Reclamation of used urban waters for irrigation purposes--a review of treatment technologies

Modelling and optimization of membrane process for removal of biologics (pathogens) from water and wastewater: Current perspectives and challenges

As one of the 17 sustainable development goals, the United Nations (UN) has prioritized "clean water and sanitation" (Goal 6) to reduce the discharge of emerging pollutants and disease-causing agents into the environment. Contamination of water by pathogenic microorganisms and their existence in treated water is a global public health concern. Under natural conditions, water is frequently prone to contamination by invasive microorganisms, such as bacteria, viruses, and protozoa. This circumstance has therefore highlighted the critical need for research techniques to prevent, treat, and get rid of pathogens in wastewater. Membrane systems have emerged as one of the effective ways of removing contaminants from water and wastewater However, few research studies have examined the synergistic or conflicting effects of operating conditions on newly developing contaminants found in wastewater. Therefore, the efficient, dependable, and expeditious examination of the pathogens in the intricate wastewater matrix remains a significant obstacle. As far as it can be ascertained, much attention has not recently been given to optimizing membrane processes to develop optimal operation design as related to pathogen removal from water and wastewater. Therefore, this state-of-the-art review aims to discuss the current trends in removing pathogens from wastewater by membrane techniques. In addition, conventional techniques of treating pathogenic-containing water and wastewater and their shortcomings were briefly discussed. Furthermore, derived mathematical models suitable for modelling, simulation, and control of membrane technologies for pathogens removal are highlighted. In conclusion, the challenges facing membrane technologies for removing pathogens were extensively discussed, and future outlooks/perspectives on optimizing and modelling membrane processes are recommended.

Combined process of chemically enhanced sedimentation and rapid filtration for urban wastewater treatment for potable reuse

The objective of this study is to propose a new post-treatment of effluents from Upflow Anaerobic Sludge Blanket (UASB) using rapid filtration, aiming at the production of water for potable reuse. The final quality of the effluent produced by the treatment using gravel, sand, clinoptilolite and activated carbon associated with disinfection was evaluated by physical chemical analysis, heavy metals and persistent organic contaminants. Experiments were carried out in jar test, filter operation time, evaluation of the efficiency using peracetic acid and free chlorine as disinfectant and all results were statistically analysed. The best conditions were those using 20 mg/L of ferric chloride and natural pH of the effluent (≈ 7.0), which resulted in less reagent consumption. The use of intermediate fund discharges made it possible to obtain approximately 91% of recovered water efficiency. The effluent treated under these conditions showed DOC <2.0 mg/L, COD <1.0 mg/L, BOD <1.0 mg/L, turbidity <1.0 NTU, TSS <1.0 mg/L, ammonia <0.1 mg/L, total phosphorus <0.1 mg/L and surfactants <0.1 mg/L. The disinfection process with free chlorine and PAA allowed the total inactivation of faecal coliforms and total coliforms. The treatment using rapid filtration with disinfection by chlorine reached the appropriate level for urban, environmental, industrial and indirect potable water reuse.

Transformation of 6PPDQ during disinfection: Kinetics, products, and eco-toxicity assessment

N-phenyl-N'-(1,3-dimethyl butyl)-p-phenylenediamine-quinone (6PPDQ) currently arouses broad concerns because of its acute lethality to coho salmon and rainbow trout at environmentally relevant concentrations and the wide occurrence in runoff-impacted water. Investigation on the fate and transformation of 6PPDQ in various treatment processes is necessary for its risk assessment and control. Here, we explored the transformation of 6PPDQ during disinfection with its precursor 6PPD as a reference, focusing on kinetics, products, and toxicity variation. 6PPDQ readily reacted with hypochlorite and chlorine dioxide with second-order rate constants of 2580 ± 143 M-1 s-1 and 614 ± 52 M-1 s-1 (pH 7.0 and 25 °C), which are slightly lower than the reactions of 6PPD. We tentatively identified thirteen transformation products for 6PPDQ and eight for 6PPD in reaction with the two disinfectants. It seems that the quinone ring of 6PPDQ and the p-phenylenediamine moiety of 6PPD are reactive sites. The transformation of these compounds probably proceeds through Cl-substitution, ring cleavage, hydroxylation, and amine oxidation and hydrolysis. Tests with zebrafish embryos revealed that the transformation products of 6PPDQ could have higher eco-toxicity than the parent compound, while the toxicity of the 6PPD products remained nearly unchanged. The increased toxicity of 6PPDQ during disinfection highlights the necessity to substantially reduce its content before the disinfection of runoff-impacted water.

Constructed wetland mesocosms improve the biodegradation of microcystin-LR and cylindrospermopsin by indigenous bacterial consortia

Cyanobacterial blooms releasing harmful cyanotoxins, such as microcystin (MC) and cylindrospermopsin (CYN), are prominent threats to human and animal health. Constructed wetlands (CW) may be a nature-based solution for bioremediation of lake surface water containing cyanotoxins, due to its low-cost requirement of infrastructure and environmentally friendly operation. There is recent evidence that microcystin-LR (MC-LR) can efficiently be removed in CW microcosms where CYN degradation in CW is unknown. Likewise, the mechanistic background regarding cyanotoxins transformation in CW is not yet elucidated. In the present study, the objective was to compare MC-LR and CYN degradation efficiencies by two similar microbial communities obtained from CW mesocosms, by two different experiments setup: 1) in vitro batch experiment in serum bottles with an introduced CW community, and 2) degradation in CW mesocosms. In experiment 1) MC-LR and CYN were spiked at 100 µg L-1 and in experiment 2) 200 µg L-1 were spiked. Results showed that MC-LR was degraded to ≤1 µg L-1 within seven days in both experiments. However, with a markedly higher degradation rate constant in the CW mesocosms (0.18 day-1 and 0.75 day-1, respectively). No CYN removal was detected in the in vitro incubations, whereas around 50 % of the spiked CYN was removed in the CW mesocosms. The microbial community responded markedly to the cyanotoxin treatment, with the most prominent increase of bacteria affiliated with Methylophilaceae (order: Methylophilales, phylum: Proteobacteria). The results strongly indicate that CWs can develop an active microbial community capable of efficient removal of MC-LR and CYN. However, the CW operational conditions need to be optimized to achieve a full CYN degradation. To the best of our knowledge, this study is the first to report the ability of CW mesocosms to degrade CYN.

Fuzzy Modeling Development for Lettuce Plants Irrigated with Magnetically Treated Water

Due to the worldwide water supply crisis, sustainable strategies are required for a better use of this resource. The use of magnetic water has been shown to have potential for improving irrigation efficacy. However, a lack of modelling methods that correspond to the experimental results and minimize error is observed. This study aimed to estimate the replacement rates of magnetic water provided by irrigation for lettuce production using a mathematical model based on fuzzy logic and to compare multiple polynomial regression analysis and the fuzzy model. A greenhouse study was conducted with lettuce using two types of water, magnetic water (MW) and conventional water (CW), and five irrigation levels (25, 50, 75, 100 and 125%) of crop evapotranspiration. Plant samples for biometric lettuce were taken at 14, 21, 28 and 35 days after transplanting. The data were analyzed via multiple polynomial regression and fuzzy mathematical modeling, followed by an inference of the models and a comparison between the methods. The highest biometric values for lettuce were observed when irrigated with MW during the different phenological stage evaluated. The fuzzy model provided a more exact adjustment when compared to the multiple polynomial regressions.

