{'fraction_non_alphanumeric': 0.030462457781241882, 'fraction_numerical': 0.01461418550272798, 'mean_word_length': 5.095407759303246, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Valorization of potato peel residues to produce a bioflocculant to be used in the treatment of liquid effluents

The present study aims primarily to investigate the flocculation capacity of a novel potato peel-based bioflocculant in wastewater treatment. The analysis of wastewater revealed high COD and BOD5 contents that could respectively reach the values 529.08 mg O2/l and 317.03 mg O2/l. In addition, the effect of experimental parameters such as the pH, coagulant/flocculant dosage, and contact time, was studied using the coagulation-flocculation treatment technique. The experiments were carried out with a lab-scale jar-test apparatus where aluminum chloride (AlCl3) was used as a coagulant agent. It should be noted that the optimal dose of AlCl3 was equal to 0.6 g at 10 mn, with turbidity reduction of 99.01%. Moreover, the flocculation tests showed higher turbidity removal (98%), for a flocculant dosage of 0.2g. The results obtained in this study indicated that using the natural potato peel-based flocculant, in the presence of a coagulant, provides an effective and environmentally friendly coagulation option for wastewater treatment.


Introduction
No one denies that industrial sites throughout the world remain the primary cause of water pollution due to the diversity of industries (textiles, paints, pharmaceuticals, metal coatings, corrosion inhibition, etc.) [1][2][3][4][5]. Nowadays, various wastewater treatment technologies, such as adsorption, oxidation, chemical precipitation, etc., with different degrees of effectiveness and success, are available to control and minimize water pollution [6,7]. Each one of these techniques, when applied, showed some advantages and limitations [8]. However, many of these methods have not been widely used due to high costs, formation of hazardous by-products and intensive energy requirements [9]. It is worth noting that the coagulation-flocculation process is being widely applied in raw water treatment, and in particular wastewater treatment. This technique is broadly used because it relatively low-cost, robust and environmentally friendly [10].
The coagulation-flocculation technique has been widely used in multiple industry sectors so far. This process is generally applied for the removal of colloidal particles, soluble compounds, and vey fine solids suspended in solutions by colloid destabilization which leads to the formation of larger particles that are commonly referred to as flocs [11,12]. Currently, this technique can be effectively achieved through the use of inorganic coagulants and fossil-based organic flocculants. Note that  [13,14]. However, it was shown that the use of synthetic flocculants causes serious environmental damage and health problems. In addition, this method generates a great deal of controversy related to the production of large volumes of toxic sludge and the dispersion of acrylamide oligomers, which engenders serious health hazard due to its harmful carcinogenic and neurotoxic effects on human beings [15][16][17]. For these reasons, as an alternative, bioflocculants have attracted increasing attention for water treatment due to their biodegradability, non-toxic properties, and remarkable flocculation performances that are sometimes comparable to those of synthetic flocculants [18][19][20][21][22]. This ecofriendly approach involves biodegradability and sustainability with the exploitation and utilization of byproducts derived from human activities such as fishing, agriculture, industry, and others. It is worth citing some examples of bioflocculants like alginate, cellulosic materials, starch, chitosan, xanthan gum, Moringa oleifera, okra, guar gum and Cassia tora gum, and tannins, which represent economical, viable, and safe substitutes for synthetic flocculants [15][16][17]. It is widely admitted that potato peel waste causes much environmental pollution when stored outside without any appropriate and safe disposal. In addition, potato peel processing can release potential pollutants that cause serious environmental problems. Consequently, due to the multifunctional nature of potato peels, it is highly urgent and essential to design and develop environmentally friendly processing procedures to deal with these wastes [23] On the other hand, it is important to indicate that some food byproducts, like potato peels, possess essential organic matter. In this context, Gebrechristos et al. (2018) [23] indicated that potato peel residues can potentially be used as a food preservative, pharmaceutical ingredient, animal food for the purpose of promoting eco-friendly food industries; they also reported that potato peels can also employed in renewable energy. Similarly, the author [24] found out that potato peel waste is an interesting low cost adsorbent which is quite efficient in the adsorption of the methylene blue (MB) dye from aqueous solutions. Indeed, the results obtained showed that the percentage of elimination of this dye can go from 61.4 to 87.6% while increasing the adsorbent mass. Based on these findings, it can be said that potato peels could be effectively used as an eco-friendly adsorbent material for the removal of methylene blue dye from an aqueous solution. Therefore, potato peel residues can be valorized to produce a flocculant agent for the treatment of wastewater through the coagulationflocculation procedure.
The primary purpose of this paper is to investigate the effect of some operational factors on the treatment of water using potato peel waste as a bioflocculant. It is worth indicating that, over the past few years, biopolymer-based flocculants have been attracting increasing interest from many researchers because they are easily biodegradable and are highly environmental friendly. However, natural flocculants, which are characterized by a moderate flocculating efficiency and short shelf life, should be used at large doses [13]. Moreover, factors such as the pH, coagulant dose and coagulant type, play an essential role in the coagulation and flocculation operations. These factors were investigated in order to determine the optimal efficiency under the best experimental conditions and to identify the most appropriate mechanisms that could be involved in the treatment process. These flocculants turned out to be highly efficient in removing COD, turbidity, color and metals, depending on the types of contaminant and coagulant/flocculant used [25].

