6.4.3 Food Chain Contamination
Wastewater irrigation affects human health in both aspects either positively or
negatively. Positive aspect of wastewater irrigation is related to food security of
the water-scarce zone and negative aspect of wastewater is based upon the presence
of different toxic potential contaminants and pathogens, etc., above their permissible
limits. Among all the wastewater irrigated food plants, vegetables are the major food
crops, consumed at a global level. Vegetables accumulated the toxicants in their
edible parts. Approximately 90% of total metals enter to the human body via intake
by vegetables and other edible crops as it is the major component of the human diet
and the remaining 10% metal through inhalation of dust and dermal contacts
(Martorell et al. 2011; Khan et al. 2014; Gupta et al. 2019a). Heavy metals negatively affect the nutritional value of the foods. The plants irrigated with wastewater
were found nutrient deficient due to antagonistic interaction between metal and
nutrient such as Cd suppress the uptake of Zn due to same carrier transporter protein
(Salgare and Acharekar 1992; Sharma and Agrawal 2006).
For security of human health and food safety, it is important to characterize the
sources and concentration of heavy metals in wastewater, irrigated soil, and growing
plants in order to establish quality standards (Sun et al. 2013). Because of higher
demands of food in the recent decades, food safety has become one of the burning
issues with respect to human health. This context provokes researchers and scientist
to work on food chain contamination by heavy metals and its associated health risks.
The concentration of heavy metal (mg/kg) in wheat grain irrigated with wastewater
varied between 0.1–0.9, 0.3–0.5, 0.7–1.4, 0.8–1.6, 0.6–0.9, 1.2–1.6, and 0.06–0.2
for Zn, Cr, Cu, Mn, Ni, Cd, and Pb, respectively. Cd concentration exceeded
permissible limit (0.2 mg/kg) set by FAO/WHO. Similarly, vegetables and other
crops as well as milk produced under wastewater irrigation regimes were also found
contaminated with potentially toxic heavy metals (Sharma et al. 2007; Gupta et al.
2019a).
6.5 Control Measures for Wastewater Reuse
Due to the rapid growth in industrialization, the level of contaminants is increasing
day by day in industrial discharge, so, for healthy and safe environment their
removal from wastewater is very important. Generally, conventional wastewater
treatment approach is the combined form of different physical, chemical, and
biological processes for the removal of contaminants including different hazardous
metals, organic materials, colloids, and types of emerging contaminants from wastewater. Each treatment process has its own advantages and disadvantages in terms of
cost, labor requirement, efficiency, reliability, practicability, feasibility, ecofriendly
nature, operation process, energy cost, and quality of byproducts, etc. Treatment
approaches also depend on the source and types of wastewater. Various physical and
6 Wastewater Reuse in Peri-Urban Agriculture Ecosystem: Current Scenario,. . .
131
Wastewater irrigation affects human health in both aspects either positively or
negatively. Positive aspect of wastewater irrigation is related to food security of
the water-scarce zone and negative aspect of wastewater is based upon the presence
of different toxic potential contaminants and pathogens, etc., above their permissible
limits. Among all the wastewater irrigated food plants, vegetables are the major food
crops, consumed at a global level. Vegetables accumulated the toxicants in their
edible parts. Approximately 90% of total metals enter to the human body via intake
by vegetables and other edible crops as it is the major component of the human diet
and the remaining 10% metal through inhalation of dust and dermal contacts
(Martorell et al. 2011; Khan et al. 2014; Gupta et al. 2019a). Heavy metals negatively affect the nutritional value of the foods. The plants irrigated with wastewater
were found nutrient deficient due to antagonistic interaction between metal and
nutrient such as Cd suppress the uptake of Zn due to same carrier transporter protein
(Salgare and Acharekar 1992; Sharma and Agrawal 2006).
For security of human health and food safety, it is important to characterize the
sources and concentration of heavy metals in wastewater, irrigated soil, and growing
plants in order to establish quality standards (Sun et al. 2013). Because of higher
demands of food in the recent decades, food safety has become one of the burning
issues with respect to human health. This context provokes researchers and scientist
to work on food chain contamination by heavy metals and its associated health risks.
The concentration of heavy metal (mg/kg) in wheat grain irrigated with wastewater
varied between 0.1–0.9, 0.3–0.5, 0.7–1.4, 0.8–1.6, 0.6–0.9, 1.2–1.6, and 0.06–0.2
for Zn, Cr, Cu, Mn, Ni, Cd, and Pb, respectively. Cd concentration exceeded
permissible limit (0.2 mg/kg) set by FAO/WHO. Similarly, vegetables and other
crops as well as milk produced under wastewater irrigation regimes were also found
contaminated with potentially toxic heavy metals (Sharma et al. 2007; Gupta et al.
2019a).
6.5 Control Measures for Wastewater Reuse
Due to the rapid growth in industrialization, the level of contaminants is increasing
day by day in industrial discharge, so, for healthy and safe environment their
removal from wastewater is very important. Generally, conventional wastewater
treatment approach is the combined form of different physical, chemical, and
biological processes for the removal of contaminants including different hazardous
metals, organic materials, colloids, and types of emerging contaminants from wastewater. Each treatment process has its own advantages and disadvantages in terms of
cost, labor requirement, efficiency, reliability, practicability, feasibility, ecofriendly
nature, operation process, energy cost, and quality of byproducts, etc. Treatment
approaches also depend on the source and types of wastewater. Various physical and
6 Wastewater Reuse in Peri-Urban Agriculture Ecosystem: Current Scenario,. . .
131