Irrigation Of Food Crops Research Articles

Potential for Beneficial Reuse of Oil and Gas-Derived Produced Water in Agriculture: Physiological and Morphological Responses in Spring Wheat (Triticum aestivum).

Produced water (PW) from oil and gas operations is considered a potential resource for food crop irrigation because of increasing water scarcity in dryland agriculture. However, efforts to employ PW for agriculture have been met with limited success. A greenhouse study was performed to evaluate the effects of PW on physiological and morphological traits of spring wheat (Triticum aestivum). Plants were irrigated with water treatments containing 10 and 50% PW (PW10 and PW50, respectively) and compared to a matching 50% salinity (NaCl50) and 100% tap water controls. Compared to controls, plants watered with PW10 and PW50 exhibited developmental arrest and reductions in aboveground and belowground biomass, photosynthetic efficiency, and reproductive growth. Decreases in grain yield ranged from 70 to 100% in plants irrigated with PW compared to the tap water control. Importantly, the PW10 and NaCl50 treatments were comparable for morphophysiological effects, even though NaCl50 contained 5 times the total dissolved solids, suggesting that constituents other than NaCl in PW contributed to plant stress. These findings indicate that despite discharge and reuse requirements focused on total dissolved solids, salinity stress may not be the primary factor affecting crop health. The results of the present study are informative for developing guidelines for the use of PW in agriculture to ensure minimal effects on crop morphology and physiology. Environ Toxicol Chem 2019;38:1756-1769. © 2019 SETAC.

Intelligent decision-making of online shopping behavior based on internet of things

The development of big data and Internet of things (IoT) have brought big changes to e-commerce. Different kinds of information sources have improved the consumers’ online shopping performance and make it possible to realize the business intelligence. Grip force and eye-tracking sensors are applied to consumers' online reviews search behavior by relating them to the research approaches in IoT. To begin with, public cognition of human contact degrees of recycled water reuses with grip force test was measured. According to the human contact degrees, 9 recycled water reuses presented by the experiment are classified into 4 categories. Based on the conclusion drawn from grip force test, purified recycled water and fresh vegetable irrigated with recycled water are regarded as the drinking for high-level human contact degree and the irrigation of food crops for low-level human contact degree respectively. Several pictures are designed for eye-tracking test by simulating an on-line shopping web page on Taobao (the most popular online shopping platform in China). By comparing the fixation time participants spent on the areas of interest (AOIs), we justify that consumers' online reviews search behavior is substantially affected by human contact degrees of recycled products. It was found that consumers rely on safety perception reviews when buying high contact goods.

Drinking Water Reuse: One-Step Closer to Overpassing the “Yuck Factor”

Water shortage, because of either augmented domestication or climatic variability, has prompted nations to diminish stress on water supplies mostly via decreasing water demand. Nevertheless, this procedure entirely is not enough to ensure the quality of life that high-quality water services boost, particularly inside the case of augmented domestication. Intrinsically, the notion of water reuse (WR) has been reaching strength for the last few decades. Decision-makers require ready and reachable data concerning public attitudes toward WR to adopt convenient and sustainable resource management plans. Applying reclaimed infrastructure must concentrate firstly on usages with more important social acceptability, like street cleaning, car washing, irrigation of parks and athletic fields or toilet flushing. Acceptance of the usage of recycled water for other goals implementations, like food crop irrigation and watering of residential lawns may augment as public knowledge of the system expands. As inhabitants begin to be more usual with the techniques and global comprehension of the linked advantages of WR increases, officials, planners, and managers may encounter reduced objection to extra usages and attain bigger water savings via prolonged application of WR schedules. For potable WR, there is only one-step closer to overpassing the “yuck factor”. However, great efforts remain to be accomplished in mater of hybrid water technologies to assure efficient pollutant removal. Finally, WR may be considered a safe tool to avoid water sources’ contamination. In other words, treating wastewater at its source of generation before its expansion at the highest level of purity will avoid pollution expansion into nature: air, soil, and water. In this case and only in this case, the “yuck factor” will be overpassed.

