Pretreated Olive Mill Wastewater Research Articles

Assessment of the impact of diluted and pretreated olive mill wastewater on the treatment efficiency by infiltration-percolation using natural bio-adsorbents.

The current study was carried out to treat the olive mill wastewater (OMW) via infiltration percolation process, using low-cost natural adsorbents that could improve the ability of the system to enhance the disposal rate of elimination of pollutant from the OMW. The experimental pilot was composed of three PVC(polyvinyl chloride)columns with 10cm in diameter and 110-cm height equipped with lateral air entries. Each column was filled with four layers of 10cm of a mixture of sand (70%), charcoal (20%) and sawdust (10%) respectively. These layers were alternated by four permeable layers of 10cm of Pouzzolane. To assess the effect of the pretreatment on the efficiency of the system, three types of OMW were used: raw OMW, diluted OMW with domestic wastewater at 1/1(v/v) ratio and OMW pretreated with lime. For the column feed with raw OMW, an average removal of total COD (41%), dissolved COD (54%), NH4-N (40.25%), NO3- (15.76%), total phosphorus (55.63%) and orthophosphate (50.84%) was recorded. The results showed that the column feed with diluted OMW with domestic wastewater was the most efficient one with a removal rate that reached 93.2% of total COD, 86.2% of dissolved COD, 92% of polyphenol, 92% of orthophosphate (OP), 97.2% of total phosphorus (TP) and 81% of NH4-N. The pretreatment of OMW with lime gave the lowest removal rate for all the parameters: total COD (34%), dissolved COD (50%), NH4-N (30%), NO3- (- 21%), total phosphorus (15.19%) and orthophosphate (9.04%). This study demonstrated that the dilution is a way to optimize the efficiency of the system of infiltration-percolation in treating the OMW.

Comparing the performance of UV/Acetylacetone and UV/O3 processes for treatment of olive mill wastewater

Background: Olive mill wastewater (OMW) is characterized by its high organic content and refractory compounds. The aim of this study was to evaluate and compare the efficiency of UV/O3 and UV/ acetylacetone (UV/AcAc) processes for treatment of pretreated OMW by coagulation/microfiltration (C&M) process. Methods: In this study, a laboratory-scale UV plug flow reactor with ancillary equipment was fabricated. The experimental factors including initial pH (5-9), O3 dosages (1.5-4.5 g/h), and AcAc concentrations (0.01-0.03 M) were measured. For both processes, a reaction time of 120 min was considered. The effect of these variables on removal of wastewater contaminants including BOD, COD, TSS, turbidity, phenol, oil, and grease were investigated. Results: Results showed that raw OMW has a high load of pollutants and very low biodegradability (BOD5 /COD=0.12). In UV/O3 process, the optimal conditions were obtained at pH 8 and ozone injection at 4 g/h. The combined C&M-UV/O3 process removed 78.75% COD, 46.66% BOD5 , 90.88% total phenol, 91.78% TSS, 99.14% oil and grease, and 98.38% turbidity, with promotion of BOD5 / COD from 0.12 to 0.33. In UV/AcAc process, the optimal conditions were achieved at pH 5 and AcAc concentration of 0.03 M. The combined C&M-UV/AcAc process removed 58.75% COD, 67.58% BOD5 , 38.03% total phenol, 83.50% TSS, 93.65% oil and grease, and 95.00% turbidity, with promotion of BOD5 / COD from 0.12 to 0.22. Conclusion: The results showed that the UV/O3 process is completely superior to the UV/AcAc process for removal of OMW contaminants, as well as promoting the biodegradability of OMW.

Phytotoxicity assessment of olive mill wastewater treated by different technologies: effect on seed germination of maize and tomato.

