Journal of Environmental Management 133 (2014) 45e50
Contents lists available at ScienceDirect
Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman
Effect of irrigation with treated wastewater on soil chemical properties and infiltration rate Saida Bedbabis a, *, Béchir Ben Rouina b, Makki Boukhris a, Giuseppe Ferrara c a
Laboratory of Environment and Biology of Arid Area, Department of Life Science, Faculty of Sciences, P.O. Box. 802, 3018 Sfax, Tunisia Laboratory of Improvement of Olive and Fruit Trees’ Productivity, Olive Tree Institute, P.O. Box. 1087, 3000 Sfax, Tunisia c Dipartimento di Scienze del Suolo, della Pianta e degli Alimenti, University of Bari ‘Aldo Moro’, via Amendola 165/A, 70126 Bari, Italy b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 13 July 2013 Received in revised form 5 November 2013 Accepted 9 November 2013 Available online
In Tunisia, water scarcity is one of the major constraints for agricultural activities. The reuse of treated wastewater (TWW) in agriculture can be a sustainable solution to face water scarcity. The research was conducted for a period of four years in an olive orchard planted on a sandy soil and subjected to irrigation treatments: a) rain-fed conditions (RF), as control b) well water (WW) and c) treated wastewater (TWW). In WW and TWW treatments, an annual amount of 5000 m 3 ha 1 of water was supplied to the orchard. Soil samples were collected at the beginning of the study and after four years for each treatment. The main soil properties such as electrical conductivity (EC), pH, soluble cations, chloride (Cl ), sodium adsorption ratio (SAR), organic matter (OM) as well as the infiltration rate were investigated. After four years, either a significant decrease of pH and infiltration rate or a significant increase of OM, SAR and EC were observed in the soil subjected to treated wastewater treatment. Ó 2013 Published by Elsevier Ltd.
Keywords: Treated wastewater Good quality water Sodium adsorption ratio Infiltration rate
1. Introduction Arid and semi-arid regions are characterized by evapotranspiration that exceeds precipitation during the largest part of the year. Therefore, agriculture in these regions relies on irrigation to achieve satisfactory yields. At the same time, one of the main environmental and social problems in these regions is the shortage of freshwater, which is expected to intensify due to both high population growth rate and increased demand from the agricultural sector. In recent years, as freshwater resources for irrigation have been rapidly reduced, emphasis has been put on the use of nonconventional water sources: agricultural drainage water, brackish or saline water and industrial or municipal wastewater. The treated wastewater (TWW) constitutes a reliable water and nutrients source for crops (Jimenez-Cisneros, 1995), with a consequent partial reduction in the use of chemical fertilizers (Gil and Ulloa, 1997) and improvements in crops yields (Shende, 1985; Chaabouni et al., 1997; Coppola et al., 2005). However, application of TWW can have some risks either for agriculture products (Yadav et al., 2002) or physical and chemical properties of the soils (Tarchouna et al.,
* Corresponding author. Tel.: þ216 74 276 400/274 923; fax: þ216 74 274 437. E-mail address: [email protected] (S. Bedbabis). 0301-4797/$ e see front matter Ó 2013 Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.jenvman.2013.11.007
2010) for the presence of heavy metals and other components. The changes of the physical and chemical properties of soil, as a consequence of irrigation with TWW, can affect water movement in the soil thus also altering the soil hydraulic properties. Tunisia belongs to the North Africa area, which is considered one of the driest regions in the world (World Bank, 1996). The reuse of TWW in Tunisia can satisfy the increasing water requirements for agriculture and may constitute an opportunity to preserve freshwater resources for human consumption. Some studies dealing with the impact of TWW on soil properties have been recently investigated (Lado and Ben Hur, 2009; Tarchouna et al., 2010) and little information is known about the effects of TWW on physical, chemical and hydraulic properties of a cultivated sandy soil. The objective of this investigation was to determine the effects of TWW used for irrigation, on soil physical, chemical and hydraulic properties, over four years. 2. Material and methods 2.1. Study area, plant material and irrigation schedules The site is located at ‘El Hajeb’ Experimental station, in the region of Sfax (34 43 N, 10 41 E) in Central-Eastern Tunisia. The study was carried out from 2003 to 2006 in an olive orchard