Reclamation of wastewater in wetlands using reed plants and biochar

To cope with water crisis, wastewater reuse has been introduced as a potential source for irrigation. On the other hand, irrigation with wastewater may negatively affect the surroundings. In this study, reed plant (Phragmits australis) and its biochar were tested as low-cost treatments to enhance the efficiency of wastewater reclamation in wetlands within only 72 h. The investigated water was of low irrigation quality and exhibited high contents of BOD₅ and fecal coliform. Moreover, this water contained high levels of soluble cations and anions; besides, being marginally contaminated with Cu, Mn and Cd. After 2 days in the sedimentation unit, wastewater was subjected to three reclamation treatments in parallel (each lasted for 24 h): (1) a "sand & gravel bed", (2) "reed plants grown on a sand & gravel bed" and (3) "biochar + a sand & gravel bed". The results showed that all treatments decreased BOD₅, fecal coliform, total cations and anions, with superiority for the second and third treatments. The levels of the potentially toxic elements also decreased to values within the permissible levels. Although the aforementioned wastewater treatment processes upgraded the quality of this water, it remained in the poor grade. Biochar or reed plants grown on sand and gravel beds significantly improved wastewater quality to the medium quality grade, with superiority for biochar treatment. In conclusion, investigated treatments are guaranteed in wetlands for wastewater reclamation; yet, further protocols should be followed to achieve safe handling of this water and attain the sustainable goals.

Effect of irrigation with treated wastewater on bermudagrass (Cynodon dactylon (L.) Pers.) production and soil characteristics and estimation of plant nutritional input

In recent years, climate change has greatly affected rainfall and air temperature levels leading to a reduction in water resources in Southern Europe. This fact has emphasized the need to focus on the use of non-conventional water resources for agricultural irrigation. The reuse of treated wastewater (TWW) can represent a sustainable solution, reducing the consumption of freshwater (FW) and the need for mineral fertilisers. The main aim of this study was to assess, in a three-year period, the effects of TWW irrigation compared to FW on the biomass production of bermudagrass [Cynodon dactylon (L.) Pers.] plants and soil characteristics and to estimate the nutritional input provided by TWW irrigation. TWW was obtained by a constructed wetland system (CWs) which was used to treat urban wastewater. The system had a total surface area of 100 m². An experimental field of bermudagrass was set up close to the system in a Sicilian location (Italy), using a split-plot design for a two-factor experiment with three replications. Results highlighted a high organic pollutant removal [five days biochemical oxygen demand (BOD₅): 61%, chemical oxygen demand (COD): 65%] and a good efficiency in nutrients [total nitrogen (TN): 50%, total phosphorus (TP): 42%] of the CWs. Plants irrigated with TWW showed higher dry aboveground dry-weight (1259.3 kg ha^-1) than those irrigated with FW (942.2 kg ha^-1), on average. TWW irrigation approximately allowed a saving of 50.0 kg TN ha^-1 year^-1, 24.0 kg TP ha^-1 year^-1 and 29.0 kg K ha^-1 year^-1 on average with respect to commonly used N-P-K fertilisation programme for bermudagrass in the Mediterranean region. Soil salinity increased significantly (p ≤ 0.01) over the years and was detected to be higher in TWW-irrigated plots (+6.34%) in comparison with FW-irrigated plots. Our findings demonstrate that medium-term TWW irrigation increases the biomass production of bermudagrass turf and contributes to save significant amounts of nutrients, providing a series of agronomic and environmental benefits.

Synergism in TiO2 photocatalytic ozonation for the removal of dichloroacetic acid and thiacloprid

The synergistic effect of the photocatalytic ozonation process (PH-OZ) using the photocatalyst TiO₂ is usually attributed to influences of the physicochemical properties of the catalyst, pollutant type, pH, temperature, O₃ concentration, and other factors. It is also often claimed that good adsorption on the TiO₂ surface is beneficial for the occurrence of synergism. Herein, we tested these assumptions by using five different commercial TiO₂ photocatalysts (P25, PC500, PC100, PC10 and JRC-TiO-6) in three advanced oxidation systems - photocatalysis (O₂/TiO₂/UV), catalytic ozonation (O₃/TiO₂) and PH-OZ (O₃/TiO₂/UV) - for the degradation of two pollutants (dichloroacetic acid - DCAA and thiacloprid) simultaneously present in water. The synergistic effect in PH-OZ was much more pronounced in the case of thiacloprid, a molecule with low adsorption on the surface of the catalyst - in contrast to DCAA with stronger adsorption. The faster kinetics of catalytic ozonation (O₃/TiO₂) correlated with the higher exposed surface area of TiO₂ agglomerates, independent of the (lower) BET surfaces of the primary particles. Nevertheless, DCAA mineralization on the TiO₂ surface was much faster than thiacloprid degradation in solution. Therefore, we propose that a high BET surface area of the photocatalyst is crucial for fast surface reactions (DCAA mineralization), while good dispersion - the high exposed surface area of the (small) agglomerates - and charge separation play an important role in photocatalytic degradation or PH-OZ of less adsorbed organic pollutants (thiacloprid).

Treated Wastewater Irrigation—A Review

As the most important resource for life, water has been a central issue on the international agenda for several decades. Yet, the world’s supply of clean freshwater is steadily decreasing due to extensive agricultural demand for irrigated lands. Therefore, water resources should be used with greater efficiency, and the use of non-traditional water resources, such as Treated Wastewater (TW), should be increased. Reusing TW could be an alternative option to increase water resources. Thus, many countries have decided to turn wastewater into an irrigation resource to help meet urban demand and address water shortages. However, because of the nature of that water, there are potential problems associated with its use in irrigation. Some of the major concerns are health hazards, salinity build-up, and toxicity hazards. The objectives of this comprehensive literature review are to illuminate the importance of using TW in irrigation as an alternative freshwater source and to assess the effects of its use on soil fertility and other soil properties, plants, and public health. The literature review reveals that TW reuse has become part of the extension program for boosting water resource utilization. However, the uncontrolled application of such waters has many unfavorable effects on both soils and plants, especially in the long-term. To reduce these unfavorable effects when using TW in irrigation, proper guidelines for wastewater reuse and management should be followed to limit negative effects significantly.