The phytotoxicity effect of olive mill wastewater (OMWW) treated in a combined system regrouping pretreatment by filtration on olive stones and coagulation-flocculation, and anaerobic digestion (AD) on seed germination of maize and tomato was evaluated through germination tests in petri dishes and growth tests in pots. Three samples, referenced as AD-40, AD-60, and AD-80, were collected from the anaerobic reactor operating with an influent at 40, 60, and 80% OMWW/water (% v/v). Concentrations between 25 and 100% were used for maize and between 5 and 25% were used for tomato using raw and pretreated samples, while anaerobic samples were used without dilution. For maize, 100% and 75% OMWW were very phytotoxic and completely prohibited seed germination, while phytotoxicity was decreased following dilution at 25% and 50% OMWW. Maize germinability was found highly enhanced when watered with anaerobic samples. For tomato, high dilution was required to reduce the phytotoxicity of raw and pretreated OMWW and a high relative germination percentage was registered at 5, 10, and 15% OMWW, while for samples anaerobically treated, a high phytotoxicity is still observed. Growth tests, showed more favorable results for maize watered with raw and pretreated samples at 25% OMWW and with biological samples. For tomato and with the exception of 25% OMWW and AD-80, seeds respond positively to all samples. It was concluded that if the OMWW will be used for irrigating maize, it could be directly used after anaerobic digestion, while for tomato further dilution is required. The phenolic profile analysis of the tested samples coupled with the results of the germination tests showed that the OMWW phytotoxicity appears to be determined by not only the monomeric phenols but also by other toxic components unaffected by the applied treatments.

Rapid and high purification of olive mill wastewater (OMV) with the combination electrocoagulation-catalytic sonoproxone processes

Background and purpose: Olive Mill Wastewater (OMW) is one of the most problematic wastewater in the food industry. Thus, its ineffective treatment causes severe pollution in the environment. In this study, the treatment of OMW by combining electrocoagulation (EC) and catalytic sonoperoxone processes was investigated. Materials and methods: The efficiency of turbidity removal and mineralization of OMW using EC was investigated by applying the following operation variables: type of electrode (iron and aluminum), reaction time (0- 60 min) and current density (0.08�0.77 A/dm 2 ). Then, a single ozonation process (SOP), a catalytic ozonation process (COP), an ultrasonic process (US), H 2 O 2 , COP/US, a peroxone process (H 2 O 2 /O 3 ) and a catalytic sonoperoxone process (H 2 O 2 /COP/US) were performed. Finally, the biodegradability of OMW was measured by using BOD 5 /TOC index. Results: Maximum removal efficiency of the turbidity, Total Organic Carbon (TOC) and consumed electrode in the EC were 82, 75 and 634 mg of iron electrode/L of OMWW, respectively. The TOC removal efficiency of the pretreated OMW by using the following oxidation processes of US, H 2 O 2 , SOP, O 3 /H 2 O 2 , COP, COP/US and H 2 O 2 /COP/US was 8, 15, 20, 25, 61, 68 and 75, respectively. In addition, the biodegradability index (BOD 5 /TOC) in the catalytic sonoperoxone process increased by as much as 32 compared to raw OMWW. Conclusion: The EC process caused an effective per-treatment of OMW and combined by sonoperoxone process improved its biological biodegradability. So, this process can be used for the efficient treatment of OMWW and the wastewater produced by similar industries. © 2019 Taiwan Institute of Chemical Engineers

Fouling modelling on a reverse osmosis membrane in the purification of pretreated olive mill wastewater by adapted crossflow blocking mechanisms

In this work, the effect of the operation parameters (crossflow, pressure and temperature) on the individual fouling mechanisms of a RO membrane used for the purification of tertiary-treated OMW is addressed. The knowledge beforehand of the possible fouling mechanisms and the adoption of adequate operating conditions accordingly is key for the control of fouling and the steady performance of the membrane plant. The build-up of a gel layer was found to be dominant from the middle to the final moments of the membrane filtration. However, in the initial filtration periods a different mechanism, the blocking of the surface defects of the membrane, and the contribution of concentration polarization (38.6%) on the boundary region of the membrane, occurred as well before the definite build-up of the cake or gel layer. By applying medium pressure (25–15bar), the intermediate blocking mechanism was reduced, and the formation of a cake or gel layer over the membrane skin predominated, a less strong form of fouling, whereas the increment of the crossflow (2.5–5.0ms−1) reduced the gel layer formation (Kgl) by 77.1%. Upon the adopted conditions, the stable operation of the membrane regarding the rejection efficiency (CODrejection 97.5–99.1%) and flux (~ 24–32Lh−1m−2) allowed to obtain a final purified effluent compatible for irrigation.

