Wastewater-irrigated Vegetables Research Articles

Metals Uptake by Wastewater Irrigated Vegetables and their Daily Dietary Intake in Peshawar, Pakistan / Pobieranie Metali Przez Warzywa Nawadniane Ściekami I Ich Dzienne Stężenie W Diecie Ludności Peszawaru, Pakistan

Abstract Vegetables are important source of nutrients for human body. Wastewater irrigation may lead to contamination of these vegetables and cause possible health risk. In the present study impact of waste water irrigation on metals uptake (Fe, Mn, Ni, Co, Zn, Cd, Cr and Pb) by five commonly consumed vegetables (radish, cabbage, lettuce, cauliflower and spinach) grown in the suburbs of Peshawar were investigated using AAS (Atomic Absorption spectrophotometer). The uptake and accumulation of metals for vegetables irrigated with wastewater were significantly (p < 0.05) higher than tube well irrigated vegetables and permissible limits of WHO/FAO. Among the edible parts of vegetables maximum accumulation of Mn, Pb and Cd occurred in radish followed by Ni and Fe in spinach while Cr and Zn were high in cauliflower and cabbage. The estimated daily intake of metals (DIM) revealed that at present the consumption of studied vegetables were under the tolerable limits of (US-EPA, IRIS), however intake of metals in waste water irrigated vegetables were significantly high and can cause health hazards in the long run

Schiff base-functionalised styrofoam resin for preconcentration of metal ions in wastewater and wastewater-irrigated vegetables samples

Polystyrene (PS) was extracted from styrofoam waste and functionalised with schiff base, N,N-bis(salicylidene)cyclohexanediamine (SCHD) through an azo spacer. The resin was characterised and used for preconcentration of Pb(II), Ni(II) and Cd(II) ions prior to their trace determinations by microsample injection system–coupled flame atomic absorption spectrometry (MIS-FAAS). The recoveries of studied metal ions were achieved ≥96.0% with relative standard deviation (RSD) ≤4.5 at optimum parameters: pH 8; resin amount 300 mg; flow rates 3.0 mL min−1 of sample solution; and 2.0 mL min−1 of eluent (2.0 mol L−1 HNO3). The limits of detection (LODs) and limits of quantification (LOQs) were found to be 0.32, 0.23 and 0.21 and 1.10, 0.78 and 0.69 μg L−1, respectively, with preconcentration factors (PFs) of 500, 800 and 1000, respectively. The linear ranges of the method were 1–40, 1–25 and 1–20 μg L−1 for Pb(II), Ni(II) and Cd(II) ions, respectively. The accuracy and validation of the method were evaluated by analysis of certified reference materials (CRMs). The method was successfully applied for preconcentration of studied metal ions in wastewater and wastewater-irrigated vegetable samples.

Modeling the die-off of E. coli and Ascaris in wastewater-irrigated vegetables: implications for microbial health risk reduction associated with irrigation cessation.

This study assessed the die-off of Escherichia coli (E. coli) and Ascaris suum on lettuce (Great Lakes 118) and cabbage (Brassica oleracea var capitata) in wastewater-irrigated fields using comparative mathematical die-off models. The study revealed that none of the survival curves of E. coli and A. suum was best fitted with the log-linear model, indicating that the classical first-order kinetic approach is inadequate in many cases. The biphasic die-off model best described the die-off of E. coli on lettuce (kmax1 = 2.62 day(-1) and kmax2 = 0.22 day(-1)) and cabbage (kmax1 = 1.06 day(-1) and kmax2 = 0.53 day(-1)). The die-off of A. suum on lettuce was best described by the biphasic model (kmax1 = 0.48 day(-1) and kmax2 = 0.01 day(-1)) and best described by log linear + tail (kmax = 0.44) on cabbage. A comparative health risk assessment associated with the consumption of lettuce showed significant underestimation of the number of days of irrigation cessation required to achieve E. coli O157:H7 and Ascaris tolerable annual infection risk when using biphasic die-off rates compared with other die-off rates. The study stresses the need to test different die-off models as inputs for quantitative microbial risk assessment (QMRA) particularly for interventions associated with health risk reduction.

