Pilot scale nanofiltration treatment of olive mill wastewater: a technical and economical evaluation

Abstract

The treatment of large volumes of olive mill wastewater is presently a challenge. This study reports the technical and economical feasibility of a sequential treatment of olive mill wastewater comprising a dissolved air flotation pre-treatment and nanofiltration. Different pilot nanofiltration assays were conducted in a concentration mode up to different volume reduction factors (29, 45, 58, and 81). Data attained demonstrated that nanofiltration can be operated at considerably high volume reduction factors and still be effective towards the removal of several components. A flux decline of approximately 50% was observed at the highest volume reduction factor, mainly due to increase of the osmotic pressure. Considerably high rejections were obtained across all experiments for total suspended solids (83 to >99%), total organic carbon (64 to 99%), chemical oxygen demand (53 to 77%), and oil and grease (67 to >82%). Treated water was in compliance with European legal limits for discharge regarding total suspended solids and oil and grease. The potential recovery of phenolic compounds was evaluated and found not relevant. It was demonstrated that nanofiltration is economically feasible, involving operation costs of approximately 2.56-3.08 €/m, depending on the working plan schedule and volume reduction factor, and requiring a footprint of approximately 52 m to treat 1000 m of olive mill wastewater.

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

“…Using the optimized conditions, higher values of rejection of all the tested parameters, except TOC, were obtained by ultrafiltration (this study, Table 5, test 4) compared to the removal values obtained by dissolved air flotation reported in a previous study (Total solids: 27%, total suspended solids: 98%, COD: 67%, TOC: 72%, Oil and grease: 77%; [39]). Ultrafiltration can therefore be applied instead of flotation for the treatment of olive mill wastewaters.…”

“…However, high contents of dissolved organic components are still present and must be further removed. Processes such as nanofiltration [39] or advanced oxidation processes [2,7,49] may be good options to reduce it and to guarantee the production of high quality water.…”

Solvent-Free Process for the Development of Photocatalytic Membranes

“…Thus, a membrane area of 82 m 2 would be needed to treat a total annual volume of 1000 m 3 (7 m 3 /day during five months, working 8 h/day) [27]. Given this, 1417 L of ethanol could be saved if these new solvent-free photocatalytic membranes were used.…”

Novel Submerged Photocatalytic Membrane Reactor for Treatment of Olive Mill Wastewaters

“…High-quality permeates can be obtained when membrane processes are used to treat olive mill wastewaters [3,4]. However, the treatment of a highly concentrated retentate produced during membrane filtration and the development of fouling on the membrane surface are problems that still need to be addressed [5].…”