46
S. Bedbabis et al. / Journal of Environmental Management 133 (2014) 45e50
planted in 1987, with ‘Chemlali’ olive trees. Trees were spaced 24.0 24.0 m, trained to vase and rain-fed. Fertilizer additions, pest control and other cultural techniques were conducted according to local practices. The climate of the area is Mediterranean with an annual average rainfall, which occurs mostly in autumn and winter, of 276 mm and a mean air temperature of 32 C. Each treatment was replicated in three rows, with nine trees for each replicate (row). The experimental design was a randomized block. Three treatments were applied: 1) rain-fed conditions (RF, as control treatment); 2) irrigation with well water (WW) and 3) irrigation with treated wastewater (TWW). The water used was either that supplied after biological treatment process (TWW), or the WW from a well situated in the area of the experimental station. Both waters were analysed once a year. The amount of water supplied to olive trees was estimated according to the Penman-Monteith-FAO equation (Doorenbos and Pruitt, 1977) as described by Ben Ahmed et al. (2007). The irrigation was delivered using a drip irrigation system, with four drip nozzles (two per side) set in a line along the rows (at 0.5 m from the trunk). Without taking rainfall into account, the daily water supply per olive tree was 4.5 m3, for a total water supply of 5000 m3 ha1 year1. Soil samples were collected in triplicate before starting the irrigation schedule (February 2003) and after the last harvest (November 2006) at the end of the trial from the surface (0e20 cm) until a depth of 0.8 m with a layer of 0.2 m. The soil samples were successively carried to the laboratory for physical and chemical analyses. 2.2. Soil chemical analysis Soil physical and chemical analyses were carried out following internationally recommended procedures (Sparks et al., 1996). Plant roots residues were removed, and the soil was air-dried, gently crushed, and passed through a 2-mm sieve. The particlesize analysis was performed by pipette method according to the method described by Gee and Or (2002). Soil pH was determined using a pH metre (420A, Orien) in water (pHH2O) and in saline solution of 0.01 M CaCl2 (pHCaCl2). Soil/water ratio of the suspensions was 1:2.5 (w/v). The soil textural classes were determined at the beginning of the trial (2003) according to the USDA soil texture classification. The soil salinity was assessed by determination of electrical conductivity (EC) at 25 C on a saturated paste using a conductivity metre (MC 226). Soil organic carbon was measured with a Shimadzu TOC-5000 Analyzer. Chloride (Cl) was determined titrimetrically with AgNO3 (Karaivazoglou et al., 2005), whereas Kþ and Naþ contents were determined on ammonium acetate soil extract (Richards, 1954) using a JENWAY flame photometer. P was determined by a vanado-molybdate colorimetric procedure with a JENWAY 6405 UV/Vis Spectrophotometer (Milan, Italy). Ca2þ and Mg2þ were measured with an atomic absorption spectrophotometer (A Analyst 200, PerkinElmer). SAR was calculated using the standard equation. 2.3. Water infiltration rate For the current study, water infiltration rate was measured in triplicate in February 2003 and in November 2006 with infiltrometer of Muntz. The infiltrometer is composed with two concentric cylinders (radius of 30 and 50 cm each) inserted at 5 and 10 cm into the soil. The external cylinder is filled of water in order to saturate soil around the central cylinder and to also limit the lateral out-flow of water infiltrated in soil. The measure is based on the principle of the infiltration to variable load. After replenishment
