Author's personal copy agricultural water management 93 (2007) 65–72
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Effects of reclaimed wastewater irrigation on soil and tomato fruits: A case study in Sicily (Italy) Rosa Aiello, Giuseppe Luigi Cirelli, Simona Consoli * Department of Agricultural Engineering, University of Catania, Italy, Via S. Sofia 100, 95123 Catania, Italy
article info
abstract
Article history:
The study aims to investigate the effects of reclaimed urban wastewater for irrigation on
Received 1 June 2006
tomato fruit quality and hydrological soil behaviour. Tomato plants were drip and sub-drip
Accepted 24 June 2007
irrigated under field conditions during the 2004 growing season in Eastern Sicily (Italy).
Published on line 8 August 2007
Different drip and sub-drip laterals and filtering technologies were tested during the trial; the most suitable irrigation technology was identified by data processing including emission
Keywords:
uniformity, flow reduction and filter performance computations. The hydraulic properties
Contamination
and microbial soil contamination were determined before and after wastewater application.
Irrigation
Tomato crop production quality and microbial plant contamination were investigated
Row crop
during the trial. Wastewater application resulted in increased microbial contamination
Soil
(Escherichia coli 3 103 MPN/100 mL; Faecal Streptococci 1.2 103 MPN/100 mL) on the soil
Wastewater
surface. A disturbed layer of soil was observed characterized by reduced soil porosity and a consequent decrease in water retention and hydraulic conductivity. The negligible microbial contamination of fruit and washing solution (up to 40 MPN/100 mL) suggested that the treated wastewater can be used as a valid alternative for irrigation of tomatoes. # 2007 Elsevier B.V. All rights reserved.
1.
Introduction
In recent years, a number of Mediterranean countries have experienced severe water supply and demand imbalances, with more frequent and longer lasting periods of drought. In particular, several regions in Italy have suffered successive droughts over the last 10 years (Coppola et al., 2004). Due to water scarcity, agricultural activities (using more than 50% of the total water resource extracted) are penalized, while higher priority demands (domestic and industrial) are satisfied. Among various water conservation practices, the use of non-conventional water resources, such as treated wastewater must be probed (Mahasneh et al., 1989; Al-Lahlam et al., 2003). Wastewater reuse for agriculture offers the greatest scope for application because it usually has the potential to meet growing water demands, conserve potable supplies, reduce disposal of pollution effluent into surface water bodies,
allow lower treatment costs and enhance the economic benefits for growers due to reduced application rates for fertilizer (Jime´nez-Cisneros, 1995; Paranychianakis et al., 2006). Benefits apart, treated wastewater can be used for irrigation under controlled conditions to minimise hazards from pathogenic and toxic contaminants of agricultural products, soils, and ground water (Al-Nakshabandi et al., 1997). The main health risks are associated with contamination of crops or groundwaters by wastewater due to its chemical composition being somewhat different from most natural waters used in irrigation (Pereira et al., 2002). Urban wastewater generally contains high concentrations of suspended and dissolved solids (chloride, sodium, boron and heavy metals) and little of any added salt is removed during conventional (secondary and tertiary) treatments. Pathogenic organisms (Helminths, Enteric bacteria, Enteric viruses) constitute one of the main
* Corresponding author. Tel.: +39 0957147547; fax: +39 0957147600. E-mail address:
[email protected] (S. Consoli). 0378-3774/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.agwat.2007.06.008
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agricultural water management 93 (2007) 65–72
health concerns in the use of wastewater for irrigation. Furthermore, hydrological soil properties are specially sensitive to wastewater compounds. Indeed, numerous studies (Pescod, 1992; Bresler, 1981; Tarchitzky et al., 1984; Vinten et al., 1991) have highlighted hydraulic conductivity reduction in wastewater irrigated soil, ascribing it to a partial biological clogging of soil pores due to increased biomass and suspended solids. However accurate effluent management strategies, including wastewater treatment level, crops grown, irrigation methods, and cultivation and harvesting practices, can reduce contamination of irrigated vegetables and soil (Phene et al., 1992; Ayars et al., 1999; Pereira et al., 2002; Assadian et al., 1999). To quantify the effects of reclaimed urban wastewater on crop production, hydrological soil behaviour and irrigation methods, a monitoring program was carried out on an open field located in S. Michele di Ganzaria (Eastern Sicily). The main objectives of this research included: (i) to assess the field performance of different commercially available filters and emitters used within drip (DI) and sub-drip (SDI) irrigation with reclaimed urban wastewater; (ii) to study the effect of irrigation by treated wastewater, as compared to fresh water, on the quality and microbial contamination of tomato fruit; (iii) to determine the persistence of microbial contaminants in the irrigated soil and evaluate potential changes in hydraulic soil properties.
