Greywater irrigation as a source of organic micro-pollutants to shallow groundwater and nearby surface water

Adsorption of common greywater pollutants and nutrients by various biochars as potential amendments for nature-based systems: Laboratory tests and molecular dynamics

Spruce wood and Typha (wetland plant) derived biochars pyrolyzed at 350 °C and 600 °C were tested for their sorption affinity for organic pollutants (diclofenac, methylparaben, benzotriazole and sodium 1-decanesulfonate) and nutrients (nitrate, ammonium, phosphate and boron) commonly found in greywater. Batch and column studies combined with molecular dynamics modelling determined the sorption capacity, kinetics, and described the underlying mechanisms. The spruce biochar (600 °C) exhibited the highest sorption capacity mainly for the tested organics. The dynamic test performed for spruce biochar (600 °C) showed that the magnitude of desorption was low, and the desorbed amount ranged between 3 and 11 %. Molecular dynamics modelling (a computational tool for elucidating molecular-level interactions) indicated that the increased sorption of nitrate and boron on spruce biochar (600 °C) could be attributed to hydrophobic interactions. The molecular dynamics shows that predominant adsorption of organic pollutants was governed by π-π stacking, with a minor role of hydrogen-bonding on the biochar surface. In summary, higher pyrolysis temperature biochar yielded greater adsorption capacity greywater borne contaminants and the reaction temperature (10-34 °C) and presence of anionic surfactant had a limited effect on the adsorption of organic pollutants, suggesting efficacious application of biochar in general for greywater treatment in nature-based systems.

Occurrence of contaminants of emerging concern and pesticides and relative risk assessment in Tunisian groundwater

Groundwater is an important source for drinking water supply, agricultural irrigation and industrial uses in the Middle East and North Africa region. Due to the growing need for groundwater use, groundwater quality studies on the presence of contaminants of emerging concern (CECs) and pesticides have gained attention. The Wadi El Bey is one of the most polluted areas in Tunisia. However, very limited data on CECs infiltration into aquifers has been described, in comparison to industrialized countries where groundwater contamination has been comprehensively addressed. To gain early insight into potential contamination, groundwater wells in northeast Tunisia, an area with high population density and intensive agricultural activity were sampled during two seasons and were analyzed with two high resolution mass spectrometry approaches: target and suspect screening. The latter was used for screening banned pesticides. A selection of 116 CECs of which 19 are transformation products (TPs) and 20 pesticides previously prioritized by suspect screening were screened in the groundwater samples. The results showed the presence of 69 CECs and 1 TP and 20 pesticides at concentrations per well, ranging between 43 and 7384 ng L-1 and 7.3 and 80 ng L-1, respectively. CECs concentrations in Tunisian groundwater do not differ from those in industrialized countries. WWTPs were considered the main source of pollution, where the main classes detected were analgesics, antihypertensives and artificial sweeteners and especially caffeine, salicylic acid and ibuprofen were found to be ubiquitous. Regarding pesticides, triazines herbicides and carbamates insecticides pose the highest concern due to their ubiquitous presence, high leachability potential for most of them and high toxicity. The environmental risk assessment (ERA) highlighted the high risk that caffeine, ibuprofen, and propoxur may pose to the environment, and consequently, to non-target organisms. This study provides occurrence and ERA analysis of CECs and pesticides in Tunisian groundwater.

Removal of hydrophilic, hydrophobic, and charged xenobiotic organic compounds from greywater using green wall media

Green walls offer a novel on-site approach for greywater treatment and reuse in densely build urban environments. However, they need to be engineered for effective removal of a wide range of emerging contaminants such as xenobiotic organic compounds (XOCs), which may be present in greywater due to extensive use of personal care products and household chemicals. This study used laboratory column design and batch experiments to investigate the performance of three lightweight green wall media (coco coir, zeolite, and perlite) and their mixture in three different combinations for the removal of twelve XOCs, covering wide range of hydrophilic, hydrophobic, and charged pollutants in greywater. The experiments were designed to assess the removal of targeted XOCs under different operational condition (i.e., hydraulic loading, infiltration rate, drying) and uncover the dominant mechanisms of their removal. Results showed excellent removal (>90%) of all XOCs in coco coir and media mix columns at the start of the experiment (i.e., fresh media and initial 2 pore volume (PV) of greywater dosing). The removal of highly hydrophobic and positively charged XOCs remained high (>90%) under all operational conditions, while hydrophilic and negatively charged XOCs exhibited significant reduction in removal after 25 PV and 50 PV, possibly due to their low adsorption affinity and electrostatic repulsion from negatively charged media. The effect of infiltration rate on the removal of XOCs was not significant; however, higher removal was achieved after 2-weeks of drying in coco coir and media mix columns. The dominant removal mechanism for most XOCs was found to be adsorption, however, a few hydrophilic XOCs (i.e., acetaminophen and atrazine) exhibited both adsorption and biodegradation removal processes. While findings showed promising prospects of unvegetated media for removing XOCs from greywater, long term studies on vegetated green wall systems are needed to understand any synergetic contribution of plants and media in removing these XOCs.

