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Use of dyes as well as colorants in industrial processes has extensively increased. Effluents from various industries such as textile, paint, food, etc. are reported to have a diverse range of colorants. The effluents from these industries are often released into natural water bodies, causing serious water and environmental pollution, to which humans and other species are constantly exposed. Continued changes in climate have also affected water availability for people around the world. Thus, advanced treatments and removal of harmful contaminants from municipal and industrial wastewater are becoming increasingly important. Removal of dyes and colorants from wastewater can be done in a variety of ways, including physical, chemical, and biological treatments. These technologies, however, differ in terms of efficiency, cost, and environmental effect. There are many technological and economic challenges for the wastewater treatment methods currently available. The search for the most suitable strategy for successful degradation or removal of dyes from effluents is an urgent requirement. Previously published research suggests that the use of enzymes for dye removal is a more economic and effective strategy as compared to traditional techniques. Nanoparticles, with their exceptional physicochemical features, have the potential to tackle the problem of wastewater purification in a less energy-intensive way. However, extensive standardization would be a necessity for the use of different nanoparticles. Therefore, intense research in the use of enzymes and nanoparticle-based technologies may provide much needed technological solution for the remediation of a diverse range of dyes from wastewater.

Freshwater shortage and its contamination with various types of pollutants are becoming the most alarming issues worldwide due to impacts on socioeconomic values. Considering an increasing freshwater scarcity, it is imperative for the growers, particularly in semiarid and arid areas, to use wastewater for crop production. Wastewaters generally contain numerous essential inorganic and organic nutrients which are considered necessary for plant metabolism. Besides, this practice provokes various hygienic, ecological and health concerns due to the occurrence of toxic substances such as heavy metals. Pakistan nowadays faces a severe freshwater scarcity. Consequently, untreated wastewater is used routinely in the agriculture sector. In this review, we have highlighted the negative and positive affectivity of wastewater on the chemical characteristics of the soil. This review critically delineates toxic metal accumulation in soil and their possible soil–plant–human transfer. We have also estimated and deliberated possible health hazards linked with the utilization of untreated city waste effluents for the cultivation of food/vegetable crops. Moreover, we carried out a multivariate analysis of data (144 studies of wastewater crop irrigation in Pakistan) to trace out common trends in published data. We have also compared the limit values of toxic metals in irrigation water, soil and plants. Furthermore, some viable solutions and future viewpoints are anticipated taking into account the on-ground situation in Pakistan—such as planning and sanitary matters, remedial/management technologies, awareness among local habitants (especially farmers) and the role of the government, NGOs and pertinent stakeholders. The data are supported by 13 tables and 7 figures.

The goal of this study was to evaluate the impact of using yeast wastewater (YW) on weed communities. The study showed that all ecological parameters including species richness, dispersion, density, frequency, and % of vegetation cover were significantly increased in the site irrigated with YW compared to a natural rain fed site and another site irrigated with fresh water. The vegetation cover (%) was significantly increased by 2-folds in the site irrigated with YW (52%) than the one irrigated with fresh water (27%). Species richness increases to 23 in the site irrigated with yeast wastewater compared to 12 species in natural rain fed site and 7 species in areas irrigated with fresh water. The 10 studied weed species germinated better at 10 and 20% dilutions of baker’s YW. However, only five species achieved few germination (3–25%) at 50% of YW and the two species Sisymbrim irio and Cardariia droba achieved (6–13%) germination using 100% YW. No germination occurred for the crop seeds (tomato, squash, lentil, and barley) at 50 and 100% YW. For tomato, 10 and 20% of YW achieved better germination (82 and 63%, respectively) than the seeds of other species, followed by barley with 80 and 53% of germination. Squash showed the lowest germination percentage with 59 and 42% at 10 and 20% of YW, respectively. Yeast wastewater seems to be crop specific and can affect weed species composition and relative abundances and care should be taken before using the effluent for irrigation of tree plantations and crops.