2.
Methodology
2.1.
Irrigation system description
The experiment was conducted in an open field near the constructed wetland (CW) system of S. Michele di Ganzaria (Eastern Sicily), during spring-summer 2004. The CW unit (surface area of about 2000 m2 and 0.6 m deep) treats secondary urban effluents from the conventional wastewater treatment plant of the municipality (about 5000 inhabitants) (Cirelli et al., 2006). The average CW effluent characteristics during the monitoring period are shown in Table 1. The E. coli concentrations for 90% of the analysed water samples were below the limit of 50 CFU/100 mL required by Italian law for 80% of samples (Ministerial Decree number 185 in effect since 2003 for the reuse of Constructed Wetland effluents); however for the remaining 10%, E. coli concentrations reached values higher (about 103 CFU/100 mL) than the permitted upper threshold of 200 CFU/100 mL. Two parallel testing systems (named T1 and T2 as reported in Fig. 1) were installed within the experimental area. Each one consisted of four plots (from S1 to S4 within T1 and from S5 to S8 within T2) irrigated by CW treated wastewater. A control system T3 (plot S9), supplied with fresh water (Table 1 for fresh water composition), was also installed within the experimental area. Each plot (total size of 108 m2) was made of four 45-m long, 16-mm external diameter surface, or subsurface (buried at 0.15 m from the surface level), polyethylene laterals with in-line labyrinth drippers (discharge rate of 2.1 L/h at a pressure of 101.2 kPa), with emitters spaced at
Table 1 – Average quality characteristics of constructed wetland effluent and fresh water used during the experiment Parameter TSS (mg L1) BOD (mg L1) COD (mg L1) pH EC (dS m1) NTOT (mg L1) PTOT (mg L1) Faecal Coliform (CFU/100 mL) Escherichia coli (CFU/100 mL) Faecal Streptococci (CFU/100 mL) Salmonella (CFU/100 mL)
Irrigation water (CW effluent) 3.3 7.8 15.7 8.2 1.1 8.6 7.8 132 132 137 0
Fresh water 0.1 8.0 14.0 7.8 1.6 0.1 5.8 n.d. n.d. n.d. n.d.
TSS: total suspended solids; BOD: biochemical oxygen demand; COD: chemical oxygen demand; EC: electrical conductivity; NTOT: total nitrogen; PTOT: total phosphorus, n.d.: not detected.