Environmentally relevant concentrations of triclosan induce lethality and disrupt thyroid hormone activity in zebrafish (Danio rerio)

Triclosan is an antimicrobial agent that has been used in common household products and can be detected in water environment. In this study, therefore, I aimed at clarifying the effects of environmentally relevant concentrations of triclosan on the early life stage development in zebrafish. A lethal effect was observed: the lowest effect and the no effect concentrations were 70.6 and 48.4μg/L, respectively. These concentrations are very close to the environmentally detected residual concentrations. In 10.9, 19.8, 48.4, and 70.6μg/L of triclosan, the iodothyronine deiodinase 1 gene expression was found to be significantly increased when compared with that of the control group. These findings indicate that triclosan can potentially disrupt the thyroid hormone activity in zebrafish. The exposure to triclosan (at 149.2μg/L) was also found to inhibit the gene expression of insulin-like growth factor-1. My findings suggest that triclosan can exert a thyroid hormone-disrupting effect on fish.

Recent insights into greywater treatment: a comprehensive review on characteristics, treatment technologies, and pollutant removal mechanisms

With the rapid socio-economic and industrial development, the problem of water shortage is becoming increasingly serious. Seeking alternative water sources to reduce the need for freshwater resources is an increasing concern. Household greywater production is high and accounts for about 50-80% of domestic wastewater. In recent years, the in situ treatment and reuse of greywater have received widespread attention. Treated greywater can be used for non-potable purposes such as toilet flushing and irrigation, which can greatly reduce the pressure of freshwater resource shortage. This paper reviews the sources and characteristics of greywater and analyzes its quantity and quality. In addition, this paper outlines and summarizes various greywater treatment technologies commonly used, including physical, biological, and chemical treatment technologies, as well as combination technologies. Understanding the mechanisms of contaminant removal is essential for effective greywater treatment. While discussing different treatment technologies, we focus on the removal mechanisms of pollutants from greywater, including organics, nutrients, surfactants, and emerging contaminants. Finally, future perspectives on greywater management and reuse are presented. Through a comprehensive review, we expect that this review will help the reader to better understand the characteristics of greywater and to more rationally select the appropriate treatment technology based on the removal mechanism of pollutants.

The comparative performance of lightweight green wall media for the removal of xenobiotic organic compounds from domestic greywater

Green walls can provide an aesthetic approach to treat domestic greywater in urban landscapes. However, the widespread adoption of green walls for greywater treatment depends on its performance to remove the emerging contaminants from greywater such as xenobiotic organic compounds (XOCs). In this study, the performance of five lightweight green wall media types (zeolite, perlite, date seeds, coffee grinds, and coco coir) was evaluated for the removal of six XOCs representing a range of hydrophilic to hydrophobic organic micropollutants in domestic greywater (acetaminophen, diethyltoluamide, bisphenol A, oxybenzone, triclosan, nonylphenol). The adsorption affinity of targeted XOCs on different green wall media types, the role of contact time on XOCs removal, and the impact of background pollutants in greywater matrix on the adsorption of XOCs were analysed. Results indicate that removal of XOCs was higher using carbonaceous waste materials (date seeds, coffee grinds, and coco coir) as compared to natural minerals (zeolite and perlite). Moreover, the adsorption of XOCs increased with the increase in pollutant hydrophobicity. All XOCs showed highest removal using coco coir with fast adsorption kinetics, achieving 90% of the removal in 30 min. The only exception was acetaminophen that showed best removal using zeolite but exhibited slow adsorption kinetics with 90% of the removal attained in 24 h. The initial adsorption kinetics (<30 min) of XOCs in greywater were adversely affected by the presence of background pollutants, indicating the need of higher residence time of greywater in green wall system for better removal of XOCs. Based on the findings of this batch study, it is recommended to design a green wall system with more than 30 min of greywater residence time using a mixture of coco coir and zeolite for effective removal of XOCs from domestic greywater.

