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Journal of Food, Agriculture & Environment Vol.13 (3&4):60-66. 2015
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Emitter clogging in drip irrigation using treated domestic wastewater Flavio Daniel Szekut 1 *, Delfran Batista do Santos 2, Carlos Alberto Vieira de Azevedo 1, Márcio Roberto Klein 1, Maycon Diego Ribeiro 1 and Salomão de Sousa Medeiros 3 Department of Agricultural Engineering, Federal University of Campina Grande (COPEAG/ UAEG/CTRN/UFCG), 882 Aprígio Veloso Street, CM Block, 58429-140, Campina Grande, Paraíba State - Brazil. 2Federal Institute of Education, Science and Technology Baiano (IF Baiano), Deputado Hidevaldo street, 46430-000, Senhor do Bonfim, Bahia State - Brazil. 3National Semiarid Institute (INSA), Street Francisco Lopes de Almeida, 58429-970 - Campina Grande - Paraíba State -Brazil. *e-mail:
[email protected],
[email protected],
[email protected] [email protected],
[email protected],
[email protected] 1
Received 6 April 2015, accepted 8 September 2015.
Abstract The lack of high-quality water for irrigation leads to the use of low-quality water or alternative water resources in irrigated agriculture, such as the application of domestic sewage wastewater, for which drip irrigation is used because it decreases the contamination of crops and workers, and provides high application uniformity. However, emitter clogging poses a problem. In this context, this study aimed to characterize and monitor three models of tubes with labyrinth-type inline drippers, subjected to irrigation with wastewater from treated domestic sewage and fresh water. The experiment was performed on a bench at the field, in the semiarid region of Brazil, in the state of Paraíba. The emitters were hydraulically characterized and monitored for 1188 h, the discharge coefficient of variation and the degree of clogging of the emitters were calculated. The latter was subjected to the analysis of variance with two factors, type of water with two levels and model of emitter with three levels, and means comparison test. At the end of the operation, the labyrinth of each emitter was subjected to scanning electron microscopy (SEM). The initial hydraulic characteristics do not change with the use of domestic sewage wastewater as the water source. Along the operation time, domestic sewage wastewater showed the greatest variability, with coefficient of variation higher than 15% and 792, 720 and 612 h of operation. For the emitter referred to as G1, there was no significant difference between the application of wastewater and fresh water for the response variable degree of clogging. According to the SEM analysis, a type of biofilm coating was observed along the labyrinth. The shape of the labyrinth channels of the emitters and the quality of the water used constituted the main characteristics for the clogging process. Thus, the connection between these factors is essential for studies on clogging of drip irrigation systems. Key words: Biofilm, drip tube, degree of clogging, scanning electron microscopy, fresh water, hydraulic characterization, discharge exponent, bacterial colony, semiarid, water quality, emitter’s labyrinth channel.
Introduction In places where water is scarce, like arid and semiarid regions, agriculture is dependent on this resource. Roig et al. 21 suggested that with this scarcity, low-quality water or alternative water sources are used, such as domestic sewage wastewater, since it is an abundant source that is available along the entire year. Wastewater is widely used in the irrigated agriculture of many countries and its use has as an economic advantage, the reduction of inputs, such as water and fertilizers. According to Muyen et al.16, besides the economic advantages, it promotes a series of environmental benefits, caused by the reductions in water catchment and in the discharge of effluents directly into water bodies. Despite its high cost, drip irrigation is indicated among the irrigation systems, for its high distribution efficiency and because it is a method that minimizes the contamination of crops and field staff as reported by Feitosa et al. 9. On the other hand, the risk of clogging, from both physicochemical and biological origin, can cause problems in the system. 60
Physical clogging results from particles that are not retained by the filtering system or from chemical precipitation inside the tubing systems. Biofilm is the main cause of biological clogging, which consists of bacterial colonies adhered onto the internal surfaces of the irrigation tubes, causing partial or total emitter clogging. According to Gamri et al.10 fragments of the biofilm detached from the tube walls can also cause clogging, by depositing on other parts of the labyrinth and blocking the flow. In labyrinth-type emitters, there is a complex structure of the flow channel in which the high pressure of the water is dissipated and then it flows through the emitters. Therefore, the quality of a drip irrigation system is verified and monitored by the hydraulic performance of the emitters as reported by Patil et al. 18. For this, the coefficients of distribution uniformity and the coefficient of variation of emitter discharge are widely used. Besides the quality of the water, dimensional characteristics of the emitters and the projects also influence emitter clogging, such as length of the labyrinth, studied by Batista et al.5, position of