0.33 m. The buffer zone spacing was 0.7 m between the laterals and 1.0 m in the middle corridor. Four different drip laterals types were provided by Irritec & Siplast, an Italian company with production firms located in different countries. They were: - surface light pipe P1 (plots S1, S5 and S9) which permits notable branch lengths with small loss in pressure; - sub-surface light pipe P1 FLAP (plots S4 and S8) which includes a check-valve for emitter closure protection from soil particles intrusion; - sub-surface high quality rigid pipe MONO (plots S3 and S7), with incorporated dripper during the extrusion cycle; - sub-surface high quality light pipe P1 Rootguard (RTG) (plots S2 and S6). The RTG technology uses Treflan, a chemical substance, in order to prevent root growth near the drip line emission points. This technology allows distribution of water and nutrients near the root zone. The two parallel testing system (T1 and T2) were supplied with different filtration technologies. The two filtering systems (manufactured by Irritec) were installed on the mainline (Ø 32 mm) (Fig. 1) and tested at the same inlet pressure, flow rate and water quality. They were: (1) a 120 mesh screen filter with a filtration surface area of 0.045 m2 (system T1), (2) a 120 mesh disk filter with a filtration surface area 0.05 m2 (system T2). Both systems were manually cleaned. Water flow rate and water pressure were monitored by control valves and manometers. All testing plots were operated automatically by electronic valves. The following quantities were measured to determine filters performance: (a) rate of pressure loss across the tested manual filters, (b) time and effort required, by a skilled operator, to clean the manual filters and (c) need for operation and maintenance (O&M) servicing. Emission Uniformity (EU, %) and Reduction factor (Rd, %) were determined to monitor the surface and subsurface drip lines performance. EU is the ratio (Eq. (1)) between average discharge of the emitters low quarter (Qmin1/4) and that of the
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agricultural water management 93 (2007) 65–72
Fig. 1 – Layout of the experimental irrigation system at S. Michele di Ganzaria.
whole pattern (Qm), both expressed in L s1 (Keller and Karmeli, 1975). EU ¼ 100
Q min1=4 Qm
(1)
EU was detected weekly by measuring the discharge of 16 emitters for each surface lateral. The EU indicator of subsurface laterals was evaluated before they were buried and at the end of the irrigation season. Rd (%) is defined as Q Rd ¼ 100 1 m Qt
(2)
where Qt is the discharge (0.33 L s1) of new unclogged emitters operating at the same pressure (101.2 kPa). Furthermore, in order to rank emitter clogging, daily and seasonal averages as well as standard deviations of surface and subsurface drip lines discharge rate were computed.
2.2.
Irrigated soil sample analysis
The experimental field was sandy-loam with a volumetric soil water content at field capacity of about 29%, a water holding capacity of 170 mm m1 on an oven dry weight basis, and a surface infiltration rate at saturation level of 0.13 cm min1. Table 2 shows the main soil characteristics to estimate NPK amounts required for fertilization (SCS, 1982). Prior to planting, N (26 kg ha1), P2O5 (35 kg ha1) and K2O (35 kg ha1) 1) were applied uniformly to the experimental field. To ascertain the changes induced in soil hydraulic and transport properties at the end of wastewater application cycle, soil characterization analyses were performed by laboratory test. About 60 undisturbed soil samples were collected (using stainless steel cylinders of 103 m3 inner volume) at beginning and end of wastewater application,
along a diagonal transept (north–south oriented) in the field at a depth of 0.30 m. In this study we used Van Genuchten’s (1980) analytical expression to describe soil water retention: u ur m ¼ ½1 þ jahjn us u r u ¼ us h 0 Se ¼
with h < 0
(3)
where Se is the effective saturation; a (cm1), n and m are shape parameters, us and ur are saturated and residual volumetric water content. Combined with the statistical pore-size distribution model for unsaturated hydraulic conductivity (Mualem, 1986), with the restriction m = 1 1/n, the analytical expression for hydraulic conductivity k(u) curve becomes: m
2
kG ðSe Þ ¼ Ste ½1 ð1 ð1 Se1=m Þ Þ
(4)
Table 2 – Characteristics of selected soil samples collected during the field campaign Sand (%) Silt (%) Clay (%) CaCO3 (g kg1) NTOT (g kg1) C (g kg1) P2O5 (g kg1) K2O (g kg1) pH EC (dS m1) C/N SAR
70.7 16.8 12.5 23.0 0.2 3 0.02 0.11 7.4 0.37 15 0.5
CaCO3: calcium carbonate; NTOT: total nitrogen; C: organic carbon; P2O5: phosphorus pentoxide; K2O: potassium oxide; EC: electrical conductivity; C/N: carbon to nitrogen ratio; SAR: specific absorption rate.