Review of water quality criteria for water reuse and risk-based implications for irrigated produce under the FDA Food Safety Modernization Act, produce safety rule

Questions related to the safety of alternative water sources, such as recycled water or reclaimed water (including grey water, produced water, return flows, and recycled wastewater), for produce production have been largely un-explored at the detail warranted for protection of public health. Additionally, recent outbreaks of Escherichia coli (E. coli) in fresh produce, in which agricultural water was suspected as the source, coupled with heightened media coverage, have elevated fruit and vegetable safety into the forefront of public attention. Exacerbating these concerns, new Federal regulations released by the U.S. Food and Drug Administration (FDA) as part of implementation of the FDA Food Safety Modernization Act (FSMA), require testing of agricultural water quality for generic E. coli. Here, we present a review of water quality criteria – including surface water, groundwater recreational water, and water reuse – in an attempt to better understand implications of new FDA regulations on irrigated produce. In addition, a Quantitative Microbial Risk Assessment (QMRA) was conducted to estimate risks from pathogen contamination of food crops eaten fresh under the context of FDA regulations to provide perspective on current water reuse regulations across the country. Results indicate that irrigation water containing 126 CFU/100 mL of E. coli correspond to a risk of GI illness (diarrhea) of 9 cases in 100,000,000 persons (a 0.000009% risk) for subsurface irrigation, 1.1 cases in 100,000 persons (a 0.0011% risk) for furrow irrigation, and 1.1 cases in 1000 persons (a 0.11% risk) for sprinkler irrigation of lettuce. In comparison to metrics in states that currently regulate the use of recycled water for irrigation of food crops eaten fresh, the FDA FSMA water quality metrics are less stringent and therefore the use of recycled water presents a reduced risk to consumers than the FDA regulations. These findings, while limited to a one-time exposure event of lettuce irrigated with water meeting FSMA water quality regulations, highlight the need for additional assessments to determine if the scientific-basis of the regulation is protective of public health.

Contamination by Pathogenic Microorganisms in Water used for Agricultural Irrigation on the Sabana de Bogota, Colombia

The aim of this study was to evaluate the microbiological quality of water used to irrigate food crops, which can lead to the spread of certain microorganism, such as <em>Escherichia coli</em>, which poses a high risk of contamination for food, especially food consumed as fresh vegetables and milk, making it important to monitor the hygienic state of water based on the detection of 'indicator' bacteria, which are normally only present in human and animal intestines, such as coliforms, which have been accepted worldwide as a unfailing parameter. To evaluate the water quality, the coliforms present in the water used for agricultural irrigation on the Sabana de Bogota were quantified in the La Ramada irrigation district. Water samples were taken at ten agricultural irrigation points in municipalities around Bogota. The methodology for the analysis included the technique that uses serial dilutions of samples in a specific culture media. In the different sampled sites where the water quality used for irrigation was evaluated, the total and fecal coliforms values were higher in CFU than the established limits (Decree 1594 of 1984) and values were found in some samples that were higher than $1×10^6 \>CFU \>100/mL$ for total coliforms and $1×10^5 \>CFU \>100/mL$ for fecal coliforms. This study indicated that, with the current conditions of some water sources on the Sabana de Bogotá, there is an inherent source of contamination, creating an obstacle for agricultural irrigation and a microbiological risk for consumers.

Water, birds, and biodiversity - key elements of education

Given the reality of the water crisis in the Western Cape (WC), especially in the City of Cape Town and the satellite towns, a unique opportunity exists to use the combination of the Paarl Bird Sanctuary and the Drakenstein Waste Water Treatment Works (PBS/WWTW) for education about water and related facts. Severe drought is not the only reason for the shortage of fresh water. It is likely that the water requirements of the burgeoning human population of the province, together with the need to use water to irrigate food crops, now exceed the water resources of the WC, despite the storage created in dams. An associated fact is that in the WC a large proportion of employed people work in Agriculture, both directly and indirectly. So any cut in water for irrigation, would increase unemployment and intensify poverty, which are already huge problems. The overall predicament has /country-wide, and even global implications, emphasising the need for water-related education.

A Review of Environmental Contamination and Health Risk Assessment of Wastewater Use for Crop Irrigation with a Focus on Low and High-Income Countries.

