assessing the environmental impacts of constructed ...

International Journal of Phytoremediation

ISSN: 1522-6514 (Print) 1549-7879 (Online) Journal homepage: http://www.tandfonline.com/loi/bijp20

Assessing environmental impacts of constructed wetland effluents for vegetable crop irrigation A. Castorina, S. Consoli, S. Barbagallo, F. Branca, A. Farag, F. Licciardello & G.L. Cirelli To cite this article: A. Castorina, S. Consoli, S. Barbagallo, F. Branca, A. Farag, F. Licciardello & G.L. Cirelli (2015): Assessing environmental impacts of constructed wetland effluents for vegetable crop irrigation, International Journal of Phytoremediation, DOI: 10.1080/15226514.2015.1086298 To link to this article: http://dx.doi.org/10.1080/15226514.2015.1086298

Accepted online: 07 Sep 2015.

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Date: 21 September 2015, At: 08:42

ACCEPTED MANUSCRIPT ASSESSING ENVIRONMENTAL IMPACTS OF CONSTRUCTED WETLAND EFFLUENTS FOR VEGETABLE CROP IRRIGATION A. Castorina1, S. Consoli1,S. Barbagallo1, F. Branca2, A. Farag3, F. Licciardello1, G.L. Cirelli1

Downloaded by [University of Catania], [FERDINANDO BRANCA] at 08:42 21 September 2015

1

Dept Agricoltura, Alimentazione e Ambiente, University of Catania, Via S. Sofia 100, 95123,

Catania, Italy 2

Dept Agricoltura, Alimentazione e Ambiente, University of Catania, Via Valdisavoia 5, 95123,

Catania, Italy 3

Dept of Agricultural Engineering, University of Benha, Egypt

Corresponding author email: [email protected]

ABSTRACT The objective of this study was to monitor and assess environmental impacts of reclaimed wastewater (RW), used for irrigation of vegetable crops, on soil, crop quality and irrigation equipment. During 2013, effluents of a horizontal sub-surface flow constructed treatment wetland (TW) system, used for tertiary treatment of sanitary wastewater from a small rural municipality located in Eastern Sicily (Italy), were reused by micro-irrigation techniques to irrigate vegetable crops. Monitoring programs, based on in situ and laboratory analyses were performed for assessing possible adverse effects on water-soil-plant systems caused by reclaimed

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ACCEPTED MANUSCRIPT wastewater reuse. In particular, experimental results evidenced that Escherichia coli content found in RW would not present a risk for rotavirus infection following WHO (2006) standards. Irrigated soil was characterized by a certain persistence of microbial contamination and among


the studied vegetable crops, lettuce responds better, than zucchini and eggplants, to the irrigation with low quality water, evidencing a bettering of nutraceutical properties and production parameters. Keywords: Microbial risk assessment; Micro-irrigation; Reclaimed Wastewater; Treatment Wetland; Vegetable crops

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1. INTRODUCTION The use of reclaimed wastewater (RW) for crop irrigation is an alternative to the scarcity of


quality water suffered in many countries of the Mediterranean basin. RW can provide an important saving of fertilizers (i.e. nitrogen and phosphorus) as well as benefits for the environment, by avoiding the discharge of contaminated water into public waterways (Martínez et al., 2013) and providing consistent available water throughout the year. It is estimated that the reuse of wastewater could reach 15% of the world’s water consumption (Asano, 1998). Possible uses of reclaimed wastewater include irrigation of food or non-food crops, irrigation of green or leisure zones (with or without direct contact), aquaculture, industry (water for refrigeration, cleaning), municipal use and aquifer recharge, among others (Cirelli et al., 2009). The use of reclaimed wastewater for crop irrigation has been a common practice for some years now. This agricultural use has been tested in crops such as forage (Bole and Bell, 1978), alfalfa and radish (Rosas et al., 1984), wheat and maize (Al-Jaloud et al., 1993), trees (Tznakis et al., 2003) and vegetable crops (Rosas et al., 1984; Keraita et al., 2007; Aiello et al., 2007; Cirelli et al., 2012). Moreover, different practices involving wastewater reuse, in terms of irrigation techniques (surface and subsurface drip irrigation) (Cirelli et al., 2012), cultivation systems (Pedrero and Alarc’on, 2009) and treatments technologies, (Pedrero et al., 2010, Barbagallo et al., 2003; Consoli et al., 2011; Barbagallo et al., 2012) have been tested. The use of wastewater for crop irrigation is perhaps one of the main sources of pathogenic microorganism contamination (Assadian et al., 2005; Aiello et al., 2013). The risk associated with this type of water depends on the presence of pathogenic

