An ASABE Conference Presentation Paper Number: Italy 12-13842
Evaluation of Drip Irrigation Clogging under Egyptian Conditions Mohamed A. Rashad Agricultural Engineering Dept., Faculty of Agric., Suez Canal Univ., 41522 Ismailia, Egypt.
[email protected].
Mohamed W. M. Elwan Department of Horticulture, Faculty of Agric., Suez Canal Univ., 41522 Ismailia, Egypt.
Khalid E. Abd El-Hamed Department of Horticulture, Faculty of Agric., Suez Canal Univ., 41522 Ismailia, Egypt.
Samy A. M. Abd El-Azeem Soil and Water Dept, Faculty of Agric., Suez Canal Univ., 41522 Ismailia, Egypt
Written for presentation at the ( 21st Century Watershed Technology Conference and Workshop Improving Water Quality and the Environment) (Sponsored by ASABE and IRSA/CNR ) (Bari, Italy) (May 27th- June 1st, 2012) Abstract. Due to scarcity of water and energy resources in Egypt, the objective of this study was to determine the ability of using unfiltered Nile Water (NW) and greywater (GW) with Drip irrigation. Drip irrigation is widely used in the new reclaimed areas with low operating pressure close to (20kPa). Field experiment was conducted from October 2010 to July 2011 in the Experimental farm, Suez Canal University to examine these conditions on the clogging of three emitters (EM) was used to irrigate three vegetable crops. Results obtained showed that, the clogging percentages were 75% and 35% with the emitter type (EM1), 69% and 39% with EM2 and 15% and 9% with EM3 when using NW and GW respectively. Pea plants showed a significantly higher yield (ton/ha) with NW, tomato plants, on the other hand, gave a significantly higher yield with GW. Cantaloupe plants showed varied results; GW gave 17% higher yield in contrast to fresh NW. The current study shows that the local emitter (EM3) is better than the other types and suggested that GW is a potential source for crop production by drip irrigation with some design and health considerations. Keywords. Low Pressure, Unfiltered water, Clogging, Vegetable Yield. The authors are solely responsible for the content of this technical presentation. The technical presentation does not necessarily reflect the official position of the American Society of Agricultural and Biological Engineers (ASABE), and its printing and distribution does not constitute an endorsement of views which may be expressed. Technical presentations are not subject to the formal peer review process by ASABE editorial committees; therefore, they are not to be presented as refereed publications. Citation of this work should state that it is from an ASABE conference presentation. (Conference Name). EXAMPLE: Author's Last Name, Initials. 2010. Title of Presentation. 10xxxx. St. Joseph, Mich.: ASABE. For information about securing permission to reprint or reproduce a technical presentation, please contact ASABE at
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1- Introduction The quantity of freshwater available worldwide is declining, raising the pressing need for its more efficient use. Egypt has an arid climate with limited irrigation water sources that depending on Nile water (NW) as a main source of irrigation (AQUASTAT, 2012). One method of conserving water is by recycling greywater (GW) for irrigation. The GW is coming from bathroom/lavatory basins (sinks), showers, and tubs and clothes washing machines typically contain less pathogens, chemicals, and fats, oil, and grease. Flows from these sources are defined as light GW, whereas blackwater consists of toilet water (DOH, 2011). This is particularly important in arid zones, were water is scarce and recycling GW for private and public landscape irrigation could reduce potable water use by up to 50% (DHWA, 2002). Due to the variation in GW types, there is big fluctuation in water quality. In the new reclaimed areas it must use modern irrigation systems; since the traditional surface irrigation has low water-use efficiency (Ragab and Prudhomme, 2002). Throughout the irrigation methods, drip irrigation is a very efficient in applying water and nutrients to crops. Most of the Egyptian farmers who are living in the new reclaimed areas are smallholder, they are facing poverty, and enforcing the use of a low head drip irrigation systems without filters. Consequently, the major problem occurring under field conditions is emitter clogging. Emitter clogging varies based on water quality, emitter type, filtering methods and environmental conditions. Frequently, clogging is caused by a combination of these factors. The type of emitter clogging problems will vary with the source of the irrigation water (Yan et al. 2010). Nakayama and Bucks (1991), Boswell (1990), Capra and Scicolone (1998) classified water quality to three classes: minor, moderate and severe. Emitters vary from sophisticated to very small, simple orifices. By using low quality irrigation water, turbulent flow regime emitter was more resistant to clogging than the laminar flow emitter and pressure compensating emitter (Mohamed A. Rashad, 2006). While most studies focus entirely on GW reuse for landscape irrigation, only a small number of studies inspected the effect of GW irrigation on edible crops and the possible transmission of human pathogens. Field's studies conducted using wastewater for vegetable irrigation have found higher bacterial counts on crop portions that grow underground or near the surface of the soil (Rosas et al., 1984). On the other hand, Jackson et al. (2006) found no significant difference in bacterial levels on plant surfaces grown in plots irrigated with GW and non-GW. Comparable results have been found by Finley et al. (2009) where no significant difference in contamination levels was identified between irrigated crops with GW and non-GW. In the same study, the plant growth and yield were unchanged by water quality (Finley et al., 2009). The same was found by Misra et al. (2010) and Rodda et al., (2011). Contradictory results were attained by Salukazana et al. (2006) regarding the growth and yield of vegetables irrigated with GW comparing with nonGW.