Advancement in Benthic Microbial Fuel Cells toward Sustainable Bioremediation and Renewable Energy Production

Anthropogenic activities are largely responsible for the vast amounts of pollutants such as polycyclic aromatic hydrocarbons, cyanides, phenols, metal derivatives, sulphides, and other chemicals in wastewater. The excess benzene, toluene and xylene (BTX) can cause severe toxicity to living organisms in wastewater. A novel approach to mitigate this problem is the benthic microbial fuel cell (BMFC) setup to produce renewable energy and bio-remediate wastewater aromatic hydrocarbons. Several mechanisms of electrogens have been utilized for the bioremediation of BTX through BMFCs. In the future, BMFCs may be significant for chemical and petrochemical industry wastewater treatment. The distinct factors are considered to evaluate the performance of BMFCs, such as pollutant removal efficiency, power density, and current density, which are discussed by using operating parameters such as, pH, temperature and internal resistance. To further upgrade the BMFC technology, this review summarizes prototype electrode materials, the bioremediation of BTX, and their applications.

The role of green roofs in urban Water-Energy-Food-Ecosystem nexus: A review

Green roofs are strategic tools that can play a significant role in the creation of sustainable and resilient cities. They have been largely investigated thanks to their high retention capacity, which can be a valid support to mitigate the pluvial flood risk and to increase the building thermal insulation, ensuring energy saving. Moreover, green roofs contribute to restoring vegetation in the urban environment, increasing the biodiversity and adding aesthetic value to the city. The new generation of multilayer green roofs present an additional layer with respect to traditional ones, which allows rainwater to be stored, which, if properly treated, can be reused for different purposes. This paper offers a review of benefits and limitations of green roofs, with a focus on multilayer ones, within a Water-Energy-Food-Ecosystem nexus context. This approach enables the potential impact of green roofs on the different sectors to be highlighted, investigating also the interactions and interconnections among the fields. Moreover, the Water-Energy-Food-Ecosystem nexus approach highlights how the installation of traditional and multilayer green roofs in urban areas contributes to the Development Goals defined by the 2030 Sustainable Agenda.

Livestock Wastewater Treatment in Constructed Wetlands for Agriculture Reuse

The aim of this study focused on the evaluation of constructed wetlands (CWs) microcosms, on a laboratory scale, for the removal of metals from a pig industry effluent while maintaining effluent organic matter and nutrients levels for its later used as a fertilizer. CWs with different macrophytes (Phragmites australis and Typha latifolia) and different substrates (light expanded clay aggregate and lava rock) were tested. Results showed high removals of metals during CWs treatment, with removal rates reaching >80% for Cd, Cr, Cu, Fe, Mn, and Zn after 2 days of treatment in CWs planted with T. latifolia and >60% in CWs planted with P. australis. Significant differences were only found between substrates for Fe and Mn in CWs with P. australis. Removal of organic matter (through chemical oxygen demand (COD)) was >77%, with no significant differences between substrates or plants. Removals of ammonium and phosphate ions ranged between 59–84% and 32–92%, respectively, in CWs with P. australis and 62–75% and 7–68% in CWs with T. latifolia, with no significant differences between substrates. Overall, CWs showed potential to be efficient in removing toxic contaminants, as metals, while maintaining moderated levels of nutrients, allowing the use of reclaimed water in agriculture, namely as fertilizer. If one aims for a short CW treatment, CW planted with T. latifolia and expanded clay as substrate could be the more suitable choice.

Optimization and economical study of electro-coagulation unit using CCD to treat real graywater and its reuse potential

The reclamation of graywater for non-potable purposes has attained utmost importance, particularly in developing nations. The present research aimed to evaluate the optimal condition of electro-coagulation system in treatment of graywater and its reuse. Moreover, the study also evaluates the impact of major operating parameters on pollutant removal and anode dissolution. To achieve this, two-factor (voltage potential and time) and 5-level (- 1, - 0.5, 0, + 0.5, and + 1) full factorial design, based on response surface methodology (RSM) has been executed for the actual design. The data were acquired after conducting 20 experiments, as suggested by RSM (response surface methodology). Design Expert 12.0.8.0 software has been used to design mathematical model to obtain optimum condition (14 V and 47 min) at pH of 7.35, which provides experimental removal efficiency (75.6% chemical oxygen demand, 78.7% total dissolved solids, 93.4% turbidity, and 63.2% chloride) with minimal electrode consumption of 1.38 mg L^-1. Adequacy of the model developed has been verified by ANOVA. The operating cost of treating graywater at the optimized condition obtained as 0.7 US$/kg COD.

Water Scarcity and Wastewater Reuse in Crop Irrigation

Due to climate change, two-thirds of mankind will face water scarcity by 2025, while by 2050, global food production must increase by at least 50% to feed 9 billion people. To overcome water scarcity, 15 million m3/day of untreated wastewater is used globally for crop irrigation, polluting the soil with pathogens, heavy metals and excess salts. Since 10% of the global population consumes food from crops irrigated with wastewater, pathogens transmitted through the food chain cause diseases especially in young children and women. In this paper, we discuss the status of water scarcity and the challenges to food security, the reuse of wastewater in agriculture and the possible risks to human and environmental health. The efficiency of different irrigation systems in limiting the risks of wastewater reuse and the latest regulations of the European Commission on effluent recovery are also presented. Hence, we emphasize that irrigation offers real perspectives for large-scale recovery of wastewater, helping to reduce the deficit and conserve water resources, and increasing food safety, with the express mention that investments must be made in wastewater treatment plants and wastewater must be properly treated before recovery, to limit the risks on human health and the environment.

Reusing greywater for cultivation of Capsicum frutescens and Calendula officinalis

This study investigated the impact of greywater application for home yard gardening. Greywater was collected and treated using screening, sedimentation and solar disinfection methods. Finally, a field experiment was conducted to investigate the impact of untreated and treated greywater on a selected vegetable, Capsicum frutescens and flowering plant, Calendula officinalis for 2 months. The findings depicted that untreated greywater contains higher macro-nutrients with excessive bacterial population compared with tap water (control), however, the treatment process reduced the concentration of most of the unwanted parameters from greywater samples to bring them into irrigation standards. Overall, treated greywater irrigation showed the species-specific impact on experimental plants with more stimulation in Capsicum frutescens species compared with tap water irrigation. Both treated and untreated greywater irrigation increased the growth parameters of Calendula officinalis in comparison with control. The impact was not significant for most of the parameters of Calendula officinalis while compared between greywater (treated and untreated) and control, and between treated and untreated greywater irrigation. Treated greywater irrigation significantly stimulated most of the parameters of Capsicum frutescens while untreated greywater increased only moisture content, and number of branches compared with control. Most interestingly, treated greywater irrigation had significant impact on Capsicum frutescens particularly for number of branches and leaves compared with untreated greywater irrigation. In fine, the greywater, after treatment was bacterially safe and had positive impact on plant growth. The findings of this study will help to conserve irrigation water and to protect and manage aquatic ecosystem from the adverse impact of wastewater.

Recent Progress in Heavy Metal Ion Decontamination Based on Metal-Organic Frameworks

Heavy metals are inorganic pollutants which pose a serious threat to human and environmental safety, and their effective removal is becoming an increasingly urgent issue. Metal-organic frameworks (MOFs) are a novel group of crystalline porous materials, which have proven to be promising adsorbents because of their extremely high surface areas, optimizable pore volumes and pore size distributions. This study is a systematic review of the recent research on the removal of several major heavy metal ions by MOFs. Based on the different structures of MOFs, varying adsorption capacity can be achieved, ranging from tens to thousands of milligrams per gram. Many MOFs have shown a high selectivity for their target metal ions. The corresponding mechanisms involved in capturing metal ions are outlined and finally, the challenges and prospects for their practical application are discussed.