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ACCEPTED MANUSCRIPT microorganisms and chemical substances, as well as on environmental conditions, safety measures, treatment types, irrigation methods and type of grown crops. Among the variety of existing crops, vegetables are the most vulnerable to contamination


(Armon and Shelef, 1991), especially when they are consumed fresh, thus demanding high-quality water for irrigation. The World Health Organization (WHO, 2006) established a limit of Escherichia Coli at 104 Colony Forming Units (CFU) per 100 mL for wastewater reuse on vegetables for consumption as fresh food. In Italy, there are specific restrictions at the state level for the use of wastewater in agriculture (Italian Ministry Decree 185/2003), which limit the presence of Escherichia coli (50 CFU 100 mL 1

for 80% of samples), as well as total suspended solids (TSS: 10 mg L -1) and another

52 parameters, 37% of which are not considered for drinking water analysis (Cirelli et al., 2008). Fulfillment of these limitations implies high-intensive treatments for wastewater (and consequently high costs for users) to be allowed for reuse. Constructed Wetland systems (herein referred as Treatment Wetland, TW) for wastewater treatment involve the use of engineered systems that are designed and constructed to utilize natural processes. These systems are designed to mimic natural wetland systems, utilizing wetland plants, soil, and associated microorganisms to remove contaminants from wastewater effluents (EPA, 1993). TW s are adopted as a tertiary-treatment technology due to their low operation and maintenance costs and efficiency in treating wastewater from small and medium communities. TW s are used for treating various wastewater types and for polishing advanced treated wastewater effluents for return to freshwater resources (Schwartz et al., 1994; Toscano et al.,

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ACCEPTED MANUSCRIPT 2009). TW s have been suggested as alternative for treating nitrate contaminated aquifers, denitrification of nitrified sewage effluents and irrigation return flow (Baker, 1998).


Generally, applied research on TW s highlights the fact that treated municipal effluent directed to irrigation may contain readily absorbable useful nutrients and easily biodegradable organics, with an average effluent quality that is compatible with the limits on treated wastewater discharge in water bodies imposed by the Italian regulations. At the light of the above considerations and potential innovations on RW reuse in agriculture, the aim of this study was to investigate the effects of reclaimed constructed treatment wetland (TW) effluents on the irrigation of vegetable crops (i.e. lettuce, zucchini and eggplants) from physical, chemical, microbiological and production perspectives. Special attention was paid to the soil contamination by pathogenic microorganisms and the irrigation technology (micro-irrigation) performance changes caused by the emitters clogging. The study was carried during the period July-Novembre 2013, at the experimental site of S. Michele di Ganzaria in Eastern Sicily, Italy. 2. METHODOLOGY 2.1 Description of the experimental irrigation system and cultivation practices Two plots, irrigated by RW and fresh water (FW) (the latter from an agricultural reservoir), were selected as treatment and control plots, respectively. The experimental plots were equipped with drip irrigation systems, consisting of surface (DI) and sub-surface (SDI) laterals, buried at a

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ACCEPTED MANUSCRIPT depth of 0.05 m. These systems supplied reclaimed wastewater (RW) or fresh water (FW) to the experimental plots. At the treatment plot, wastewater from the community of S. Michele di Ganzaria (Eastern Sicily,


37°16’ N, 14° 25’ E), a small municipality of about 5,000 inhabitants, was conveyed to a Constructed Treatment Wetland (TW) designed to provide tertiary treatment. Figure 1 summarizes some relevant characteristics of the horizontal sub-surface flow constructed TW (HSSF2), which, after a sand filter, supplies RW to the experimental irrigation plot. The H-SSF2 is part of the tertiary wastewater reclamation plant of the community. The system consists of four CWs integrated with three storage reservoirs, tanks and filters. The area of study has a Mediterranean-arid climate. Rainfall (with a annual value of about 350 mm in 2013) occurs mostly in winter and is almost absent in summer. The average mean daily temperature was 15.7°C in 2013. The soil textural analysis revealed the presence of 29% of sand, 22% of silt and 49% of clay (USDA textural soil classification), with a volumetric content at field capacity of approximately 44% and a surface infiltration rate at the saturation level on the order of 10-3 cm/d (Cirelli et al., 2012). Meteorological variables (air temperature and humidity, rainfall, wind velocity and direction, and solar radiation) were measured hourly by a weather station placed at the experimental site. The experimental irrigation system is described in Figure 2. Lettuce (Lactuca sativa L.) (cultivar Canasta), was transplanted at a density of 2.8 plants m-2 , and included 4 replicates of 32 plants; zucchini (Cucurbita pepo L.; cultivar President) and eggplant (Solanum melongena L.) (two cultivars Dalia -DA and Birga- BI) were transplanted at a density of,and 1.7 plants m-2 respectively; four replicates of 11 eggplants and 16 zucchini were used for analysis and

