high operating and maintenance cost, these systems are often unsuited to address the local challenges of wastewater treatment. Therefore, treated municipal water is commonly under-exploited throughout the region. To address these challenges, the AQUACYCLE project aims to develop an eco-innovative wastewater treatment process scheme, comprised of anaerobic digestion, constructed wetlands and a solar photocatalytic reactor, for cost-effective treatment of urban wastewater and maximum environ-mental benefits. This paper presents the distinct features of the novel process scheme and the characteristics of three such demonstration units to be installed in Tunisia, Lebanon and Spain to test and validate the efficiency and cost-effectiveness of the hybrid system.