Optimization Study of the Fouling Build-Up on a RO Membrane for Pretrated Olive Mill Wastewater Purification

Even though membranes are considered in many aspects a mature technology, a range of features are still in development and under investigation. Regarding this, the main handicap of this technology is inevitably membrane fouling. Fouling issues have investigated by many research groups in the last years to convince investors to implement membranes as substitutes of a range of unit operations at industrial scale. In the wastewater treatment field, this is especially problematic, given the low economic value of the product, that is, treated water. On another hand, the management of the effluents generated by olive oil industries, olive mill wastewaters (OMW), is a task of global concern not anymore constrained to a specific region. These wastewaters represent an ever-increasing problem still unresolved. The present work was aimed for the modelling and optimization of a reverse osmosis (RO) membrane operation for the purification of pretreated olive mill wastewater, with a focus on the dynamic fouling development minimization on the selected membrane as a function of the set-up of the operating conditions. For this goal, beforehand a factorial design was implemented for the optimization of the RO treatment of the OMW stream. The results gathered were thereafter interpreted by means of the response surface methodology. A significant impact was noted to be driven by the operating pressure and the tangential velocity on the fouling rate on the RO membrane. The response surfaces withdrawn from the experimental data support the previous results, and the optimised parameters - ambient temperature range (24 - 25 °C), moderate operating pressure (25 - 30 bar) and turbulent tangential flow (3.1 - 3.5 m s-1) - were found to provide a stable permeate flux of 32.3 - 38.5 L h-1m-2. These results reveal the proposed process could be operated successfully at ambient temperature conditions and medium operating pressure, boosting the economic efficiency of the RO purification of this effluent. Finally, the parametric quality standards stablished to reuse the purified effluent for irrigation purposes were checked and found to be satisfactory.

Volatile fatty acid production dynamics during the acidification of pretreated olive mill wastewater

This study focuses on the dynamics of VFA production from pretreated olive mill wastewater (OMW). Acidogenic anaerobic sequencing batch reactors (AcASBR) were operated with the pretreated OMW at hydraulic retention time (HRT) of 2days and pH of 5,5 for different organic loading rates (OLRs) ranging from 5gCOD/L.d to 40gCOD/L.d. VFA production reached to the highest value of about 27,000mg/L with the increase in the organic load applied (20gCOD/L.d). The highest acidification rate was calculated as 68%. Acetic acid was found to be as the dominant VFA compound for all stage of the study. At steady state, VFA production during a day-cycle period (24th hour) in AcASBR is also monitored, VFA production gradually increased after the 3rd and 6th hours (about 20%) and a rapid increase (about 40%) was observed reaching the maximum at the end of the cycle (24th hour).

Biodegradation of pretreated olive mill effluent in mixture with a domestic sewage or compatible wastewater stream

AbstractBACKGROUNDThe study focused on the biodegradation of pretreated olive mill wastewater (OMW) properly diluted in and mixed with a biodegradable substrate and/or domestic sewage stream. It utilized the permeate of a chemically conditioned two‐stage ultrafiltration/nanofiltration system with COD of 5700 mg L−1 and a total phenol content of 100 mg L−1. Peptone mixture with similar characteristics to domestic sewage was adopted as the biodegradable synthetic substrate. The study relied on two sets of microbial culture; one acclimated to peptone and the other to a mixture of peptone and domestic sewage. Respirometric analyses were conducted on pretreated OMW diluted in the selected substrate using corresponding biomass seeding.RESULTSModel evaluation of the oxygen uptake rate profiles indicated that the pretreated OMW was fully consumed in the respirometric tests. There were no inhibitory/toxic impacts of OMW dosing on the biomass. The entire biomass participated in the utilization of OMW/substrate with no metabolic adjustment problems.CONCLUSIONExperimental results provided conclusive evidence that co‐treatment with a domestic sewage stream is a viable option for OMW management, after a chemically conditioned two‐stage filtration used as the pretreatment step. Pretreatment removes the recalcitrant nature of the wastewater, which becomes fully biodegradable under appropriate dilution and mixing conditions. © 2016 Society of Chemical Industry

Performance investigation of a jet loop membrane bioreactor for the treatment of an actual olive mill wastewater