Effects of different filtration techniques on quality and toxicology of post treatment effluent from an anaerobic reactor

The early stages of the fish life cycle correspond to the phase that is most susceptible to deleterious effects caused by exposure to pollution. The aim of this study was to evaluate the quality of the anaerobic reactor effluent after three filtration-based treatments, namely, Double-Filtration in gravel and sand (DF), Triple-Filtration in gravel, sand and Activated Charcoal (TF-AC) and Triple-Filtration in gravel, sand and clinoptilolite (TF-C). The toxic effects on the population dynamics of larvae and embryos of catfish (Rhamdia quelen) to the final effluent were evaluated using an individual-based model (IBM). The results indicate that the three post-treatments produced effluents with significant improvement of the physicochemical parameters evaluated in relation to the anaerobic reactor effluent. In addition, all post-treatments improved the removal of metal ions. Experimental data showed high mortality rates for Rhamdia quelen embryos and larvae for most treatments, except for the effluent treated by TF-C. The results demonstrated that the concentration of ammoniacal nitrogen in relation to AR treatments (69.0); DF (44.0); TF-AC (46.6) and TF-C (0.33) in mg/L can be a limiting factor for the development of embryos and larvae during the ecotoxicity tests.

A review of the impact of wastewater on the fate of pesticides in soils: Effect of some soil and solution properties

Reuse of wastewater (WW) as an agricultural irrigation source is being considered with increasing interest, mainly in arid and semiarid zones. However, due to the complex nature of WW its reuse can have an impact on the fate of the pesticides added to the soils and crops for pest control. This review provides a detailed insight about the main processes involved in pesticide-soil-WW interactions (adsorption/desorption, degradation, transport, plant uptake and field assays) focusing on the role of dissolved organic matter and salt content in the mentioned processes. The influence of pesticide and soil properties in these processes is also discussed. The review explores current research gaps in the pesticide-soil-WW interactions and identifies areas that merit further research, providing a perspective for further scientific exploration.

Wastewater Reclamation in Major Jordanian Industries: A Viable Component of a Circular Economy

Water scarcity remains the major looming challenge that is facing Jordan. Wastewater reclamation is considered as an alternative source of fresh water in semi-arid areas with water shortage or increased consumption. In the present study, the current status of wastewater reclamation and reuse in Jordan was analyzed considering 30 wastewater treatment plants (WWTPs). The assessment was based on the WWWTPs’ treatment processes in Jordan, the flowrates scale, and the effluents’ average total dissolved solid (TDS) contents. Accordingly, 60% of the WWTPs in Jordan used activated sludge as a treatment technology; 30 WWTPs were small scale (<1 × 104 m3/day); and a total of 17.932 million m3 treated wastewater had low TDS (<1000 ppm) that generally can be used in industries with relatively minimal cost of treatment. Moreover, the analysis classified the 26 million m3 groundwater abstraction by major industries in Jordanian governorates. The results showed that the reclaimed wastewater can fully offset the industrial demand of fresh water in Amman, Zarqa, and Aqaba governorates. Hence, the environmental assessment showed positive impacts of reclaimed wastewater reuse scenario in terms of water depletion (saving of 72.55 million m3 groundwater per year) and climate change (17.683 million kg CO2Eq reduction). The energy recovery assessment in the small- and medium-scale WWTPs (<10 × 104 m3/day) revealed that generation of electricity by anaerobic sludge digestion equates potentially to an offset of 0.11–0.53 kWh/m3. Finally, several barriers and prospects were put forth to help the stakeholders when considering entering into an agreement to supply and/or reuse reclaimed water.

Required Chlorination Doses to Fulfill the Credit Value for Disinfection of Enteric Viruses in Water: A Critical Review

A credit value of virus inactivation has been assigned to the disinfection step in international and domestic guidelines for wastewater reclamation and reuse. To fulfill the credit value for water disinfection, water engineers need to apply an appropriate disinfection strength, expressed as a CT value (mg × min/L), which is a product of disinfectant concentration and contact time, against enteric viruses in wastewater. In the present study, we extracted published experimental data on enteric virus inactivation using free chlorine and monochloramine and applied the Tobit analysis and simple linear regression analysis to calculate the range of CT values (mg × min/L) needed for 4-log₁₀ inactivation. Data were selected from peer-reviewed papers containing kinetics data of virus infectivity and chlorine residual in water. Coxsackie B virus and echovirus require higher CT values (lower susceptibility) for 4-log₁₀ inactivation than adenovirus and a human norovirus surrogate (murine norovirus) with free chlorine. On the other hand, adenovirus has lower susceptibility to monochloramine compared to murine norovirus, coxsackievirus, and echovirus. The factors that influence the required CT value are virus type, pH, water temperature, and water matrix. This systematic review demonstrates that enteroviruses and adenovirus are appropriate representative enteric viruses to evaluate water disinfection using free chlorine and monochloramine, respectively.

Effectiveness of wastewater treatment systems in removing microbial agents: a systematic review

Background

Due to unrestricted entry of wastewater into the environment and the transportation of microbial contaminants to humans and organisms, environmental protection requires the use of appropriate purification systems with high removal efficiency for microbial agents are needed. The purpose of this study was to determine the efficacy of current wastewater treatment systems in removing microbes and their contaminants.

Methods

A systematic review was conducted for all articles published in 5 Iranian environmental health journals in 11 years. The data were collected according to the inclusion and exclusion criteria and by searching the relevant keywords in the articles published during the years (2008–2018), with emphasis on the efficacy of wastewater treatment systems in removing microbial agents. Qualitative data were collected using a preferred reporting items for systematic reviews and meta-analyzes (PRISMA) standard checklist. After confirming the quality of the articles, information such as the name of the first author and the year of publication of the research, the type of study, the number of samples, the type of purification, the type of microbial agents and the rate of removal of microbial agents were entered into the checklist. Also the removal rates of the microbial agents mentioned in the studies were compared with united states environmental protection agency (US-EPA) standards.

Results

In this study, 1468 articles retrieved from 118 issues of 5 environmental health journals were reviewed. After reviewing the quality of the articles in accordance with the research objectives, 14 articles were included in the study that were published between 2010 and 2018. In most studies, two main indicators Total coliforms and Fecal coliforms in wastewater were investigated. Removing fungi and viral contamination from wastewater was not found in any of the 14 studies. Different systems (activated sludge, stabilization ponds, wetlands, and low and medium pressure UV disinfection systems were used to remove microbial agents in these studies. Most articles used active sludge systems to remove Total coliforms and Fecal coliforms, which in some cases were not within the US-EPA standard. The removal of Cysts and Parasitic eggs was only reporte from stabilization pond systems (SPS) where removal efficiency was found in accordance with US-EPA standards.