2. Materials and methods 2.1 Experimental Location and Setup Two experiments were conducted in laboratory and Experimental farm, Suez Canal University, Ismailia, Egypt from October 2010 to July 2011. The first experiment was a laboratory calibration of the three emitters used in the field experiment. The discharge for 40 of each emitter was measured at five operating pressure 20, 40, 60, 80 and 100kPa in three replications, then the emitter discharges equation constants (k and x) and manufacturing coefficient of variation (Cv) was calculated (see Table 1).
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Table 1. Some hydraulic characteristics of tested emitter types with municipal water. Cv Parameters Nominal Measured Emitter Type q (ℓ/h) q (ℓ/h) Value Classification k x EM1 (Normal) 4 4.1 0.018 Excellent 1.52 0.44 EM2 (NEIN) 4 4.17 0.05 Average 1.29 0.51 EM3 (Alquds) 4 25 0.34 Unacceptable 2 0.54 In the second experiment, a drip irrigation system was constructed in the field. Three turbulent flow emitter types with a same nominal discharge were chosen for the experiment due to its wide use for their quality and price in Egypt. Water operating pressure at the lateral inlet was 20kPa. Figure (1) illustrates a schematic layout of the drip irrigation system, including three similar subunits for each one of NW and GW source. Each subunit consists of five laterals with 20m length at distance of 1 meter, and each lateral has composed of 40 emitters, 0.5m apart. Each subunit was equipped with a water meter, valve and pressure gauge. All subunits were connected to a control station equipped with a pump, and pressure gauges.
⇨Put figure here—it will be centered automatically⇦
Figure 1. Schematic layout of the field experiment.
2.3 Emitter Characteristics The emitter discharges performance is characterized by the k and x parameters of Keller and Karmeli (1974) Equation:
q k hx
------ (1)
Where: q = emitter discharge rate (L/h.); h = h is entry water pressure (m), k = a dimensionless constant of proportionality that characterizes each emitter and x = a dimensionless emitter discharge exponent that is characterized by the flow regime.
The manufacturing coefficient of variation (CV) of new emitters determined using ASABE (2003):
C
V
S
-------------- (2)
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where: CV=manufacturer’s coefficient of variation (Dimensionless); S = the standard deviation of the emitters discharge in the sample (ℓ/h) and
= emitter discharges mean (ℓ/h).
2.4 Emitter Clogging Evaluation After all the experimental measurements were completed, some lateral sections and emitters were analyzed for visual evidence of clogging. Moreover, three criteria to measure emitter clogging were used as follows: average of the emitter discharges; percentage of clogged emitters and percentage of discharge reduction from the initial at the experiment beginning were calculated by (eq. 3):
q
r
q q d b 100 ------ (3) q b
Where: qr = percentage of discharge reduction from the initial at the experiment beginning(%); qd = emitter discharges at the season date, (ℓ/h) and qb= emitter discharges at the experiment beginning date, (ℓ/h).
