Environmental Contaminants in Drinking Water of Urban Dairy Farms in Dhaka, Bangladesh: Microbial and Iron Burdens as Emerging One Health Threats Under Climate Stress

Abstract

With direct implications for One Health and environmental resilience, water quality remains a critical yet underexplored determinant influencing livestock health, productivity, and food safety in Bangladesh’s urban dairy systems. In rapidly urbanizing regions such as Dhaka, underground supply water infrastructure is increasingly vulnerable to microbial contamination, structural decay, and climate-linked stressors. This study evaluated the microbiological and physicochemical quality of drinking water supplied to five representative urban dairy farm locations. Sampling followed a 5-site design with 4 replicates per location (n = 20), using standard microbiological and biochemical methods to detect total coliforms, Escherichia coli, and protozoa (Giardia spp., Balantidium spp.), alongside measurements of pH, total dissolved solids (TDS), iron, chloride, and total hardness. All samples showed 100% prevalence of coliforms and E. coli, with bacterial loads significantly exceeding WHO safety limits. The highest coliform count was recorded in Mirpur-1 (2.63×10⁸ CFU/ml; P = 0.012), while the lowest was at the SAU campus (1.73×10⁸ CFU/ml). E. coli loads ranged from 5.50×10⁷ to 7.05×10⁷ CFU/ml (P = 0.043) while no protozoan parasites were detected. Iron concentrations exceeded recommended levels across all sites, with Mirpur-1 showing the highest mean (0.972 ± 0.02 ppm; P = 0.001). TDS and chloride levels were highest in the 60 Feet area (397.0 ± 3.14 ppm and 0.945 ± 0.03 ppm; both P = 0.001). Water hardness ranged from 75.0 ± 2.04 to 165.0 ± 1.23 ppm, while pH values remained within acceptable limits (6.12 ± 0.03 to 6.70 ± 0.07). TDS showed a moderately strong positive correlation with coliforms (R² = 0.697; P = 0.079), while chloride had a moderate negative correlation with E. coli (R² = 0.460; P = 0.208). These findings emphasize the need for climate-resilient water safety protocols, regular microbial surveillance, and improved sanitation to protect livestock and public health in urban dairy environments.