of the two cylinders, water level variations in the central cylinder are measured during the time. The infiltration rate data were fitted to the Darcy law, as expressed by the following formula: I ¼ Hs (1 hf/Zf), where I is infiltration rate, Hs is the saturated hydraulic conductivity, hf is the wetting front pressure (80 < hf < 5 cm), Zf is the wetting front depth (Ben Rouina, 2007). 2.4. Statistical analysis ANOVA analysis was performed for all the results, treatments and times were the independent variables. All statistical analyses were carried out with the program SPSS 10 statistical software (SPSS Inc., Chicago, IL, USA). LSD test (P 0.05 and P 0.01) was used to separate the mean values of the treatments. 3. Results and discussion 3.1. Chemical properties of TWW and WW The physical and chemical characteristics of TWW and WW waters at the beginning of the trial are reported in Table 1. The pH of TWW and WW were 7.60 and 7.95, respectively, thus falling within the limits for fruit trees irrigation, which range from 6.0 to 9.0 (Pescod, 1992). The electrical conductivity (EC) was 6.30 dS m1 for TWW and 4.70 dS m1 for WW, indicating, respectively, a high and moderate level of salinity (Rhoades et al., 1992; Weisman et al., 2004). Cl concentration was higher than the threshold values, as reported by Chartzoulakis (2005) in the guidelines for olive irrigation. As expected, the concentration of almost all elements was higher in TWW than in WW, with the exception of Ca2þ and Mg2þ (Table 1). Both chemical and biological oxygen demands (COD and BOD) of TWW were below the Tunisian thresholds for water reuse. According to the chemical parameters, the TWW used for irrigation could be a source of major nutrients, although Naþ and Cl contents indicated a possible risk of soil salinization. Table 1 Chemical characteristics of the irrigation waters used in the experiment. Characteristics
WW
pH EC (dS m1) TDS (g L1) 1 HCO 3 (mg L ) 1 SO2 4 (mg L ) N total (mg L1) 1 NeNO 3 (mg L ) 1 NeNHþ (mg L ) 4 1 NeNO 2 (mg L ) P total (mg L1) Kþ (mg L1) Naþ (mg L1) Cl (mg L1) Ca2þ (mg L1) Mg2þ (mg L1) Pb2þ (mg L1) Cd2þ (mg L1) Zn2þ (mg L1) Mn2þ (mg L1) SM (mg L1) COD (mg L1) BOD (mg L1)
7.95 4.70 1.51 288.50 87.50 e 1.11 2.24 0.08 0.80 30.00 355.00 1580 184.50 126.20 0 0 0.10 0.19 4.30 0 0
TWW
0.10 0.02 0.02 0.3 0.8
0.01 0.01 0.02 0.11 0.09 0.01 0.04 0.01 0.01
0.01 0.01 0.02
7.60 6.30 1.82 370.00 363.00 58.80 15.90 37.90 5.00 10.30 38.00 470.00 1999.00 95.80 83.80
Contents lists available at ScienceDirect
Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman
Effect of irrigation with treated wastewater on soil chemical properties and infiltration rate Saida Bedbabis a, *, Béchir Ben Rouina b, Makki Boukhris a, Giuseppe Ferrara c a
Laboratory of Environment and Biology of Arid Area, Department of Life Science, Faculty of Sciences, P.O. Box. 802, 3018 Sfax, Tunisia Laboratory of Improvement of Olive and Fruit Trees’ Productivity, Olive Tree Institute, P.O. Box. 1087, 3000 Sfax, Tunisia c Dipartimento di Scienze del Suolo, della Pianta e degli Alimenti, University of Bari ‘Aldo Moro’, via Amendola 165/A, 70126 Bari, Italy b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 13 July 2013 Received in revised form 5 November 2013 Accepted 9 November 2013 Available online
In Tunisia, water scarcity is one of the major constraints for agricultural activities. The reuse of treated wastewater (TWW) in agriculture can be a sustainable solution to face water scarcity. The research was conducted for a period of four years in an olive orchard planted on a sandy soil and subjected to irrigation treatments: a) rain-fed conditions (RF), as control b) well water (WW) and c) treated wastewater (TWW). In WW and TWW treatments, an annual amount of 5000 m 3 ha 1 of water was supplied to the orchard. Soil samples were collected at the beginning of the study and after four years for each treatment. The main soil properties such as electrical conductivity (EC), pH, soluble cations, chloride (Cl ), sodium adsorption ratio (SAR), organic matter (OM) as well as the infiltration rate were investigated. After four years, either a significant decrease of pH and infiltration rate or a significant increase of OM, SAR and EC were observed in the soil subjected to treated wastewater treatment. Ó 2013 Published by Elsevier Ltd.
