Review Article

Wastewater Irrigation Possess a Risk on Food Chain, Health, and its Treatment with Constructed Wetlands

Hasnain Raza1*, Maryam Maqsood2, Muhammad Muzamil Nazir1, Iqra Tariq1, Kaynat Ahmed1, Qurat-ul-Ain1, Ali Raza2, Huda Bilal3, Muhammad Bilal Shoukat1, Attiq ur Rehman1, Awais Rasheed1 and Muhammad Zeshan Gulzar1

1Department of Soil and Environmental Sciences, MNS-University of Agriculture, Multan, Pakistan; 2Department of Food Science and Technology, MNS-University of Agriculture, Multan, Pakistan; 3Institute of Plant Protection, MNS-University of Agriculture, Multan, Pakistan.

Received | August 03, 2021; Accepted | September 22, 2021; Published | November 08, 2021

*Correspondence | Hasnain Raza, Department of Soil and Environmental Sciences, MNS-University of Agriculture, Multan, Pakistan; Email: Hasnainraza662@gmail.com

Citation | Raza, H., M. Maqsood, M.M. Nazir, I. Tariq, K. Ahmed, Q-u. Ain, A. Raza, H. Bilal, M.B. Shoukat, A. Rehman, A. Rasheed and M.Z. Gulzar. 2021. Wastewater irrigation possess a risk on food chain, health, and its treatment with constructed wetlands. Journal of Innovative Sciences, 7(2): 258-266.

DOI | https://dx.doi.org/10.17582/journal.jis/2021/7.2.258.266

Keywords | Wastewater irrigation, Food chain, Health, Constructed wetlands, Phytoremediation

1. Introduction

In 2050, the global population is predicted to reach 9.5 billion people, requiring an additional 60% increase in food production (Mbow et al., 2019). Freshwater scarcity is a global issue, with 60% of the world’s population expected to face a shortage by 2025 (Alexandratos and Bruinsma, 2012). Between 2006 and 2017, Pakistan’s per capita water availability decreased from 1100 to 908 m3 (Imran et al., 2018). To meet the demands, agriculture must cut off its share of freshwater usage and search for alternative supplies, due to the growing imbalance between supply and demand, as well as the expected effects of climate change. Agricultural use of water and wastewater is currently the highest in the world, accounting for over 70% of total water usage (Winpenny et al., 2010).

Wastewater reuse is becoming more popular as a way to fulfill the growing demand for water. This resource, in general, comprises significant concentrations of both helpful nutrients and hazardous contaminants, which present both prospects and challenges for agriculture (Alghobar and Suresha, 2017). As a result, irrigation with municipal or industrial wastewater for a long time may result in a heavy metal deposition in soils and plants (Singh et al., 2010). Since heavy metals are non-biodegradable and have a lengthy biological half-life, they can accumulate in body parts, their contamination in soils and crops has been considered a serious environmental hazard (Khan et al., 2010; Muhammad et al., 2011).

The removal of pollutants from wastewater is extremely important to minimize the threat to public health and the environment. The wastewater is treated through various conventional and non-conventional methods including reverse osmosis (Al-Alawy and Salih, 2017), chemical precipitation (Huang et al., 2017), adsorption, and solvent extraction (Burakov et al., 2018), are some of the conventional and non-conventional technologies used to treat wastewater. However, for the removal of unwanted toxic materials, most of these approaches are very expensive, inefficient, time-consuming, and need a large capital investment (Bolisetty et al., 2019). An environment-friendly and cost-effective indigenous wastewater treatment system is urgently needed to treat wastewater contaminated with heavy metals and pollutants (Ashraf et al., 2018). For wastewater treatment in developing countries like Pakistan, constructed wetlands (CWs) are an environmentally friendly, energy-efficient, and low-cost option.

1.1 Wastewater irrigation a global health challenge

Wastewater irrigation of food crops is a common practice in urban, suburban, and rural areas around the world, and it has gained popularity in recent years in water-scarce areas (Hajjami et al., 2013). Its continued usage on agricultural fields has the potential to contaminate and compromise the safety of the food crops produced (Hu et al., 2013), it poses a significant risk to humans through feeding on contaminated food crops. The generation of worldwide wastewater is projected to be 1500 billion m3 per year (Kachenko and Singh, 2006). Wastewater is used to irrigate approximately 20 million hectares of land in 50 countries (Abaidoo et al., 2010).

