Impact of Wastewater Spreading on Properties of Tunisian Soil under Arid Climate
by
and
Boutheina Gargouri
1, 
Samia Ben Brahim
1,
Fatma Marrakchi
1,
Bechir Ben Rouina
2,
Wojciech Kujawski
3,* and
Mohamed Bouaziz
1,4,* 1
Laboratoire d’Electrochimie et Environnement, Ecole Nationale d’Ingénieurs de Sfax, University of Sfax, BP “1173”, Sfax 3038, Tunisia
2
Laboratoire d’Amélioration de la Productivité Oléicole et des Arbres Fruitiers, Olive Tree Institute of Sfax, BP “1087”, Sfax 3000, Tunisia
3
Faculty of Chemistry, Nicolaus Copernicus University in Torun, 7 Gagarina Street, 87-100 Toruń, Poland
4
Institut Supérieur de Biotechnologie de Sfax, University of Sfax, BP “1175”, Sfax 3038, Tunisia
*
Authors to whom correspondence should be addressed.
Sustainability 2022, 14(6), 3177; https://doi.org/10.3390/su14063177
Submission received: 16 January 2022
/
Revised: 20 February 2022
/
Accepted: 21 February 2022
/
Published: 8 March 2022
(This article belongs to the Special Issue Wastewater Treatment and Sustainability of Development)
Abstract
:The environmental impacts of irrigating an olive field with olive mill wastewater (OMW) and treated wastewater (TWW) on soil properties were investigated. The effect of different irrigation treatments of OMW (50 m3 ha−1, 100 m3 ha−1, and 200 m3 ha−1) and TWW at different soil depths was studied. The obtained findings revealed that TWW application augmented soil pH; EC values; and P, K and Ca contents in all soil layers. However, Mg and Na concentrations, as well as organic matter content (OM), were proven to decrease with TWW irrigation throughout the experiment. Whereas soil adjusted with OMW showed a decrease in K, Ca, Mg and Na contents with soil depth, a significant increase was observed with the increase in applied OMW dose. On the other hand, total phenols and OM content increased significantly with the rise in OMW levels in all the investigated layers compared to the control sample.
1. Introduction
Freshwater demand frequently surpasses water accessibility. As the global population expands, water resources are limited or even diminishing, which will aggravate water use issues and widen regional conflicts [1]. Urban and semi-urban centers, industries and agriculture are in competition for freshwater use, which puts agriculture (especially irrigated agriculture) under severe pressure. Nowadays, the vegetables and fruits irrigated with wastewater are consumed by at least one-tenth of the world’s population [2]. Agricultural irrigation with wastewater is commonly used in arid areas around the world and has been gradually adopted by more regions, owing to the increase in food demand and the scarcity of freshwater [3]. Given its water scarcity, Tunisia, which is an arid region, has introduced the treatment and reuse of wastewater as an option as an irrigation resource to preserve the country’s environment and natural capital [4]. Treated wastewater (TWW) has been used in Tunisia for the irrigation of citrus fruits since 1965. It is authorized for different cultures, such as fruit trees, namely dates, palms and vines. TWW maintains a considerable amount of organic and metallic compounds (C, N, P, and K), which have a beneficial impact on the growth of some crops [5,6]. However, Tunisia suffers from a large amount of extremely polluting olive mill wastewater (OMW) produced after the olive oil extraction process. This residue causes serious environmental problems, as its efficient remediation and disposal is difficult. Different treatment methods have been developed to reduce the environmental impact of OMW, including its direct amendment in agricultural soils as an alternative irrigation method. In fact, some OMW components are possibly advantageous for agriculture application, characterized by 83% to 96%water, 3.5% to 15% organic matter and 0.5% to 2% minerals [7]. Generally, although wastewater is a source of plant nutrients and organic matter, it is likely to entail unfavorable chemical constituents and pathogens that may lead to environmental and health risks [8]. Therefore, it is essential to study the impact of the application of these two types of wastewater (TWW and OMW) on soil properties. Tunisia is ranked fourth in the world for olive oil production, with an average production of 180,000 tons per year (2012) [9]. However, policies need to be developed to preserve water resources in response to the strong international competition in the oleoculture sector.
In this context, only a few studies have described the possibility the land spreading of olive mile wastewater under specific Mediterranean agroclimatic conditions [10,11,12]. Hence, research highlighting the impact of wastewater irrigation on soil quality is not sufficient to allow for the effective use of wastewater olive-irrigation fields.
The utmost goal of the present research work was to evaluate the effect of diverse rates of application of OMW (50 m3/ha, 100 m3/ha, and 200 m3/ha) and TWW irrigation on soil chemical properties at three different depths in an experimental olive field under Mediterranean conditions. Moreover, a full factorial design was used to determine the applicability of these two irrigation treatments in the improvement of soil fertility compared to conventional water.
2. Materials and Methods
2.1. Experimental Site
The experiment was carried out in 2016 in an olive orchard located 10 km southwest of Sfax city in central eastern Tunisia (El Hajeb–Sfax region, 34°43′ N,10°41′ E). The location is characterized by a specific rainfall pattern, reaching peaks in June and September and a phenomenal break in August. The mean annual rainfall is about 180 mm, whereas the mean minimum and maximum temperatures are18 °C and 40 °C, respectively. The soil of the irrigated area is characterized by 84.4% sand, 9.8% clay and 5.8% silt.
2.2. Experimental Design
A two-level factorial design, 2k, with center points was performed for each wastewater type (OMW and TWW-Table 1), with superscript k being the studied factor and 2 representing the levels of each employed factor [13]. To dispense superfluous error effects, soil samples were taken in a random order [14]. Center points were repeated in triplicate to verify the nonlinearity of the responses and to assess experimental error. This method allows for the generation of linear main effects, two-factor interactions and a Pareto chart. For each examined factor, a histogram called a “Pareto chart” was plotted, in which fundamental values are arranged from high to low. Concerning the vertical line in the Pareto chart, it shows the minimum statistically significant effect magnitude for 5 % significance level. As for the horizontal column lengths, they are proportional to the degree of significance for each effect. Any effect surpassing the vertical line is deemed significant. For the analysis of data and plot charts, Minitab statistical software was used. Table 2 and Table 3 illustrate the different treatments of OMW and TWW applied on soil at different depths.
Selected Factors were OMW spread levels (0, 100, and 200 m3 ha−1), TWW dose and soil surface layer. Three soil layers were considered, each of corresponding to a specific soil depth: 1 = 0–20 cm; 2 = 20–50 cm; and 3 = 50–80 cm.
2.3. Irrigation Treatment and Horticultural Practices
For the experiment, we collected and used two types of wastewater, namely olive mill wastewater (OMW) and treated wastewater (TWW). With respect to OMW, it was collected from an olive oil production plant located in the city of Sfax (Tunisia). This plant uses the traditional olive oil production process for the extraction of olive oils (a three-phase continuous centrifugation system). It produces two types of waste: an olive press-cake (OPC) and a dark liquid effluent called olive oil mill wastewater or vegetation water (OMW). As regards TWW, it was collected from domestic and industrial sources and normally recovered by a pilot unit following a simplified treatment. The latter omitted biological process for organic matter and nitrogen removal from the wastewater so as to regain and use them as fertilizing substances. The bottles containing the wastewater samples were consequently categorized, sealed, refrigerated and taken to the laboratory for analysis.