2.5 Water Resources The unfiltered NW source for the field experiments was obtained from one branch of Ismailiacanal. Meanwhile, the GW source was obtained from Mosque ablution basin which classified as a light GW (Fig. 1). Table (2) shows the chemical, physical and biological analysis of irrigation water samples. Table 2. Influence of water quality on emitter clogging. Parameters
Units
Water Source
Minor a* b** < 7.0 N.C. N.C. < 1.0
Risk of Emitter Clogging Moderate Severe a b a b 7.0-8.0 N.C. > 8.0 N.C. N.C. 1.0-4.5 N.C. > 4.5
NW GW pH 8.01 7.11 EC dSm-1 0.36 0.38 Physical: TSS ppm 120 64 < 50 < 200 50-100 200-400 > 100 > 400 Chemical: Ca ppm 19.40 17.80 N.C. < 250 N.C. 250-450 N.C. > 450 Mg ppm 2.40 9.36 N.C. < 25 N.C. 25-90 N.C. > 90 Biological: Bacterial CFU ml-1 44 x 102 71 x 104 50 000 N.C. Populations a*: Nakayama and Bucks (1991), b**: Capra and Scicolone (1998); TSS: total suspended solids; CFU ml-1: colony forming unit per milliliter: ppm: part per million. EC: electrical conductivity, dS/m: deci Siemens per meter and N.C. = Not classified. NW = Nile Water and GW = greywater.
2.6 Vegetable Crops Three vegetable crops (pea, tomato and cantaloupe) were grown in the field during the study in each subunit. Pea seeds were cultivated in the field directly while; tomato and cantaloupe were transplanted in the greenhouse after the germination (in the growth stage). Recommended practices in terms of disease and insect control were followed for each crop.
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2.7 Statistical Analysis Data were statistically analyzed using ANOVA/MANOVA of Statistica 6 software (Statsoft, 2001) with mean values compared using Duncan's multiple range with a significance level of p≤ 0.001, 0.01 and 0.05.
3. Results and Discussion Table (2) shows some criteria of water quality influence on emitter clogging for NW and GW. The values of pH with criteria (a) were moderate for GW and severe for NW. While EC for NW and GR were minor with criteria (b). TSS for NW and GW was classified as minor risk with criteria (b) while by criteria (a) NW was severe and GW was moderate. The concentration of Calcium (Ca) and Magnesium (Mg) in NW and GW were minor with criteria (b).The bacterial populations were minor with NW by the criteria (a) and severe for GW.
3.1 Emitter Performance The laboratory experiment showed no significant differences between Emitter types EM1 and EM2 in nominal and real discharge at operating pressure 100kPa (table 1). Whereas there were big difference's values measured for EM3 from 4 to 25 L/h. The manufacturing coefficients of variation Cv of the emitter discharges was classified as excellent for EM1, average for EM2, Clogging NW Clogging while it was unacceptable with EM3. Furthermore, the flow regime wasGW proportionally turbulent for all emitter types. 50
EM1 EM2 EM3
60
EM1 EM2 EM3
40
Emitter Clogging (%)
Emitter Clogging (%)
80
40
20
0
30 20 10 0
NW Nov
Dec
Jan
Feb Mar
GW Apr
Date (Month)
May
Jun
Jul
Nov
Dec
Jan
Feb Mar
Apr
May
Jun
Jul
Date (Month)
Figure 2. Clogging percentage of different emitter types with Nile Water (NW) and greywater (GW). The results showed at the field experiment end that the clogging percentages were 75% and 35% with the emitter type (EM1), 69% and 39% with EM2 and 15% and 9% with EM3 when using NW and GW respectively (Fig. 2). Table (3) showed the average of the emitter discharge. Each value represents the mean flow rate over 30-day period of emitters in a subunit for three different types of emitters. The discharge reduction percentage from the initial at the beginning of the experiment was calculated to show similar results for all types of emitters with GW. It was 86.21 and 79.31% for EM1, 78.43 and 80.00% for EM2 and 77.76 and 79.31% for EM3 with NW and GW (Fig 3). Unexpected outcome results identified at the end of the field experiment compared to the laboratory experiment. Emitter type EM1 and EM2 showed better results with Laboratory experiment, Where EM3 was unacceptable. The result showed that with both NW
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100 EM1 EM2 EM3
95
90
85
80
NW 75 Nov Dec
Jan
Feb Mar
Apr
May
Jun
Discharge Percentage from Initial (%)
Discharge Percentage from Initial (%)
and GW, EM3 was better than other types under these conditions of low operating pressure and GW Emitter Q from Initial Discharge Reduction Percentage unfiltered NW water. 100 EM1 EM2 EM3
95
90
85