Effects of ecohydrological interfaces on migrations and transformations of pollutants: A critical review

With the rapid development of society, the soil and water environments in many countries are suffering from severe pollution. Pollutants in different phases will eventually gather into the soil and water environments, and a series of migrations and transformations will take place at ecohydrological interfaces with water flow. However, it is still not clear how ecohydrological interfaces affect the migration and the transformation of pollutants. Therefore, this paper summarizes the physical, ecological, and biogeochemical characteristics of ecohydrological interfaces on the basis of introducing the development history of ecohydrology and the concept of ecohydrological interfaces. The effects of ecohydrological interfaces on the migration and transformation of heavy metals, organic pollutants, and carbon‑nitrogen‑phosphorus (C-N-P) pollutants are emphasized. Lastly, the prospects of applying ecohydrological interfaces for the removal of pollutants from the soil and water environment are put forward, including strengthening the ability to monitor and simulate ecohydrological systems at micro and macro scales, enhancing interdisciplinary research, and identifying main influencing factors that can provide theoretical basis and technical support.

Immobilised rGO/TiO2 Nanocomposite for Multi-Cycle Removal of Methylene Blue Dye from an Aqueous Medium

This work presents the immobilisation of titanium dioxide (TiO2) nanoparticles (NPs) and reduced graphene oxide (rGO)-TiO2 nanocomposite on glass sheets for photocatalytic degradation of methylene blue (MB) under different radiation sources such as ultraviolet and simulated solar radiation. The TiO2 NPs and rGO-TiO2 nanocomposite were synthesised through a simple hydrothermal method of titanium isopropoxide precursor followed by calcination treatment. Deposition of prepared photocatalysts was performed by spin-coating method. Additionally, ethylene glycol was mixed with the prepared TiO2 NPs and rGO-TiO2 nanocomposite to enhance film adhesion on the glass surface. The photocatalytic activity under ultraviolet and simulated solar irradiation was examined. Further, the influence of different water matrices (milli-Q, river, lake, and seawater) and reactive species (h+, •OH, and e−) on the photocatalytic efficiency of the immobilised rGO/TiO2 nanocomposite was careful assessed. MB dye photocatalytic degradation was found to increase with increasing irradiation time for both irradiation sources. The immobilisation of prepared photocatalysts is very convenient for environment applications, due to easy separation and reusability, and the investigated rGO/TiO2-coated glass sheets demonstrated high efficiency in removing MB dye from an aqueous medium during five consecutive cycles.

Heavy Metals and Microbes Accumulation in Soil and Food Crops Irrigated with Wastewater and the Potential Human Health Risk: A Metadata Analysis

Wastewater is actively used for irrigation of vegetable and forage crops in arid lands due to water scarcity and cost advantages. The objective of this review was to assess the effect of wastewater (mixture sources) reuse in irrigation on soil, crop (vegetable and forage crops), animal products, and human health. The metadata analysis of 95 studies revealed that the mean of toxic heavy metals including nickel (Ni), chromium (Cr), cadmium (Cd), lead (Pb), and zinc (Zn) in untreated wastewater were higher than the world standard limits in wastewater-irrigated regions. Although heavy metals in treated wastewater were within the standard limits in those areas, the concentration of those toxic elements (Pb, Cd, Ni, Cr, and As) exceeded the allowable limits in both soil and vegetables’ edible parts. In fact, the concentration of heavy metals in vegetables’ edible parts increased by 3–9 fold when compared with those irrigated with fresh water. Escherichia coli in wastewater-irrigated soil was about 2 × 106 (CFU g−1) and about 15 (CFU g−1) in vegetables’ edible parts (leaf, bulb, tuber and fruit) while the mean total coliforms was about 1.4 × 106 and 55 (CFU g−1) in soil and vegetables’ edible parts, respectively. For human health risk assessment, the estimated daily intake (EDI) and human health risk index (HRI) ranged from 0.01 to 8 (EDI and HRI > 1.0 associated with adverse health effects). Although the mean of EDI for heavy metals from wastewater-irrigated vegetables were less than 1, the HRI for Cd and Pb were above the limits for safe consumption. Overall, heavy metal levels in wastewater that used for irrigation of agricultural crops could be within the recommended levels by the world standards, but the long-term use of this reused water will contaminate soil and crops with several toxic heavy metals leading to potential carcinogenic risks to humans. Therefore, rigorous and frequent testing (wastewater, soil, and plant) is required in cultivated farms to prevent the translocation of heavy metals in the food chain.