Conclusions

Different types of activated sludge systems have higher efficacy to remove microbial agents and are more effective than other mentioned systems in removing the main indicators of sewage contamination including Total coliforms and Fecal coliforms. However, inappropriate operation, maintenance and inadequate handling of activated sludge can also reduce its efficiency and reduce the removal of microbial agents, which was reported in some studies. Therefore, it is recommended to conduct research on how to improve the operation, maintenance, and proper management of activated sludge systems to transfer knowledge to users of sludge systems and prevent further health issues related to microbial agents.

Hydroponic technology as decentralised system for domestic wastewater treatment and vegetable production in urban agriculture: A review

Water scarcity, nutrient-depleted soils and pollution continue to be a major challenge worldwide and these are likely to worsen with increasing global populations particularly, in urban areas. As a result, environmental and public health problems may arise from the insufficient provision of sanitation and wastewater disposal facilities. Because of this, a paradigm shifts with regard to the sustainable management of waste disposal in a manner that could protect the environment at the same time benefits society by allowing nutrient recovery and reuse for food production is required. Hence, the use of urban wastewater for agricultural irrigation has more potential, especially when incorporating the reuse of nutrients like nitrogen and phosphorous, which are essential for crop production. Among the current treatment technologies applied in urban wastewater reuse for agriculture, hydroponic system is identified as one of the alternative technology that can be integrated with wastewater treatment. The integration of hydroponic system with municipal wastewater treatment has the advantage of reducing costs in terms of pollutants removal while reducing maintenance and energy costs required for conventional wastewater treatment. The efficiency of a hydroponic system with regard to municipal wastewater reuse is mainly linked to its capacity to allow continuous use of wastewater through the production of agricultural crops and the removal of pollutants/nutrients (nitrogen and phosphorus), resulting to increased food security and environmental protection. Moreover, the suitability of hydroponic system for wastewater treatment is derived from its capacity to minimize associated health risks to farmers, harvested crop and consumers, that may arise through contact with wastewater.

Characterization of implementation limits and identification of optimization strategies for sustainable water resource recovery through life cycle impact analysis

How we manage alternative freshwater resources to close the gap between water supply and demand is pivotal to the future of the environment and human well-being. Increased scarcity of water for agricultural irrigation in semi-arid and arid regions has resulted in a growing interest in water reuse practices. However, insight into the life cycle impacts and potential trade-offs of these emerging practices are still limited by the paucity of systematic evaluations of different water reuse implementations. In this study, a host of environmental and human health impacts at three implementation levels of allowing water reclamation for crop irrigation was comparatively evaluated across the operational landscape via a combination of scenario modelling, life-cycle impact analyses and Monte Carlo simulations. Net harvesting of reclaimed water for irrigation was found to be dependent upon the sophistication of the treatment processes, since multistage and complex configurations can cause greater direct water consumption during processing. Further, the direct benefits of water resource recovery can be essentially offset by indirect adverse impacts, such as mineral depletion, global warming, ozone depletion, ecotoxicity, and human health risks, which are associated with increased usage of energy and chemicals for rigorous removal of contaminants, such as heavy metals and contaminants of emerging concern. Nonetheless, expanded simulations suggest the significance of concurrently implementing energy recovery, nutrient recycling, and/or nature-based, chemical-free water technologies to reduce the magnitude of negative impacts from engineered water reclamation processes.

Sustainable Approach to Eradicate the Inhibitory Effect of Free-Cyanide on Simultaneous Nitrification and Aerobic Denitrification during Wastewater Treatment

Simultaneous nitrification and aerobic denitrification (SNaD) is a preferred method for single stage total nitrogen (TN) removal, which was recently proposed to improve wastewater treatment plant design. However, SNaD processes are prone to inhibition by toxicant loading with free cyanide (FCN) possessing the highest inhibitory effect on such processes, rendering these processes ineffective. Despite the best efforts of regulators to limit toxicant disposal into municipal wastewater sewage systems (MWSSs), FCN still enters MWSSs through various pathways; hence, it has been suggested that FCN resistant or tolerant microorganisms be utilized for processes such as SNaD. To mitigate toxicant loading, organisms in SNaD have been observed to adopt a diauxic growth strategy to sequentially degrade FCN during primary growth and subsequently degrade TN during the secondary growth phase. However, FCN degrading microorganisms are not widely used for SNaD in MWSSs due to inadequate application of suitable microorganisms (Chromobacterium violaceum, Pseudomonas aeruginosa, Thiobacillus denitrificans, Rhodospirillum palustris, Klebsiella pneumoniae, and Alcaligenes faecalis) commonly used in single-stage SNaD. This review expatiates the biological remedial strategy to limit the inhibition of SNaD by FCN through the use of FCN degrading or resistant microorganisms. The use of FCN degrading or resistant microorganisms for SNaD is a cost-effective method compared to the use of other methods of FCN removal prior to TN removal, as they involve multi-stage systems (as currently observed in MWSSs). The use of FCN degrading microorganisms, particularly when used as a consortium, presents a promising and sustainable resolution to mitigate inhibitory effects of FCN in SNaD.

Reduction of Arcobacter at Two Conventional Wastewater Treatment Plants in Southern Arizona, USA

This study aimed to identify the bacterial community in two wastewater treatment plants (WWTPs) and to determine the occurrence and reduction of Arcobacter, along with virulence genes (ciaB and pldA). A total of 48 samples (24 influent and 24 effluent) were collected at two WWTPs in southern Arizona in the United States, monthly from August 2011 to July 2012. Bacterial DNA extract was utilized for 16S rRNA metagenomic sequencing. Quantification of Arcobacter 16S rRNA gene was conducted using a recently developed SYBR Green-based quantitative PCR assay. Among 847 genera identified, 113 (13%) were identified as potentially pathogenic bacteria. Arcobacter 16S rRNA gene was detected in all influent samples and ten (83%) and nine (75%) effluent samples at each plant, respectively. Log reduction ratios of Arcobacter 16S rRNA gene in Plant A and Plant B were 1.7 ± 0.9 (n = 10) and 2.3 ± 1.5 (n = 9), respectively. The ciaB gene was detected by quantitative PCR in eleven (92%) and twelve (100%) of 12 influent samples from Plant A and Plant B, respectively, while the pldA gene was detected in eight (67%) and six (50%) influent samples from Plant A and Plant B, respectively. The prevalence of potentially pathogenic bacteria in WWTP effluent indicated the need for disinfection before discharge into the environment.