Population densities and freshwater resources are not evenly distributed worldwide. This has forced farmers to use wastewater for the irrigation of food crops. This practice presents both positive and negative effects with respect to agricultural use, as well as in the context of environmental contamination and toxicology. Although wastewater is an important source of essential nutrients for plants, many environmental, sanitary, and health risks are also associated with the use of wastewater for crop irrigation due to the presence of toxic contaminants and microbes. This review highlights the harmful and beneficial impacts of wastewater irrigation on the physical, biological, and chemical properties of soil (pH, cations and anions, organic matter, microbial activity). We delineate the potentially toxic element (PTEs) build up in the soil and, as such, their transfer into plants and humans. The possible human health risks associated with the use of untreated wastewater for crop irrigation are also predicted and discussed. We compare the current condition of wastewater reuse in agriculture and the associated environmental and health issues between developing and developed countries. In addition, some integrated sustainable solutions and future perspectives are also proposed, keeping in view the regional and global context, as well as the grounded reality of wastewater use for crop production, sanitary and planning issues, remedial techniques, awareness among civil society, and the role of the government and the relevant stakeholders.

Quantitative microbial risk assessment of Greywater on-site reuse

Recycle domestic greywater for on-site non-potable uses can lessen the demand on potable water and the burden on wastewater treatment plants. However, lack of studies to assess health risk associated with such practices has hindered their popularity. A Quantitative Microbial Risk Assessment was conducted to estimate the public health risks for two greywater reuse scenarios: toilet flushing and food-crop irrigation. Household greywater quality from three sources (bathroom, laundry and kitchen) was analyzed. Mathematical exposure rates of different scenarios were established based on human behavior using Monte-Carlo simulation. The results showed that, greywater from all three household sources could be safely used for toilet flushing after a simple treatment of microfiltration. The median range of annual infection risk was 8.8 × 10−15–8.3 × 10−11 per-person-per-year (pppy); and the median range of disease burden was 7.6 × 10−19–7.3 × 10−15 disability-adjusted life years (DALYs) pppy. In food-crop irrigation scenario, the annual infection risks and disease burdens of treated greywater from bathroom and laundry (2.8 × 10−8, 4.9 × 10−8 pppy; 2.3 × 10−12–4.2 × 10−12 DALYs pppy) were within the acceptable levels of U.S. EPA annual infection risk (≤10−4 pppy) and WHO disease burden (≤10−6 DALYs pppy) benchmarks, while kitchen greywater was not suitable for food-crop irrigation (4.9 × 10−6 pppy; 4.3 × 10−10 DALYs pppy) based on these benchmarks. The model uncertainties were discussed, which suggests that a more accurate risk estimation requires improvements on data collection and model refinement.

An impact assessment for urban stormwater use.

Stormwater has the potential to provide a non-potable water supply which requires less treatment than municipal wastewaters with the added benefit of reducing pollution and erosion issues in receiving water bodies. However, the adoption of stormwater collection and use as an accepted practice requires that the perceived risks, particularly those associated with public health, are addressed. This paper considers the human health concerns associated with stormwater quality when used for a range of non-potable applications using E. coli, a commonly found pollutant in urban stormwater which is also widely included in human health-based water quality standards and guidelines. Based on a source-pathway-receptor model, scores are allocated, on a scale of 0 to 5, to benchmark increasing the likelihoods of exposure to stormwater during different occupational and non-occupational applications and magnitude of impacts which may result. The impacts are assessed by comparing median stormwater E. coli levels with the reported guideline levels relating to different stormwater uses. Combination of the exposure and impact scores provides an overall risk score for each stormwater application. Low or medium risks are shown to be associated with most stormwater uses except for domestic car washing and occupational irrigation of edible raw food crops where the predicted highest levels of risk posed by median E. coli levels in stormwater necessitate the introduction of remedial actions.

A risk-based approach for developing standards for irrigation with reclaimed water