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where kG is relative hydraulic conductivity, and t accounts for the dependence of tortuosity and correlation factors of water content. Eq. (4) estimates hydraulic conductivity when kS is known. In laboratory, soil samples were slowly saturated from the base up in four increments. Then, saturated water content uS and hydraulic conductivity at saturation kS were determined with the falling-head method (Klute and Dirksen, 1986). Soil contamination analysis assessed Escherichia coli, Faecal Streptococci (FS) and Salmonella concentrations within soil columns (from 0.1 to 0.4 m of depth) taken near the emitters. Laboratory processing for soil microbial and constituent analyses were performed as outlined in APHA (1998). Soil sample (about 20 g) microbial levels (MPN/100 mL) were enumerated using the phosphate (about 180 mL) buffer solution (PBS) technique.
2.3.
Row crop conditions
During the trial, two varieties of tomato plant, ‘‘Incas’’ and ‘‘Missouri’’, were transplanted into the open field (about 1500 m2), at a density of 3.6 plant/m2. Irrigation wastewater was applied in a randomized block design (Fig. 2); each block was split into sections (surface area of 6.0 m 0.7 m) that consisted of one tomato variety and plastic mulching or bare soil. Wastewater irrigation scheduling was based on water balance equation (Eq. (5)): I ¼ ETc P DSW þ Dp þ Rf
(5)
where I is irrigation water applied (mm), ETc, crop evapotranspiration (mm) rate calculated as product of Penman-Monteith-based reference evapotranspiration (ET0) (Allen et al., 1998) and the FAO-56 crop coefficient (Kc). ET0 reference data were determined by daily climatic factors consisting of solar radiation (RS), air temperature (T), relative humidity (RH), wind speed (U2) and direction, rainfall (P), using an on-site CR510 automatic weather station (Campbell Scientific, Logan, UT). To monitor soil water content (DSW) during water infiltration, time domain reflectometry (TDR) probes were inserted horizontally at different depths, starting at 0.15 m from the surface. In addition, tensiometers for measuring pressure heads
Fig. 2 – Block scheme of the first treatments combination for ANOVA application.
were also horizontally inserted in a soil column between 0.15 and 0.30 m of depth. The terms Dp and Rf represent deep percolation (mm) and runoff (mm), respectively. Since irrigation water was controlled, deep percolation and runoff were assumed negligible. Irrigation water volumes were administered at a frequency of 1 day (with applications of 30 min) during initial rapid-growth season and midseason (DOY 120– 235) and 2 days during late season (DOY 236–265). Standard cultivation practices were adopted during cropgrowing season. Tomatoes were hand harvested at full red maturity starting from the end of July until the end of September at weekly intervals. During each harvest, five fruits from each section were used to sample the main crop production features, such as marketable total yield (MTY, Mg/ha), crop mean weight (MW, g) and no marketable total yield (N-MTY, tomatoes/m2). The effect on tomato crop production features (MTY, MW and N-MTY) of different treatments combination, two water qualities (treated wastewater and fresh water), two crop cultivars (Incas and Missouri), two soil coverages (bare and plastic mulching) and four drip lines (P1, P1 FLAP, P1 RTG and MONO), was evaluated during the trial. The analysis did not include different filtration technologies (screen and disk filters) because of their quite similar performance, in terms of pressure rate loss across the filters, and time and effort required for maintenance. In particular, the following treatments combinations were analysed: 1. first combination concerned plots S1 and S9, that presented the same drip line type (P1—surface light pipe); the analysed treatments (reported in the block scheme of Fig. 2) were: two water qualities (wastewater and fresh water), two crop cultivars (Incas and Missouri) and two soil coverages (bare and plastic mulching); the block was replicated three times. 2. second combination concerned plots S2, S4, S6 and S8, supplied by wastewater and covered by plastic mulching; the analysed treatments were: two crop cultivars (Incas and Missouri) and two drip lines (P1 FLAP, P1 RTG); 3. third combination concerned plots S1, S3, S5 and S7; the analysed treatments were: two crop cultivars (Incas and Missouri), two drip lines (P1 and MONO) and two soil coverage (bare and plastic mulching). Analyses of variance (ANOVA) identified the main treatments effects and their interactions on crop production; Tukey’s significant difference test was used for mean separation. Treatment means were compared by the least significant difference test at P = 0.05. Harvest tomatoes were washed with sterile water, and the washing solutions were analysed using membrane filtration techniques. Fruit skin was removed and mixed thoroughly with sterile distilled water using a sterilized mixer; the same procedure was used for fruit flesh. Samples from the two parts were used for microbial testing using the phosphate buffer solution (PBS) method (APHA, 1998). Salmonella protocol consisted of a ‘‘pre-enrichment’’ stage using a buffered peptone water solution, a non-selective culture medium to revitalize the microorganism. An inoculum
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culture was prepared in selenite and cystim medium and incubated at 36 1 8C for 48 h. After the incubation period, several cultures were inoculated and incubated in parallel on ss-agar gel to identify and enumerate any Salmonella colonies.