OMW modification was realized in January in one application. In all cases, after 24 h sedimentation at the olive mill, fresh OMW was used. The application of olive mill wastewater was realized between rows of olive trees at a 70cm distance from the trunk by means of a tractor with tank trailer (spreading machine). As regards TWW, ‘Chemlali’ olive trees were irrigated with a drip system with four drip nozzles (two per side) of 4.3 m3 day−1 per tree set in a line along the rows (at 0.5 m from the trunk).
2.4. Soil Physicochemical Properties
Soil samples were taken at three depths 1 month after application of the treatments (0–20 cm, 20–50 cm, and 50–80 cm). They were air-dried at room temperature and ground to pass a 2mm sieve. The samples were analyzed for pH, EC, Na, Cl, Ca, Mg, N, P, K, Fe, Cu, Zn, Mn, SO4, Pb, organic matter (%) and total phenols. The analyses were carried out according to methods of soil analysis [15].
Soil pH was determined using a pH meter (420A, Orien). Soil textural classes were determined the beginning of the trial (2003) following USDA soil texture classification. Soil salinity was evaluated by determining the electrical conductivity (EC) at 25 °C on a saturated paste by means of a conductivity meter (MC 226). Soil organic carbon was measured with a Shimadzu TOC-5000 analyzer. Total nitrogen was determined with the Kjeldahl method, and chloride (Cl−) was determined titrimetrically with AgNO3 [16], whereas K, Na, Cu, SO4 and Mg contents were realized on ammonium acetate soil extract [17] using a JENWAY flame photometer. Phosphor (P) was determined by a vanado-molybdate colorimetric procedure with a JENWAY 6405 UV/vis spectrophotometer (Milan, Italy). In addition, heavy metals (Zn, Mn, Fe, Cd, Cu, and Pb) were measured with an atomic absorption spectrophotometer (Analyst200, PerkinElmer). Chemical oxygen demand (COD) was determined by a colorimetric method (RAYLEIGH spectrophotometer, Vis-7220G), and BOD5 was determined by the manometric method with a respirometer (BOD IS 602) [18]. Finally, total phenols were extracted and purified with ethyl acetate using the method of Bouaziz et al. [19]. Samples were then assayed using Folin–Ciocâlteu reagent.
Phenolic monomers were identified by high-performance liquid chromatography (HPLC) analysis, which was carried out on a Shimadzu apparatus made up of an LC-10ATvp pump and an SPD-10Avp detector. A C-18 column was used (4.6 mm × 250 mm; Shimpack VP-ODS), and its temperature was retained at 40◦C with a flow rate of 0.5 mL min−1. The mobile phase was 0.1% phosphoric acid in water (A), versus 70% acetonitrile in water (B), for a total running time of 50 min. The following proportions of solvent B were used for the elution: 0–30 min, 20–50%; 30–35 min, 50%; and 35–50 min, 50–20%. Regarding physicochemical analysis, it was repeated in triplicate, and the final values are expressed as means and standard deviations.
3. Results and Discussion
3.1. Physical and Chemical Properties of Wastewater Samples
Table 1 displays the physicochemical characteristics of the two wastewaters used for the experiments. The TWW and OMW pH values were 7.60 and 5.9, respectively, falling within the irrigation limits of 6.00 and 9.00 [20]. The electrical conductivity (EC) was 6.30 mS cm−1 for TWW and 9.1 mS cm−1 for WW, indicating high levels of salinity [21]. The obtained results show that both TWW and OMW contain elevated amounts of N, P and K, considered crucial nutrients for the growth and development of plants. Overall, the levels of Ca, Mn, Zn, Pb and Cd in TWW were below the advocated maximum concentrations and within the guidelines for agricultural crop irrigation [22]. Both chemical and biological oxygen demands (COD and BOD) in both wastewater sources were below the Tunisian limits for water reuse (90 and 30 mg L−1, respectively). OMW is an important source of organic matter and total phenol contents, with 52.30 and 8.4 g L−1, respectively. In addition, a great deal of research has indicated that OMW has a large potential as a valuable fertilizer for plant growth and soil fertilization.
The results of phenolic compound analysis by HPLC (Figure 1) show that the most important phenolic monomers in the fresh OMW were as follows: (1) 3,4-dihydroxyphenylglycol (219 mg L−1); (2) hydroxytyrosol (681 mg L−1); (3) 3,4-dihydroxyphenylacetic acid (285 mg L−1); (4) tyrosol (956 mg L−1); (5) p-hydroxyphenylacetic acid (87.5 mg L−1); (6) caffeic acid (21 mg L−1); (7) p-coumaric acid (20 mg L−1); (8) oleuropein aglycone (113 mg L−1); and (9) oleuropein (52 mg L−1). These results are in agreement with those obtained in our previous research [7].
3.2. Effect of Olive Mill Wastewater (OMW) and Treated Wastewater (TWW) Irrigation on Soil Properties
3.2.1. pH and EC
Figure 2a1,a2 presents how the variations of TWW and OMW pH values altered the soil samples taken from the different layers after treatments. As can be seen in Figure 2a1, although the addition of TWW increased the pH of the initial soil, its values remained within the range of 7.57–8.08. Other studies have demonstrated that municipal wastewaters comprise elevated concentrations of bicarbonate [23], and therefore, their application to soils through irrigation can increase soil pH [24]. Moreover, Bedbabis et al. [12] reported an increase in pH with TWW irrigation, which suggests that soil texture represents a major factor in the determination of soil acidity.
Throughout the process of OMW treatment, the pH values of the soil at horizons (0–80 cm), especially those of the soil samples treated with 200 m3 ha−1, were proven to decline slightly compared with those of the control. This could be accredited to theacidic nature of OMW. These findings are in accordance with those obtained in previous works [25,26]. Recent research reported that OMW had comparable short-term effects on the chemical properties of semi-arid Mediterranean soil samples which pH promptly underwent a diminution from 8.3 to 7.4 at surface layers (0–10 cm) after applying 80 m3 ha−1 crude OMW tracked by a gradual augmentation during 42 days of treatment under laboratory conditions [27].
Although thesoil pH-OMW value was significantly influenced by the soil depth (p = 0.002), pH-TWW was substantially (p = 0.0002) affected only by the use of treated wastewater (Table 4). The difference can be explained by the richness of TWW owing to bicarbonate. However, the results revealed that the pH values of all soil layers lingered within the range necessaryfor the development of olive trees (7.0–8.5) [12].
The measure of soil salinity is the electrical conductivity (EC), which is an important indicator of soil health. Soil salinity affects the crop yields, crop suitability, plant nutrient availability and activity of soil microorganisms. The latter influences key processes of the soil, including the emission of greenhouse gases, such as nitrogen oxides, methane and carbon dioxide. EC levels can operate as an implicit indicator of the amount of water and water-soluble nutrients available for plant uptake, such as nitrate N [28].
Soil EC is affected by cropping, irrigation, and land use, as well as the application of fertilizer, manure and compost. Irrigation water salinity must be measured when managing salinity in irrigated lands. Under irrigation with TWW, EC values (0.13–0.40 mS cm−1) were minimal in each run (Table 2) and comparable to those detected in Mediterranean-type climates with low seasonal rainfall [29]. As illustrated in Table 4, the EC values significantly increased with the addition of TWW and soil layers (p < 0.0001). The considerable EC increase emanated from the more elevated salt and TDS concentrations in both waters, which is in agreement with what has been suggested by the literature [30,31,32].