A generalised quantitative risk assessment (QRA) is developed to assess the potential harm to human health resulting from irrigation with reclaimed water. The QRA is conducted as a backward calculation starting from a pre-defined acceptable risk level at the receptor point (defined as an annual infection risk of 10−4 for pathogens and by reference doses (RfD) for chemical hazards) and results in an estimate of the corresponding acceptable concentration levels of the given hazards in the effluent. In this way the QRA is designed to inform the level of water treatment required to achieve an acceptable risk level and help establish reclaimed water quality standards. The QRA considers the exposure of human receptors to microbial and chemical hazards in the effluent through various exposure pathways and routes depending on the specific irrigation scenario. By considering multiple pathways and routes, a number of key aspects relevant to estimating human exposure to recycled water can be accounted for, including irrigation and crop handling practices (e.g., non-edible vs edible, spray vs. drip, withholding time) and volumes consumed (directly vs indirectly). The QRA relies on a large number of inputs, many of which were found to be highly uncertain. A possibilistic approach, based on fuzzy set theory, was used to propagate the uncertain input values through the QRA model to estimate the possible range of hazard concentrations that are deemed acceptable/safe for reclaimed water irrigation. Two scenarios were considered: amenity irrigation and irrigation of ready-to-eat food crops, and calculations were carried out for six example hazards (norovirus, Cryptosporidium, cadmium, lead, PCB118 and naphthalene) and using UK-specific input values. The human health risks associated with using reclaimed water for amenity irrigation were overall deemed low, i.e. the calculated acceptable concentration levels for most of the selected hazards were generally far greater than levels typically measured in effluent from wastewater treatment plants; however the predicted acceptable concentration levels for norovirus and Cryptosporidium suggested that disinfection by UV may be required before use. It was found that stricter concentration standards were required for hazards that are more strongly bound to soil and/or are more toxic/infectious. It was also found that measures that reduce the amount of effluent directly ingested by the receptor would significantly reduce the risks (by up to 2 orders of magnitude for the two pathogens). The results for the food crop irrigation scenario showed that stricter concentration standards are required to ensure the effluent is safe to use. For pathogens, the dominant exposure route was found to be ingestion of effluent captured on the surface of the crops indicating that risks could be significantly reduced by restricting irrigation to the non-edible parts of the crop. The results also showed that the exposure to some organic compounds and heavy metals through plant uptake and attached soil particles could be high and possibly pose unacceptable risk to human health. For both scenarios, we show that the predicted acceptable concentration levels are associated with large uncertainty and discuss the implications this has for defining quality standards and how the uncertainty can be reduced.

Impact of the reusing of food manufacturing wastewater for irrigation in a closed system on the microbiological quality of the food crops

In order to evaluate if the reuse of food industry treated wastewater is compatible for irrigation of food crops, without increased health risk, in the present study a cropping system, in which ground water and treated wastewater were used for irrigation of tomato and broccoli, during consecutive crop seasons was monitored. Water, crop environment and final products were monitored for microbial indicators and pathogenic bacteria, by conventional and molecular methods. The microbial quality of the irrigation waters influenced sporadically the presence of microbial indicators in soil. No water sample was found positive for pathogenic bacteria, independently from the source. Salmonella spp. and Listeria monocytogenes were detected in soil samples, independently from the irrigation water source. No pathogen was found to contaminate tomato plants, while Listeria monocytogenes and E. coli O157:H7 were detected on broccoli plant, but when final produce were harvested, no pathogen was detected on edible part.The level of microbial indicators and detection of pathogenic bacteria in field and plant was not dependent upon wastewater used. Our results, suggest that reuse of food industry wastewater for irrigation of agricultural crop can be applied without significant increase of potential health risk related to microbial quality.

Obstacles to Low Quality Water Irrigation of Food Crops in Morogoro, Tanzania

Knowledge on users’ and regulators’ views regarding obstacles on the use of low quality water forms the basis for the improvement of water reuse in food crops irrigation. A qualitative study was conducted to assess the obstacles to the use of low quality water for irrigation of food crops in urban and peri-urban areas in Tanzania. The study considered Morogoro urban and peri-urban areas as a case study due to the existence of paddy and vegetable production using the effluent from the waste stabilisation ponds. Both primary and secondary data were used. Primary data were collected through in-depth interviews with 22 key informants, and 4 focus group discussions with farmers. Content analysis was used in this study. Findings show that domestic wastewater was poorly disposed, waste stabilisation ponds as treatment facilities had limited management, and quality monitoring of effluent from the waste stabilisation ponds was limited to permit safe use of the effluent in food crops irrigation. The government officials were of the view that the effluent from the waste stabilisation ponds should not be used for leafy vegetables irrigation while farmers viewed vegetables farming as a quick source of income and livelihood strategy for many years. The study therefore suggests that the relevant agencies should improve the treatment of wastewater and quality monitoring of the effluent for safe use of low quality water for food crops irrigation in urban and peri-urban areas.