Journal of Food, Agriculture & Environment, Vol.13 (3&4), July-October 2015
the emitters and internal architecture 20 and topographic conditions12. These characteristics should be studied in order to improve the efficiency of unclogging with products, processes or prevention methods. Given the above, this study aimed to monitor and characterize the clogging of three models of labyrinth-type drip emitters subjected to irrigation using fresh water and wastewater from treated domestic sewage in a semiarid region. In addition, images from scanning electron microscopy were used to observe the material causing the clogging. Materials and Methods Location: The experiment was carried out at the headquarters of the National Semiarid Institute (INSA), located in the municipality of Campina Grande-PB, Brazil (7º16’20’’ S; 35º56’29’’ W; 550 m). The local climatic conditions during the experiment were dry, with no rainfalls. The fresh water (FW) used in the experiment was provided by the Company of Water and Sewerage of Paraíba (CAGEPA). The wastewater (WW) came from the sewage treatment plant (STP), which receives the sewage produced by INSA. Emitters: For the tests, three tubes with non-compensating, labyrinth-type, inline drippers were used. In this model of emitter, the clogging is favored by the long labyrinth path by which the flow needs to go in order to lose energy and become uniform. These models of tubes are found in the irrigation systems in the Brazilian semiarid area, especially in Mossoró, in the state of Rio Grande do Norte, and Petrolina, in the state of Pernambuco, Brazil. The selected models of inline emitter tubing were: Streamline 16080 (Netafim), with nominal flow rate of 1.60 L h-1 at 100 kPa and emitters at every 0.30 m, referred to as G1, Taldrip (Naadanjain), with nominal flow rate of 1.70 L h-1 at 100 kPa and emitters at every 0.20 m, referred to as G2 and Tiran 16010 (Netafim), with nominal flow rate of 2.00 L h-1 at 100 kPa and emitters at every 0.40 m. System composition: A bench was set at the field, in order to be influenced by the characteristics of the local climate, closely representing the actual conditions for the clogging of the irrigation system. The bench was 10.00 m long, 2.00 m wide and 1.50 m high, with return gutters connected to the storage system for wastewater and fresh water, as shown in Fig. 1. The discharge system was installed individually for each type of water (wastewater and fresh water) and was composed of controller with disc filter with 120 mesh (IRRITEC®, model FLD), valves, hydrometer (LAO®, model UJB1) with nominal flow rate of 1.5 m3 h-1, glycerin-filled Bourdon tube pressure gauge (GE) with resolution of 0.10 kg cm-2 and direct-action pressure regulators
(BERMAD®, model 0075 PRVy), in order to maintain the fixed input pressure at 100 kPa. Each lateral line was 10.00 m long, suspended at 0.30 m from the bench in order to facilitate the obtention of the flow rate of the emitters. There was one lateral line for each model of emitter and type of water, totaling six lateral lines. The wastewater used in the experiment came from an anaerobic sewage treatment plant (STP) in operation using the sewage produced by the INSA. The treatment process constituted mainly of a septic tank for the sedimentation of solid particles and fatty material. Then, the process continues with the action of an anaerobic biological layer anchored on the surface of the stone inside the STP. Hydraulic characterization: For the hydraulic characterization of the emitters, the characteristic curve was obtained, following the recommendations of the Brazilian technical norm ABNT 3 for experiments with emitters. For the tests, air and water temperatures were between 20ºC and 26ºC, and the number of samples was at least 25 emitters. The pressure values did not exceed 50 kPa, with a minimum of four intervals between the minimum pressure and 1.2 of the maximum pressure. The pressure values used for the characteristic curve of the emitter are shown in Table 1. Table 1. Pressure values used for the characteristic curve of the emitters G1, G2 and G3. G1 - Streamline 60 70 80 90 100 110 120
G2 - Taldrip kPa 50 100 150 200 250 300 360
G3 - Tiran 100 140 180 220 260 300 360
The general equation of the emitters characterizes their flow rate as a function of the pressure and the flow regime (Equation 1): q = K .hx
(1)
where: q - flow rate (L h-1), K - coefficient of proportionality, h operating pressure (kPa), x - discharge exponent.