As shown in Table 3, the EC values vary from 0.10 to 0.37mS cm−1 at different soil layers and different OMW spreading rates. These results reveal that the application of OMW provoked an insignificant decrease in the EC of the soil layers for all experimented treatments, which was observed to be OMW-dose-dependent (Table 4). These findings are in excellent agreement with those obtained by Mechri et al. [10]. In their study, the authors noted that the increase in recorded EC values at 0–20 cm in the modified soils after 30 days of treatment under natural conditions were proportional to the quantity of added OMW (maximum 150 m3 ha−1). Similarly, Di Serio et al. [33] revealed that EC increased at depths of 10–20 cm and 20–40 cm in OMW-treated soils planted with olive trees after 1 month of treatment, which could be related not only to the natural process of evaporation that takes place at the surface layers but also to OMW infiltration. Furthermore, Jarboui et al. [34] observed a large increase in the EC value of a clay-sandy soil receiving OMW, which was explained by the interaction of the effluent rich in minerals and organic compounds with the clay-sandy layers of the soil. This permitted the retention of minerals, enhancing the EC.
3.2.2. Soil Organic Matter (OM)
The addition of TWW negatively affects the organic matter content in soil (p = 0.009) (Table 4). These results are similar to those found by other studies reporting a decrease in OM content in a coarse, sandy soil irrigated with domestic TWW rich in nutrients [35], [36].
When compared, the recorded soil organic matter values demonstrated that major soil OM contents were obtained with higher rates of OMW spreading (Table 3). OM contents reached the highest values at 200 m3/ha, which suggests that increasing OM in the soil layers receiving OMW was advantageous for both microbial activity and soil fertility. These results are in agreement with those found in many previous reports in the literature [37]. Moreover, since organic matter content was negatively affected (p = 0.02) by soil depth (Table 4), the soil surface horizons (0–20 cm) revealed elevated levels of soil organic matter content. This result could most likely be accredited not only to the growing impact of current OMW spreading but also to the closeness of the soil horizon to the surface.
3.2.3. Fertilizing Elements (N, P and K)
Table 4 and Figure 2 present the effect of wastewater dose and soil layer of TWW and OMW on soil quality. Available phosphorus was significantly (p ≤ 0.0001) affected by TWW irrigation compared to OMW (Table 4 and Figure 3a1,a2). Concerning the content of available K, it was significantly affected by the addition of TWW (p ≤ 0.0001), whereas it was positively affected by soil depth (p ≤ 0.0001). Nevertheless, the content of available K was significantly (p = 0.041) positively affected by OMW dose and negatively affected by soil layers (p = 0.028) (Table 4). Regarding the content of available N, it was only detected in soils treated with OMW. The data also revealed that available N was higher (417.06 mg/kg) in the subsoil (0–20 cm) than in the surface layer.
Available P and K contents gradually augmented with soil depth under TWW irrigation. An increase in recorded P and K was noted, indicating a likely certain fertilizing effect of TWW due to (i) its high soluble P and K contents and (ii) organic matter adsorption. This was proven by previous research in an experimental field irrigated with treated wastewater [38,39]. In fact, TWW may not only represent a source of P and K but also reveal ecological and economic benefits precluding or lowering the use of P and K fertilizers [33].
With respect to soil phosphorus content, there was no considerable variation between the treatments over the three successive spreadings (0–100–200 m3 ha−1) and for the different levels of OMW soil modification (Figure 3a2). This is probably related to the immobilization brought to the element by the soil humic fraction and the lessened disposal of P [40]. By the same means, Chartzoulakis et al. [41] reported the absence of any amelioration in soil P content after 3 years of raw OMW treatment. Irrigation with OMW led to a rise in the K content in the soil upper layers (0–20 and 20–40 cm). The higher the OMW treatment, the more important the soil K content. The highest level of soil K content (983.25 mg kg−1) was recorded at the surface layer (0–20 cm) of the soil treated with 200 m3 OMW ha−1, and the lowest soil K content values were noted in the deeper soil layers (20–50 and 50–80 cm) with the various tested OMW spreading treatments. Hence, the obtained findings represent supplementary and solid support for former proposals in the literature advocating that OMW is a potential candidate as an alternative K fertilizer [33,42,43]. For exemple, Chartzoulakis et al. [41] revealed a substantial augmentation of K concentration with an approximate value of 800 mg kg−1 in the range of 0–25 cm layer depths after applying OMW in an olive orchard for three successive years at a maximum annual rate of 420 m3 ha−1. Therefore, OMW substantially boosted soil fertility and diminished the demand for chemical fertilizers.
The application of OMW was also proven to ameliorate the total nitrogen content in the soil. This augmentation is favorable to vegetable production, taking into account that nitrogen is the vital element in fertilization. This also indicates that the nitrogen infiltration in the soil reserve is converted into a mineral form. The most elevated levels of N content were recorded at depths of 0–20 cm for all treatments. A higher amendment of OMW soil leads to a substantial total N content of the soil (Table 2). The obtained data in the 0–20 cm layer revealed that the nitrogen total supply was equal to 196.05, 370.84 and 416.94 mg kg−1 for doses of 0, 100 and 200 m3 ha−1, respectively. Moraetis et al. [44] reported that crude OMW contained 1.53 g L−1 of the total nitrogen directly applied to the soil during five experimental years and allowed for an annual supply of this element equal 12% compared to the control treatment. Given the improvement in nitrogen content, the oversupply of this mineral is likely to sustain retrogradation from the mineral form to organic form by a temporary immobilization of mineral nitrogen under organic form by soil microorganisms.
3.2.4. Basic Exchangeable Cations: Ca, Mg, and Na
The application of OMW in soil amendment resulted in a decrease in the content of exchangeable Ca, Mg and Na with soil depth, whereas a significant increase was shown with an OMW dose (Table 4).
The content of exchangeable calcium (Ca) was insignificantly affected by the soil depth and TWW irrigation. Although the contents of exchangeable Mg and Na increased with TWW irrigation at the highest value, they were shown in the soil layer (50–80 cm). The high Na concentration in the soil solution can be explained by the antagonistic activity of either K+ or NH4+, which lessened the Na adsorption on exchangeable complexes [11].
3.2.5. Total Phenol Content
The concentration of phenolic compounds was substantially higher in the OMW-treated soil compared with the control, especially in the upper soil layer (0–20 cm). These findings revealed that despite the application of OMW during the rainy season, neither K nor phenols moved quickly across the soil profile. Such results correlate well with those found in earlier research studies of OMW spreading [10,45]. It has been reported that the concentration of phenolic compounds in the soil augmented shortly after OMW application. Nonetheless, their concentration in the soil was promptly diminished afterwards, reaching low levels at the end of the season as a result of their decomposition or incorporation into the humic fraction of the organic matter present in the soil [38,41,46].
4. Conclusions
After applying fresh OMW and TWW to the soil of an olive orchard, an improvement in soil fertility was clearly seen without negatively affecting soil quality. These results demonstrate that the controlled application of OMW augmented soil fertility, offering the opportunity to recycle various compounds. Nonetheless, the findings about organic matter and total phenolic content in OMW are indicative that a dose of 200 m3 ha−1 is likely to affect the properties of the soil after long-term and frequent applications. With regards to TWW irrigation, it increased the pH and major nutrients P, K, Ca and Na in all the soil layers, particularly in the upper layers next to olive roots. The present research work confirms that TWW and OMW can be useful as supplementary water resource and fertilizers for olive irrigation in Mediterranean environments, where water is scarce. In conclusion, our results provide useful indications for a more rational nutrition schedule of olive trees, saving both mineral and water inputs, towards a more sustainable management of olive orchards. In addition, the use of TWW and OMW for irrigation could improve the rational use of natural resources and promote the principles of the circular economy.
