Wastewater Reuse for Sustainable Agriculture in Punjab, Pakistan: Feasibility, Productivity, Environmental Risk, and Circular Economy Implications

Water scarcity, groundwater depletion, deteriorating surface-water quality, and rapid urban growth are intensifying pressure on irrigated agriculture in Punjab, Pakistan.This study evaluated wastewater reuse as a circulareconomy strategy by synthesizing quantitative secondary evidence on wastewater availability, treatment coverage, water quality, crop performance, socioeconomic outcomes, soil and river impacts, and water-energy-food (WEF) interactions, drawn mainly from peer-reviewed studies and reports published between 2010 and 2025.Punjab was estimated to generate approximately 4.5 billion L of wastewater per day, of which only about 568 million L d⁻¹ (approximately 10-13%) was treated.Reported untreated wastewater contained biochemical oxygen demand (BOD) of 250-350 mg L⁻¹, chromium of 1.5-2.0mg L⁻¹, cadmium of 0.8-1.2mg L⁻¹, and fecal coliforms approaching 10⁶ CFU 100 mL⁻¹.Treated wastewater was associated with yield gains of about 20% in wheat, 14-15% in rice, and 25% in sugarcane, and with wheat water productivity rising from 0.9 to 1.2 kg m⁻³.In contrast, long-term untreated reuse was associated with higher electrical conductivity (0.9 to 1.6-1.8dS m⁻¹), sodicity (+20-25%), and soil cadmium (2.5-3.0 mg kg⁻¹).A heatmap, principal component analysis (PCA), and Pearson correlation matrix of three urban profiles revealed one dominant pollution gradient (PC1 = 94.1%) with Lahore at the high end; these multivariate outputs are exploratory because only three profiles were available.Overall, the evidence supports treatmentdependent rather than unrestricted reuse.Expanding treatment, source control, routine monitoring, farmer engagement, and nutrient and energy recovery could convert a major pollution stream into a strategic irrigation resource while protecting food and environmental safety.