Development and adoption of wastewater treatment system for peri-urban agriculture in Multan, Pakistan

The present research was conducted to assess the feasibility of biological treatment of a typical wastewater (WW) stream in Multan, Pakistan, using daily trends of WW characteristics and to design a wastewater treatment (WWT) system for that stream. The pH (5.8-6.2), temperature (24-30 °C), biological oxygen demand (BOD₅: 128-265 mg/L), ultimate BOD (BOD_u: 227-438 mg/L), BOD/total Kjeldahl nitrogen (BOD₅/TKN:5.9-11.2), BOD_u/BOD₅ (1.6-2.0), carbonaceous BOD_u/nitrogenous BOD_u (CBOD_u/NBOD_u:1.6-2.8) of the WW was found to support the biological WWT. The inclusion of NBOD also indicated the need for nitrification-denitrification. The linear regression analysis of volatile suspended solids (VSS) with total suspended solids (TSS) indicated the high content of organic solids, which also made the WW suitable for biological treatment. The BOD/COD (chemical oxygen demand) <0.8 indicated the requirement for biomass acclimation. The major process units of the WWT system developed included a primary clarifier, cascade aeration, trickling filter, adsorption filter and chlorination contact tank. During the validation of design procedures, considerable removal of TSS (91%), TDS (46%), BOD₅ (88%), COD (87%) was observed over the 15 week operational period of the secondary WWT system. The WWT system developed was appropriate as a sustainable WWT system that consumed less energy and had lower operational costs.

Evaluating the Willingness to Pay for Using Recycled Water for Irrigation

The present study attempts to estimate individuals’ willingness to pay for recycled water irrigation, in order to enhance the water supply and ensure the continuation of irrigated agriculture in Nestos catchment. Contingent valuation method has been developed for the investigation of farmers’ preferences, in monetary terms, to adopt this alternative water source for irrigation purposes. The applied method is regularly followed in the framework of environmental valuation. The results of the survey are based on data collected from questionnaires, which were answered by respondents at a river basin scale. In a representative sample of 302 farmers, we find that 64.2% of them expressed a positive stance towards using recycled water, a fact that results in lower environmental impacts. However, findings indicate that participants are willing to pay a significantly less amount of money than they already pay, for freshwater. Additionally, the analysis demonstrates that the use of recycled water in agriculture is more acceptable to respondents who are aware of its environmental benefits. Therefore, the provision of complete information on the welfare of using recycled water for irrigation to farmers may lead to greater adoption intention and a greater environmental benefit.

Recycling of Date Pits Into a Green Adsorbent for Removal of Heavy Metals: A Fractional Factorial Design-Based Approach

Date pits (DPs) have been recycled into a low-cost adsorbent for removing of selected heavy metals (HMs) from artificially contaminated aqueous solutions. Adsorption of targeted HMs, both by raw date pits (RDP) and burnt date pits (BDP) was tested. Results showed that BDP is more efficient as an adsorbent and mostly adsorbing Cu(II). A novel approach; fractional factorial design (2^k−p – FrFD) was used to build the experimental pattern of this study. The effects of four factors on the maximum percentage (%) of removal (Y) were considered; pH, adsorbent dose (AD), heavy metal concentration (HMC), and contact time (CT). Statistically significant variables were detected using Pareto chart of standardized effects, normal and half-normal plots together with analysis of variance (ANOVA) at 95.0 confidence intervals (CI). Optimizing (maximizing) the percentage (%) removal of Cu(II) by BDP, was performed using optimization plots. Results showed that the factors: pH and adsorbent dose (AD) affect the response positively. Scanning electron microscopy (SEM) was used to study the surface morphology of both adsorbents while fourier-transform infrared spectroscopy (FTIR) was employed to get an idea on the functional groups on the surface and hence the adsorption mechanism. Raman spectroscopy was used to characterize the prepared adsorbents before and after adsorption of Cu(II). Equilibrium studies show that the adsorption behavior differs according to the equilibrium concentration. In general, it follows Langmuir isotherm up to 155 ppm, then Freundlich isotherm. Free energy of adsorption (ΔG_ad) is −28.07 kJ/mole, when equilibrium concentration is below 155 ppm, so the adsorption process is spontaneous, while (ΔG_ad) equals +17.89 kJ/mole above 155 ppm, implying that the process is non-spontaneous. Furthermore, the adsorption process is a mixture of physisorption and chemisorption processes, which could be endothermic or exothermic reactions. The adsorption kinetics were described using a second order model.

Assessing Reclaimed Urban Wastewater for Reuse in Agriculture: Technical and Economic Concerns for Mediterranean Regions

Direct reuse of treated wastewater can offer a realistic supply alternative for irrigation in Mediterranean areas. In this study, we conducted a spatial cost-benefit analysis to quantify and locate the volume of technically and economically feasible and readily available reclaimed urban wastewater. We considered the case of Puglia (Italy) and the results are discussed in terms of the implications for policy-making and pointing out future research needs. The results showed that the main technical barrier is the shortness of the irrigation season. On the other hand, the main economic concern is related to filtration followed by lack of conveyance systems. While our results are based on estimates, future research should try to include practical experiments based on actual data. Further research should also address the issue of transaction costs by establishing the obligations of wastewater treatment plants to deliver reclaimed water to farmers.

Land Use Change and Water Quality Use for Irrigation Alters Drylands Soil Fungal Community in the Mezquital Valley, Mexico

Soil fungal communities provide important ecosystem services, however, some soil borne representatives damage agricultural productivity. Composition under land-use change scenarios, especially in drylands, is rarely studied. Here, the soil fungal community composition and diversity of natural shrubland was analyzed and compared with agricultural systems irrigated with different water quality, namely rain, fresh water, dam-stored, and untreated wastewater. Superficial soil samples were collected during the dry and rainy seasons. Amplicon-based sequencing of the ITS2 region was performed on total DNA extractions and used the amplicon sequence variants to predict specific fungal trophic modes with FUNGuild. Additionally, we screened for potential pathogens of crops and humans and assessed potential risks. Fungal diversity and richness were highest in shrubland and least in the wastewater-irrigated soil. Soil moisture together with soil pH and exchangeable sodium were the strongest drivers of the fungal community. The abundance of saprophytic fungi remained constant among the land use systems, while symbiotic and pathogenic fungi of plants and animals had the lowest abundance in soil irrigated with untreated wastewater. We found lineage-specific adaptations to each land use system: fungal families associated to shrubland, rainfed and part of the freshwater were adapted to drought, hence sensitive to exchangeable sodium content and most of them to N and P content. Taxa associated to freshwater, dam wastewater and untreated wastewater irrigated systems show the opposite trend. Additionally, we identified potentially harmful human pathogens that might be a health risk for the population.

Membrane-based technology in greywater reclamation: A review

Greywater reclamation has been well recognized as an alternative water resource for non-potable or potable use. To meet greywater reuse standards, various membrane-based techniques have been widely adopted to treat greywater for producing water with superior quality. This paper aims to present a comprehensive review on membrane-based techniques in greywater treatment, including direct pressure-driven and osmotic-driven membrane processes, hybrid membrane processes (such as membrane bioreactors and integrating membrane separation with other processes), and resource recovery oriented membrane-based processes. Membrane performance and treatment efficiency in the reported membrane-based greywater treatment systems are evaluated and membrane fouling mechanisms and control strategies are illustrated. The advantages, limitations, and influencing factors on membrane-based greywater treatment processes are highlighted. Towards long-term sustainability of greywater reclamation, the challenges and prospects of membrane-based greywater treatment are discussed.