Author Contributions
Conceptualization, B.G., S.B.B. and M.B.; formal analysis, F.M.; methodology, B.G.; resources, B.B.R. and W.K.; software, F.M.; supervision, M.B.; validation, B.B.R. and M.B.; visualization, B.G. and S.B.B.; writing—original draft, B.G.; writing—review and editing, B.G., S.B.B., F.M. and W.K. All authors have read and agreed to the published version of the manuscript.
Funding
We thank the Ministry of Higher Education and Scientific Research of Tunisia (Contract program LR 14ES08) for its support of this research work.
Informed Consent Statement
This article does not contain any studies with human or animal subjects.
Data Availability Statement
All data generated or analyzed during this study are included in this published article.
Acknowledgments
The authors are grateful to Leila Mahfoudhi, Teacher of English in the Faculty of Sciences of Sfax, for editing and polishing the language of the manuscript.
Conflicts of Interest
The authors declare no conflict of interest.
References
- Orlofsky, E.; Bernstein, N.; Sacks, M.; Vonshak, A.; Benami, M.; Kundu, A.; Maki, M.; Smith, W.; Wuertz, S.; Shapiro, K.; et al. Comparable levels of microbial contamination in soil and on tomato crops after drip irrigation with treated wastewater or potable water. Agric. Ecosyst. Environ. 2016, 215, 140–150. [Google Scholar] [CrossRef]
- Kauser, S. Water Use in Vegetable Production in District Faisalabad. MSc Thesis, Department of Environmental and Resource Economics, University of Agriculture, Faisalabad, Pakistan, 2007. [Google Scholar]
- Zhang, Y.; Sallach, J.B.; Hodges, L.; Snow, D.; Bartelt-Hunt, S.L.; Eskridge, K.M.; Li, X. Effects of soil texture and drought stress on the uptake of antibiotics and the internalization of Salmonella in lettuce following wastewater irrigation. Environ. Pollut. 2016, 208, 523–531. [Google Scholar] [CrossRef] [PubMed]
- Mekki, A.; Fki, F.; Kchaou, M.; Sayadi, S. Short-term Effects of Gray Wastewater on a Mediterranean Sandy Soil. CLEAN Soil Air Water 2014, 43, 754–760. [Google Scholar] [CrossRef]
- Al-Hamaiedeh, H.; Bino, M. Effect of treated grey water reuse in irrigation on soil and plants. Desalination 2010, 256, 115–119. [Google Scholar] [CrossRef]
- Abegunrin, T.; Awe, G.O.; Idowu, D.; Adejumobi, M. Impact of wastewater irrigation on soil physico-chemical properties, growth and water use pattern of two indigenous vegetables in southwest Nigeria. CATENA 2016, 139, 167–178. [Google Scholar] [CrossRef]
- Ben Brahim, S.; Gargouri, B.; Marrakchi, F.; Bouaziz, M. The Effects of Different Irrigation Treatments on Olive Oil Quality and Composition: A Comparative Study between Treated and Olive Mill Wastewater. J. Agric. Food Chem. 2016, 64, 1223–1230. [Google Scholar] [CrossRef] [PubMed]
- Papadopoulos, I. Wastewater management for agriculture protection in the Near East Region. In Technical Bulletin; FAO, Regional Office for the Near East: Cairo, Egypt, 1995. [Google Scholar]
- IOOC. Trade Standard Applying to Olive Oil and Olive-Pomace Oil; IOOC: Madrid, Spain, 2013. [Google Scholar]
- Mechri, B.; Ben Mariem, F.; Baham, M.; Ben Elhadj, S.; Hammami, M. Change in soil properties and the soil microbial community following land spreading of olive mill wastewater affects olive trees key physiological parameters and the abundance of arbuscular mycorrhizal fungi. Soil Biol. Biochem. 2008, 40, 152–161. [Google Scholar] [CrossRef]
- Magdich, S.; Jarboui, R.; Ben Rouina, B.; Boukhris, M.; Ammar, E. A yearly spraying of olive mill wastewater on agricultural soil over six successive years: Impact of different application rates on olive production, phenolic compounds, phytotoxicity and microbial counts. Sci. Total Environ. 2012, 430, 209–216. [Google Scholar] [CrossRef]
- Bedbabis, S.; Ben Rouina, B.; Boukhris, M.; Ferrara, G. Effect of irrigation with treated wastewater on soil chemical properties and infiltration rate. J. Environ. Manag. 2014, 133, 45–50. [Google Scholar] [CrossRef]
- Antony, J. Design of Experiments for Engineers and Scientists; Elsevier: Amsterdam, The Netherlands, 2014. [Google Scholar]
- Coo, M.; Pheeraphan, T. Effect of sand, fly ash, and coarse aggregate gradation on preplaced aggregate concrete studied through factorial design. Constr. Build. Mater. 2015, 93, 812–821. [Google Scholar] [CrossRef]
- Jones, J.B., Jr. Laboratory Guide for Conducting Soil Tests and Plant Analysis; CRC Press: Boca Raton, FL, USA, 2001. [Google Scholar]
- Karaivazoglou, N.; Papakosta, D.; Divanidis, S. Effect of chloride in irrigation water and form of nitrogen fertilizer on Virginia (flue-cured) tobacco. Field Crop. Res. 2005, 92, 61–74. [Google Scholar] [CrossRef]
- Richards, L. Diagnosis and Improvement of Saline and Alkali Soils.: Soil Science. 1954. In LWW. Available online: http://journals.lww.com/soilsci/Fulltext/1954/08000/Diagnosis_and_Improvement_of_Saline_and_Alkali.12.aspx (accessed on 9 May 2016).
- Gargouri, B.; Gargouri Dridi, O.; Gargouri, B.; Kallel Trabelsi, S.; Abdelhedi, R.; Bouaziz, M. Application of electrochemical technology for removing petroleum hydrocarbons from produced water using lead dioxide and boron-doped diamond electrodes. Chemosphere 2014, 117, 309–315. [Google Scholar] [CrossRef] [PubMed]
- Bouaziz, M.; Feki, I.; Ayadi, M.; Jemai, H.; Sayadi, S. Stability of refined olive oil and olive-pomace oil added by phenolic compounds from olive leaves. Eur. J. Lipid. Sci. 2010, 112, 894–905. [Google Scholar] [CrossRef]
- Pescod, M.B. Wastewater Treatment and Use in Agriculture. 1992. Available online: http://eprints.icrisat.ac.in/8638/ (accessed on 9 May 2016).