Assessing the risk from trace organic contaminants released via greywater irrigation to the aquatic environment

Onsite non-potable reuse of greywater reduces the energy costs associated with the transport of wastewater and the stress on traditional source waters. However, greywater contains trace organic contaminants (TOrCs) that can be harmful to the aquatic environment when released via irrigation. In this work, the risk associated with TOrCs was evaluated for two potential irrigation scenarios, the use of untreated greywater and the use of greywater treated via conventional activated sludge. Risk quotient (RQ) ratios were calculated using the maximum concentration of each compound in the untreated or treated greywater divided by the relevant aquatic predicted no effect concentration. The TOrCs with RQs > 0.1 or 1 were classified as moderate and high priority, respectively. A review of greywater literature showed that a total of 350 compounds have been detected, with 132 classified as moderate or high priority in untreated greywater. Post-treatment 44 TOrCs remained as high priority due to high concentrations in greywater and/or poor removal during treatment, but only 14 of them were detected in multiple geographic locations. The final list of 14 TOrCs includes plasticizers/flame retardants (di-(2-ethylhexyl) phthalate, bisphenol A, and triphenyl phosphate), surfactants/preservatives/fragrances (4-nonylphenol, benzyldimethyl dodecylammonium chloride, tonalide, methylparaben, and 2-6-di-tert-butyl-4-methylphenol), UV-filters (benzophenone-3 and octocrylene), and pharmaceuticals/antibiotics (acetaminophen, trimethoprim, caffeine, and triclosan). This subset of TOrCs would be useful surrogates to monitor during greywater treatment for irrigation as potential hazards for nearby aquatic environments.

Determination of pharmaceuticals and heavy metals in groundwater for human and animal consumption and crop irrigation in Galicia

Pharmaceuticals and heavy metals are contaminants present in groundwaters, which are the main source of drinking water in most parts of the world. In the northwest region of Spain, Galicia, groundwater harvesting is a common practice for drinking water supply, crop irrigation, cattle watering, as well as recreational use such as filling pools. In order to assess the quality of Galician groundwaters, the presence of 21 pharmaceuticals and 10 heavy metals was analysed by UPLC-MS/MS and ICP/MS methods, respectively, in a total of 118 groundwater samples from private wells. Seventeen of the 21 compounds studied were detected in 28% of the samples, with the highest presence of pharmaceuticals belonging to the antimicrobial group (52%), specifically the sulphonamides group in a range of concentration between 21 and 14.9 ng/L. In addition, 30% of the samples contained at least one heavy metal (Mn, As and Fe) above the legally permitted levels. Evaluation of the risk associated with the consumption of the analysed groundwater indicated no human risk for any of the detected pharmaceuticals but high cancer risk for children due to Cd, Cr and As concentrations was observe.

Suitability of Different Titanium Dioxide Nanotube Morphologies for Photocatalytic Water Treatment

Photocatalysis has long been touted as one of the most promising technologies for environmental remediation. The ability of photocatalysts to degrade a host of different pollutants, especially recalcitrant molecules, is certainly appealing. Titanium dioxide (TiO₂) has been used extensively for this purpose. Anodic oxidation allows for the synthesis of a highly ordered nanotubular structure with a high degree of tunability. In this study, a series of TiO₂ arrays were synthesised using different electrolytes and different potentials. Mixed anatase-rutile photocatalysts with excellent wettability were achieved with all the experimental iterations. Under UVA light, all the materials showed significant photoactivity towards different organic pollutants. The nanotubes synthesised in the ethylene glycol-based electrolyte exhibited the best performance, with near complete degradation of all the pollutants. The antibacterial activity of this same material was similarly high, with extremely low bacterial survival rates. Increasing the voltage resulted in wider and longer nanotubes, characteristics which increase the level of photocatalytic activity. The ease of synthesis coupled with the excellent activity makes this a viable material that can be used in flat-plate reactors and that is suitable for photocatalytic water treatment.