System evaluation: The evaluation consisted in the simultaneous collection of water in all the determined points for 4 min, using collectors. Twenty five sampling points were randomly chosen in the lateral line. Then, the volume was measured using a graduated cylinder and the values were transformed into 10.00 m flow rate (L h-1). The evaluations after the first characterization were performed every 36 h, with 12 h of operation per day. The limit for the system operation was higher than 1000 h, the time necessary for a probable severe emitter clogging according to Liu et al. 15. At the end of the experiment, thirty three evaluations had been performed, totaling 1188 h of operation. Figure 1. Cross-sectional view of the irrigation system installed on the bench, controllers With the characterization data and the and systems of storage and pumping. Journal of Food, Agriculture & Environment, Vol.13 (3&4), July-October 2015
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subsequent evaluations, the discharge coefficient of variation (CVq) (Equation 2) and the degree of clogging (DC) (Equation 3): were calculated:
CVq - Discharge coefficient of variation, %; Sused - Standard deviation of flow rates of used emitters, L h-1; qused - Average flow rate of used emitters, L h-1; q DC = ( 1 – qused ) 100 initial
1.8 Flow rate (Lh -1)
Sused CV q = q 100 used
(2)
2.0
1.4 1.2 1.0
40
60
80 Pressure (kPa)
(3) Catalog Catalog
DC - Degree of clogging, % qused - Average flow rate of used emitters, L h-1; qinitial - Average flow rate of brand-new emitters, L h-1;
100
Fresh water Fresh water
120
Wastewater Wastewater Wastewater
(a) 3.0
Water analysis: Physicochemical and microbiological analyses were performed at the beginning of the experiment for characterization, and the main elements of risk for emitter clogging in the drip irrigation system, according to Ayers and Westcot 4, Capra and Scicolone 8and Nakayama et al. 17, were analyzed. Statistical methods: Statistical analyses were performed using the software Minitab 16: analysis of variance for two factors, type of water with two levels (wastewater and fresh water) and model of emitter with three levels (G1, G2 and G3). Tukey’s means comparison test was performed, at 5% of significance. Results and Discussion The curves of flow rate as a function of pressure were obtained for each model of emitter and type of water (Fig. 2). The curve of the brand-new emitter was calculated using the characteristic equation provided by the manufacturer. The emitter G2 broke at 1.2 of the maximum pressure (360 kPa). The characteristic equation obtained with the curves showed satisfactory determination coefficient R2, with values close to 1. The elements of the characteristic equation are shown in Table 2. There were differences between the obtained characteristic equation and the equation provided by the manufacturer, with the highest discharge exponents observed for the use of wastewater, however, these small variations do not compromise the flow regime. During the operation time of the emitters, changes in the discharge exponent modify the flow rates of the system. However, with adequate conditions of water and materials, these variabilities
Flow rate (Lh -1)
2.5 2.0 1.5 1.0 0.5 0.0
00
50 50
Catalog Catalog
100 100
150 200 250 150 200 250 Pressure Pressure (kPa) (kPa)
Fresh Fresh wate water r
300 300
350 350
Wastewater Wastewater
(b) 4.0 3.5 Flow rate (Lh -1)
Scanning electron microscopy: The scanning electron microscope (SEM) is a device used especially in engineering that is able to produce high-magnification and -resolution images through an electron beam. The model of SEM used in this study was Superscan SSX-550 (Shimadzu Corporation®). In order to improve the level of electron emission, samples were subjected to a metallization process using gold ions, placed in a pressure chamber under 0.01-0.005 kPa. The metallic target (gold) was bombarded with atoms of inert gas, which causes the atoms to be deposited on the sample. For the SEM analyses, one groove of the flow labyrinth of each model of emitter, for both types of water, were cut and removed at the end of the experiment, totaling six samples. The images were magnified forty times for the viewing of the clogging material.
