Abstract— Water scarcity has severely impacted the global economy, livelihoods, and environmental quality, driving the use of municipal and industrial wastewater as an alternative irrigation source in urban and peri-urban agriculture. This practice addresses water deficits but raises concerns about risks to human and environmental health from contaminants. This study evaluated the effect of diluted domestic sewage wastewater (used in semi-urban Palakkad) versus well water (used in rural areas) on pigeon pea (Cajanus cajan). We conducted a comprehensive analysis of irrigation water, soil, and various plant parts (seeds, leaves, stems, pods) for physicochemical parameters, proximate composition, full mineral profile, heavy metals, and in vitro antioxidant activity. Results indicated that most physicochemical parameters of the irrigation water were within FAO permissible limits, though the semi-urban source showed elevated iron, phosphate, and alkalinity. Critically, concentrations of toxic heavy metals (Ni, Cr, Cd, Pb, Cu) in soils and, most importantly, in the edible seeds remained well below WHO/FAO safety thresholds. Proximate analysis confirmed good nutritional quality in seeds from both sources (e.g., protein: 15.5-17.6 g/100g). Plants irrigated with both water types exhibited significant in vitro antioxidant activity across five complementary assays (FRAP, DPPH, ABTS, Metal Chelating, NO Scavenging), which was strongly correlated with phenolic content. A notable finding was the elevated iron content in seeds, suggesting a natural bioaccumulation propensity in C. cajan. The study concludes that, under the observed conditions, the use of diluted domestic sewage wastewater did not induce harmful heavy metal accumulation in C. cajan, maintained its nutritional value, and preserved its bioactive potential. This supports its role as a viable and sustainable irrigation alternative, contributing to water security and nutrient recycling. Non-seed tissues (leaves, pods) showed high phenolic content, indicating value for nutraceutical use or animal feed.
Dhanya et al. (Sat,) studied this question.