An Assessment of Treated Greywater Reuse in Irrigation on Growth and Protein Content of Prosopis and Albizia

This study investigated the influence of treated greywater on growth and protein content of multipurpose (forage and ornamental) transplants, Prosopis juliflora L., Prosopis tamarugo L., and Albizia lebbeck L. Transplants of tested species were irrigated with treated greywater, diluted greywater (grey + distilled water, 1:1/by volume), and distilled water (control) for seven months. Water quality analysis showed that the concentrations of nutrients and heavy metals found in the greywater were within the acceptable range compared with Jordan Institution for Standard and Metrology (JISM) and the World Health Organization (WHO) thresholds for safe use of greywater. Escherichia coli found in the greywater were lower compared to JISM and WHO guidelines for the safe use of greywater. Irrigation with treated greywater increased shoot fresh weight by 24–39% and dry weight by 34–40% compared to diluted greywater and control. No significant difference in crude protein was noticed between water treatments. Prosopis species (P. juliflora Albizia lebbeck L. and P. tamarugo Albizia lebbeck L.) had higher shoot fresh (35%) and dry weight the same species had lower crude protein (44%) when compared to Albizia lebbeck Albizia lebbeck L. The reuse of treated greywater for landscaping or forage production alleviates the demand for water resources and reduces the pressure on wastewater treatment plants. However, considering the controversial findings of previous studies on greywater quality (especially, long-term reuse), the reuse of treated greywater needs to be considered with caution and periodic quality analyses and economic assessments are required.

Occurrence of Pharmaceutical Compounds in Groundwater from the Gran Canaria Island (Spain)

The presence of pharmaceutical compounds in the whole environment is a growing concern. These compounds might be present in the effluents of wastewater treatment plants and, hence, irrigation with treated sewage may be a source of groundwater pollution. The volcanic aquifer that lies NE of Gran Canaria (Spain) was studied to address the relationship of the occurrence of pharmaceutical compounds and a golf course that has been irrigated with regenerated water since 1973. Of the 14 analyzed groundwater samples, five wells were chosen to perform annual monitoring. Irrigation water and soil leachate were also evaluated. The target analytes were atenolol, metamizole, fluoxetine, ibuprofen, nicotine, permethrin, caffeine, and their metabolite paraxanthine. The environmental risk is limited as the concentrations of the pharmaceuticals measured in the sampled wells were always below 60 ng·L−1 (lower than the detected caffeine and nicotine concentrations). Wide variations for the same wells were measured among sampling campaigns, and also among the different wells. The study points to the importance of sample conservation during transport and the need to perform analyses immediately, or to follow an in-situ extraction procedure to carry concentrated samples under better conditions.

The invasive butterbur contaminates stream and seepage water in groundwater wells with toxic pyrrolizidine alkaloids

Pyrrolizidine alkaloids (PAs) are persistent mutagenic and carcinogenic compounds produced by many common plant species. Health authorities recommend minimising human exposure via food and medicinal products to ensure consumer health and safety. However, there is little awareness that PAs can contaminate water resources. Therefore, no regulations exist to limit PAs in drinking water. This study measured a PA base concentration of ~ 70 ng/L in stream water adjacent to an invasive PA-producing plant Petasites hybridus (Asteraceae). After intense rain the PA concentration increased tenfold. In addition, PAs measured up to 230 ng/L in seepage water from groundwater wells. The dominant PAs in both water types corresponded to the most abundant PAs in the plants (senkirkine, senecionine, senecionine N-oxide). The study presents the first discovery of persistent plant toxins in well water and their associated risks. In addition, it for the first time reports monocrotaline and monocrotaline N-oxide in Petasites sp.