Environmentally relevant concentrations of aminopolycarboxylate chelating agents mobilize Cd from humic acid

Although Cd is a pollutant of public health relevance, many dietary sources from which it can be absorbed into human tissues remain unknown. While it is well established that the biogeochemical cycle of Cd involves its complexation with environment-derived ligands (e.g., humic acids, HAs) and anthropogenic ones (e.g., chelating agents, CAs), the interaction of Cd with both of these ligands is less well understood. To gain insight, a HA–Cd complex was injected on a size-exclusion chromatography (SEC) column coupled on-line with a flame atomic absorption spectrometer (FAAS) using 10mmol/L Tris buffer (pH8.0) as the mobile phase. This approach allowed us to observe the intact HA–Cd complex and the retention behavior of Cd as a function of 2–20μmol/L concentrations of ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA) or methylglycinediacetic acid (MGDA) that were added to the mobile phase. An increase of the retention time of Cd was indicative of a partial or complete abstraction of Cd from HA. Our results revealed that all CAs abstracted Cd from the HA–Cd complex at concentrations of 5μmol/L, while MGDA and DTPA were effective at 2μmol/L. The bioavailability of some of the on-column formed CA–Cd complexes explains the previously reported increased accumulation of Cd in periphyton in the ecosystem downstream of wastewater treatment plants. In addition, our results imply that the use of effluents which contain CAs and Cd for the irrigation of food crops can introduce Cd into the food supply and compromise food safety.

Benefits of an integrated water and nutrient reuse system for urban areas in semi-arid developing countries

Urban areas of developing countries face the challenge to implement adequate water and sanitation infrastructures while using natural and financial resources sustainably. The objective of this study was to identify benefits and challenges of different nutrient and water reuse systems. For this, we evaluated and compared four systems; (1a) the local conventional water and sanitation system, (2a) a novel water and nutrient reuse system connecting sanitation, advanced wastewater treatment and nutrient-rich water reuse for the irrigation of human food crops, (1b) the local conventional water and sanitation system adapted for water reuse and (2b) the novel water and nutrient reuse system adapted to be low-tech. Our case study, a town in Namibia, exemplifies the typical problems of urban areas in developing countries. We compared the four systems using ecological, economic, societal, institutional, political, and technical criteria, via multi-decision criteria analysis with the Analytic Hierarchy Process (AHP). Our results indicate that the novel water and nutrient reuse system (2a) scores highest with environmental and societal criteria when weighting all evaluation criteria equally. Its challenges lay especially in the economic criteria. Nonetheless, for our case study, an urban area in a developing country, the novel water and nutrient reuse system (2a) is a viable sanitation, wastewater and irrigation infrastructure for using fewer resources, being economically feasible, institutionally and politically practical and technically sound. However, the preference for a particular water and sanitation infrastructure also depends on which criteria the decision-maker is willing to assign the highest weight to. The presented methodology helps decision-makers and engineers with complex decision–making by evaluating numerous criteria in order to have proper information on the benefits and challenges of water and sanitation systems.

Incentives for low-quality water irrigation of food crops in Morogoro, Tanzania

This article highlights the link between low-quality water and food crops irrigation. A cross-sectional research was conducted to assess factors motivating farmers to use low-quality water from the waste stabilisation ponds for food crops irrigation in urban and peri-urban areas in Morogoro Urban and Mvomero, in Morogoro Region, Tanzania, from October 2013 to March 2015. Data were collected through farmers’ survey (n = 80), in-depth interviews with key informants (n = 7) and focus group discussions (n = 4). Both descriptive and inferential statistics were used in results presentation. The findings indicated alternative way of earning income during dry seasons, lack of alternative sources of irrigation water, alternative source of employment, the need to produce food, land availability near the low-quality water, plant nutrients in the water and limited awareness of the health problems associated with low-quality water irrigation as incentives for farmers to irrigate food crops using low-quality water. The results further showed that farming using low-quality water has been their livelihood strategy; farmers meet their family needs such as school fees, health and food by using the income generated from the sale of vegetables and paddy. Regardless of all these benefits, the existing use of low-quality water in farming activities is informal. Besides, there are no regulations guiding its use with no declaration to whether the resource is suitable for food crops irrigation. However, banning the practice on the ground of health risks might be devastating to farmers. This practice should therefore be regulated in such a way that low-quality water disposed from the ponds is considered as a potential source of water for food crops irrigation.

Public perceptions of water shortages, conservation behaviors, and support for water reuse in the U.S.