3.
Results
3.1.
Filter-emitter system performance
During monitoring there were slight differences in filters performance, most likely due to low amounts of TSS and organic matter (BOD5, COD) in irrigation wastewater (Table 1). Head losses below 10% of inlet pressure were observed for the filtering systems. Some difference may be ascribed to the type of filter elements because the disk filter took longer to clean. Table 3 reports mean discharge values to the entire field (Qm, L s1), reductions (Rd, %) of mean discharge and variation coefficients (CV) evaluated during the trial. Differences of up to 25% were detected between Qm and Qt in plots S2 and S6 supplied by P1 RTG sub-surface laterals, thus obtaining discharge reduction Rd rates higher than 20%. Low performance of soft pipe P1 RTG is most likely related to excessive emitter clogging because of being buried too deep. Table 4 indicates mean field emission uniformities (EU,%) of drip and sub-drip irrigated plots during the trial. Lower EU values were detected within plots S1, S5 and S4, S8 supplied by soft pipes P1 and P1 FLAP, respectively. High EU performances were obtained using MONO sub-surface rigid pipe.
3.2. Hydraulic and microbial contamination of the irrigated soil Initial hydraulic and physical soil sample parameters showed average values of conductivity at saturation kS, water content
Fig. 3 – Average values of water retention for the investigated soil samples.
at saturation uS and bulk density rb of 7.5 cm/h, 0.39, and 1.5 g/ cm3, respectively. Both for the initial and final characterization, hydraulic functions were obtained using equations illustrated in Section 2.2. In Figs. 3 and 4, dashed lines represent the retention and hydraulic conductivity curves with reference to a disturbed layer, 0.30 m deep, at the end of wastewater application. Comparison with the initial curves shows lower water retention for higher pressure head values and reduced hydraulic conductivity in response to a change in pore distribution. Fig. 5 reports mean bacteriological contents of selected soil columns (in plots S1 and S5) at the end of wastewater application. Soil samples at 0.1 m from surface level revealed mean E. coli contents of 3 103 MPN/100 mL, with a decrease of about 3 log units at 0.4 m of depth. Faecal Streptococci (FS) concentrations were found in the whole sampled soil columns, with an average concentration, at 0.1 m of depth, of 1.2 103 MPN/100 mL.
Table 3 – Drip line emitters discharge (L sS1) during the experimental period Plots
S1
Laterals type 1
Qm (L s ) Rd (%) CV
S2
S3
S4
P1
P1 RTG
MONO
P1 FLAP
0.31 6.06 0.11
0.25 24.24 0.14
0.31 6.06 0.10
0.30 9.09 0.12
S5
S6
S7
S8
S9
P1
P1 RTG
MONO
P1 FLAP
P1
0.31 6.06 0.12
0.26 21.21 0.12
0.31 6.06 0.09
0.30 9.09 0.13
0.32 3.03 0.10
Qm: average discharge in the entire field; Rd: reduction of the mean discharge; CV: variation coefficient; S1, . . ., S9: plots; P1: Surface light pipe; P1 RTG: subsurface light pipe with rootguard system (buried at 0.15 m from the surface level); MONO: subsurface rigid pipe (buried at 0.15 m from the surface level); P1 FLAP: subsurface light pipe with emitter closure system (buried at 0.15 m from the surface level).