Pakistan generates 6.414 billion m3 of wastewater annually, receiving 4.953 billion m3 from municipal and 0.395 billion m3 from industry (Yamin et al., 2015). In agriculture, 0.876 billion m3 of wastewater from the total wastewater produced is being used for crop production (Murtaza et al., 2010), by irrigating about 32500 ha of land. Almost one-tenth of the crops in the world is irrigated with untreated wastewater (Qadir et al., 2007). Untreated wastewater contains a wide variety of pollutants from agricultural, municipal, and industrial sources. Farmers, their families, people living near wastewater irrigation, and consumers of wastewater-irrigated crops are all at risk from excreta-related infections, skin irritants, and hazardous compounds originating from these sources (Qadir et al., 2007). Heavy metal exposure from contaminated foods or inhalation of irrigated soil or occupational ingestion has been related to a wide range of chronic health problems, including cadmium, arsenic, lead, and mercury poisoning.

 

Table 1: Effects of heavy metals on humans.

Heavy metals	Toxic form	Effects on Humans	References
Cr	Cr+6	Cancer of respiratory tract, nose ulcers, and multi-organ toxicity	(Medda and Mondal, 2017)
Hg	Methylmercury (Me Hg)	Neurotoxicity, nephrotoxicity, Gastrointestinal and carcinogenesis	(Azevedo et al., 2018); (Gardner et al., 2010)
Cd	Cd+2	Renal dysfunction, risk of lung cancer, bone demineralization and impair lung function	(Loi et al., 2018)
Pb	Pb+2	Damage to the reproductive system, affect CNS and PNS and kidney failure	(Zhou et al., 2018)
As	As+3	Portal fibrosis, neurologic, cardiovascular, developmental anomalies, carcinoma, and hematologic disorders	(Signes-Pastor et al., 2019); (Abbas et al., 2018)
Ni	Ni salts and dust	Diarrhea, lungs and nasal cancer, vomiting, and dermatitis	(Ahmad and Ashraf, 2012)
Zn	Zn+2	Cytotoxicity, Hematological change, Detrimental effect on neuronal development, immunity, and growth	(Maurya et al., 2019); (Plum et al., 2010)
Cu	Cu salts and fumes	Kidneys and liver damage, hypotension, gastrointestinal discomfort, hematemesis, and melena	(Sheldon and Menzies, 2005)

 

Food contamination with heavy metals is a major contributing channel to human exposure (more than 90%), surpassing other paths such as dermal contact and inhalation (Loutfy et al., 2006). Heavy metals have a negative impact on human and animal populations even at low concentrations (Uzu et al., 2011a, b) by causing nervous, cardiovascular, mental impairment, kidney and bone diseases (Yargholi et al., 2008). Acute and chronic exposure can result in dermal, cardiovascular, respiratory, gastrointestinal, renal, hematological, neurological, hepatic, developmental, immunological, reproductive, genotoxic, carcinogenic, and mutagenic effects e.g., liver cancer (Lin et al., 2013). The detail about effects of heavy metals on human are given in (Table 1).

1.2 Impact of heavy metals in soils

Due to the tremendous expansion of the industry sector, more effluents are being released into the environment, contaminating soil and water, and accumulating in living organisms. Heavy metals can’t be degraded into less harmful forms, they have long-term environmental impacts when they are discharged haphazardly into the soil and rivers (Dixit et al., 2015). Heavy metal pollution of soil is a worldwide issue that affects human health and agricultural production (Liu et al., 2018). Heavy metals are found in agricultural soils due to natural and anthropogenic sources (Rahimi et al., 2017; Ratul et al., 2018).

Agricultural soil becomes contaminated when wastewater is used to irrigate it (Hajjami et al., 2013). Long-term wastewater application causes a heavy metal build-up in soil and crops, which affects crop toxicity, soil functioning, food chain contamination, and vegetable nutritional quality (Chen et al., 2010; Singh et al., 2010). Heavy metals bio accumulate into vegetables, crops, and humans as a result of continual ingestion.