Reclaimed water programs treat wastewater to remove hazardous compounds, pathogens, and organic matter and provide reclaimed water for non-potable applications. Reusing water may significantly reduce demands on freshwater resources and provide sustainable water management strategies. Though production of reclaimed water is highly regulated, public acceptability has historically hindered the implementation of successful reclaimed water systems. The public generally opposes the use of reclaimed water due to the “yuck factor”, which is the instinctive disgust associated with the idea of recycling sewage and the fear that exposure to reclaimed water is unsafe. This paper reports the results of an extensive survey that was conducted to evaluate the potential acceptability of reclaimed water use. A total of 2800 respondents across the U.S. participated in the survey. Results demonstrate that a small percentage of the population is concerned about water shortages, the majority of the population practices some level of water conservation, and a substantial percentage of the population supports the use of reclaimed water. Climate, demographic variables, and financial incentives were tested for influence on attitudes and behaviors regarding water, including awareness, conservation, and support for water reuse. Sex, age, last monthly water bill, and location (as EPA region) showed no significant effect on the acceptance of water reuse, while ethnicity, education level, metro/non metro, and income showed significant effects. Drought conditions do not have a statistically significant effect on the number of reclaimed water supporters, but increase the number of respondents who are water concerned, the number of respondents who are the most active water conservers, and the number of respondents who limit their use of water for lawn and garden watering. Financial incentives influence the willingness of respondents to participate in water reuse programs, and a decrease in the monthly water bills increased the likelihood that respondents would participate in a reclaimed water program. Support for the use of reclaimed water for various applications ranked positively, on average, except for the application of water reuse for food crop irrigation and use of reclaimed water at respondents’ own residences. Results and conclusions of the survey can provide insight for implementing successful reclaimed water programs.

Effects of greywater irrigation on germination, growth and photosynthetic characteristics in selected African leafy vegetables

The reuse of greywater, wastewater from sources other than toilets, could enable low-income households to save potable water for drinking and cooking. Greywater irrigation of food crops is widely practised but its effects on African leafy vegetables (ALVs), which hold potential for cultivation to improve food security, are unknown. This study investigated the effects of synthetic greywater irrigation on germination in three ALVs, viz., Amaranthus dubius, Cleome gynandra and Solanum nigrum, and subsequent seedling growth in A. dubius and S. nigrum. Seeds and seedlings were treated with chlorinated and dechlorinated greywater and tap water, supplemented with nutrients. Greywater application decreased germination capacity (by 23–25%) when assessed in Petri dishes in A. dubius only. However, greywater application was less harmful to A. dubius seeds sown in soil. Vigour was compromised in greywater-treated seeds of all three species but greywater can be used to irrigate freshly-sown seeds of A. dubius without reducing percentage seedling production. However, greywater irrigation reduced capacity (by 21–23%) and rate of shoot emergence in S. nigrum, and growth and chlorophyll content in both species. These negative effects were accompanied by increased soil electrical conductivity (after 21 d) and pH (after 14 d). The reduced growth under greywater irrigation was most likely based on a reduction in light-harvesting capacity and/or nutrient availability. Overall, S. nigrum seedlings were significantly more sensitive to the negative effects of greywater, possibly due to increased transpirational water loss under greywater irrigation. The effects of greywater were largely independent of chlorine content. Applying greywater in excess of plant requirements and/or alternating greywater irrigation events with freshwater watering events could promote leaching of salts found in greywater. The effects of greywater irrigation on soil water and nutrient availability demand further investigation for ALVs.Keywords: African leafy vegetables, greywater irrigation, germination, seedling growth

Optimization of ozone disinfection and its effect on trihalomethanes

Ozone is an attractive disinfection alternative to chlorine as chlorine has some environmental consequences due to its disinfection byproducts potential. In the present study ozone was used for the disinfection of secondary treated effluent of sewage treatment plant which is based on rotating biological contactor, process, Malaviya National Institute of Technology (Jaipur). From the experimental results it was found that ozone dose of 30mg/L was required to achieve WHO standards for Total Coliform Count (TCC) of 1000CFU/100mL for food crop irrigation and recreational impoundments. One factorial design method of response surface methodology (RSM) was used for statistically obtaining optimum ozone dose that satisfies the norms for COD and TCC simultaneously. The optimized ozone dose suggested by the model was 30mg/L to bring TCC within norms and the value of COD at this dose was 21mg/L. Experimental verification of the results was in good agreement with the predicted results of one factorial design. Analysis of scanned electron microscopy (SEM) images, shows the effect of ozone doses on bacterial cell membrane. Effect of ozone on four trihalomethanes was also studied using GC–MS/MS.