Table 4 – Field emission uniformity of surface and sub surface laterals during the trial Plots
S1
S2
S3
S4
S5
S6
S7
S8
S9
Laterals type
P1
P1 RTG
MONO
P1 FLAP
P1
P1 RTG
MONO
P1 FLAP
P1
EU (%) CV
87 0.07
91 0.01
91 0.02
87 0.01
88 0.08
92 0.03
94 0.01
83 0.07
89 0.05
EU: emission uniformity; CV: variation coefficient; S1,. . ., S9: plots; P1: surface light pipe; P1 RTG: subsurface light pipe with rootguard system (buried at 0.15 m from the surface level); MONO: subsurface rigid pipe (buried at 0.15 m from the surface level); P1 FLAP: subsurface light pipe with emitter closure system (buried at 0.15 m from the surface level).
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Fig. 4 – Average values of hydraulic conductivity (k) for the investigated soil samples.
Fig. 5 – Average concentrations of E. coli and Faecal Streptococci (FS) on selected soil profiles between 0.1 and 0.4 m from soil surface.
3.3.
Crop yield evaluation and microbial analyses
Fig. 6 plots daily values of maximum crop evapotranspiration (ETc) fluxes during the experimental period and crop coefficient (Kc) values during rapid, middle and late crop growth phase. Crop evapotranspiration presents average values of 3.4 mm d1, with 60% of variation (CV). Soil water balance was computed for periods of about 1 day across the irrigation date, in order to take into account the temporal variability of soil hydraulic properties. A mean reduction of daily soil water
Fig. 6 – Crop evapotranspiration (ETc) and crop coefficient (Kc) values during the experiment.
content DSW of 0.48 mm of the field capacity was found, with an average pressure head of 22.4 cbar. The amount of irrigation water applied to the open field was of 5800 m3 ha1 during the whole experiment, with volume rates at each irrigation varying between 32 and 63 m3 ha1, depending on irrigation frequency. Generally, the amount of wastewater distributed by subsurface laterals was 25% less than surface lateral volumes; no significant differences in distributed water volumes were detected between surface plots and control plot S9. Table 5 reports tomato fruit production features. The mean value of marketable total yield (MTY) reached 100 Mg/ha, with mean fruit weight (MW) of 72 g, and no marketable total yield (N-MTY) of 57 tomatoes/m2. MTY data were higher than national (40–50 Mg/ha) and regional (17 Mg/ha) yield values. Crop production for Missouri genotype increased during the trial, whereas Incas genotype decreased owing to pathological diseases of the variety. Effects of the first treatment combination on tomato crop marketable total yield (Mg/ha), crop mean weight (g) and no marketable total yield (tomatoes/m2) were reported in Table 6; results of the 2nd and the 3rd combinations did not produce significant effects on selected crop production features. Analyses of Incas genotype showed an increase in MTY (that reached 85 Mg/ha) of about 58% with respect to the same genotype (36 Mg/ha) irrigated using fresh water. Similarly, MTY (171 Mg/ha) for Missouri genotype irrigated
Table 5 – MTY, MW and N-MTY of irrigated crop at the end of the experiment Water quality Wastewater
Genotype Incas Missouri
Fresh water
Incas Missouri
Average values
N-MTY (tomatoes/m2)
Soil coverage
MTY (Mg/ha)
MW (g)
Mulching film Bare soil Mulching film Bare soil
95 75 121 125
69 62 81 79
40 108 64 16
Mulching film Bare soil Mulching film Bare soil
36 35 193 148
53 54 87 92
99 75 28 26
103
72
57
MTY: marketable total yield; MW: mean weight; N-MTY: no marketable total yield.
