and industrial practices. Uniquely, their role in sustainability of ecosystems is immensely vital. Therefore, the sustainability of groundwater quality and quantity itself is very important for the above‐mentioned phenomena. However, owing to various anthropogenic activities in the recent past, groundwater resources are undergoing catastrophic depletion and deterioration. Particularly, the overexploitation and continuous groundwater pollution works in a synergic fashion and cause non‐availability of groundwater and making it unfit for any use. Here, in this section we are putting forward few global examples that illustrates the devastating impacts of polluted groundwater on smaller and bigger scales.
Boateng et al. have studied the extent of heavy metal contamination in Oti landfill site, Kumasi, and further evaluated the effect of this contamination on human health. Through the standard methods and procedures for the examination of water and wastewater, authors reported that the concentration of many metals like Pb, Cd, Fe, and Cr was above the acceptable limits as set by the WHO for drinking water. It was reported that only the concentration of Zn and Cu was within the permissible limit. Further, it was revealed that this high level of heavy metal contamination in groundwaters of Oti has grave health consequences and water needs to be pretreated before its consumption (Boateng et al. 2019).
In a recent report, a meta‐analysis on the impact of consumption of polluted groundwater on health of children was executed in 10 developing countries including India. The research shows that blood of the children from these countries have relatively higher levels of heavy metals than normal cases and this problem is only attributed to the polluted groundwater by the researchers Horton et al. (2013); (Singaraja et al. 2015; Mohankumar et al. 2016). The groundwater pollution problem is a very serious concern across the world, however, the situation in developing economies, especially heavily populated ones, is very critical. In these countries, industrial growth and agricultural practices are rapidly increasing and consequently, offering more and complex hurdles in the sustainable management of groundwater resources. For instance, the Kurichi Industrial Cluster near Coimbatore city does not have agricultural activities and waste dumping nearby it, however, it has given a comprehensive Environmental Pollution Index (CEPI) score of 58.75 by the Central Pollution Control Board (CPCB, India) in 2009, which implies that the water was critically polluted (Action plan for critically polluted area, Tamilnadu Pollution Control Board, 2010, www.tnpcb.gov.in/pdf/Action_plan_cbe.PDF). This is because of the release of unchecked wastewater streams of local industries in groundwater. This transformed the local groundwater and nearby groundwater tables into highly toxic systems. The groundwater sources are not suitable for domestic and agricultural practices. Further, many ill effects on human health, soil fertility, bioaccumulation, and biomagnification of the toxic heavy metals are spreading with a higher pace in the region. To mitigate the issues, the local authorities had imposed stronger legislations on the industries and wastewater treatment plants were commissioned in many industries.
Many such studies are now published by many research groups, NGOs (nongovernmental organizations), environmentalists, and local governments. However, the real scenario is even worse than that reported in these studies, especially in the areas where infrastructure is not that strong. Moreover, many examples of the hazardous effects of consumption of groundwater contaminated with heavy metals are presented throughout the chapter.
Therefore, a comprehensive review on such aspects and illustration of the true picture of the problem is required for making the sustainable policies and strategies to propagate the sustainability of groundwater resources and their uses.
4.5 Recent Strategies to Control Heavy Metals
As discussed, the main sources of heavy metal pollution are anthropogenic sources, which are the major concern for contaminants in groundwater as well as surface water resources. To overcome these problems, government must take appropriate action to solve these issues. In this regard, government has taken a decision to prevent and overcome heavy metal pollution in water.
NEERI (National Environmental Engineering Research Institute) has addressed the technique to decontaminate the water from heavy metals as well as for waste management of the land sector. The kit is also receommended to check the quality of drinking water (Marg 2011).
For preventing Hg pollution, the major Hg pollution sources like medical devices and CFL (compact fluorescent light) bulbs should be replaced by non‐mercury containing products (Marg 2011). The industries should set up treatment technology for spontaneous remediation of the heavy metal‐based wastewater before discharging the wastewater into water bodies.
Domestic wastage like municipal and sewage waste should be prevented from discharging in water. It should be monitored and made a rule to stop the disposal of waste in water. To cure the drinking water, the metal‐based pesticides and insecticides should be bonded within the agricultural field. Government must give proper attention to organic farming. Phytoremediation is a best tool to control the heavy metal contamination. Other spontaneous chemical and physical treatments have been utilized to overcome heavy metal pollution in water (Marg 2011; Talabi and Kayode 2019).
4.6 Remediation Methods of Heavy Metals
To solve this problem, over the last decades various types of methods are used for the elimination of heavy metals from water (see Figure 4.2). The literature reveals that some methods, such as membrane filtration, oxidation, ion exchange, coagulation‐flocculation, phytoremediation, electro‐kinetics, and adsorption are carried out to eliminate the heavy metals from contaminated water (Barakat 2011; Agarwal and Singh 2017; Azimi et al. 2017). All these methods with their advantages and limitation are explained in brief.
4.6.1 Oxidation
The oxidation method includes the use of an oxidizing agent (Cl2, ClO2, O3, H2O2, NH2Cl, MnO4−, FeO42−, etc.) to eliminate heavy metals from water (Sharma et al. 2007; Mondal et al. 2013; Bora and Dutta 2019). Investigation of the photochemical and photocatalytic oxidation process includes the oxidation of heavy metals using UV radiation, O2, etc. for the removal of dissolved pollutants. UV/solar radiation assists to develop the hydroxyl radicals during the photolysis of iron and iron hydroxide (fe(OH)3), hydroxyl radicals and O2 oxidizes the toxic metals like As(III) to As(V). The presence of these radicals, the oxidation reaction becomes faster (Yoon and Lee 2005; Sharma et al. 2007). On the other hand, the photocatalytic reaction is carried out in the presence of TiO2 for oxidation of the heavy metals (Miller et al. 2011).
Figure 4.2 Schematic of conventional different conventional methods to decontaminate water from heavy metals.
4.6.2 Coagulation‐Flocculation
The coagulation and flocculation method has been investigated to eliminate the toxic metal pollution from contaminated water (Abouri et al. 2019; Bora and Dutta 2019). In this process, the coagulant is incorporated into the contaminated water and then forms the floc, which has the potential to eliminate heavy metals from the water. The positively charged coagulants such as aluminium and iron salts, which are widely used for heavy metal like As removal, help to decrease the negative charge of colloids. The larger particles (floc) form due to agglomeration of the particles, which settle down in water due to the influence