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1.6
3.0 2.5 2.0 1.5
50 50
100 100
150 150
200 250 200 250 Pressure (kPa) Pressure (kPa)
Catalog Catalog
Fresh Freshwater water
300 300
350 350
Wastewater Wastewater
(c)
Figure 2. Characteristic curves for the emitters G1 (a), G2 (b) and G3 (c) using wastewater and fresh water, and the curve calculated by the manufacturer.
Table 2. Elements of the general equation of the emitters, coefficient of proportionality, discharge exponent and the determination coefficient of the regression equation. Emitter G1
G2
G3
Water Fresh water Wastewater Catalog Fresh water Wastewater Catalog Fresh water Wastewater Catalog
K 0.195 0.165 0.201 0.218 0.162 0.205 0.195 0.191 0.240
x Variation x (%) 0.438 -2.580 0.478 6.130 0.450 0.432 -6.070 0.486 5.740 0.460 0.502 9.020 0.501 8.980 0.460
R² 0.995 0.993 1.000 0.998 0.998 1.000 0.999 0.999 1.000
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Table 3. Physicochemical and microbiological analyses for fresh water and wastewater, with the classification for the risk of clogging. Physicochemical parameters Electrical conductivity (mmho/cm at 25ºC) pH Calcium (mg/L) Magnesium (mg/L) Potassium (mg/L) Total Iron (mg/L) Chloride (mg/L) Nitrate (mg/L) Bicarbonate (mg/L) Silica (mg/L) Total Dissolved Solids at 180ºC (TDS) (mg/L)
Results Fresh water 1092.0 ** a
Wastewater 2139.0 ** a
6.6 * a 26.6 * ab 35.0 * ac 5.3 *** a 0.01 * abc 305.3 * a 0.04 * a 84.0 * a 3.7 a 662.4 ** bc
7.6 * a 48.0 * ab 37.2 * ac 60.6 *** a 0.08 * abc 388.7 * a 0.6 * a 203.2 * a 6.2 a 1160.0 ** bc
Microbiological parameter Total Coliforms (Colony-forming units)
520.0* ab
10112.0** ab
* Low risk of clogging, ** Intermediate risk of clogging, *** High risk of clogging, Classification according to: (a) 4, (b) 17, and (c) 8.
All physicochemical parameters were classified with the same risk of clogging for wastewater and fresh water, except for potassium (high risk) and electrical conductivity and total dissolved solids (intermediate risk). The microbiological parameter total coliforms showed low risk of clogging for fresh water and intermediate for wastewater. The restrictions for potassium are mainly related to the use in
soil and to crop nutrition. High degree of clogging with the application of potassium sources, especially white and red potassium chlorides, was not observed, but they point to the importance of not having any other element in the composition of these sources as reported by Ribeiro et al. 19. Batista et al. 6 stated that the total coliforms indicate the presence of bacterial charge that, when interact with algae, result in a biofilm, causing partial or total clogging in the emitters. The coefficient of variation of the emitters is a measurement of the dispersion and can be interpreted as the data variability in relation to the mean; the lower the value, the better the data homogeneity indices. The variation of CV over time for the thirty three evaluations of wastewater and fresh water is shown in Fig. 3. 100 100 90 90 80 80 70 70 CV (%) CV (%)
are minimized. There is no statistical difference for the discharge exponent in emitters with up to two years of use as reported by Yavuz et al. 25. Despite the strict quality control by the manufacturers of emitter tubes, there are variations in the flow rate. Analyzing the measured data of hydraulic losses in emitters, observed differences between emitters and between tubes, although the emitter tubes have standard classifications as reported by Li et al. 23. The emitters, using both wastewater and fresh water, showed coefficient of variation (CV) lower than 7% in the initial characterization, for all pressure values, suggesting that, in the design of drip irrigation systems, small variations in the emitters flow rate do not interfere with projects using wastewater. Li et al. 14 concluded that small variations in the discharge of the emitters related to pressure changes are not significant and also indicate the increase of the discharge exponent for lower pressures. The input pressure can be one of the factors contributing to the worsening of the clogging in the system. Silva et al. 22 stated that using effluent from the cashew nut processing, observed greater clogging at lower pressures, with the highest degree of clogging for 70 kPa, which can be explained by the lower flow speed inside the tubes, compared with higher pressures, as in the case of 140 kPa. The quality of the different types of water was verified through physical, chemical and microbiological analyses, showing the main risk elements for the clogging. The quality parameters for irrigation water were classified according to Ayers and Westcot 4, Capra and Scicolone 8 and Nakayama et al. 17. The main clogging agents and the classification for their respective risk of clogging, for wastewater and fresh water, are shown in Table 3.