In this study, following the pre-treatment of olive mill wastewater (OMW), its treatment in a jet loop membrane bioreactor (JLMBR) was investigated. Among the pre-treatment options, the configuration composed of physical settling, cartridge filter and ceramic membrane showed the best performance in terms of investigated parameters. For the JLMBR that was fed by pretreated OMW, up to 93 and 87% removal efficiencies were achieved for the chemical oxygen demand (COD) and total phenol, respectively, at volumetric organic load (VOL) of 17.8 kg COD/m3 day. The calculated specific oxygen uptake rate (SOUR) values were in the range 7.7–34.7 g O2/kg MLVSS h. When even hydraulic retention times (HRT) values decreased by a factor of 1:24, system performance in terms of COD and total phenol removal remained almost stable. Decreasing the sludge retention time (SRT) to three days made considerable perturbations for the system performance, increasing the effluent COD and total phenol values in 900 and 80 mg/L, respectively. The JLMBR showed a high overall performance for the treatment of an actual OMW under the evaluated operational conditions.

Pretreatment of olive mill wastewater for citric acid production by Yarrowia lipolytica

Pretreatment of olive mill wastewater for citric acid production by Yarrowia lipolytica

Membrane fouling insight during reverse osmosis purification of pretreated olive mill wastewater

Abstract The chronological sequence and the relative importance of the individual fouling mechanisms were investigated on a polymeric RO membrane used for final purification of secondary-treated olive mill wastewater (OMW2ST). An insight of membrane fouling under different operating conditions is reported. The goodness of the fitting (R2 → 0.99) points for the formation of a cake or gel layer over the membrane as the dominant fouling mechanism in the transient and steady-state operation stages. A non-uniform cake was built-up, as shown in the HR-SEM analysis on the fouled membrane, principally formed by the organic matter (188.7 ± 37.9 mg L−1) and residual iron colloids carried by the OMW2ST feedstream. However, about 39.0% of the initial flux drop could be attributed to concentration polarization on the boundary region of the membrane. Moreover, it is relevant that the partial blocking model describes correctly the incipient fouling formation on the membrane, disregarding the operating conditions. This behavior was attributed to surface defects, more permeable zones of the membrane that may act as pores during the initial and intermediate operation stages, and in particular to the small organic particles (up to 63.3% between 3 and 30 kDa) remaining in the OMW2ST feedstream.

Iron removal and reuse from Fenton-like pretreated olive mill wastewater with novel strong-acid cation exchange resin fixed-bed column

The performance of a fixed-bed cation exchange process was examined for final purification of the iron load derived from catalyst usage in the secondary treatment of olive mill wastewater, which led to unacceptable iron levels. Results showed an increase in the pH value up to 4 enhanced the iron ion exchange (IE) efficiency, which decreased upon higher pH. Furthermore, Thomas model provided utmost accurate dynamic behavior modeling for all inlet concentrations studied (20, 50 and 100mgL−1). Additionally, up to 100% recovery efficiencies were maintained even after 10 complete cycles. Finally, an effluent with quality for irrigation reuse was obtained.

Thermal pretreatment of olive mill wastewater for efficient methane production: control of aromatic substances degradation by monitoring cyclohexane carboxylic acid

Anaerobic digestion is investigated as a sustainable depurative strategy of olive oil mill wastewater (OOMW). The effect of thermal pretreatment on the anaerobic biodegradation of aromatic compounds present in (OMWW) was investigated. The anaerobic degradation of phenolic compounds, well known to be the main concern related to this kind of effluents, was monitored in batch anaerobic tests at a laboratory scale on samples pretreated at mild (80 ± 1 °C), intermediate (90 ± 1 °C) and high temperature (120 ± 1 °C). The obtained results showed an increase of 34% in specific methane production (SMP) for OMWW treated at the lowest temperature and a decrease of 18% for treatment at the highest temperature. These results were related to the different decomposition pathways of the lignocellulosic compounds obtained in the tested conditions. The decomposition pathway was determined by measuring the concentrations of volatile organic acids, phenols, and chemical oxygen demand (COD) versus time. Cyclohexane carboxylic acid (CHCA) production was identified in all the tests with a maximum concentration of around 200 µmol L−1 in accordance with the phenols degradation, suggesting that anaerobic digestion of aromatic compounds follows the benzoyl-CoA pathway. Accurate monitoring of this compound was proposed as the key element to control the process evolution. The total phenols (TP) and total COD removals were, with SMP, the highest (TP 62.7% – COD 63.2%) at 80 °C and lowest (TP 44.9% - COD 32.2%) at 120 °C. In all cases, thermal pretreatment was able to enhance the TP removal ability (up to 42% increase).