Post-treatment of anaerobic reactor effluent for reuse using a triple filtration system

This study evaluated the triple filtration technology efficiency as a post-treatment of anaerobic reactor effluent. This study was carried out employing different concentrations of ferric chloride as coagulant and peracetic acid or calcium hypochlorite as oxidant. The filtration rates used were 150 m³/m² d and 120 m³/m² d. The efficiency of the system was evaluated through physicochemical and microbiological parameters. The best conditions found were those using 20 mg/L ferric chloride, 120 m³/m² d filtration rate and 0.8 and 1.6 mg/L free chlorine. These conditions resulted in turbidity <1.0 NTU, Total Organic Carbon <1.5 mg/L, Chemical Oxygen Demand <1.0 mg/L, Biochemical Oxygen Demand <1.0 mg/L, in addition 100% removal of Total Phosphorus and Linear Alkylate Sulfonate. The post-oxidation process promoted inactivation of 100% Total Coliforms and E. coli. The post-treatment was able to produce effluent with characteristics that enable its urban, damming, creation and maintenance of wetlands, industrial and agricultural reuse proposed by USEPA.

Evaluation of phytotoxicity of effluents from activated sludge and constructed wetland system for wastewater reuse

The aim of this study was to evaluate the phytotoxicity of wastewater treated with horizontal subsurface flow (HSSF) constructed wetlands (CWs) and activated sludge (AS) system using disinfection treatment such chlorination and ultraviolet (UV) system. To assess the impact of the reuse of different effluents (HSSF-Cl, HSSF-UV, AS-Cl and AS-UV), bioassays using seeds of Raphanus sativus (R. sativus) and Triticum aestivum (T. aestivum), were performed on both Petri dishes and soil. Different treated wastewater concentrations were varied (6.25%, 12.5%, 25%, 50% and 100%) and the percentage of germination inhibition (PGI), percentage of epicotyl elongation (PEE) and germination index (GI) were determined. Positive effects (PGI and PEE <0% and GI >80%) of HSSF-Cl, HSSF-UV, AS-Cl and AS-UV effluents on germination and epicotyl elongation of R. sativus and T. aestivum were observed in Petri dishes bioassays. However, toxic effects of HSSF-Cl, HSSF-UV and AS-Cl on seeds germination and epicotyl elongation of both plant species were detected in soil samples (PGI and PEE >0% and GI <80%). Only R. sativus seeds to be irrigated with AS-UV achieved GI values above 86% for all concentrations evaluated. These results indicated that AS-UV effluent had a positive effect on seeds germination and can be recommended for treated wastewater reuse in agricultural irrigation.

Risk-Yuck Factor Nexus in Reclaimed Wastewater for Irrigation: Comparing Farmers’ Attitudes and Public Perception

The successes and failures of water reuse schemes are shaped by complex interrelationships between technological, economic, and socio-political factors. However, it has long been recognized that the main challenges to more effective water management are largely social rather than technical. This article reviews the recent literature (2007–2017) to analyze driving factors associated with farmers’ concerns and public perception of reclaimed wastewater for irrigation. The aim of the paper is to synthetize how both environmental and health risks and the yuck factor could be addressed in order to promote mutual understanding between farmers and the public. Results show: (1) how farmers and the public perceive environmental and health risks in a similar way, (2) how the yuck factor is more noticeable for the public than farmers, and (3) how constructed wetlands, reclaimed water exchange consortiums, product certification, and direct site visits to water reuse infrastructure could be promoted in order to foster understanding between farmers and the public. The article concludes by providing key research questions for managers and public authorities relating to how to focus on the study of technical and social issues related to water reuse.

The role of the operating parameters of SBR systems on the SMP production and on membrane fouling reduction

In this work, six identical laboratory SBRs treating simulated wastewater were operated in parallel studying the effect of three food-to-microorganisms ratio (F/M ratio; 0.20, 0.35 and 0.50 kg COD·kg MLSS^-1·d^-1), two hydraulic retention times (HRT; 24 and 16 h) and two values of number of cycles per day (3 and 6). Influence of these operational parameters on the SMPs production and reactor performance, were studied. Results indicated that the highest F/M ratio, HRT and cycles/day produced 72.7% more of SMP. In a second experimental series, biological process yielding the maximal and the minimal SMPs production were replicated and both mixed liquors (ML) and treated effluents were ultrafiltrated. The flux decay in the conditions of minimum and maximum SMPs production were 52% and 72%, when the SBRs effluents were ultrafiltrated while no significant differences in the ultrafiltration of ML were found. In terms of permeability recovery, this was lower for the case of the ML (73% and 49% of initial permeability recovered for effluent and ML ultrafiltration, respectively).

Wetlands for wastewater treatment and subsequent recycling of treated effluent: a review

Due to water scarcity challenges around the world, it is essential to think about non-conventional water resources to address the increased demand in clean freshwater. Environmental and public health problems may result from insufficient provision of sanitation and wastewater disposal facilities. Because of this, wastewater treatment and recycling methods will be vital to provide sufficient freshwater in the coming decades, since water resources are limited and more than 70% of water are consumed for irrigation purposes. Therefore, the application of treated wastewater for agricultural irrigation has much potential, especially when incorporating the reuse of nutrients like nitrogen and phosphorous, which are essential for plant production. Among the current treatment technologies applied in urban wastewater reuse for irrigation, wetlands were concluded to be the one of the most suitable ones in terms of pollutant removal and have advantages due to both low maintenance costs and required energy. Wetland behavior and efficiency concerning wastewater treatment is mainly linked to macrophyte composition, substrate, hydrology, surface loading rate, influent feeding mode, microorganism availability, and temperature. Constructed wetlands are very effective in removing organics and suspended solids, whereas the removal of nitrogen is relatively low, but could be improved by using a combination of various types of constructed wetlands meeting the irrigation reuse standards. The removal of phosphorus is usually low, unless special media with high sorption capacity are used. Pathogen removal from wetland effluent to meet irrigation reuse standards is a challenge unless supplementary lagoons or hybrid wetland systems are used.

Drylands soil bacterial community is affected by land use change and different irrigation practices in the Mezquital Valley, Mexico

Dryland agriculture nourishes one third of global population, although crop irrigation is often mandatory. As freshwater sources are scarce, treated and untreated wastewater is increasingly used for irrigation. Here, we investigated how the transformation of semiarid shrubland into rainfed farming or irrigated agriculture with freshwater, dam-stored or untreated wastewater affects the total (DNA-based) and active (RNA-based) soil bacterial community composition, diversity, and functionality. To do this we collected soil samples during the dry and rainy seasons and isolated DNA and RNA. Soil moisture, sodium content and pH were the strongest drivers of the bacterial community composition. We found lineage-specific adaptations to drought and sodium content in specific land use systems. Predicted functionality profiles revealed gene abundances involved in nitrogen, carbon and phosphorous cycles differed among land use systems and season. Freshwater irrigated bacterial community is taxonomically and functionally susceptible to seasonal environmental changes, while wastewater irrigated ones are taxonomically susceptible but functionally resistant to them. Additionally, we identified potentially harmful human and phytopathogens. The analyses of 16 S rRNA genes, its transcripts and deduced functional profiles provided extensive understanding of the short-term and long-term responses of bacterial communities associated to land use, seasonality, and water quality used for irrigation in drylands.

