Impact assessment of the reuse of two discrete treated wastewaters for the irrigation of tomato crop on the soil geochemical properties, fruit safety and crop productivity

Abstract

Advanced tertiary treatment and disinfection technologies have enabled the production of wastewater (WW) with quality complying with the established criteria for reuse in agriculture. This study assessed the impacts of tomato crop irrigation with two qualitatively distinct treated WW effluents, as compared to control tubewell water (TW) irrigation, on the soil geochemical properties, tomato fruit safety and crop productivity. The treated effluents reused for irrigation were produced in two Municipal Wastewater Treatment Plants (MWTPs) utilizing two discrete tertiary treatment and disinfection technologies, i.e. Slow Sand Filtration and chlorination (MWTP I), and Membrane Bioreactor and UV radiation (MWTP II), respectively. The impacts on soil pH, electrical conductivity, total organic C, Cl − , NO 3 − and heavy metal (Zn, Mn, Ni, Cu, Co) content were evaluated. In addition, the heavy metal content in tomato fruits and leaves, as well as the microbial load in fruit flesh and peel was determined. Crop productivity was measured by the mean fruit weight and maximum diameter, and by the number of fruits per harvest. Irrigation with either WW did not significantly affect the soil pH, organic C and heavy metal content, as well as crop productivity, in comparison to control TW irrigation. Furthermore, the heavy metal content of tomato fruits and leaves in all irrigation treatments was found to be below the maximum permissible levels set for fruit safety and the critical tissue concentration for phytotoxicity, respectively. Moreover, no microbiological contamination (total coliform, fecal coliform, Escherichia coli, Salmonella spp., Listeria spp.) of tomato fruits was found from any irrigation treatment. Overall, results obtained with regard to the parameters examined strongly suggest that advanced tertiary treated effluent of good quality might be safely reused, in terms of both environmental sustainability and public health safety, for vegetable irrigation, concurrently promoting water use efficiency in dry areas.

Effects of treated agro-industrial wastewater irrigation on tomato processing quality

“…Our results are in agreement with other recent studies that have shown low impact for the microbial contamination of tomato crops irrigated by treated secondary wastewaters (Cirelli et al, 2012;Christou et Gatta et al, 2014). This will be due to several factors, such as: the drip irrigation system and mulching system adopted, and the effects of UV radiation exposure on the fruit and leaf surfaces.…”

“…Some studies have investigated the influence of irrigation with treated wastewater on tomato crop yields, but there remains the need to better define the full effects on the fruit quality parameters and the acceptable levels of biological contamination (Aiello et al, 2007;Christou et al, 2014;Gatta et al, 2014). For this purpose, the present study was designed to evaluate the effects of two water irrigation sources, as the groundwater (GW) control, and treated agro-industrial wastewater (SW), on the main quality parameters and microbiological safety of processing tomato fruit.…”

Comparable levels of microbial contamination in soil and on tomato crops after drip irrigation with treated wastewater or potable water

“…While several previous studies have evaluated the effect of application of raw WW to irrigate crops (Fattal et al, 1986;Minhas et al, 2006;Rosas et al, 1984) and determined it unfit, few studies have examined the implications of applying TWW for irrigation of vegetable crops (Christou et al, 2014;Cirelli et al, 2012;Forslund et al, 2010Forslund et al, , 2012Martinez et al, 2013). Treatment of WW is intended to reduce organic matter, nitrogen, and microbial contaminants (Bitton, 2011).…”

“…In fact, reports from around the world indicate that irrigation with TWW presents no greater risk than irrigation with potable water (Bichai et al, 2012;Christou et al, 2014;Cirelli et al, 2012;Forslund et al, 2012Forslund et al, , 2010Jang et al, 2013;Martínez et al, 2013;Shuval, 2010). However, these reports rely either on epidemiological data (reviewed in Shuval, 2010) or mainly on fecal indicator bacteria (FIB) such as coliforms or Escherichia coli to assess possible health risks (Bichai et al, 2012;Christou et al, 2014;Forslund et al, 2012Forslund et al, , 2010Jang et al, 2013), neglecting major pathogen groups such as viruses and protozoa. The lack of correlation between pathogens and FIB, currently used in microbiological monitoring standards (Bitton, 2011;Edberg et al, 2000;WHO, 2006), is well established (Harwood et al, 2005;Ottoson et al, 2006;Payment et al, 2001) and may lead to under-or over-estimation of the risks to public health.…”

Wastewater reuse in irrigation: A microbiological perspective on implications in soil fertility and human and environmental health

“…In addition, methods that increase the probability of direct contact between waste-water and edible part of plants (e.g., furrow irrigation) seem to promote greater contamination of plants than subsurface drip irrigation (Song et al, 2006a). However, Christou et al (2014) reused a tertiary treated effluent for irrigation of tomato crops and did not find evidences of microbiological contamination of the edible parts.…”