When urban areas expand without concomitant increases in wastewater treatment capacity, vast quantities of wastewater are released to surface waters with little or no treatment. Downstream of many urban areas are large areas of irrigated croplands reliant on these same surface water sources. Case studies document the widespread use of untreated wastewater in irrigated agriculture, but due to the practical and political challenges of conducting a true census of this practice, its global extent is not well known except where reuse has been planned. This study used GIS-based modeling methods to develop the first spatially-explicit estimate of the global extent of irrigated croplands influenced by urban wastewater flows, including indirect wastewater use. These croplands were further classified by their likelihood of using poor quality water based on the spatial proximity of croplands to urban areas, urban wastewater return flow ratios, and proportion of wastewater treated. This study found that 65% (35.9 Mha) of downstream irrigated croplands were located in catchments with high levels of dependence on urban wastewater flows. These same catchments were home to 1.37 billion urban residents. Of these croplands, 29.3 Mha were located in countries with low levels of wastewater treatment and home to 885 million urban residents. These figures provide insight into the key role that water reuse plays in meeting the water and food needs of people around the world, and the need to invest in wastewater treatment to protect public health.

Arid and semi-arid locations are increasingly utilizing nontraditional irrigation water including reclaimed wastewater. Human health risk associated with reclaimed wastewater use was determined by testing reservoir, distribution line and home spigot water (n=190) and 14 types of vegetables and fruits (n=90) harvested from 5 home gardens for 7 waterborne pathogens, 47 antibiotic resistance genes and 12 pharmaceuticals and personal care products (PPCPs). Based on surveys of the residents’ use of the reclaimed wastewater, two exposure routes were modeled: irrigation of fruits and vegetables and drinking from irrigation hoses. Probabilistic quantitative microbial risk assessment indicated that consumption of raw vegetables and fruits exceeded a 0.015 benchmark illness rate due to adenovirus and enterococci. Chemical risk assessments indicated that consumption of tons of vegetables per day and hundreds to millions of gallons of water per day would be needed to reach an unacceptable risk among the 10 PPCPs detected in home spigot water, indicating de minimis risk from PPCPs. Eight different drug resistance gene families were detected in the water samples and crops indicating that antibiotic-resistant organisms are present on foods irrigated with reclaimed water containing pharmaceuticals. These results elucidate the combined risk from pathogens and PPCPs from reclaimed wastewater irrigation.

Untreated wastewater is routinely used for agricultural activities in water-stressed regions, thereby causing severe ecological risks by various pollutants. Hence, management strategies are needed to cope with the environmental issues related to wastewater use in agriculture. This pot study evaluates the effect of mixing either freshwater (FW) or groundwater (GW) with sewage water (SW) on the buildup of potentially toxic elements (PTEs) in soil and maize crop. Results revealed that SW of Vehari contains high levels of Cd (0.08 mg L −1 ) and Cr (2.3 mg L −1 ). Mixing of FW and GW with SW increased soil contents of As (22%) and decreased Cd (1%), Cu (1%), Fe (3%), Mn (9%), Ni (9%), Pb (10%), and Zn (4%) than SW “alone” treatment. Risk indices showed high-degree of soil-contamination and very-high ecological risks. Maize accumulated considerable concentrations of PTEs in roots and shoot with bioconcentration factor > 1 for Cd, Cu, and Pb and transfer factor > 1 for As, Fe, Mn, and Ni. Overall, mixed treatments increased plant contents of As (118%), Cu (7%), Mn (8%), Ni (55%), and Zn (1%), while decreased those of Cd (7%), Fe (5%), and Pb (1%) compared to SW “alone” treatments. Risk indices predicted possible carcinogenic risks to cow (CR 0.003 > 0.0001) and sheep (CR 0.0121 > 0.0001) due to consumption of maize fodder containing PTEs. Hence, to minimize possible environmental/health hazards, mixing of FW and GW with SW can be an effective strategy. However, the recommendation greatly depends on the composition of mixing waters.

Use of wastewater-based epidemiology as a tool to record and manage the course of SARS-CoV-2 infections in human populations requires information about the efficiency of methods to concentrate the virus from wastewater. In the present study, we spiked untreated wastewater with quantified SARS-CoV-2 positive clinical material and enriched the virus by polyethylene glycol precipitation and ultrafiltration with Vivaspin 10 kDa MWCO columns. SARS-CoV-2 was detected and quantified by reverse transcription quantitative PCR (E- and S-gene) and droplet digital PCR. The concentration of virus with precipitation resulted in mean recoveries between 59.4% and 63.7% whereas rates from 33.0% to 42.6% after ultrafiltration of samples were demonstrated. The results suggest that the use of both methods allows an effective and practicable enrichment of SARS-CoV-2 from raw wastewater.