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Table 6 – Effects of water qualities, soil coverage and tomato genotypes on MTY, MW and N-MTY of the monitored row crop Main treatments
MTY (Mg/ha)
MW (g)
104 103 n.s.
73 71 n.s.
57 57 n.s.
Soil coverage (SC) Mulching film Bare soil Significance
111 96
72 72 n.s.
57 56 n.s.
Cultivar (CV) Incas Missouri Significance
60 147
60 85
80 33
***
***
***
***
***
n.s. n.s.
**
n.s. n.s.
Water quality (WQ) Wastewater Fresh water Significance
Interactions WQ CV WQ SC CV SC WQ CV SC
*
*
n.s. n.s.
N-MTY (tomatoes/m2)
* **
n.s. not significant P < 0.05. ** P < 0.01. *** P < 0.001. *
71
features and irrigation technologies. Recycled wastewater applications generally result in a disturbed layer at a soil depth of 0.3 m, exhibiting changes in physical properties (increase in bulk density). The investigated layer shows reduced soil porosity, translation of pore size distribution towards narrower pores and a consequent decrease in permeability. Near the surface level, soil samples (collected around the emitter) show a certain growth in microbial content (E. coli and FS). Microbial crop analyses revealed slight accumulation of E. coli on tomato fruits irrigated with wastewater, with a concentration of about 40 MPN/100 for 80% of the samples. Results also showed that tomato yield increased for both varieties when irrigated with wastewater. Among the various filter-emitter technologies tested during the experiment, high values of EU and Rd were obtained using rigid high quality sub-surface pipes ‘‘MONO’’. Notwithstanding the combination of tertiary treated wastewater and irrigation technologies (DI and SDI), a not negligible level of contamination on tomato fruit and irrigation soil surface was determined; these results confirm that CW effluents cannot be used for irrigation without additional disinfection. The planned realization, within wastewater reuse project of San Michele di Ganzaria (Cirelli et al., 2006), of batch stabilization reservoirs should be the sustainable and suitable technology to integrate with CW system.
Table 7 – Microbiological examination of the irrigated crop within plots S1 and S5
Acknowledgments
Bacteriological parameter (MPN/100 mL)
The work was included in AQUATEC project (2000–2006) O.R. 3.2 and received its financial support by European Union and Italian Minister of Education and Scientific Research. The Authors thank Prof. Nunzio Romano and research staff of the University of Napoli Federico II for their collaboration in hydraulic soil sample analyses. Our special thanks to Irritec & Siplast (www.siplast.it) company for supporting the research. The Authors have contributed with equal effort to the study.
Total Coliform Faecal Coliform Escherichia coli Faecal Steptococci Salmonella Helminths a
Tomato fruita 3 10 3 5 10 2 5 10 2 5 10 2 0 0
Tomato washing solutiona 1 10 3 4 10 2 4 10 2 5 10 2 0 0
Means are the average of 20 readings.
with fresh water was about 39% higher than the MTY obtained, 123 Mg/ha, for the same genotype irrigated with wastewater. The use of mulch resulted in about a 16% increase in MTY with respect to bare soil. Furthermore, the mean MTY (193 Mg/ha) for Missouri genotype irrigated with fresh water was higher on mulched soils than on bare soils (about 148 Mg/ha). No marketable total yield for Incas genotype was higher (108 tomatoes/m2) on bare soil than on mulched soil (40 tomatoes/m2). Bacteriological analyses carried out on tomato samples and their washing solutions revealed very low concentrations of E. coli of about 40 MPN/100 mL for 80% of the samples (Table 7). Just few samples (about 10% of the total) showed higher E. coli content (about 5 102 MPN/100 mL).
4.
Conclusions
The principal objective of this research was to examine the impact of reclaimed wastewater on soil, tomato production
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