- Wiseman, E.; Seiler, J.R. Soil CO2 efflux across four age classes of plantation loblolly pine (Pinus taeda L.) on the Virginia Piedmont. For. Ecol. Manag. 2004, 192, 297–311. [Google Scholar] [CrossRef]
- Ayers, R.S.; Westcot, D.W. Water Quality for Agriculture; Food and Agriculture Organization of the United Nations: Rome, Italy, 1985. [Google Scholar]
- Arienzo, M.; Christen, E.; Quayle, W.; Kumar, A. A review of the fate of potassium in the soil–plant system after land application of wastewaters. J. Hazard. Mater. 2009, 164, 415–422. [Google Scholar] [CrossRef] [PubMed]
- Suarez, D.L.; Rhoades, J.D.; Lavado, R.; Grieve, C.M. Effect of pH on Saturated Hydraulic Conductivity and Soil Dispersion. Soil Sci. Soc. Am. J. 1984, 48, 50–55. [Google Scholar] [CrossRef] [Green Version]
- Levi-Minzi, R.; Riffaldi, R.; Saviozzi, A. Carbon mineralization in soil amended with different organic materials. Agric. Ecosyst. Environ. 1990, 31, 325–335. [Google Scholar] [CrossRef]
- Di Giovacchino, L.; Basti, C.; Costantini, N.; Surricchio, G. Olive Vegetable Water Spreading and Soil Fertilization. Acta Hortic. 2002, 586, 389–392. [Google Scholar] [CrossRef]
- Piotrowska, A.; Iamarino, G.; Rao, M.A.; Gianfreda, L. Short-term effects of olive mill waste water (OMW) on chemical and biochemical properties of a semiarid Mediterranean soil. Soil Biol. Biochem. 2006, 38, 600–610. [Google Scholar] [CrossRef]
- Singh, B.P.; Hatton, B.J.; Singh, B.; Cowie, A.L.; Kathuria, A. Influence of Biochars on Nitrous Oxide Emission and Nitrogen Leaching from Two Contrasting Soils. J. Environ. Qual. 2010, 39, 1224–1235. [Google Scholar] [CrossRef]
- Shalhevet, J. Using water of marginal quality for crop production: Major issues. Agric. Water Manag. 1994, 25, 233–269. [Google Scholar] [CrossRef]
- Gil, I.; Ulloa, J.J. Positive aspects of the use of water: The reuse of urban wastewater and its effect on areas of tourism. Options Mediterr Ser Semin. Mediterr CIHEAM 1997, 217–229. [Google Scholar]
- Xanthoulis, D.; Kayamanidou, M. Utilisation des eaux usées en irrigation, approche globale du traitement des effluents, comparaison de différents systèmes d’irrigation sur diverses cultures et leurs aspects institutionnel et organisationnel. In Avcienne AVI-CT-94-0002; Faculté Universitaire des Sciences Agronomiques de Gembloux: Gembloux, Belgium, 1998. [Google Scholar]
- Massena, P.A. Valorisation des Eaux Usées en Irrigation Localisée; Office International de L’eau: Valbonne, France, 2001. [Google Scholar]
- Di Serio, M.; Lanza, B.; Mucciarella, M.; Russi, F.; Iannucci, E.; Marfisi, P.; Madeo, A. Effects of olive mill wastewater spreading on the physico-chemical and microbiological characteristics of soil. Int. Biodeterior. Biodegrad. 2008, 62, 403–407. [Google Scholar] [CrossRef]
- Jarboui, R.; Sellami, F.; Kharroubi, A.; Gharsallah, N.; Ammar, E. Olive mill wastewater stabilization in open-air ponds: Impact on clay–sandy soil. Bioresour. Technol. 2008, 99, 7699–7708. [Google Scholar] [CrossRef]
- Jueschke, E.; Marschner, B.; Tarchitzky, J.; Chen, Y. Effects of treated wastewater irrigation on the dissolved and soil organic carbon in Israeli soils. Water Sci. Technol. 2008, 57, 727–733. [Google Scholar] [CrossRef]
- Tarchouna, L.G.; Merdy, P.; Raynaud, M.; Pfeifer, H.-R.; Lucas, Y. Effects of long-term irrigation with treated wastewater. Part I: Evolution of soil physico-chemical properties. Appl. Geochem. 2010, 25, 1703–1710. [Google Scholar] [CrossRef]
- Sierra, J.; Martí, E.; Garau, M.A.; Cruañas, R. Effects of the agronomic use of olive oil mill wastewater: Field experiment. Sci. Total Environ. 2007, 378, 90–94. [Google Scholar] [CrossRef]
- Emongor, V.; Ramolemana, G. Treated sewage effluent (water) potential to be used for horticultural production in Botswana. Phys. Chem. Earth Parts A/B/C 2004, 29, 1101–1108. [Google Scholar] [CrossRef]
- Heidarpour, M.; Mostafazadeh-Fard, B.; Koupai, J.A.; Malekian, R. The effects of treated wastewater on soil chemical properties using subsurface and surface irrigation methods. Agric. Water Manag. 2007, 90, 87–94. [Google Scholar] [CrossRef]
- Madejón, P.; Murillo, J.M.; Marañón, T.; Cabrera, F.; Soriano, M.A. Trace element and nutrient accumulation in sunflower plants two years after the Aznalcóllar mine spill. Sci. Total Environ. 2003, 307, 239–257. [Google Scholar] [CrossRef]
- Chartzoulakis, K.; Psarras, G.; Vemmos, S.; Loupassaki, M.; Bertaki, M. Response of Two Olive Cultivars to Salt Stress and Potassium Supplement. J. Plant Nutr. 2006, 29, 2063–2078. [Google Scholar] [CrossRef]
- Saviozzi, A.; Levi-Minzi, R.; Riffaldi, R.; Lupetti, A. Effettidellospandimento di acque di vegetazionesulterrenoagrario. Agrochimica 1991, 35, 135–147. [Google Scholar]
- Montemurro, F.; Convertini, G.; Ferri, D. Mill wastewater and olive pomace compost as amendments for rye-grass. Agronomie 2004, 24, 481–486. [Google Scholar] [CrossRef] [Green Version]
- Moraetis, D.; Stamati, F.; Nikolaidis, N.; Kalogerakis, N. Olive mill wastewater irrigation of maize: Impacts on soil and groundwater. Agric. Water Manag. 2011, 98, 1125–1132. [Google Scholar] [CrossRef]
- Paredes, M.; Moreno, E.; Ramos-Cormenzana, A.; Martinez, J. Characteristics of soil after pollution with waste waters from olive oil extraction plants. Chemosphere 1987, 16, 1557–1564. [Google Scholar] [CrossRef]
- Saadi, I.; Laor, Y.; Raviv, M.; Medina, S. Land spreading of olive mill wastewater: Effects on soil microbial activity and potential phytotoxicity. Chemosphere 2007, 66, 75–83. [Google Scholar] [CrossRef]
Figure 1.
HPLC analyses of the continuous ethyl acetate extracts from fresh OMW. (1) 3,4-dihydroxyphenylglycol (219 mg/L); (2) hydroxytyrosol (681 mg/L); (3) 3,4-dihydroxyphenylacetic acid (285 mg/L); (4) tyrosol (956 mg/L); (5) p-hydroxyphenylacetic acid (87.5 mg/L); (6) caffeic acid (21 mg/L); (7) p-coumaric acid (20 mg/L); (8) oleuropeinaglycone (113 mg/L); and (9) oleuropein (52 mg/L).
Figure 1.
HPLC analyses of the continuous ethyl acetate extracts from fresh OMW. (1) 3,4-dihydroxyphenylglycol (219 mg/L); (2) hydroxytyrosol (681 mg/L); (3) 3,4-dihydroxyphenylacetic acid (285 mg/L); (4) tyrosol (956 mg/L); (5) p-hydroxyphenylacetic acid (87.5 mg/L); (6) caffeic acid (21 mg/L); (7) p-coumaric acid (20 mg/L); (8) oleuropeinaglycone (113 mg/L); and (9) oleuropein (52 mg/L).