Trace metals in vegetables grown with municipal and industrial wastewaters

By inducing elevated concentrations of certain trace metals in soil, irrigation with domestic and industrial wastewater creates a potential risk to human health. This study was conducted to assess the concentrations of the trace metals Cd, Cr, Cu, Ni, and Pb in some vegetable crops irrigated with industrial and municipal wastewater and to estimate the potential health risks of these metals to humans via the consumption of those foods (eggplant, pepper, and tomato). Vegetable samples from wastewater-irrigated fields were collected from 17 locations around Gaziantep City in Southeastern Turkey. The mean concentrations of Cd, Cr, Cu, Ni, and Pb in edible portions of eggplant, pepper, and tomato were 0.17 (0.01–0.52), 2.6 (1.4–4.8), 16 (7.41–60.54), 2.9 (0.6–6.1) and 0.70 (0.08–4.48) mg kg−1, respectively. Cr, Cu, and Ni concentrations in all the 38 vegetable samples exceeded the Food and Agriculture Organization and World Health Organization (FAO/WHO) and the World Health Organization and European Union (WHO/EU) limits, Cd concentrations in 36 samples exceeded the WHO/EU and in 14 the FAO/WHO limit, Pb concentrations in nine samples exceeded the FAO/WHO and in 24 samples the Turkish regulations. These values indicate that the consumption of vegetables irrigated with industrial and municipal wastewater may represent an important exposure pathway to humans. Monitoring of wastewater-irrigated vegetables is essential to reduce or eliminate unnecessary risks.

Parasitological Contamination of Wastewater Irrigated and Raw Manure Fertilized Vegetables in Mekelle City and Its Suburb, Tigray, Ethiopia

Watering of vegetables in developing countries including Ethiopia is done using untreated wastewater and raw manure of domestic animal origin is used as fertilizer. Thus, vegetables are considered to be the principal sources of human infection with bacterial, protozoan and helminth parasites. Therefore, the objective of this study was to evaluate the rate of parasitological contamination of pre-harvest vegetables in Mekelle city and its suburban village, ‘Mariam Dahan’. Pre-harvest vegetables were collected from the field during the dry season, washed using physiological saline solution, allowed to sediment overnight, centrifuged and examined microscopically for infective stages of intestinal parasites. Out of the vegetable samples examined, 32.41% in Mekelle city and 30.49% in ‘Mariam Dahan’, contained at least one parasitic contaminant. Strongyloides stercoralis was most encountered parasitic contaminant in the study areas, followed by, Taenia and Entamoeba spp . Highest rate of parasitic contamination was detected on Swiss chard, that was 45.5 and 41.67% in Mekelle city and ‘Mariam Dahan’, respectively. Occurrence of infective stages of intestinal parasites on wastewater-irrigated vegetables may pose public health hazards to farming communities in the study areas. Therefore, evaluation and surveillance of parasitological quality of vegetables is crucial in an attempt to control vegetable-transmitted parasitic infections. Keywords : Untreated wastewater, Raw manure, Pre-harvest Vegetables, Parasitological contamination, Tigray, Ethiopia

Effectiveness of common and improved sanitary washing methods in selected cities of West Africa for the reduction of coliform bacteria and helminth eggs on vegetables

To analyse and improve the effectiveness of common indigenous washing methods for the reduction of faecal coliform (FC) populations on the surface of wastewater-irrigated vegetables and to determine simple factors affecting their efficacy. Questionnaire interviews were used to gather information on common methods used for washing vegetables in seven West African countries. The efficacy of the most common decontamination methods was measured in terms of log reductions in FC populations on homogenised contaminated lettuce, cabbage and spring onion samples. The large majority of urban households and restaurants in the subregion are aware of vegetable-related health risks and wash vegetables before consumption. Methods used vary widely within and between Ghana and neighbouring francophone West African countries. However, several of the most common methods do not reduce the contamination to any desirable level. Significantly, different log reductions are achieved depending on the washing method, contact time and water temperature. Tests to improve the apparent ineffective methods were especially promising in view of the relatively expensive vinegar. However, up to 3 log units reduction is also possible at a much lower price with 'Eau de Javel' (household bleach), which is commonly used in francophone West Africa. Washing vegetables before consumption is an important component of a multiple barrier approach for health risk reduction. The high risk perception among consumers demands that more information be made available on the appropriate use of these washing methods. Any washing method will need complementary efforts to reduce contamination before the vegetables enter the kitchen, such as safer irrigation practices.