Evaluation of Horizontal–Vertical Subsurface Hybrid Constructed Wetlands for Tertiary Treatment of Conventional Treatment Facilities Effluents in Developing Countries

In this study, four large pilot-scale horizontal–vertical hybrid constructed wetlands (CWs) were constructed for the tertiary treatment of effluent of North Wastewater Treatment Plant in Isfahan, Iran. The plant effluent did not meet the regulation limits of wastewater reuse for various applications (e.g., irrigation of food and non-food crops, forests and green areas, groundwater recharge, and urban reuse applications). So the hybrid CW system was set up to provide a suitable effluent for this purpose. Each hybrid unit consisted of a 100-m2 horizontal flow (HF) and a 32-m2 vertical flow (VF) subsurface CW operating in series. Three emergent plants consisting of Phragmites australis, Typha latifolia, and Arundo donax were planted in the CWs and one unit left unplanted. The filling material was fine grain from 3–7 mm. The average organic load and the average hydraulic loading rate (HLR) of the system were 15 g biochemical oxygen demand (BOD5) m−1 day−1 and 5.3 cm day−1, respectively. The k-C* first-order model constant was computed for seven physical, chemical, and microbiological parameters—BOD5, chemical oxygen demand (COD), total suspended solids (TSS), NO3-N, NH4-N, total phosphorus (TP), and fecal coliforms—based on the influent/effluent concentration data for estimation of required surface area of full-scale CWs in the future. The results of 12-month sampling showed that the hybrid HF-VF CWs are highly efficient in removing of the BOD5 (85 % medium), COD (80 % medium), TSS (79 % medium), NH4-N (78 % medium), TP (74 % medium), and fecal coliforms (99 % medium). Also, there were no significant differences between various planted hybrid CWs in removal efficiency and first-order model constant for BOD5, COD, TSS, and coliforms, nor were there significant differences between planted and unplanted CWs for these parameters. But, for nutrients, the removal efficiencies of planted CWs were higher than those of control CW during the operation time. Among the CWs, the Phragmites showed the best efficiency for removal of nutrients followed by Arundo. It was observed that the removal efficiencies in HFCWs were higher than those in VFCWs due to longer hydraulic retention time (HRT), but for coliform removal, the VFCWs showed a higher efficiency. The effluent quality met the requirements for its reuse in various applications, but bacterial contents were equal to levels that permit the reuse of effluent in the non-food crop, forest and other green area irrigation, groundwater recharge, and some urban applications with restricted public exposure. The results of this pilot-scale research study showed that the performance of a single HFCW was probably not sufficient to achieve a suitable water quality for reuse of effluents and the hybrid CWs are more efficient and feasible systems for this purpose.

Accumulation of contaminants of emerging concern in food crops-part 2: Plant distribution.

Arid agricultural regions often turn to using treated wastewater (reclaimed water) to irrigate food crops. Concerns arise, however, when considering the potential for persistent contaminants of emerging concern to accumulate into plants intended for human consumption. The present study examined the accumulation of a suite of 9 contaminants of emerging concern into 2 representative food crops, lettuce and strawberry, following uptake via the roots and subsequent distribution to other plant tissues. Calculating accumulation metrics (concentration factors) allowed for comparison of the compartmental affinity of each chemical for each plant tissue compartment. The root concentration factor was found to exhibit a positive linear correlation with the pH-adjusted octanol-water partition coefficient (DOW ) for the target contaminants of emerging concern. Coupled with the concentration-dependent accumulation observed in the roots, this result implies that accumulation of these contaminants of emerging concern into plant roots is driven by passive partitioning. Of the contaminants of emerging concern examined, nonionizable contaminants, such as triclocarban, carbamazepine, and organophosphate flame retardants displayed the greatest potential for translocation from the roots to above-ground plant compartments. In particular, the organophosphate flame retardants displayed increasing affinity for shoots and fruits with decreasing size/octanol-water partition coefficient (KOW ). Cationic diphenhydramine and anionic sulfamethoxazole, once transported to the shoots of the strawberry plant, demonstrated the greatest potential of the contaminants examined to be then carried to the edible fruit portion.