Keywords: Treated wastewater Good quality water Sodium adsorption ratio Infiltration rate
1. Introduction Arid and semi-arid regions are characterized by evapotranspiration that exceeds precipitation during the largest part of the year. Therefore, agriculture in these regions relies on irrigation to achieve satisfactory yields. At the same time, one of the main environmental and social problems in these regions is the shortage of freshwater, which is expected to intensify due to both high population growth rate and increased demand from the agricultural sector. In recent years, as freshwater resources for irrigation have been rapidly reduced, emphasis has been put on the use of nonconventional water sources: agricultural drainage water, brackish or saline water and industrial or municipal wastewater. The treated wastewater (TWW) constitutes a reliable water and nutrients source for crops (Jimenez-Cisneros, 1995), with a consequent partial reduction in the use of chemical fertilizers (Gil and Ulloa, 1997) and improvements in crops yields (Shende, 1985; Chaabouni et al., 1997; Coppola et al., 2005). However, application of TWW can have some risks either for agriculture products (Yadav et al., 2002) or physical and chemical properties of the soils (Tarchouna et al.,
* Corresponding author. Tel.: þ216 74 276 400/274 923; fax: þ216 74 274 437. E-mail address: [email protected] (S. Bedbabis). 0301-4797/$ e see front matter Ó 2013 Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.jenvman.2013.11.007
2010) for the presence of heavy metals and other components. The changes of the physical and chemical properties of soil, as a consequence of irrigation with TWW, can affect water movement in the soil thus also altering the soil hydraulic properties. Tunisia belongs to the North Africa area, which is considered one of the driest regions in the world (World Bank, 1996). The reuse of TWW in Tunisia can satisfy the increasing water requirements for agriculture and may constitute an opportunity to preserve freshwater resources for human consumption. Some studies dealing with the impact of TWW on soil properties have been recently investigated (Lado and Ben Hur, 2009; Tarchouna et al., 2010) and little information is known about the effects of TWW on physical, chemical and hydraulic properties of a cultivated sandy soil. The objective of this investigation was to determine the effects of TWW used for irrigation, on soil physical, chemical and hydraulic properties, over four years. 2. Material and methods 2.1. Study area, plant material and irrigation schedules The site is located at ‘El Hajeb’ Experimental station, in the region of Sfax (34 43 N, 10 41 E) in Central-Eastern Tunisia. The study was carried out from 2003 to 2006 in an olive orchard
46
S. Bedbabis et al. / Journal of Environmental Management 133 (2014) 45e50
planted in 1987, with ‘Chemlali’ olive trees. Trees were spaced 24.0 24.0 m, trained to vase and rain-fed. Fertilizer additions, pest control and other cultural techniques were conducted according to local practices. The climate of the area is Mediterranean with an annual average rainfall, which occurs mostly in autumn and winter, of 276 mm and a mean air temperature of 32 C. Each treatment was replicated in three rows, with nine trees for each replicate (row). The experimental design was a randomized block. Three treatments were applied: 1) rain-fed conditions (RF, as control treatment); 2) irrigation with well water (WW) and 3) irrigation with treated wastewater (TWW). The water used was either that supplied after biological treatment process (TWW), or the WW from a well situated in the area of the experimental station. Both waters were analysed once a year. The amount of water supplied to olive trees was estimated according to the Penman-Monteith-FAO equation (Doorenbos and Pruitt, 1977) as described by Ben Ahmed et al. (2007). The irrigation was delivered using a drip irrigation system, with four drip nozzles (two per side) set in a line along the rows (at 0.5 m from the trunk). Without taking rainfall into account, the daily water supply per olive tree was 4.5 m3, for a total water supply of 5000 m3 ha1 year1. Soil samples were collected in triplicate before starting the irrigation schedule (February 2003) and after the last harvest (November 2006) at the end of the trial from the surface (0e20 cm) until a depth of 0.8 m with a layer of 0.2 m. The soil samples were successively carried to the laboratory for physical and chemical analyses. 