Physicochemical and Microbiological Investigation of Groundwater in Al-Salman District, Southern Iraq

Abstract

Background: In many of southern Iraq's rural and semi-arid areas, groundwater serves as the primary supply of drinking and household water. However, inappropriate waste disposal, agricultural practices, and natural geochemical processes—which can result in microbial and chemical pollution—are rapidly endangering its purity.  The study's objective is to provide a thorough assessment of the water safety for human consumption by evaluating the physicochemical and biological quality of groundwater in the Al-Salman district of Iraq by identifying bacterial contaminants, analyzing their antibiotic resistance, and measuring important chemical parameters. Material and methods In the spring of 2024, groundwater samples were taken from two sites in the Al-Salman district using sterile bottles (100 mL for bacteriological examination and 1 L for chemical analysis). Standard analytical techniques were used to determine physicochemical parameters including pH, temperature, electrical conductivity (EC), total dissolved solids (TDS), alkalinity, nitrate, nitrite, sodium, potassium, and phosphorus. Samples were enriched in Brain Heart Infusion (BHI) broth and incubated for 24 hours at 37 °C before being subculture on MacConkey agar, blood agar, and Mannitol salt agar for bacteriological examination. Biochemical assays and colony morphology were used to identify the bacterial isolates. The Kirby-Bauer disk diffusion method was used to test for antibiotic susceptibility against a variety of antibiotics in accordance with CLSI standards. Results: According to the physicochemical investigation, the groundwater had a nearly neutral pH ranging from 7.00 to 7.10 and relatively high temperatures between 30 and 33?°C, which may promote microbial growth. Electrical conductivity (EC) and total dissolved solids (TDS) were very high, indicating a large amount of salt and minerals in the water. Alkalinity (ALK) was within permissible limits at less than 250?mg/L. Nitrate (NO??) levels exceeded the allowable limit of 50?mg/L, while nitrite (NO??) remained within the safe range around 50?mg/L. Potassium (K?) concentrations were higher than the recommended limit of 10–15?mg/L, and sodium (Na?) was also elevated above 250?mg/L, whereas phosphorus (P) was within acceptable levels around 0.4?mg/. The biological analysis showed several pathogenic bacteria were isolated, including Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Staphylococcus epidermidis, Proteus vulgaris, Enterobacter spp., and Pseudomonas aeruginosa, many of which exhibited multidrug resistance. However, antibiotics such as meropenem, gentamicin, amikacin, and netilmicin showed the highest effectiveness against most isolates. Conclusion: These findings indicate that groundwater in the studied area is unsuitable for direct drinking without proper treatment and continuous monitoring to minimize potential public health risks.