Preparation of potato Peel
Nowadays, food processing industries are producing huge amounts of waste. In particular, potato processing factories are rapidly expanding and are generating enormous volumes of potato peel waste. When decomposed, this potato byproduct can cause serious environmental pollution [23]. For this reason, potato peel has been investigated by many researchers as a good source for biopolymer production. In addition, it was found that potato peel waste represents an interesting source of vegetable starch. It should also be noted that this type of starch swells well and possesses high viscosity. For the purpose of understanding the physicochemical properties of potato peels, it is required to determine their physical and chemical composition.

IOP
It was revealed that potato peels contain various polyphenols and phenolic acids, which are responsible for its antioxidant activities, as well as fatty acids and lipids, which exhibit interesting antibacterial activities [26,27]. In addition, potato peels contain starch (25%), non-starch polysaccharides (30%), proteins (18%), acid-soluble and acid-insoluble lignin (20%), lipids (1%) and ash (6%) on dry matter basis [28]. Furthermore, the lipid fraction includes long-chain fatty acids, alcohols, triglycerides and sterol esters. Moreover, lignin units were also found in the cell wall of potato [29]. It was also found that potato peel waste is rich in starch (52% dry weight), but the content of fermentable reducing sugar is quite low (0.6% dry weight) [30].
In this study, potato peel is used as a bioflocculant without any modification or prior purification. For this, the potato peels to be tested were first washed with tap water and then dried in the open air for several days. Afterwards, they were cut into small pieces and finely crushed to powder. Then, the samples thus obtained were placed in bottles and stored at room temperature.

Characterization
In order to characterize the potato peels, to be used as a bioflocculant, Fourier-transform infrared spectroscopy analyses were carried out to study the surface functional groups of this material using potassium bromide pellets. The infrared analysis was performed with a PerkinElmer Spectrum One FT-IR Spectrometer version 10.4.1.

Wastewater
The wastewater used in this study was brought from the wastewater treatment plant in the small town of Rebahia, located near wadi Saida, in the northwestern part of the City of Saida. The procedures applied for the physicochemical measurements were carried out in accordance with the Standards described by the French national organization for standardization (AFNOR).
The turbidity is expressed in nephelometric turbidity units. In addition, factors such as the pH, conductivity and turbidity were measured using a Hanna Instruments pH meter, a conductivity meter and an infrared AQUA LYTIC Model AL250T-IR turbidity meter, respectively. The results of the physicochemical measurements of the wastewater under study are summarized in Table 1.

Coagulation experiments
Coagulation and flocculation processes proved to be essential in a number of diverse disciplines, including raw water and wastewater treatment. In this study, these two procedures were carried out using the jar-test apparatus. To do this, the coagulant was first injected at the beginning of the rapid mixing phase, at the speed of 150 rpm, for 10 min, 20 min, 30 min and 1 h to ensure complete dispersion, followed by slow stirring, at 50 rpm, for 10 min. It should be noted that all the experiments were conducted at neutral pH. Moreover, aluminum chloride was selected to be used as a coagulant in the chemical treatment.
Afterwards, the coagulant was introduced into wastewater with different amounts (0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.6 and 2 g). In the next step, the samples were allowed to decant for a period ranging between 30 and 60 minutes. It should be noted that flakes were observed during and after agitation. After decantation, some samples were taken from each beaker in order to measure physical parameters such as the pH, turbidity, COD and BOD5. The coagulant dose was chosen so as to obtain the highest percentages of removal of each of the above mentioned parameters.