2.2. Soil chemical analysis Soil physical and chemical analyses were carried out following internationally recommended procedures (Sparks et al., 1996). Plant roots residues were removed, and the soil was air-dried, gently crushed, and passed through a 2-mm sieve. The particlesize analysis was performed by pipette method according to the method described by Gee and Or (2002). Soil pH was determined using a pH metre (420A, Orien) in water (pHH2O) and in saline solution of 0.01 M CaCl2 (pHCaCl2). Soil/water ratio of the suspensions was 1:2.5 (w/v). The soil textural classes were determined at the beginning of the trial (2003) according to the USDA soil texture classification. The soil salinity was assessed by determination of electrical conductivity (EC) at 25 C on a saturated paste using a conductivity metre (MC 226). Soil organic carbon was measured with a Shimadzu TOC-5000 Analyzer. Chloride (Cl) was determined titrimetrically with AgNO3 (Karaivazoglou et al., 2005), whereas Kþ and Naþ contents were determined on ammonium acetate soil extract (Richards, 1954) using a JENWAY flame photometer. P was determined by a vanado-molybdate colorimetric procedure with a JENWAY 6405 UV/Vis Spectrophotometer (Milan, Italy). Ca2þ and Mg2þ were measured with an atomic absorption spectrophotometer (A Analyst 200, PerkinElmer). SAR was calculated using the standard equation. 2.3. Water infiltration rate For the current study, water infiltration rate was measured in triplicate in February 2003 and in November 2006 with infiltrometer of Muntz. The infiltrometer is composed with two concentric cylinders (radius of 30 and 50 cm each) inserted at 5 and 10 cm into the soil. The external cylinder is filled of water in order to saturate soil around the central cylinder and to also limit the lateral out-flow of water infiltrated in soil. The measure is based on the principle of the infiltration to variable load. After replenishment
of the two cylinders, water level variations in the central cylinder are measured during the time. The infiltration rate data were fitted to the Darcy law, as expressed by the following formula: I ¼ Hs (1 hf/Zf), where I is infiltration rate, Hs is the saturated hydraulic conductivity, hf is the wetting front pressure (80 < hf < 5 cm), Zf is the wetting front depth (Ben Rouina, 2007). 2.4. Statistical analysis ANOVA analysis was performed for all the results, treatments and times were the independent variables. All statistical analyses were carried out with the program SPSS 10 statistical software (SPSS Inc., Chicago, IL, USA). LSD test (P 0.05 and P 0.01) was used to separate the mean values of the treatments. 3. Results and discussion 3.1. Chemical properties of TWW and WW The physical and chemical characteristics of TWW and WW waters at the beginning of the trial are reported in Table 1. The pH of TWW and WW were 7.60 and 7.95, respectively, thus falling within the limits for fruit trees irrigation, which range from 6.0 to 9.0 (Pescod, 1992). The electrical conductivity (EC) was 6.30 dS m1 for TWW and 4.70 dS m1 for WW, indicating, respectively, a high and moderate level of salinity (Rhoades et al., 1992; Weisman et al., 2004). Cl concentration was higher than the threshold values, as reported by Chartzoulakis (2005) in the guidelines for olive irrigation. As expected, the concentration of almost all elements was higher in TWW than in WW, with the exception of Ca2þ and Mg2þ (Table 1). Both chemical and biological oxygen demands (COD and BOD) of TWW were below the Tunisian thresholds for water reuse. According to the chemical parameters, the TWW used for irrigation could be a source of major nutrients, although Naþ and Cl contents indicated a possible risk of soil salinization. Table 1 Chemical characteristics of the irrigation waters used in the experiment. Characteristics
WW
pH EC (dS m1) TDS (g L1) 1 HCO 3 (mg L ) 1 SO2 4 (mg L ) N total (mg L1) 1 NeNO 3 (mg L ) 1 NeNHþ (mg L ) 4 1 NeNO 2 (mg L ) P total (mg L1) Kþ (mg L1) Naþ (mg L1) Cl (mg L1) Ca2þ (mg L1) Mg2þ (mg L1) Pb2þ (mg L1) Cd2þ (mg L1) Zn2þ (mg L1) Mn2þ (mg L1) SM (mg L1) COD (mg L1) BOD (mg L1)
7.95 4.70 1.51 288.50 87.50 e 1.11 2.24 0.08 0.80 30.00 355.00 1580 184.50 126.20 0 0 0.10 0.19 4.30 0 0
TWW
0.10 0.02 0.02 0.3 0.8
0.01 0.01 0.02 0.11 0.09 0.01 0.04 0.01 0.01
0.01 0.01 0.02
7.60 6.30 1.82 370.00 363.00 58.80 15.90 37.90 5.00 10.30 38.00 470.00 1999.00 95.80 83.80