Figure 2.
Main effects plots of irrigation by TWW and OMW on pH (a1,a2) and EC (b1,b2).
Figure 3.
Pareto chart plots of the effect of WW dose and soil layer on the fertilizer elements NPK: (a1) P_TWW; (a2) P_OMW; (b1) K_TWW; (b2) K_OMW; and (c) N_OMW.
Figure 3.
Pareto chart plots of the effect of WW dose and soil layer on the fertilizer elements NPK: (a1) P_TWW; (a2) P_OMW; (b1) K_TWW; (b2) K_OMW; and (c) N_OMW.
Table 1.
Physicochemical characteristics of the studied OMW and TWW (National Sanitation Office, Sfax, Tunisia).
Table 1.
Physicochemical characteristics of the studied OMW and TWW (National Sanitation Office, Sfax, Tunisia).
| Chemical Parameters | Unit | Tunisian Norm | TWW | OMW |
|---|---|---|---|---|
| pH (at 25 °C) | - | 6.5–8.5 | 8.0 ± 0.01 | 5.9 ± 0.01 |
| EC | ms cm−1 | 7 | 6.30 ± 0.01 | 9.1 ± 0.02 |
| COD | g O2 L−1 | 90 | 77 ± 0.40 | 93 ± 0.32 |
| BOD5 | g O2 L−1 | 30 | 22 ± 0.62 | 13 ± 0.37 |
| P | (mg L−1) | 0.05 | 10.30 ± 0.31 | 720 ± 1.02 |
| K | (mg L−1) | 50 | 38 ± 0.90 | 6200 ± 1.53 |
| N | (mg L−1) | - | 58.8± | 1340 ± 5.90 |
| SS | (mgL−1) | 30 | 56 | N/D |
| Total phenols | (g L−1) | - | N/D | 8.4 ± 0.25 |
| Organic Matter | (g L−1) | - | N/D | 52.30 |
| NH4+ | (mgL−1) | - | 37.90 ± 0.42 | N/D |
| NO3− | (mgL−1) | 50 | 15.90 ± 0.88 | N/D |
| Na+ | (mgL−1) | 300 | 470 ± 0.98 | 1450 ± 1.72 |
| Cl− | (mgL−1) | 600 | 1999 ± 2.50 | N/D |
| Ca2+ | (mgL−1) | - | 95.80 ± 1.10 | 820 ± 1.53 |
| Mg2+ | (mgL−1) | - | 83.80 ± 1.02 | 600 ± 2.30 |
| Pb2+ | (mgL−1) | 0.100 | <0.004 | N/D |
| Cd2+ | (mgL−1) | 0.005 | <0.004 | N/D |
| Zn2+ | (mgL−1) | 5 | 0.24 | N/D |
| Mn2+ | (mgL−1) | - | 0.50 | N/D |
BOD, biochemical oxygen demand; COD, chemical oxygen demand; SS, suspended solid; EC, electrical conductivity; TSS, total suspended solid.
Table 2.
Factorial design matrix of effects of treated wastewater (TWW) on soil properties.
| Run Order | Factors | Responses | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Soil Layer | TWW Dose | Humidity | pH | EC | P | K | Na | Mg | Cl | Ca | Fe | Pb | OM | TOC | |
| 1 | 3 | Without | 4.83 | 7.70 | 0.190 | 89.73 | 219.95 | 199.95 | 144.95 | 1671.80 | 0.037 | 37.80 | 2.08 | 0.29 | 0.29 |
| 2 | 1 | With | 6.24 | 7.91 | 0.310 | 115.49 | 699.95 | 499.95 | 282.95 | 1472.85 | 0.037 | 12.18 | 23.78 | 2.47 | 0.99 |
| 3 | 3 | With | 10.59 | 7.95 | 0.400 | 189.22 | 299.95 | 639.95 | 363.95 | 1691.50 | 0.027 | 40.72 | 18.06 | 1.44 | 1.49 |
| 4 | 1 | Without | 3.18 | 7.73 | 0.130 | 63.61 | 599.95 | 188.95 | 107.95 | 1679.77 | 0.037 | 68.37 | 3.17 | 0.37 | 0.45 |
| 5 | 3 | With | 10.77 | 8.03 | 0.403 | 193.44 | 300.05 | 640.05 | 364.05 | 1700.50 | 0.033 | 41.08 | 18.26 | 1.46 | 1.51 |
| 6 | 3 | Without | 5.07 | 7.72 | 0.191 | 92.73 | 220.05 | 200.05 | 145.05 | 1678.20 | 0.043 | 38.40 | 2.16 | 0.31 | 0.31 |
| 7 | 1 | Without | 3.02 | 7.83 | 0.131 | 65.71 | 600.05 | 189.05 | 108.05 | 1684.23 | 0.043 | 68.83 | 3.27 | 0.39 | 0.47 |
| 8 | 1 | With | 6.44 | 7.93 | 0.311 | 119.51 | 700.05 | 500.05 | 283.05 | 1479.15 | 0.043 | 12.48 | 23.94 | 2.49 | 1.01 |
| 9 | 2 | Without | 4.52 | 7.57 | 0.15 | 74.71 | 409.95 | 179.45 | 124.95 | 1693.83 | 0.027 | 48.97 | 2.17 | 0.33 | 0.50 |
| 10 | 2 | With | 8.52 | 8.01 | 0.315 | 151.70 | 499.95 | 529.95 | 252.45 | 1675.81 | 0.017 | 72.20 | 19.41 | 2.14 | 1.18 |
| 11 | 2 | Without | 4.69 | 7.60 | 0.17 | 77.97 | 410.05 | 179.55 | 125.05 | 1698.18 | 0.033 | 49.34 | 2.26 | 0.35 | 0.58 |
| 12 | 2 | With | 8.18 | 8.08 | 0.315 | 155.87 | 500.05 | 530.05 | 252.55 | 1682.19 | 0.023 | 72.92 | 19.60 | 2.16 | 1.28 |
Table 3.
Factorial design matrix of effects of olive mill wastewater (OMW) on soil properties.