Editorial: Wastewater use – food safety and health aspects

This supplement presents information on food safety and health aspects of wastewater use in agriculture and aquaculture in selected developing countries in Asia and Africa. Wastewater use in agriculture and aquaculture is increasing world-wide as a result of growing water scarcity and its ready availability. In many developing countries, wastewater is discharged untreated and urban and periurban farmers use wastewater directly from sewage drains or indirectly through wastewater-polluted irrigation water. The use of wastewater for food production provides jobs and income for the farmers and in some urban areas is an important food source for the urban populations. At the same time wastewater use systems reduce organic and inorganic nutrient levels in the wastewater as such nutrients fertilize the growth of plants, fish and other produce. The production systems thereby act as natural ‘low-cost wastewater treatment’ systems. Wastewater use areas are often also important in preventing floods and also represent green ‘spaces’ and recreational areas. However, the use of wastewater for agricultural purposes can also pose a significant occupational and public health risk. The major groups at risks include consumers of wastewater irrigated produce, farm workers and their families and nearby communities. Risks may be infectious or non-infectious, e.g. consumption of produce with accumulated toxic elements. Recently the World Health Organization (WHO) published revised guidelines for the safe use of wastewater, excreta and greywater (http:// www.who.int/water_sanitation_health/wastewater/ gsuww/en/index.html). The aim of these guidelines is to maximize public health protection and the beneficial use of important resources and it is stressed that the guidelines should be adapted considering national, sociocultural, economic and environmental factors. In fact, too strict standards are not sustainable and can lead to reduced health protection. A more detailed introduction to the WHO guidelines was recently provided by Ensink, J.H.J. & van der Hoek, W. (Trop. Med. Int. Health. 2007, 12: 575–577). The revised guidelines with their health risk assessment based approach represent a significant improvement compared with previous guidelines. But it is also clear that there remains a strong need for more fieldbased research under different environmental, climatic and socio-economic conditions that combine water and produce quality with epidemiological assessment of health risks in farmers and consumers, as this will improve the risk assessment models and mitigation strategies proposed in the WHO guidelines. The studies included in the Supplement document the microbiological and chemical food safety of vegetables and fish produced in wastewater use systems in Cambodia and Vietnam as well as risks of diarrhoea and helminth infections among wastewater farmers and their families. Evidence is provided that skin problems are a significant occupational health hazard among farmers exposed to wastewater, but that such exposure was not a main risk factor for helminth infections. Studies in Ghana show how simple, cheap and easily adoptable wastewater irrigation methods as well as cessation of irrigation before harvest can reduce faecal contamination of crops. Common indigenous washing methods were also tested for their effectiveness for the reduction of faecal contamination on the surface of wastewater-irrigated vegetables. In Pakistan, it was found that unhygienic post-harvest handling was the major source of produce contamination highlighting that interventions at the market may be better and more cost effective ways to protect public health than wastewater treatment. I hope that the articles will inspire other researchers in their efforts to study and document benefits and health aspects of wastewater use. With the growing water scarcity the challenge is to safely use wastewater even when modern wastewater treatment facilities are not available. Low-cost decentralized treatment alternatives and improved wastewater application methods can significantly reduce human health hazards. This should be combined with treatment of people at high risk of helminth infection and general improvements in personal and food hygiene practices, sanitation and water supply. I would like to thank the researchers who responded positively on providing research results for this Supplement. Thanks also to the organizations and others who provided the funding for the various studies, including the Danish International Development Assistance (Danida), the European Union, The CGIAR – Challenge Program for Water and Food, the International Water Management Institute and the International Foundation of Science in Stockholm.

Epidemiological Evidence for Helminth and Cholera Transmission by Vegetables Irrigated with Wastewater: Jerusalem – A Case Study

This paper reviews and reanalyzes epidemiological data on the transmission of the helminthic diseases ascariasis and trichuriasis as well as cholera by vegetables and salad crops irrigated with untreated wastewater in Jerusalem between 1935 and 1982, based on a series of published papers and unpublished reports not generally available to professionals in the field of water pollution control. The findings provide strong evidence that both Ascaris and Trichuria infections were actively and massively transmitted to the general public who consumed vegetables irrigated with raw wastewater. The levels of infection dropped dramatically when the supply of contaminated vegetables was cut off but increased again rapidly on reintroduction of the wastewater-irrigated crops. The infection level subsided again when the practice was finally stopped in 1970. The epidemiological evidence from the 1970 cholera outbreak in Jerusalem indicates that wastewater-irrigated vegetables were the primary route of secondary infection once a few subclinical or clinical cases of cholera entered the city from areas outside the country where a cholera epidemic was underway. The evidence also indicates that farmers in an area where cholera is not endemic are particularly at risk when practicing irrigation with raw wastewater from a city underdoing a cholera outbreak. The need to treat wastewater to remove these pathogens prior to the irrigation of such vegetable crops is stressed.