1.3 Toxicity of heavy metals and their bioaccumulation through food chain contamination

Anthropogenic activities, such as industrial processes, release Heavy metals into the environment, resulting in the accumulation of heavy metals toxicity in living organisms (Koivula et al., 2011). Agrochemicals, industrialization, and fossil fuel burning discharge a variety of heavy metals, which are the primary source for pollution such as mercury (Hg), arsenic (As), cobalt (Co), copper (Cu), nickel (Ni), zinc (Zn), lead (Pb), chromium (Cr) and cadmium (Cd) into water channels and soils (Kumar et al., 2019a; b). Bioaccumulation occurs when Heavy metals are ingested by plants and subsequently biomagnified when top consumers consume them (Pollard et al., 2014). Once heavy metals enters the food chain, they can’t be removed easily from the top of the chain, and they’re spread out across the entire food web.

There are several hyper-accumulated plants that are used as food by humans and animals alike. As heavy metals have a potential to persist in the environment, produce a variety of negative impacts because plants carry them from the soil to humans. The extent of contamination in crops is determined by the effectiveness of the soil-to-plant transfer. Possibly harmful health effects could result from the consumption of contaminated crops containing heavy metals (Clemens and Ma, 2016). Vegetables are an essential part of the human diet because they contain essential nutrients and minerals (Nankishore, 2014). Unfortunately, plants can absorb and store heavy metals in both edible and inedible parts of their bodies, exceeding the permissible limits (Tasrina et al., 2015). In the last few years, high quantities of heavy metals have been detected in vegetables (leaves, roots, and fruits) (Wai et al., 2017) in detailed (Table 2). During the transition from one sector of the food chain to the next, several heavy metals have the potential to accumulate in the tissues of top consumers (liver, feathers, muscles, kidneys, and other organs).

1.4 Constructed wetlands an efficient option for wastewater treatment

Constructed wetlands (CWs) are an efficient wastewater treatment systems that use physical, chemical, and biological processes which are similar to those found in natural treatment wetlands (Uysal, 2013). CWs have been used to reduce pollution in the environment by eliminating various contaminants from wastewater, including heavy metals, organic compounds, nutrients, suspended solids, and pathogens (Gikas and Tchobanoglous, 2009). Over the last 50 years, the use of CWs is a common wastewater treatment technique in many countries.

Furthermore, it is a viable alternative treatment technology to traditional wastewater treatment methods due to their high pollution removal efficiency, low energy requirements, ease of operation and maintenance, high water recycling rate, and potential for providing significant natural habitat for flora and

 

Table 2: Heavy metals bioaccumulation in different vegetable organs.

Vegetables	Plant organ Analyzed	Heavy metals	Concentration (mg/kg)	Reference
Coriandrum sativum, Lepidium sativum, Spinacia olarecea	Leaves	Co, Ni, Cu, Zn, As, Pb, Cd, and Cr	Co– 0.005-0.21 Ni – 0.04-0.81 Cu – 0.59-2.23 Zn – 1.7 - 6.7 As–0.018-0.126 Pb – 0.2-4.7 Cr – 0.1-1.87 Cd – 0.02-0.52	(Souri et al., 2018)
Solanum Lycopersicum, Brassica oleracea, Capsicum annuum	Edible parts	Pb and Cd	Pb – BDL-0.05, Cd – 0.01-0.07	(Ametepey et al., 2018)
Anolis lividus, Basella alba, Trichosanthes cucumerina, Cucurbita moschata, Spinacia oleracea	Edible parts	Ni, Cu, Cd, Pb, Cr, and Zn	Zn - 19.762 Pb - 3.699 Cu - 9.373 Ni - 2.92 Cd - 0.168 Cr - 1.127	(Ratul et al., 2018)
Solanum melongena	Edible parts	Cd, Ni, and Pb	Cd – 0.07-11.14 Ni – 0.01-4.82 Pb – 0.88-42.7	(Youssef and Abd El-Gawad, 2018)
Cucumis melo, Solanum melongena, Pinacia oleracea	Edible parts	Mn, Cd, Cr, Ni, Cu, Fe, and Zn	Cr – 2.7-3.7 Mn – 18.7-137 Cu – 22.2-65 Cd – 0.05-0.39 Ni – 1.8-5.05 Zn – 19.5-41 Fe – 129-968	(Latif et al., 2018)
Cucurbita maxima, Solanum lycopersicum	Fruits	Pb, Zn, Cu, and Cd	Cu – 0.38-7.7 Zn – 1.1-128.5 Pb –up to 14.2 Cd – up to 2.2	(Zafarzadeh et al., 2018)
Lactuca sativa	Leaves, Roots, and Shoots	Cu	Cu – 0.5-2.3	(Shiyab, 2018)
Lycopersicon esculentum, Abelmoschus esculentus	Fruits	Pb, Cd, Ni, and Zn	Cd – 0.01-0.05 Pb – 0.53-1.39 Zn – 0.02-0.09 Ni – 0.31-0.86	(Ali et al., 2017)