80
GW 75
Jul
Nov Dec
Jan
Date (Month)
Feb Mar
Apr
May
Jun
Jul
Date (Month)
Figure 3. Discharge percentage of unclogged emitters from initial discharge with Nile Water (NW) and greywater (GW). On the other hand, the effect of GW was less than NW on emitter clogging. The reason for these results may be due to the sophisticated design of imported emitters (EM1 and EM2) compared to local one (EM3). Also the EM3 flow passages were larger than the imported types. The main reason of emitter clogging in GW was due to increase the bacterial population, but with NW was due to increase the bacterial population combined with physical particles. Table 3. Discharge (L/H) of unclogged emitter types with different irrigation water. Emitter Type Water Date 15/10/2010 15/11/2010 15/12/2010 15/01/2011 15/02/2011 15/03/2011 15/04/2011 15/05/2011 15/06/2011 15/07/2011
EM1
EM2
EM3
NW
GW
NW
GW
NW
GW
2.9 2.8 2.70 2.60 2.70 2.80 2.70 2.60 2.55 2.50
2.90 2.80 2.65 2.70 2.64 2.55 2.50 2.40 2.35 2.30
2.04 1.9 1.85 1.80 1.90 1.75 1.85 1.70 1.65 1.60
2.00 1.90 1.80 1.85 1.80 1.70 1.65 1.60 1.70 1.60
5.8 5.2 4.85 5.10 5.00 4.82 4.64 4.55 4.62 4.51
5.80 5.75 5.70 5.60 5.55 5.60 5.30 5.10 4.80 4.60
EM = the emitter type , NW = Nile Water and GW = greywater.
3.2 Crop Yield Table (4) summarized the effects of irrigation water source on yield of vegetables tested in the current study. Different species responded in different manners to water sources. While pea plants showed a significantly higher yield (ton/hectare) with NW, tomato plants, on the other
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hand, gave a significantly higher yield with GW. Cantaloupe plants showed varied results. GW gave 17% higher yield in contrast to NW. The inconsistent yield reaction of different vegetables used in the present study was reported by Salukazana et al., (2006) where, one trial showed that nutrient irrigated plants gave a considerably superior enhancement in plant growth compared to GW irrigated plants. In the second trial, irrigation with GW produced significantly higher yield and overall plant growth in comparison with what was achieved with nutrient solution. Table 4. Crop yields (ton/ha.) for emitter types with Nile and greywater resources.
Water source
Nile water
Greywater
Emitter type
EM1 EM2 EM3 EM1 EM2 EM3
Water source (WS) Emitter type (ET) WS*ET
Crop yield (ton/ha.)
Crop yield (ton/ha.)
Pea Tomato 6.41 22.20 8.34 36.06 11.30 37.55 6.32 50.99 5.66 37.52 8.65 55.19 Significance (P value) 0.000*** 0.000*** 0.000*** 0.076 ns 0.000*** 0.004**
Crop yield (ton/ha.) Cantaloupe 2.93 4.68 7.10 5.76 5.02 7.25 0.011* 0.008** 0.000***
Conclusion Two experiments were conducted in the current study; a laboratory and field experiment on three emitter types with unfiltered NW and GW. The laboratory experiment showed that the emitter types (EM1and EM2) were excellent and has superior characteristics than the local one (EM3). The field experiment results showed that the unfiltered water was the main causes of the emitters clogging. The season of irrigation started from October 2010 until July 2011. This period was characterized by high temperature, which causes biological clogging of emitters. The reduction in discharge with GW was low compared to NW for all emitter types. The main reason of emitter clogging in GW was due to increase the bacterial population in the GW, but with NW was due to increase the bacterial population combined with physical particles. The clogging percentages were 75% and 35% with EM1, 69% and 39% with EM2 and 15% and 9% with EM3 when using NW and GW respectively. EM3 performed the best emitter among the investigated types for irrigation under the Egyptian condition of a smallholder. These differences in emitters clogging are making difficulties to the farmer to choose the appropriate emitter type; especially the imported emitter price in the local market equal 45 fold of that for the local one in average. Hence, under the Egyptian condition, it is preferable to use simple turbulent drip emitter design with a wide exit hole to avoid clogging. These results also indicate that the crop yield with GW was acceptable but some design and health care should be considered. As an example, applying GW directly to irrigate the vegetative parts must be avoided. The study suggested using mulching layer to prevent the direct contact of GW irrigation.
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