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ACCEPTED MANUSCRIPT comparisons in the present study. Total length of the irrigated plots was 30 m; each plot (supplied by RW or FW) was equipped with two surface (DI) or subsurface (SDI) polyethylene laterals with 16 mm external diameters. All the laterals were supplied by in-line labyrinth


drippers (theoretical discharge rate of 0.8 L h -1 at a pressure of 100 kPa), with emitters spaced at 0.1 m. The buffer zone width was 1.2 m between the laterals and 2.0 m in the middle corridor. In order to limit evaporation increasing due to bordering conditions (which can be significant, especially under windy conditions) the two outermost laterals (BL) (Figure 2) of each plot were planted and irrigated but not sampled during the experiment. Irrigation plots were covered by black/white plastic mulching. Mulch provides a better soil environment, moderates soil temperature, reduce splash effects and increases water infiltration during intensive rains, and controls weeds (Rashidi and Gholami, 2011). Irrigation scheduling was based on crop evapotranspiration (ET c, mm d-1) rate estimates. The ETc rate was calculated by multiplying the reference evapotranspiration (ET 0, mm d-1) via PenmanMonteith method (Allen et al., 1998) and the FAO-56 crop coefficient (Kc). The value of Kc was assumed equal to 1.0 for the trial. ET c rates were further corrected by a Kmulch of 0.7 which accounts for soil evaporation decreasing due to mulching. By using this approach, irrigation water was applied at 3-day intervals in order to replace 100% of the ETc occurring since the previous irrigation. Irrigation rates were adjusted when necessary due to the rainfall effects. Because irrigation was controlled, deep percolation and runoff were assumed to be negligible.

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ACCEPTED MANUSCRIPT The performance of DI and SDI laterals was analysed by evaluating the emission uniformity (EU, %). The EU is the ratio between the average discharge of the emitters in the bottom 25 th percentile (Qmin1/4) and that of all the emitters (Q), both expressed in (L s -1) (Keller and Karmeli,


1975). The EU was determined at the beginning and at the end of the irrigation season by measuring the discharge from 30 randomly selected emitters along each lateral supplying RW or FW. Standard cultivation practices were adopted during the cropping season. N (55 kg ha-1), P2O5 (110 kg/ha) and K2O (80 kg/ha) were applied uniformly to the experimental field by a single fertilisation. Lettuce heads were harvested in mid September 2013, corresponding to the commercial stage; zucchini were harvested from mid August through the end of September with a frequency of two times per week; eggplants were harvested, twice a week, from mid September to the first week of November 2013. During each harvest operation, the number of fruits, fruit weight, and plant stem diameter (only at the end of the growing cycle) were registered; for lettuce, plant weight and number of leaves per plant were determined at harvesting. 2.2 Monitoring program 2.2.1 Water sampling and analysis Figure 3 provides the schematic of the RW sampling points along the treatment line. FW samples were collected at the storage reservoir. Main physical-chemical and microbial characteristics of FW and RW were monitored during the irrigation season at intervals of approximately 30 days. Standard methods (APHA, 2005) were used in the laboratory to measure Total Suspended Solids (TSS at 105°C), Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD),

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ACCEPTED MANUSCRIPT Total Phosphorus (TP), Total nitrogen (TN), Electrical Conductivity (EC), pH, Sulfur Trioxide, (SO3), Iron (Fe), Chlorine (Cl), SAR. Escherichia coli (E.coli) and Salmonella were measured trough microbiological analysis (APHA, 2005).


2.2.2 Soil contamination analysis Soil contamination analysis assessed E.coli and Salmonella concentrations within soil columns (from 0.1 to 0.3 m of depth beneath soil surface) near the emitters. Laboratory processing for soil microbial and constituent analyses were performed as outlined in APHA (2005). Soil samples (about 100 g) microbial levels (CFU 100 mL -1), in 100 g soil samples, were enumerated using membrane filtration techniques. 2.2.3

Crop yield and microbial contamination

The effects of irrigation water quality, QW (RW versus FW), micro-irrigation system (IS) performance, and of their interactions on crop production features (i.e. total yield, fruit numbers and fruit mean weight) were evaluated through the analysis of variance (n-ways ANOVA with randomized block design) at significant levels of 0.01