Oilfield water treatment by electrocoagulation-reverse osmosis for agricultural use: effects on germination and early growth characteristics of sunflower

This study aims to evaluate the effects of oilfield water (OW), treated by a hybrid process of electrocoagulation and reverse osmosis (EC-RO), on seed germination and early growth characteristics of sunflower (Heliantus annus L.). In the EC step, tests were conducted with 28.6 A m^-2 current density and 4 min. reaction time. In the RO step, the system was operated with 1 L min^-1 constant flow and 2 MPa, 2.5 MPa and 3 MPa feed pressures. In all feed pressures, RO polymeric membranes achieved very high removals of chemical oxygen demand (up to 89%) and oils and greases (100%) from EC-treated effluent. In best feed pressure (2.5 MPa), turbidity, total dissolved salts, electrical conductivity, salinity, toxic ions and sodium adsorption ratio values attained internationally recognized standards for irrigation water. Using EC-RO (feed pressure:2.5 MPa) treated OW, germinated sunflower seeds percentage (86 ± 6%), speed of germination (30 ± 2) and biomass production (49 ± 5 mg) were statistically similar to control (distilled water) results. Vigor index average values obtained using OW treated by EC-RO (3871)were higher than that obtained by OW water treated by EC (3300). The results of this study indicate that EC-RO seems to be a promising alternative for treatment of OW aiming sunflower crops irrigation, since the use of this treated effluent did not affect adversely seed germination and seedling development, and improved seedling vigor. Furthermore, OW treatment by EC-RO reduces sodium levels into acceptable standards values avoiding soil degradation.

Effects of residual disinfectant on soil and lettuce crop irrigated with chlorinated water

The accidental or continuous release of residual chlorine in water reclaimed for irrigational purposes could compromise the crop yield and increase the load of toxic organo-halogenated compounds, posing additional risks for environment and human health. This study was aimed at assessing the consequences of using chlorinated water for irrigating lettuce crops grown in pots with two different types of soil. The results show that the accumulation of extractable organo-halogenated compounds (EOX) in soil, roots and leaves is directly related to the chlorine concentration in the irrigation water. The accumulation of EOX in sandy soils is not significant, while it reached up to 300% of the control in the silty-clay soil, demonstrating that the phenomenon is linked to the organic matter content in the soil. The accumulation of EOX in the soil appears to play a significant role in subsequent bioaccumulation in cultures irrigated with tap water (long term memory effect). Chloramines also demonstrated to have similar impacts as the free chlorine from hypochlorite. The consistent bioaccumulation of 400-700μg_Clkg^-1 of EOX in the leaves of crops irrigated with just 0.2mg_ClL^-1 of residual chlorine, as compared to levels below the detection limit of 75μg_Clkg^-1 in the control crops, evidences the potential impact on food chain and human health.

Constructed wetlands for the removal of metals from livestock wastewater - Can the presence of veterinary antibiotics affect removals?

The presence of emergent antibiotics, in livestock wastewater may affect constructed wetlands (CWs) performance in the removal of other pollutants. The main objective of this study was to evaluate the influence of two antibiotics commonly used in livestock industry, enrofloxacin and ceftiofur, on metal removal by CWs. Microcosms (0.4m×0.3m×0.3m), simulating CWs, were constructed with Phragmites australis to treat livestock wastewater spiked or not with 100µg/L of enrofloxacin or ceftiofur (individually or in mixture). Wastewater was treated during 20 one-week cycles. After one-week cycle wastewater was removed and replaced by new wastewater (with or without spiking). At weeks 1, 2, 4, 8, 14, 18 and 20, treated wastewater was analysed to determine the removal rates of metals (Zn, Cu, Fe and Mn) and of each antibiotic. At weeks 1, 8 and 20 portions of the plant root substrate were collected and metals determined. At the end of the experiment metal levels were also determined in plant tissues. Removal rate of Fe from wastewater was 99%. Removal rates of Cu and Zn were higher than 85% and 89%, respectively, whereas for Mn removal rates up to 75% were obtained. In general, no significant differences were observed through time in the removals of the different metals, indicating that the systems maintained their functionality during the experimental period. Antibiotics did not interfere with the system depuration capacity, in terms of metals removals from wastewater, and ceftiofur even promoted metal uptake by P. australis. Therefore, CWs seem to be a valuable alternative to remove pollutants, including antibiotics and metals, from livestock wastewaters, reducing the risk the release of these wastewaters might pose into the environment, although more research should be conducted with other antibiotics in CWs.

Ozonation and UV254nm radiation for the removal of microorganisms and antibiotic resistance genes from urban wastewater

Conventional wastewater treatment has a limited capacity to reduce antibiotic resistant bacteria and genes (ARB&ARG). Tertiary treatment processes are promising solutions, although the transitory inactivation of bacteria may select ARB&ARG. This study aimed at assessing the potential of ozonation and UV_254nm radiation to inactivate cultivable fungal and bacterial populations, and the selected genes 16S rRNA (common to all bacteria), intI1 (common in Gram-negative bacteria) and the ARG vanA, bla_TEM, sul1 and qnrS. The abundance of the different microbiological parameters per volume of wastewater was reduced by ∼2 log units for cultivable fungi and 16S rRNA and intI1 genes, by∼3-4 log units, for total heterotrophs, enterobacteria and enterococci, and to values close or below the limits of quantification for ARG, for both processes, after a contact time of 30min. Yet, most of the cultivable populations, the 16S rRNA and intI1 genes as well as the ARG, except qnrS after ozonation, reached pre-treatment levels after 3days storage, suggesting a transitory rather than permanent microbial inactivation. Noticeably, normalization per 16S rRNA gene evidenced an increase of the ARG and intI1 prevalence, mainly after UV_254nm treatment. The results suggest that these tertiary treatments may be selecting for ARB&ARG populations.

Nitrogen removal and power generation from treated municipal wastewater by its circulated irrigation for resource-saving rice cultivation

This study aims at improving the performance of the cultivating system of rice for animal feed with circulated irrigation of treated municipal wastewater by applying a larger amount of wastewater, as well as adding a microbial fuel cell (MFC) to the system. The results of bench-scale experiments indicate that this modification has increased the rice yield, achieving the target for the rice cultivar used in the experiment. In addition, an assessment of protein content of the harvested rice showed that the value of the rice as animal fodder has improved. Compared with normal one-way irrigation, circulated irrigation significantly enhanced the plant growth and rice production. The direction of the irrigation (bottom-to-top or top-to-bottom) in the soil layer had no significant effect. This modified system demonstrated >96% for nitrogen removal from the treated wastewater used for the irrigation, with approximately 40% of the nitrogen being used for rice plant growth. The MFC installed in the system facilitated power generation comparable with that reported for normal paddy fields. The power generation appeared to be enhanced by bottom-to-top irrigation, which could provide organic-rich treated wastewater directly to the bacterial community living on the anode of the MFC set in the soil layer.