60 60 50 50 40 40 30 30 20 20 10 10 0
0 0
200 200 G1_WW
400 600 800 400 600 800 Operation time (h) Operation time (h) G2_WW
G3_WW
G1_FW
1000 1000 G2_FW
1200 1200 G3_FW
Figure 3. Coefficient of variation for the three models of emitter as a function of the operation time for wastewater and fresh water.
The CV of the system using wastewater showed the highest values, high variability, for the three tested emitters, ending with 30.59, 78.63 and 90.51% for G1, G2 and G3, respectively. The ABNT 3 establishes that 7% is the maximum CV value. Using wastewater, the emitters G1, G2 and G3 exceeded the value of 7% with 540, 576 and 324 h of operation, respectively. As recommended by ASABE 2, until 7% the CV is classified as intermediate and, from 15% on, as unacceptable. For wastewater, the emitters G1, G2 and G3 reached values higher than 15% with 792, 720 and 612 h of operation, respectively. Using fresh water, the emitters G1, G2 and G3 reached values higher than 7% with 144, 1116 and 216 h of operation, respectively. The emitters G1 and G2 reached CV of 15% with 252 and 1188 h of operation; however, G3 did not reach CV of 15%. Katz et al.11 stated that the problems of reduction in the flow rate and increase of the coefficient of variation are intensified in drippers with a spatial structure that favors the formation of a biofilm, even with the application of anti-clogging chemical treatments. The degree of clogging (DC) is the variation of the flow rate compared with the one of a brand-new emitter. It expresses the percent decrease of the flow rate, which can result from manufacturing problems or clogging of many types. The DC of the emitters as a function of the operation time for wastewater and fresh water is shown in Fig. 4. The emitters subjected to irrigation using wastewater showed the highest DC, with values of 20.74, 55.12 and 70.40% for G1, G2 and G3, respectively, with 1188 h of operation. In the application of fresh water, the highest DC was obtained by G1, with 18.35%,
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100 90 80 70 DC (%)
60 50 40 30 20 10 00 - 10 0
200 G1_WW
400 G2_WW
600 Operation time (h) G3_WW
800
G1_FW
1000 G2_FW
1200 G3_FW
Figure 4. Degree of clogging of three models of emitter using wastewater and fresh water as a function of the operation time.
followed by G2, with 9.57%, and G3, with 8.57%. For the operation time of 400 h, emitter clogging remained lower than 10% using wastewater, which is a possible point for the application of products or unclogging processes. Li et al. 12 concluded that the clogging of emitters using treated domestic sewage is low in the first 256 h of operation. Therefore, the worsening of the clogging process requires procedures with higher impacts in order to recover the application efficiency. During the initial observation of G1 and G3, using wastewater, and G3, using fresh water, there was a small increase in relation to the flow rates of first evaluation with the brand-new emitter, generating negative values of DC, and the highest variation was observed for G3 with fresh water, 3.86% in 180 h of operation. These variations are related to a lower pressure drop inside the tubes, resulting from the organic material adhered onto the tube walls. Observed an increment of 1% in the flow rate of a dripper subjected to irrigation with low-quality water, in 700 h of operation 7. In the analysis of variance, at 5% of significance, the factors model of emitter and type of water were statistically different, as well as the interaction between them, indicating that the direct analysis of the individual factors is not necessary, since they do not act independently. Thus, in the unfolding of the interaction, a new analysis of variance and means comparison test were performed for each factor in relation to the other. For the unfolding of the type of water with the G1 emitter, there was no significant difference between the levels of the factor water, which indicates no influence of the type of water on G1. The means were subjected to Tukey’s test, and Table 4 shows the classification of the means and the grouping for each level of the factors. For the factor wastewater, there was no significant difference between G1 and G2, but they differed from G3, which showed the highest DC mean (34.85%), for G2 and G3 using fresh water, no significant difference was observed for the response variable DC Table 4. Means comparison test for the unfolding of the interaction between the factors type of water and model of emitter. Factors Wastewater Fresh water
G1 12.85 aA 11.15 aA
G2 20.28 aA 2.35 bB
G3 34.85 aB 2.58 bB
Pairs followed by the same letter, lowercase in the column and uppercase in the row, do not differ by Tukey test at 5% of probability.