| Run Order | Factors | Responses | |||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Soil Layer | OMW Dose | Humidity | pH | EC | P | K | Na | Mg | Cl | N | SO4 | Ca | Fe | Cu | Pb | Mn | Zn | OM | TOC | Phenols | |
| 1 | 1 | 0 | 4.86 | 8.45 | 0.13 | 123.72 | 124.2 | 43.20 | 235.15 | 135.15 | 196.05 | 198.60 | 1846.88 | 2935.15 | 0.96 | 2.30 | 67.08 | 10.71 | 0.67 | 0.34 | 1.06 |
| 2 | 3 | 200 | 7.67 | 8.18 | 0.25 | 102.76 | 76.89 | 41.20 | 104.50 | 290.75 | 95.09 | 533.69 | 1430.88 | 4690.32 | 2.00 | 1.15 | 68.46 | 8.16 | 1.21 | 0.43 | 1.53 |
| 3 | 3 | 0 | 4.32 | 8.31 | 0.16 | 97.83 | 75.53 | 37.75 | 83.15 | 95.80 | 25.04 | 234.40 | 1350.02 | 2651.30 | 0.53 | 1.37 | 49.92 | 9.03 | 0.34 | 0.37 | 1.02 |
| 4 | 1 | 200 | 5.84 | 8.41 | 0.33 | 148.54 | 978.75 | 69.92 | 302.70 | 380.34 | 416.94 | 424.20 | 2573.45 | 5937.44 | 1.59 | 1.95 | 91.86 | 10.20 | 2.29 | 1.28 | 2.07 |
| 5 | 3 | 200 | 7.49 | 8.16 | 0.23 | 100.98 | 75.11 | 38.80 | 99.50 | 288.25 | 94.91 | 527.61 | 1423.12 | 4685.68 | 1.90 | 1.07 | 68.28 | 7.98 | 1.19 | 0.41 | 1.51 |
| 6 | 1 | 0 | 4.76 | 8.35 | 0.13 | 121.42 | 121.80 | 40.80 | 232.85 | 132.85 | 195.95 | 196.10 | 1839.12 | 2932.85 | 0.94 | 2.28 | 66.98 | 10.41 | 0.33 | 0.65 | 1.04 |
| 7 | 1 | 200 | 5.96 | 8.43 | 0.37 | 151.82 | 983.25 | 76.08 | 307.30 | 385.66 | 417.06 | 428.80 | 2576.55 | 5940.56 | 1.61 | 1.97 | 91.98 | 10.52 | 2.31 | 1.30 | 2.09 |
| 8 | 3 | 0 | 4.24 | 8.25 | 0.10 | 92.77 | 70.47 | 36.25 | 80.85 | 92.20 | 24.96 | 227.60 | 1341.98 | 2646.70 | 0.51 | 1.29 | 49.84 | 8.87 | 0.26 | 0.35 | 1.00 |
| 9 | 2 | 100 | 6.33 | 8.36 | 0.23 | 167.49 | 134.03 | 42.05 | 124.66 | 220.01 | 159.97 | 370.84 | 1731.93 | 6001.98 | 1.47 | 2.24 | 73.47 | 9.99 | 0.86 | 1.08 | 1.48 |
| 10 | 2 | 100 | 6.40 | 8.36 | 0.24 | 165.85 | 135.98 | 40.95 | 125.84 | 220.99 | 160.04 | 370.92 | 1734.07 | 6001.03 | 1.47 | 2.27 | 73.54 | 10.01 | 0.82 | 1.04 | 1.47 |
Table 4.
Main effects and ANOVA analysis of wastewater dose and soil layer on chemical properties of the soils.
Table 4.
Main effects and ANOVA analysis of wastewater dose and soil layer on chemical properties of the soils.
| Responses | Source of Variance | Wastewater Type | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Olive Mill Wastewater (OMW) | Treated Wastewater (TWW) | ||||||||||||
| Effect | SS | df | MS | F | P | Effect | SS | df | MS | F | P | ||
| Humidity | Soil layer | 0.5750 | 0.661 | 1 | 0.661 | 1.398 | 0.276 NS | −44.84 | 10,268.88 | 1 | 10,268.88 | 1.454 | 0.258 NS |
| WW dose | 2.1950 | 9.636 | 1 | 9.636 | 20.370 | 0.003 ** | −2.36 | 6237.17 | 1 | 6237.17 | 0.883 | 0.372 NS | |
| Error | - | 3.311 | 7 | 0.473 | - | 63,538.24 | 9 | 7059.80 | |||||
| Total SS | - | 13.609 | 9 | - | 80,044.29 | 11 | |||||||
| pH | Soil layer | −0.185 | 0.068 | 1 | 0.0684 | 24.877 | 0.002 ** | 0.288 | 0.000 | 1 | 0.000 | 0.000 | 1.000 NS |
| WW dose | −0.045 | 0.004 | 1 | 0.004 | 1.472 | 0.264 NS | 0.009 | 0.255 | 1 | 0.255 | 35.300 | 0.0002 *** | |
| Error | - | 0.019 | 7 | 0.003 | - | 0.065 | 9 | 0.007 | |||||
| Total SS | - | 0.092 | 9 | - | 0.320 | 11 | |||||||
| EC | Soil layer | −0.055 | 0.006 | 1 | 0.006 | 4.361 | 0.075 NS | 0.153 | 0.011 | 1 | 0.0112 | 36.066 | 0.0002 *** |
| WW dose | 0.165 | 0.054 | 1 | 0.054 | 39.253 | 0.0004 *** | 0.090 | 0.099 | 1 | 0.0990 | 317.409 | ≤0.0001 *** | |
| Error | - | 0.010 | 7 | 0.001 | - | 0.003 | 9 | 0.0003 | |||||
| Total SS | - | 0.070 | 9 | - | 0.113 | 11 | |||||||
| P | Soil layer | −37.79 | 2856.168 | 1 | 2856.168 | 4.858 | 0.063 NS | 58.33 | 5040.08 | 1 | 5040.08 | 39.157 | 0.0001 *** |
| WW dose | 17.09 | 584.136 | 1 | 584.136 | 0.993 | 0.352 NS | 57.56 | 17,691.65 | 1 | 17,691.65 | 137.449 | ≤0.0001 *** | |
| Error | - | 4115.759 | 7 | 587.966 | - | 1158.42 | 9 | 128.71 | |||||
| Total SS | - | 7556.063 | 9 | - | 23,890.15 | 11 | |||||||
| K | Soil layer | −477.50 | 456,013 | 1 | 456,012.5 | 7.666 | 0.028 * | 191.0 | 304,200.0 | 1 | 304,200.0 | 13,686.95 | ≤0.0001 *** |
| WW dose | 430.50 | 370,661 | 1 | 370,660.5 | 6.231 | 0.041 * | −314.8 | 24,300.0 | 1 | 24,300.0 | 1093.34 | ≤0.0001 *** | |
| Error | - | 416,379 | 7 | 59,482.7 | - | 200.0 | 9 | 22.2 | |||||
| Total SS | - | 1,243,052 | 9 | - | 328,700.0 | 11 | |||||||
| N | Soil layer | −246.50 | 121,524.5 | 1 | 121,524.5 | 69.355 | ≤0.0001 *** | ||||||
| WW dose | 145.50 | 42,340.5 | 1 | 42,340.5 | 24.164 | 0.0017 ** | |||||||
| Error | - | 12,265.4 | 7 | 1752.2 | - | ||||||||
| Total SS | - | 176,130.4 | 9 | - | |||||||||
| Na | Soil layer | −19.00 | 722.000 | 1 | 722.000 | 10.398 | 0.015 * | 326.17 | 11,400.5 | 1 | 11,400.5 | 9.541 | 0.013 * |
| WW dose | 17.00 | 578.000 | 1 | 578.000 | 8.324 | 0.023 * | 127.79 | 404,434.1 | 1 | 404,434.1 | 338.474 | ≤0.0001 *** | |
| Error | - | 486.063 | 7 | 69.437 | - | 10,753.9 | 9 | 1194.9 | |||||
| Total SS | - | 1786.063 | 9 | - | 426,588.4 | 11 | |||||||