 

fauna (Kadlec and Wallace, 2008). Different aquatic floating plants play an important role in the detoxification process in CW by absorbing pollutants directly into their tissues. To remove toxins from wastewater, these plants use physicochemical and biological methods (DalCorso et al., 2019), which help in the remediation process (Khan and Faisal, 2018).

The main functions of plants in constructed wetlands are, provision of physical effect through its roots which helps some physical treatment in a wetland such as filtering effect, velocity reduction, promotion of sedimentation, decreased resuspension, prevention of medium clogging, improved hydraulic conductivity (Uysal, 2013), plants roots are used as a base for microorganisms, under this function plants provide a surface for microbial attachment and release of gas and exudates, also plant roots release oxygen that increased aerobic degradation and supports precipitation of heavy metals (Shelef et al., 2013). Metal uptake is done through phytoremediation processes, (in detailed Table 3) also plants increase evapotranspiration that accelerates water loss in the wetland (Dalcorso et al., 2019). Plants provide microclimatic conditions such as light attenuation that reduces algal growth, insulation from frost in the winter, insulation from radiation in the spring, reduced wind velocity as well as stabilization of the sediment surface (Chao et al., 2014). The major aquatic plants that are used for the treatment of wastewater in constructed wetlands are Pistia stratiotes (water cabbage), Typha latifolia (cattail), Pistia stratiotes (Water lettuce), Lemna gibba (duckweed), common reed (Phragrmites), Eichhornia crassipes (Water hyacinth), Centella Asiatica (Pennywort) and Alternanthera philoxeroides (Alligator weed) (Wang et al., 2015).

 

Table 3: Potential of constructed wetlands by using plants for the removal of heavy metals.