Physicochemical characteristics of wastewater
The results of the physicochemical analyses of wastewater before treatment are summarized in table 1. It can be seen that the pH is equal to 8.12. It is worth also noting that the wastewater under study has an unpleasant odor. This bad odor is probably due to the presence of some chemicals or decomposing organic matter, or may be to Clostridium perfringens that give off hydrogen sulfide (H2S). One may clearly note that the chemical oxygen demand (COD) and biochemical oxygen demand (BOD5) values are much higher than those of other pollutants. Further, the results show that the pollution level of this wastewater is quite high; the turbidity is equal to 350 UNT as a result of the high presence of solid materials, especially suspended solids. It is important to mention that this parameter is essential in the coagulation processes primarily because it is easy to measure and is quite sensitive to coagulation processes.

Coagulation-flocculation treatment method 4.3.1. Optimization of coagulant dosage
The coagulant used in this study is aluminum chloride (AlCl3), with doses ranging from 0.1 to 2g. Also, the variation of the turbidity rate (%) in terms of doses of coagulant (AlCl3) is presented in  This figure indicates that the turbidity continuously decreases as the quantity of the coagulant added increases. It is observed that turbidity starts decreasing after the addition of 0.1 g of aluminum chloride; it then continues declining. It should be noted that the optimal coagulant dose can be determined by measuring the turbidity and also considering the stirring time. On the basis of the results obtained, it can be seen that in the absence of flocculant, the mass of 0.6 g of aluminum chloride coagulant allows achieving a very good flocculation with a turbidity rate equal to 99.01% after for a stirring period of 10 mn. This represents the first step in wastewater treatment. The next step consists in adding the flocculant.

Effect of pH on coagulation efficiency
It is broadly acknowledged that the pH is a fundamental parameter. Figure 3 clearly displays the evolution of the pH as a function of the dosage of aluminum chloride coagulant, for different time periods. This figure shows that an increase in aluminum chloride dosage results in a lower pH value. In addition, depending on the characteristics of the water under study, there is an optimum pH value that allows achieving the best coagulation. It should also be noted that this pH is often within the range where the solubility of the coagulant used is minimal; this should therefore give good precipitation. Consequently, the most adequate pH value, which gives the optimal turbidity rate of 4.1, leads to the best coagulation efficiency. Note also that controlling the pH allows improving coagulation when the temperature of water is low [33]. The coagulation-flocculation treatment was carried out through the addition of a constant dose of aluminum chloride (0.6g) to wastewater samples kept under continuous stirring. Next, various masses of potato peel powder, ranging between 0.1 and 1 g, were added to the resulting coagulated product. The results obtained suggested that potato peel powder with the optimum dose of 0.2g allowed flocculating wastewater efficiently, with a turbidity reduction of 98% (Figure 4). In addition, the BOD5 dropped from 317.03 mg of O2 / l to 0 mg of O2 / l, which represents a 100 % reduction. The pH is another critical factor affecting the coagulation-flocculation process. Aluminum chloride is among the most common coagulants that are used to achieve flocculation and clarification of water as well. The combination of the aluminum chloride coagulant with potato peels results in a slight drop, followed by a rise and then a decrease in pH ( Figure 5). This fluctuation is primarily due to the hydrolysis of the salts used. .

. Conclusions
This work was an attempt to recover and valorize potato peel waste, which is largely available, to be used as a low cost flocculation agent for the treatment of wastewater in the City of Saida through the coagulation-flocculation process.
The results obtained indicated that the optimum dose of aluminum chloride coagulant of 0.6 g allowed achieving high turbidity removal efficiency (99.01%) for a contact time of 10 mn. The bioflocculant dosage used was quite efficient in reducing the suspended solids, color, COD, BOD5 and turbidity of wastewater. The findings confirmed the successful flocculation process, which led to a 100% BOD5 reduction. It was therefore concluded that the coagulation-flocculation process can be viewed as a viable technique for the treatment of wastewater.