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and they differed from G1, which showed the highest mean (11.1%). Among the emitters, G1 did not differ statistically with respect to the type of water, indicating a relation with the internal configuration of the emitter. Ribeiro et al. 20 stated that the internal architecture of the drippers is a determinant factor for the characterization of the clogging process. The other models of emitters showed statistical difference, with the highest means for the wastewater. The high-resolution images from SEM show the formation of a biofilm (Fig. 5). The interactions of bacterial colonies covered the entire labyrinth, avoiding water flow and leading to a decrease in flow rate and the consequent low application uniformity. Besides the water quality promoting higher proliferation of bacteria and algae constituting the biofilm, which is the main cause of clogging in drip irrigation systems using wastewater, the dimensions of the labyrinth, which is designed to reduce the pressure and increase flow rate uniformity, are regions of easy adherence. In the water flow inside the labyrinths, there are lowvelocity regions close to the walls, which favor the deposition of small particles as reported by Li et al. 13. Thus, the removal of these regions promotes higher self-cleaning capacity. The images of the emitters using wastewater (Fig. 5b, 5d and 5f) show a biofilm covering thicker than that in emitters using fresh water (Fig. 5a, 5c and 5e); for the G3 emitter with wastewater (Fig. 5f), the detachment of the biological material offers a higher risk of clogging along the lateral line. Albuquerque et al. 1 concluded that the extracellular matrix of the biofilm is produced by the microorganisms themselves, this polymeric matrix is known as Extracellular Polymeric Substance (EPS) and is constituted of polysaccharides, proteins, exoenzymes, nucleic acids and lipids, which allow the immobilization of biofilm cells, keeping it cohesive. The shape of the grooves in the labyrinth, combined with the quality of the water used, forms a biofilm layer along the entire labyrinth, which avoids water flow. SEM and observed the biofilm continuously deposited at the entrance and at the exit of the labyrinth path, which was the main cause of emitter clogging as reported by Li et al.12. Yan et al. 24 using scanning electron microscopy, reported that the structure of the biofilm matrix is formed by linked exopolysaccharides and sediments developed in the flow path of the emitter. In addition, these authors reported the correlation between biofilm biomass and the discharge reduction after 360 h of operation using treated sewage effluent. Further studies relating labyrinth size and water quality are necessary, especially on the adherence and proliferation of bacterial colonies, called biofilms, which is the main cause of clogging in emitters subjected to irrigation with wastewater. The deposition of chemical elements is another important factor that should be studied. Another relevant issue to be studied in the future is the economic depreciation of the clogged pipes, which leads to many problems for the hydraulic system and the irrigated crops. Conclusions The initial hydraulic characteristics do not change with the use of treated domestic sewage as water source for drip irrigation. Along the operation time, the domestic sewage wastewater showed the highest variability, with a coefficient of variation higher
Journal of Food, Agriculture & Environment, Vol.13 (3&4), July-October 2015
Figure 5. Images of the biofilm adhered onto the walls of the emitter labyrinth, magnified 40x by the scanning electron microscope, for fresh water: (a) G1, (c) G2 and (e) G3; and wastewater: (b) G1, (d) G2 and (f) G3.
than 15%, with 792, 720 and 612 h of operation, for the emitters referred to as G1, G2 and G3, respectively. For the G1 emitter, there was no statistical difference between the application of wastewater and fresh water for the response variable degree of clogging.