Type of constructed wetlands	Plants species	Contaminants treated	Reference
Floating treatment wetlands	Typha domingensis	Cu, Zn, Pb, and Cd	(Bauer et al., 2021)
Constructed wetlands microcosms	Typha latifolia	Fe, Cu	(Meitei and Prasad, 2021)
Horizontal subsurface flow constructed wetlands	Hydrilla verticillata, Water hyacinth, T. latifolia and Echornia crassipes	Cu, Pb, Cd, and Cr	(Wang et al., 2021)
Horizontal subsurface flow constructed wetlands	Phragmites australis	Pb, As, and Fe	(Lizama-Allende et al., 2021)
Natural Wetlands	P. australis	Cr, Fe, Zn, and Pb	(Attili, 2020)
Free water surface constructed wetlands	L. paucicostads	V, Cd, Pb, and Cr	(Ekperusi et al., 2019)
Natural wetlands	S. polyrhiza, Echornia crassipes and Pistia stratiotes	Cu, Fe, Zn, Cd, Cr, and N	(Rai, 2019)
Constructed wetlands microcosms	Alocasia puber	Zn, Cd, Cu, Cr, and Ni	(Thani et al., 2019)
Horizontal subsurface flow constructed wetlands	Aster amellus, Tagetes patula, Gaillardia grandiflora and Portulaca grandiflora	Mn, Cu, and Fe	(Chandanshive et al., 2018)
Horizontal constructed wetlands	P. australis Cav. Trin. ex Steud, Canna indica L. T. latifolia L., and Hydrocotyle umbellata L.	Pb, Cu, Mg, Co, Zn, and Cd	(Ali et al., 2018)
Vertical surface flow constructed wetlands	T. latifolia, Cyperus alternifolius, and Cynodon dactylon	Cr, Cu, Zn, Cd, Pb, and Fe	(Mustapha et al., 2018)
Horizontal subsurface flow constructed wetlands	P. australis	Cd, Pb, and Cr	(Šíma et al., 2017)
Free water surface constructed wetlands	T. latifolia, P. australis	Cd, Pb, Cu, and Zn	(Gill et al., 2017)
Horizontal subsurface flow constructed wetlands, vertical flow constructed wetlands	P. australis, T. latifolia	Cu, Zn, Pb, and Cr	(Papaevangelou et al., 2017)
Free water surface constructed wetlands	Azolla pinnata	Mg, Fe, Mn, Zn, and Pb	(Akinbile et al., 2016)
Horizontal flow constructed wetlands	V. zizanioides	Ni, Cr, Pb, and Zn	(Bakhshoodeh et al., 2016)
Vertical flow constructed wetlands	Erianthus arundinaceus, Typha angustifolia and P. australis.	Cu, Zn, Mn, Ni, Fe, and Cd	(Arivoli et al., 2015)
Horizontal subsurface flow constructed wetlands	T. latifolia, P. australis	Cr, Cd, Pb, Hg, and As	(He et al., 2015)
Horizontal subsurface flow constructed wetlands	T. latifolia, P. australis	Cu, Zn, and Pb	(Kumari and Tripathi, 2015)
Vertical flow constructed wetlands	V. zizanioides	Mg, Ni, and Zn	(Mudhiriza et al., 2015)
Horizontal subsurface flow constructed wetlands	T. latifolia, P. australis	Cu, Cr, Zn, Pb, and As	(Rai et al., 2015)
Vegetative submerged bed constructed wetlands	Phragmites karka and Veteveria nigritana	Fe, Pb, Mn, Zn, Cr, and Mg	(Badejo et al., 2015)

 

Conclusions and Recommendations

Water resources are under threat because of the growing population. Wastewater treatment is one of many countries’ major concerns, as rising levels of unwanted or unknown pollutants are extremely hazardous to human health and the environment. We looked at the environmental and public health concerns related to the use of untreated wastewater in agriculture in this paper. There is a significant correlation between wastewater irrigation and concentrations of heavy metals and their existence (retention) in soil and accumulation in the crops, vegetables, and plants. Therefore, wastewater irrigation poses a health risk by contaminating the food chain through the consumption of contaminated crops and vegetables. We have focused on the current state of affairs concerning wastewater treatment with the constructed wetland with phytoremediation. Constructed wetland is an efficient, reliable, and active biogeochemical method for the removal of pollutants from wastewater. Several processes such as sedimentation volatilization, microbial activity, adsorption, filtration, and phytoaccumulation are used in CW to remove contaminants. In CW different aquatic floating plants plays a vital role in the enhancement of decontamination process by directly accumulating pollutants in their tissues. These plants utilize some physiochemical and biological processes to remove contaminants from wastewater, which help in remediation process.

Novelty Statement

Wastewater reuse is becoming more popular as a way to fulfill the growing demand of water for irrigation purpose. We have focused on the current state of affairs concerning wastewater treatment with the constructed wetland with phytoremediation. Constructed wetland is an efficient, reliable, and active biogeochemical method for the removal of pollutants from wastewater.

Author’s Contribution

Hasnain Raza, Muhammad Muzamil Nazir, Muhammad Bilal Shoukat, and Attiq ur Rehman planed the work and gather the information related to the constructed wetland, and Iqra Tariq, Kaynat Ahmed, Qurat-ul-Ain, Awais Rasheed, and Muhammad Zeshan Gulzar wrote the portion of the water scarcity of the manuscript Maryam Maqsood and Ali Raza has done the portion of Food chain and health. Huda Bilal reviewed this article and gave fruitful suggestions and format the manuscript according to the journal.

Conflict of interest

The authors have declared no conflict of interest.

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