Greywater in Egypt: the sustainable future of non-conventional water resources

Egypt is a country with limited water resources. Egypt water needs are growing rapidly as a result of the population increase, climate change and development activities. The aim of the study is to analyse how Egypt can sustain its mega urban projects by utilizing greywater as a non-conventional water resource. A quantitative-based assessment has been conducted to investigate the overall evaluation of the greywater resources in Egypt. Greywater accounts for between 40 and 80% of the total water discharged from the house, and the total use of water for drinking and health use can be estimated at 10.4 billion cubic meters per year. The results show that the greywater resources may support a sustainable future of non-conventional water resources in a very positive way. Greywater can provide Egypt with about 4.15-8.30 billion cubic meters annually, which is a good support for water resources in Egypt. The paper concluded that greywater is an important resource to facilitate the success of the new mega urban projects. Egypt should maximize the share of greywater resources, especially in its new mega urban projects. Greywater resources can support Egypt and other arid and semiarid regions and countries in transition to a sustainable future.

Distributed treatment systems

This section presents a review of the scientific literature published in 2019 on topics relating to distributed treatment systems. This review is divided into the following sections: constituent removal, treatment technologies, planning and treatment management, and other topics. PRACTITIONER POINTS: Highlights changes and innovation in removal techniques and technologies in water treatment. Reviews management systems of distributed treatment systems. Discusses point-of-use treatment systems.

Enhanced Photocatalytic Degradation of Caffeine Using Titanium Dioxide Photocatalyst Immobilized on Circular Glass Sheets under Ultraviolet C Irradiation

This work presents the development of titanium dioxide (TiO2) film immobilized on circular glass sheets for photocatalytic degradation of caffeine under ultraviolet C (UVC) irradiation. TiO2 was synthesized through the ultrasonic-assisted sol–gel method and immobilized on circular glass sheets by the doctor blade technique. Polyvinylpyrrolidone (PVP) was used to mix with the TiO2 precursor solution to enhance film adhesion on the glass surface. TiO2 film was mainly composed of anatase phase with a small amount of rutile phase. Caffeine removal was found to increase with increasing irradiation time. Caffeine (20 mg/L) in the synthetic wastewater could not be detected after 3 h of UVC irradiation. The reaction rate of caffeine degradation followed the pseudo-first-order model. The concentrated caffeine solutions required a longer irradiation time for degradation. The used TiO2-coated glass sheets could be easily separated from the treated wastewater and reusable. The caffeine removal efficiency of TiO2-coated glass sheets in each cycle maintained a high level (~100%) during fifteen consecutive cycles.

Evaluation of chemical and biological contaminants of emerging concern in treated wastewater intended for agricultural reuse

The occurrence of chemical and biological contaminants of emerging concern (CECs) was investigated in treated wastewater intended for reuse in agriculture. An agarose hydrogel diffusion-based passive sampler was exposed to the outlet of a wastewater treatment plant (WWTP) located in Cyprus, which is equipped with membrane bioreactor (MBR). Passive samplers in triplicate were exposed according to a time-series exposure plan with maximum exposure duration of 28 days. Composite flow-proportional wastewater samples were collected in parallel with the passive sampling exposure plan and were processed by solid phase extraction using HORIZON SPE-DEX 4790 and the same sorbent material (Oasis HLB) as in the passive sampler. The analysis of passive samplers and wastewater samples enabled (i) the field-scale calibration of the passive sampler prototype by the calculation of in situ sampling rates of target substances, and (ii) the investigation of in silico predicted transformation products of the four most ecotoxicologically hazardous antibiotics (azithromycin, clarithromycin, erythromycin, ofloxacin). Additionally, the wastewater samples were subjected to the analysis of seven preselected antibiotic resistant genes (ARGs) and one mobile resistant element (int1). All extracts were analyzed for chemicals in a single batch using a highly sensitive method for pharmaceuticals, antibiotics and illicit drugs by liquid chromatography tandem MS/MS (LC-QQQ) and for various other target compounds (2316 compounds in total) by liquid chromatography high-resolution mass spectrometry (LC-HRMS). 279 CECs and all investigated ARGs (except for bla_CTX-M-32) were detected, highlighting potential chemical and biological hazards related to wastewater reuse practices. 16 CECs were prioritized following ecotoxicological risk assessment, whereas sul1 and the mobile resistant element (int1) showed the highest abundance. Comprehensive monitoring efforts using novel sampling methods such as passive sampling, wide-scope target screening and molecular analysis are required to assure safe application of wastewater reuse and avoid spread and crop uptake of potentially hazardous chemicals.