| Mg | Soil layer | −177.50 | 63,012.50 | 1 | 63,012.50 | 70.484 | ≤0.0001 *** | 142.25 | 6962.0 | 1 | 6962.00 | 8.145 | 0.02 * |
| WW dose | 45.50 | 4140.50 | 1 | 4140.50 | 4.631 | 0.068 NS | 98.43 | 90,654.1 | 1 | 90,654.08 | 106.064 | ≤0.0001 *** | |
| Error | - | 6257.97 | 7 | 894.00 | - | 7692.4 | 9 | 854.71 | |||||
| Total SS | - | 73,410.97 | 9 | - | 105,308.4 | 11 | |||||||
| Cl | Soil layer | −66.750 | 8911.1 | 1 | 8911.13 | 41.801 | 0.0003 *** | −106.62 | 22,684.50 | 1 | 22,684.50 | 5.397 | 0.045 NS |
| WW dose | 222.250 | 98,790.1 | 1 | 98,790.13 | 463.420 | ≤0.0001 *** | 122.46 | 13,601.33 | 1 | 13,601.33 | 3.236 | 0.105 NS | |
| Error | - | 1492.2 | 7 | 213.18 | - | 37,825.42 | 9 | 4202.82 | |||||
| Total SS | - | 109,193.5 | 9 | - | 74,111.25 | 11 | |||||||
| Ca | Soil layer | −822.50 | 1,353,013 | 1 | 1,353,013 | 43.304 | 0.0003 *** | −0.0066 | 0.000 | 1 | 0.000 | 0.761 | 0.405 NS |
| WW dose | 406.50 | 330,484 | 1 | 330,484 | 10.577 | 0.01 * | −0.0003 | 0.0001 | 1 | 0.000 | 2.029 | 0.188 NS | |
| Error | - | 218,708 | 7 | 31,244 | - | 0.0006 | 9 | 0.000 | |||||
| Total SS | - | 1,902,205 | 9 | - | 0.0008 | 11 | |||||||
| Fe | Soil layer | −768.0 | 1,179,648 | 1 | 1,179,648 | 1.262 | 0.298 NS | −9.514 | 1.862 | 1 | 1.862 | 0.003 | 0.953 NS |
| WW dose | 2522.0 | 12,720,968 | 1 | 12,720,968 | 13.606 | 0.008 * | −1.583 | 301.301 | 1 | 301.301 | 0.592 | 0.461 NS | |
| Error | - | 6,544,369 | 7 | 934910 | - | 4582.854 | 9 | 509.206 | |||||
| Total SS | - | 20,444,985 | 9 | - | 4886.018 | 11 | |||||||
| Pb | Soil layer | −0.905 | 1.638 | 1 | 1.638 | 20.616 | 0.003 * | 19.159 | 23.120 | 1 | 23.120 | 14.906 | 0.004 * |
| WW dose | −0.275 | 0.151 | 1 | 0.151 | 1.903 | 0.210 NS | −3.649 | 970.740 | 1 | 970.740 | 625.868 | ≤0.0001 *** | |
| Error | - | 0.556 | 7 | 0.079 | - | 13.959 | 9 | 1.5510 | |||||
| Total SS | - | 2.345 | 9 | - | 1007.820 | 11 | |||||||
| OM | Soil layer | −0.590 | 0.696 | 1 | 0.696 | 8.120 | 0.02 * | 1.973 | 0.616 | 1 | 0.616 | 11.131 | 0.009 * |
| WW dose | 1.410 | 3.976 | 1 | 3.976 | 46.377 | 0.0002 *** | −0.886 | 8.551 | 1 | 8.551 | 154.507 | ≤0.0001 *** | |
| Error | - | 0.600 | 7 | 0.085 | - | 0.498 | 9 | 0.055 | |||||
| Total SS | - | 5.272 | 9 | - | 9.665 | 11 | |||||||
| COT | Soil layer | −0.585 | 0.684 | 1 | 0.684 | 12.410 | 0.009 ** | 0.686 | 0.058 | 1 | 0.057800 | 2.00565 | 0.190 NS |
| WW dose | 0.345 | 0.238 | 1 | 0.238 | 4.316 | 0.076 NS | 0.391 | 1.976 | 1 | 1.976 | 68.581 | ≤0.0001 *** | |
| Error | - | 0.386 | 7 | 0.055 | - | 0.259 | 9 | 0.029 | |||||
| Total SS | - | 1.309 | 9 | - | 2.293 | 11 | |||||||
| SO4 | Soil layer | 68.90 | 9494.4 | 1 | 9494.4 | 18.98 | 0.003 * | ||||||
| WW dose | 264.40 | 139,814.7 | 1 | 139,814.7 | 279.56 | ≤0.0001 *** | |||||||
| Error | - | 3500.8 | 7 | 500.1 | |||||||||
| Total SS | - | 152,810.0 | 9 | ||||||||||
| Cu | Soil layer | −0.04 | 0.003 | 1 | 0.003 | 0.059 | 0.815 NS | ||||||
| WW dose | 1.040 | 2.163 | 1 | 2.163 | 39.811 | 0.0004 ** | |||||||
| Error | - | 0.380 | 7 | 0.054 | - | ||||||||
| Total SS | - | 2.547 | 9 | - | |||||||||
| Mn | Soil layer | −20.350 | 828.245 | 1 | 828.245 | 118.956 | ≤0.0001 *** | ||||||
| WW dose | 21.690 | 940.912 | 1 | 940.912 | 135.138 | ≤0.0001 *** | |||||||
| Error | - | 48.738 | 7 | 6.962 | - | ||||||||
| Total SS | - | 1817.895 | 9 | - | |||||||||
| Zn | Soil layer | −1.950 | 7.605000 | 1 | 7.605 | 68.179 | ≤0.0001 *** | ||||||
| WW dose | −0.540 | 0.583200 | 1 | 0.583 | 5.228 | 0.056 * | |||||||
| Error | - | 0.780810 | 7 | 0.112 | - | ||||||||
| Total SS | - | 8.969010 | 9 | - | |||||||||
| Total phenols | Soil layer | −0.300 | 0.180 | 1 | 0.180 | 8.885 | 0.02 * | ||||||
| WW dose | 0.770 | 1.186 | 1 | 1.186 | 58.533 | 0.000121 | |||||||
| Error | - | 0.141 | 7 | 0.02 | - | ||||||||
| Total SS | - | 1.507 | 9 | - | |||||||||
SS: sumofsquares; df: degrees of freedom; MS: mean squares; F: F ratio; P: p values. The mean difference is significant at: * p ˂ 0.05; ** p˂ 0.01; *** p ˂ 0.001.
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. |
© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
Share and Cite
MDPI and ACS Style
Gargouri, B.; Ben Brahim, S.; Marrakchi, F.; Ben Rouina, B.; Kujawski, W.; Bouaziz, M. Impact of Wastewater Spreading on Properties of Tunisian Soil under Arid Climate. Sustainability 2022, 14, 3177. https://doi.org/10.3390/su14063177
AMA Style
Gargouri B, Ben Brahim S, Marrakchi F, Ben Rouina B, Kujawski W, Bouaziz M. Impact of Wastewater Spreading on Properties of Tunisian Soil under Arid Climate. Sustainability. 2022; 14(6):3177. https://doi.org/10.3390/su14063177
Chicago/Turabian StyleGargouri, Boutheina, Samia Ben Brahim, Fatma Marrakchi, Bechir Ben Rouina, Wojciech Kujawski, and Mohamed Bouaziz. 2022. "Impact of Wastewater Spreading on Properties of Tunisian Soil under Arid Climate" Sustainability 14, no. 6: 3177. https://doi.org/10.3390/su14063177
Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.