Use of nitrogen- and phosphorus-based synthetic fertilizers shows an increasing trend, but this has led to large-scale influx of reactive nitrogen in the environment, with serious implications on human health and the environment. On the other hand, phosphorus, a non-renewable resource, faces a serious risk of depletion. Therefore, recovery and reuse of nitrogen and phosphorus is highly desirable. For nitrogen recovery, an ion exchange/adsorption-based process provides concentrated streams of reactive nitrogen. Bioelectrochemical systems efficiently and effectively recover nitrogen as NH 3 (g) or (NH 4 ) 2 SO 4 . Air stripping of ammonia from anaerobic digestate has been reported to recover 70–92 % of nitrogen. Membrane separation provides recovery in the order of 99–100 % with no secondary pollutant in the permeate.With regard to phosphorus (P) removal, physical filtration and membrane processes have the potential to reduce suspended P to trace amounts but provide minimal dissolved P removal. Chemical precipitation can remove 80–99 % P in wastewater streams and recover it in the form of fertilizer (struvite). Acid hydrolysis can convert recovered P into usable phosphoric acid and phosphate fertilizers. Physical-chemical adsorption and ion exchange media can reduce P to trace or non-detect concentrations, with minimal waste production and high reusability. Biological assimilation through constructed wetlands removes both N (83–87 %) and P (70–85 %) from wastewaters, with recovery in the form of fish/animal feeds and biofuel. The paper discusses methods and important results on recovery of nitrogen and phosphorus from wastewater.

The growing world population has augmented the generation of wastewater significantly and its proper management has become a worldwide challenge as the disposal of untreated wastewater contaminates the water sources and spreads water-linked health issues. Proper management of this huge volume of wastewater is also vital for realizing many UN’ SDGs such as “SDG6 (Clean Water and Sanitation), SDG11 (Sustainable Cities and Communities), and SDG12 (Responsible Consumption and Production)”. Moreover, good-quality water resources are inadequate to fulfill the rising demands of the growing population. Under this condition, the application of treated wastewater for crop production is a viable alternative. Wastewater contains basic plant supplements that enhance crop production. Wastewater irrigation has been associated with some other advantages as well, for example, decreased requirement of chemical fertilizer that results in better and healthy farm produce. Most of the previous studies, however, revealed that long-term utilization of wastewater can cause environmental issues in agro-environments. For instance, it can build nitrogen and phosphorus concentrations alongside other hazardous components in the soil over time. It can also change the physical properties of soil, for example, hydraulic conductivity and leaching efficiency which additionally blocks the draining of damaging salts through the soil. The aforementioned environmental and soil-related problems of wastewater irrigation can be minimized by executing some better approaches such as the partition of industrial wastewater to contain the most toxic wastewater portions and by developing a better treatment infrastructure. This paper presents an outlook on wastewater use for crop production. All the possible sources of related and up-to-date literature have been accessed and more than 120 publications were collected and thoroughly analyzed. The implication of the study along with its rationale is provided. The impact of wastewater on soil and the environment is discussed. Its environmental impacts are described and some conclusions are summarized which is followed by recommendations for future research based on the existing knowledge gaps.

Although epidemiological studies have found a significant amount of toxins in surface water, a complex link between animals’ access to wastewater and associated animal and human welfare losses needs to be explored. The scarcity of safe water has put stress on the utilization of wastewater for crops and livestock production. The access of animals to wastewater is related to the emergence of dangerous animal’s diseases, hampering productivity, increasing economic losses, and risking human health along the food chain. This review explores use of wastewater for agriculture, epidemiological evidence of microbial contamination in wastewater, and animal and human welfare disruption due to the use of wastewater for crop and livestock production. More specifically, the review delves into animals exposure to wastewater for bathing, drinking, or grazing on a pasture irrigated with contaminated water and related animal and human welfare losses. We included some scientific articles and reviews published from 1970 to 2017 to support our rational discussions. The selected articles dealt exclusively with animals direct access to wastewater via bathing and indirect access via grazing on pasture irrigated with contaminated wastewater and their implication for animal and human welfare losses. The study also identified that some policy options such as wastewater treatments, constructing wastewater stabilization ponds, controlling animal access to wastewater, and dissemination of necessary information to ultimate consumers related to the source of agricultural produce and wastewater use in animal and crop production are required to protect the human and animal health and welfare.