Abstract

Olive oil extraction generates a large quantity of wastewater which is a strong pollutant due to its high organic load and phytotoxic. However, its content in antibacterial phenolic substances displays to be resistant to biological degradation. The discharge of olive mill wastewater (OMWW) is not allowed through the municipal sewage system and/or in a natural effluent. Unfortunately, the current technologies for the treatment of OMWW are expensive and complicated to be operated in a mill factory where the objective of this study. We have designed and implemented a process that permitted both the treatment of agro-food processing water and the recovering of compounds of market interest. The process was applied in the effluents of olive oil mill factories to recover polyphenols with a possible significant reduction of organic waste. The nanofiltration fraction obtained from a sequential treatment involved coagulation, photocatalysis, ultrafiltration and nanofiltration was performed to separate the most valuable compounds using column adsorption runs. Competitive adsorption and the selectivity were obtained for phenol and hydroxytyrosol onto macro-reticular aromatic polymer (FPX66) and macroporous polystyrene cross-linked with divinylbenzene (MN202), respectively. The investigations were followed by a single component of phenol or tyrosol, binary phenol and tyrosol and ternary components in NF concentrate of OMWW for valuable compounds recovery conducted in a fixed-bed adsorber of resins. During the intermediate stage of the column operation, adsorbed tyrosol molecules were replaced by the incoming phenol molecules due to the lower tyrosol affinity for FPX66 resin and the tyrosol concentration was higher than its feed concentration.

Keywords: OMWW, ultrafiltration, nanofiltration, fixed-bed column, polyphenols recovery, polymeric resins

## 1. Introduction

Phenol and phenolic species are chemicals commonly found in various industrial waste in general and in a particular in olive mill wastewater. Phenol is also known as carbolic acid. It's a white crystalline toxic solid with a sweet tarry odor commonly referred to as a "hospital smell"; with a pKa of 9.98 and solubility of 8% (wt.) in the water at 25°C. In fact, the US Environmental Protection Agency (EPA) and the European Union (EU) directive number 80/778/EC consider phenol as a priority pollutant [1]. The concentration of phenol in wastes varies in a wide range from several ppm to 2–3% and phenols degradability are limited. Several techniques are available currently for the treatment of phenolic effluents.

2. Materials and methods

of the steps described below.

2.2.1 Sieving of OMWW

photocatalysis.

2.2.3 Photocatalysis

membrane treatment.

2.2.4 Ultrafiltration

nanofiltration.

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2.2.5 Nanofiltration step

2.1 Packaging of wastewaters from olive mills

DOI: http://dx.doi.org/10.5772/intechopen.90087

2.2 Protocol processing of OMWW in laboratory pilot

2.2.2 Clarification by coagulation-flocculation for removing particles

and valuable compounds recovery are the following:

The samples of water were placed in 30 L bottles and were transported to the laboratory. The samples of OMWW were kept at 20°C for the later use. The research process developed in the laboratory for processing OMWWs is comprised

Treatment of Agro-Food Wastewaters and Valuable Compounds Recovery by Column…

The processes applied during the treatment of agro-food wastewaters (OMWW)

The OMWW were separated from solid particles by using a 300-micron sieve.

The coagulation helps to destabilize the suspended particles and facilitate their agglomeration. This method is characterized by injecting and dispersing chemicals. The flocculation aims to promote contact between the destabilized particles through slow mixing. These particles combine to form a flock which is removed by decantation. The water flocculation was performed by nitric acid at the temperature of 50°C and the initial pH of 5.2 was reduced to 3.0; followed the

The heterogeneous photocatalysis is based on the interaction of the light and nanoparticles. Photocatamysis has been an innovative and promising technique for the purification of wastewater. The titanium dioxide (TiO2) is the most of the common catalyst used nowadays due to its high performance, low cost, high photoactivity, low toxicity, chemical stability, insolubility and the resistance to photo-corrosion. The photocatalysis of clarified water stirred by a stirrer type Heidolph RZR 2014 was carried out by [16, 17]; on magnetic nanoparticle size of 79 nm coated with titanium oxide. The device is irradiated by a UV lamp VL-315 BLB 3x15W-385 nm Tube Power 90 W made in France for 4 h followed by the

The clarified OMWW was ultra-filtered on GM membranes, GK, GH and GE Type (TFM) tubular listed in Table 1 with the cutoff between 100 and 200 kDa, and the recovering of the permeate. The ultrafiltration method is followed by

The permeate obtained by ultrafiltration is nano-filtered on DK and DL; spiral and tubular membranes type (TFM) listed in Table 1 with the cutoff between 150

Adsorption processes have been intensively used in wastewater treatment for phenol and other organic compounds. Phenols in olive mill wastewaters (OMWW) have very complex compositions and the treatment feasibility has to be separately made through experimental approaches [2–6]. Conventional fixed bed processes involve a saturation, adsorption or loading step, followed by desorption, elution or regeneration steps [7]. The use of granular activated carbon (GAC) for removing toxic organic chemicals including phenol from wastewater is one of the best commercially proven methods. Although activated carbons exhibit an excellent adsorption capacity for the removal of phenol from wastewater, this method exhibited the difficulty to its regeneration and quite expensive to dispose of [7–12].

Therefore, the necessity of the alternative adsorbents which are equally effective and easier to regenerate and recently, a new kind of hypercrosslinked polymeric adsorbent was found to be very effective for removing aromatic compounds from aqueous solutions [5, 7, 13, 14]. Macroreticular resins are the most promising in the separation processes due to its easier regeneration and it is well used in industrial practices. The wide variations in functionality, surface area, and porosity available for macroreticular resins present the possibility of its selective separation of the effective components. Furthermore, the regeneration of the resins can easily be accomplished with a solvent and hence, the adsorption of phenol can be realized by macroreticular resins. Numerous studies on the removal of metals and organic pollutants by these adsorbents in discontinuous systems have been reported [10, 11, 15]. However, the application in continuous systems i.e. in a fixed-bed column is often preferred, since it is simple to operate, given to high yields and can be scaledup in the laboratory process. In order to design and operate fixed-bed adsorption process successfully, both equilibrium and dynamic adsorptions in specified systems must be known. The indicators are the breakthrough curves under specified operating conditions must be predictable. The shape of this curve is determined by the shape of the isotherm equilibrium and it is influenced by the individual transport processes in the column of adsorbent [10, 11, 15].

In this chapter, the experimental results on adsorption tests performed by resins were presented. The polyphenols are extracted from a nanofiltration concentrate stream produced during the purification of olive vegetation wastewater from a 3 phase process. This wastewater contains many polyphenols, mostly hydroxytyrosol, which may have a market.

The high organic content of olive wastewater exhibits to its impossible direct recovering of polyphenols content. The high suspended solids in the raw stream will quickly block the adsorption column, making the recovery process difficult. Moreover, many other interfering and undesired pollutants would interfere with the recovery process. For this reason, the recovery of polyphenols will be accomplished on a pretreated stream that is the concentrate of nanofiltration which is produced after the treatment of the raw wastewater by flocculation, photocatalysis and ultrafiltration. The concentrate of nanofiltration is rich enough of polyphenols to permit a suitable recovery from a technical and economical point of view.

Treatment of Agro-Food Wastewaters and Valuable Compounds Recovery by Column… DOI: http://dx.doi.org/10.5772/intechopen.90087