Cloud point extraction of phenolic compounds from pretreated olive mill wastewater

Olive mill wastewater (OMW) causes many environmental problems, mainly in the Mediterranean area. The phenolic content of OMW is principally responsible for the phytotoxicity and microbial growth inhibitory effects. However, these effluents can be considered as a source of powerful natural antioxidants. Cloud point extraction method was used to recover and separate phenolic compounds from pretreated olive mill wastewater. The OMW samples were ultrafiltered on 50kDa polyethersulfone (PES) membrane. The Triton X-100 was used as surfactant at concentrations ranging from 1 to 10% (w/w). Three temperatures (70°C, 80°C and 90°C) above the cloud point temperature of the surfactant were tested. After 30min at the desired temperature the mixture form two phases: a diluted phase and a concentrated phase called coacervate. The efficiency of the extraction was evaluated by determining the phenolic compounds concentration and the volume of the both phases. The obtained results show the possibility to extract up to 66.5±3.2% of the phenolic content from OMW using one step CPE. The highest yield was obtained when using 10% of Triton X-100 at 90°C. The results obtained for volume fraction (ϕc) and rate of recovery (R%), by response surface methodology were in agreement with the experimental data. The results show that the CPE can be an efficient alternative to the classic methods of extraction since it can offer a mixture of natural antioxidants suitable for pharmaceutical, cosmetic or food applications.

Ozone pretreatment of olive mill wastewaters (OMW) and its effect on OMW biochemical methane potential (BMP)

The possibility of coupling a physicochemical pretreatment (ozonation) with a biological treatment (anaerobic digestion) was investigated for the case of olive mill wastewaters (OMW). Batch ozonation experiments were performed in a glass bubble reactor. The parameters which were tested included the ozone concentration in the inlet gas stream, the reactor temperature and the composition of the liquid medium in terms of raw or fractionated OMW used. In the sequel, ozone-pretreated OMW samples were tested for their biochemical methane potential (BMP) under mesophilic conditions and these results were compared to the BMP of untreated OMW. The ozonation process alone resulted in a 57-76% decrease of total phenols and a 5-18% decrease of total carbohydrates contained in OMW, depending on the experimental conditions. Nevertheless, the ozone-pretreated OMW exhibited lower chemical oxygen demand removal and methane production during BMP testing compared to the untreated OMW.

A Three Year Long Experience of Effective Fouling Inhibition by Threshold Flux Based Optimization Methods on a NF Membrane Module for Olive Mill Wastewater Treatment

The operation of a spiral-wounded nanofiltration membrane module used continuously for three years in order to purify different pretreated olive mill wastewater streams will be discussed. The membrane module was for the first time used at the beginning of year 2006 on a batch pilot scale plant for studies and wastewater treatment in our laboratories. The olive mill wastewater is a waste stream produced by the olive oil mill factories, characterized by very high organic matter load and polyphenols concentration. Without fouling inhibition at all, nanofiltration membranes will reach zero-flux conditions within days. This is not the case of this nanofiltration membrane module, which was successfully operated continuously for three years during our laboratory work. This result was reached by proper fouling inhibition control, relaying on both measurements and the development of an optimized operation method. Although the theory was successfully applied to this system, it was not capable to explain the observed fouling behavior of the examined membrane system. The doubt to work on a membrane system that does not follow perfectly the laws grow throughout the years. In year 2011, Field et al. introduced the threshold concept as an extension to particular membrane systems treating real wastewater streams, and this latter theory fits to the observations made on olive mill wastewater. In this work, a revision of previously obtained results in terms of will be performed, using the threshold theory as discussion basis. In the examined system, both and threshold points were found at 7-8 bar depending of the used feedstock and membrane condition. Moreover, it will be checked why the adopted critical flux approach was successful in inhibiting fouling for so many years despite it was not the correct approach.