Through the scanning electron microscopy analysis, a biofilm covering the entire groove of the labyrinth was observed, which was more intense for the emitters subjected to irrigation with wastewater from treated domestic sewage. The shape of the grooves in the emitter labyrinths combined
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with the quality of the water used are the main characteristics for clogging, and the connection between these factors is essential for studies on the clogging of drip irrigation systems. Acknowledgements The Conselho Nacional de Desenvolvimento Cientifico e Tecnológico - CNPq for the financial support the project execution Nº. 94/2013 MEC / SETEC / CNPq and the Instituto Nacional do Semiárido - INSA for the material and logistical support. References Albuquerque, A. C., Andrade. C. and Neves. B. 2014. Biocorrosion from biofilm’s integrity to integrity of materials. Corrosão e Protecção de Materiais 33(1):18-23. 2 American Society of Agricultural and Biological Engineers - ASAE 2008. Design and Installation of Micro Irrigation Systems. EP405.1 APR1988, ASABE, St. Joseph. 5 p. 3 Associação Brasileira de Normas Técnicas - ABNT 2006. NBR ISO 9261. Agricultural irrigation equipment - emitting and emitting tubes - Specifications and test methods. São Paulo, Brazil. 4 Ayers, R. S. and Westcot, D. N. 1989. Water Quality for Agriculture. FAO 29 – United Nations Agriculture and Food - Irrigation and Drainage, University of California, Davis, California, USA, 218 p. 5 Batista, R. O., Soares, A. A., Souza, J. A. R. and Batista, R. O. 2008. Empirical models for trickle irrigation with treated sanitary sewage. Engenharia na Agricultura 16(3):369-377. 6 Batista, R. O., Souza, J. A. R. and Ferreira, D. C. 2010. Effect of treated domestic sewage on the performance of a drip irrigation system. Revista Ceres 57(1):18-22. 7 Busato, C. C. M. and Soares, N. A. 2010. Drip lines performance using water of low chemical and biological quality. Biosci. J. 26(5):739-746. 8 Capra, A. and Scicolone, B. 1998. Water quality and distribution uniformity in drip/trickle irrigation system. Journal Agriculture Engineering Research 70:355-365. 9 Feitosa, A. P., Lopes, H. S. S., Batista, R. O., Costa, M. S. and Moura, F. N. 2011. Performance evaluation of system for treatment and utilization of grey water in rural area of Brazilian semiarid. Espírito Santo do Pinhal 8(3):96-206. 10 Gamri, S., Soric, A., Tomas, S., Molle, B. and Roche, N. 2014. Biofilm development in micro-irrigation emitters for wastewater reuse. Irrigation Science 32:77-85. 11 Katz, S., Dosoretz, C., Chen, Y. and Tarchitzky, J. 2014. Fouling formation and chemical control in drip irrigation systems using treated wastewater. Irrigation Science 32:459-469. 12 Li, Y. K., Liu, Y. Z., Li, G. B., Xu, T. W., Liu, H. S., Ren, S. M., Yan, D. Z. and Yang P. L. 2012. Surface topographic characteristics of suspended particulates in reclaimed wastewater and effects on clogging in labyrinth drip irrigation emitters. Irrigation Science 30(1):43–56. 13 Li, Y., Yang, P., Xu, T., Ren, S., Lin, X., Wei, R. and Xu, H. 2008. CFD and digital particle tracking to assess flow characteristics in the labyrinth flow path of a drip irrigation emitter. Irrigation Science 26:427-438 14 Li, Y.,Yang, P. and Ren, S. 2006. Hydraulic characterizations of tortuous flow in path drip irrigation emitter. Journal of Hydrodynamics 18(4):449-457. 15 Liu, H. and Huang, G. 2009. Laboratory experiment on drip emitter clogging with fresh water and treated sewage effluent. Agricultural Water Management 96(5):745-756. 16 Muyen, Z., Moore, G. A. and Wrigley, R. J. 2011. Soil salinity and sodicity effects of wastewater irrigation in South East Australia. Agricultural Water Management 99(1):33-41. 17 Nakayama, F. S., Boman, B. J. and Pitts, D. Maintenance. In Lamm, F. R., Ayars, J. E. and Nakayama, F. S. (eds) 2006. Microirrigation for Crop Production: Design, Operation, and Management. Elsevier, Amsterdam, pp. 389-430. 1
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Journal of Food, Agriculture & Environment, Vol.13 (3&4), July-October 2015
