Ozonation and ultrafiltration for the treatment of olive mill wastewaters: effect of key operating conditions and integration schemes

Abstract

With the objective of reaching suitable techniques for olive mill wastewater treatment, ozonation and ultrafiltration were studied individually and combined. A continuous reactor was run for the treatment of a phenolic mixture mimicking an actual olive mill wastewater (OMW) by ozonation. The effect of the main operating parameters was analysed (pH, liquid flow rate and ozone inlet concentration). The increase of pH and ozone dose improved ozonation efficiency. As expected, the highest residence time led to higher steady-state degradation (35 % of chemical oxygen demand (COD) abatement). Even if the rise on ozone inlet gas concentration was able to remove COD in a higher extent, it should be taken into consideration that with the lowest oxidant load (15 g O3/m(3)), the maximum steady-state biochemical oxygen demand (BOD5)/COD ratio was reached which would reduce the process costs. These operating conditions (pH 9, 1 mL/min of liquid flow rate and 15 g O3/m(3)) were applied to an actual OMW leading to 80 % of phenolic content abatement and 12 % of COD removal at the steady state. Regarding ultrafiltration, it was concluded that the best total phenolic content (TPh) and COD abatement results (55 and 15 %) are attained for pH 9 and using a transmembrane pressure drop of 1 bar. Among the integration schemes that were tested, ultrafiltration followed by ozonation was able to reach 93 and 20 % of TPh and COD depletion, respectively. Moreover, this sequence led to an effluent with a BOD5/COD ratio of about 0.55 which means that it likely can be posteriorly refined in a municipal wastewater treatment plant.

Multistage treatment for olive mill wastewater: Assessing legal compliance and operational costs

“…( 26)), one must still consider the occurrence of direct oxidation by molecular O 3 , that has high selectivity towards compounds containing aromatic rings and double bonds (such as phenolic compounds). In this case, after 3 h of O process with 20 mg O 3 min − 1 , the removal of phenols was 91%, which is in agreement with high phenols degradation reported by other researchers [16,24,69,70]. For the treatment of undiluted OMW previously coagulated and bio-treated, the optimized OD I for the ozonation stage (without requiring initial or final pH correction) was 20 mg O 3 min − 1 (C O3,I = 100 mg Ndm − 3 and Q g = 0.2 Ndm 3 min − 1 ).…”

“…Taking the above, and considering the bio-OMW pH value of ~8-8.3, no pH adjustment was used on the O 3 treatment and the process was evaluated for increasing OD I (in this case, by increasing C O3,I ) which is an important parameter because it rules not only ozonation efficiency but also its associated costs [69]. Results showed (Fig.…”

Assessment of a New Silicon Carbide Tubular Honeycomb Membrane for Treatment of Olive Mill Wastewaters

“…However, good percent removals were achieved when compared with other studied membrane processes: Coskun et al [40] achieved the same range of removals combining ultrafiltration and nanofiltration to treat olive mill wastewaters. A previous study [41] obtained a maximum removal of 15% of COD from an olive mill wastewater using a regenerated cellulose membrane in dead-end configuration. The results obtained in this study are extremely promising since tests were performed using robust ceramic membranes and in conditions closer to reality in terms of flow dynamics.…”

Impact of legislation on olive mill wastewater management: Jordan as a case study

“…The obtained removal efficiency might not meet the enforced allowable limits even at the very high treatment costs reported at 32 €/m 3 (Paraskeva et al, as cited in Gebreyohannes et al, 2016). Other tested treatment technologies include coagulation-flocculation (Vuppala et al, 2019); electro-coagulation (Neffa et al, 2010;Haksevenler & Alaton, 2014;Abou-Taleb et al, 2018;Jalo et al, 2018); aerobic biological treatment (El-Hajjouji et al, 2014;El-Moussaoui et al, 2018); anaerobic digestion (Gunay & Karadag, 2015;Enaime et al, 2019); electrolysis (Bouhssine et al, 2013); Fenton treatment (Amor et al, 2015); photo-Fenton treatment (Ahmed et al, 2011); and ozonation (Martins et al, 2015). Reported removal efficiencies for the COD and phenols for these systems are generally lower than membrane systems, although less costly.…”