Anaerobic digestion of olive mill wastewater

Anaerobic digestion of olive-mill wastewater (OMW) was carried out in a continuously fed
 mode bioreactor. The bioreactor was operated at different hydraulic retention times (HRTs),
 using OMW, either raw or pre-treated with white-rot fungi. Two different kinds of feed were
 tested in this process, one which was thermally treated and subjected to sedimentation, in
 order to remove the solids contained and the other without any physicochemical treatment
 (raw OMW). Thermally pretreated OMW did not allow a stable operation even at an HRT of
 30d. Further pretreatment of the OMW with a white-rot fungus for removal of the contained
 phenolics, allowed a stable operation at an HRT of 30 d. On the other hand, simple dilution of
 the raw wastewater, without any solids removal, lead to a stable operation at an HRT of 30d
 and was accompanied by higher production of biogas. The presence of the solids in the OMW
 proved to be a determining factor for the stability of the process and could be attributed to a
 possible adsorption on the solids of hydrophobic compounds, such as long-chain fatty acids
 that are toxic to methanogens.

Threshold flux measurements of a nanofiltration membrane module by critical flux data conversion

Recently, for some membrane separation processes, the concept of threshold flux was introduced in substitution of the critical one. The new concept applies to all systems which trigger fouling formation from start of operation, even at very low operating conditions, and in particular to the purification of olive mill wastewater streams by membranes.The operation of a spiral-wound nanofiltration membrane module used to purify different pretreated olive mill wastewater streams and how pretreatments affect the threshold flux values and the threshold flux fitting parameters will be discussed.

Pre-treatment of olive mill wastewaters at laboratory and mill scale and subsequent use in agriculture: Legislative framework and proposed soil quality indicators

The present study investigates the potential of pre-treatment of olive mill wastewaters (OMW) at laboratory and mill scale and their subsequent use in agriculture to satisfy irrigation and fertilisation needs for widely cultivated crops. The ultimate objective of this approach is the development of a feasible decentralized treatment scheme in parts of the Mediterranean region where most olive mills are small family businesses, soils have low organic matter and the risk of desertification is high. Tests carried out both at lab and pilot scale involving mainly the use of low cost and readily available industrial/agricultural wastes/by-products such as saw dust, lime, iron fillings and goat manure. The aim of pre-treatment was two-fold (a) to produce OMW suitable for land application and (b) to allow its safe disposal in unprotected evaporation ponds, thus minimizing the risk for soil, surface- and groundwater contamination. Trials investigating the effect of pre-treated OMW on the growth of spinach and beetroot, using application rates 4, 10 and 20L/m2 (40, 100 and 200m3/ha), were also carried out in 0.5×0.5×0.2m containers. The parameters studied include emergence from soil, plant height, root length, aerial biomass, soil pH and conductivity as well as content of phenols, K, N and P in soils. Furthermore, in order to assess the long term impacts of OMW application on soil, soil quality data are provided from a field where occasional disposal of OMW from an operating evaporation pond takes place for a period of more than ten years. Furthermore, an overview of the existing EU legislation is provided to identify gaps and address important issues related to the management of OMW, its application/disposal on land and the potential risk for soil and water bodies. Finally, a set of indicators is proposed to define a code of good practice for OMW application on soils, safeguard soil quality in disposal areas and improve the overall sustainability of the olive oil sector.

Impacts of operating conditions on reverse osmosis performance of pretreated olive mill wastewater

Management of the effluent from the olive oil industry is of capital importance nowadays, especially in the Mediterranean countries. Most of the scarce existing studies concerning olive mill wastewater (OMW) treatment by means of membrane processes not only do fix their aims simply on achieving irrigation standards, but lack suitable pretreatments against deleterious fouling issues. With the target of achieving the parametric requirements for public waterways discharge or even for reuse in the production process, a bench-scale study was undertaken to evaluate the feasibility of a thin-film composite reverse osmosis (RO) membrane (polyamide/polysulfone) for the purification of OMW. Previously, OMW was pretreated by means of chemical oxidation based on Fenton’s reagent, flocculation–sedimentation and biosorption through olive stones. Impacts of the main operating parameters on permeate flux and pollutants rejection of the RO process, as well as fouling on the membrane surface, were examined for removing the significant ionic concentration and remaining organic matter load of the pretreated OMW. Combining operating parameters adequately in a semibatch operating regime ensured high and sustainable permeate flux, yielding over 99.4% and 98.5% removal efficiencies for the chemical oxygen demand and ionic content respectively, as well as complete rejection of phenols, iron and suspended solids.