Spatial Assessment of Physicochemical and Microbiological Water Quality in Laligan River, Valencia City, Bukidnon, Philippines

Rivers are one of the most vital freshwater resources on Earth, but human activities often cause degradation, emphasizing the need for water quality monitoring. To capture maximum environmental variability, water samples were collected from three strategically mapped sites along the Laligan River using standardized preservation and transport protocols. The analysis was compared against the Department of Environment and Natural Resources Class C water standards. Physicochemical results were mixed. Parameters like Total Dissolved Solids (188.41 mg/L), Turbidity (0.78 NTU), pH (7.76), and Total Alkalinity (98.11 mg/L) were compliant. However, two parameters exceeded the limit: Nitrate (8.81 mg/L average, limit 7 mg/L) and the toxic heavy metal Cadmium (0.006 mg/L average, limit 0.005 mg/L), with both peaking midstream. Most critically, the average Dissolved Oxygen (DO) was 4.48 mg/L, falling below the 5.0 mg/L minimum standard, decrease sharply midstream and downstream due to likely organic pollution. The microbiological quality showed severe contamination. Fecal Coliforms (FC) were already non-compliant upstream at 4,000 MPN/100 mL (limit 400 MPN/100 mL). This concentration dramatically escalated to 17,000 MPN/100 mL midstream and downstream, exceeding the standard by over 42 times and indicating a massive influx of domestic or animal waste. Total Coliforms (TC) mirrored this trend, soaring from a compliant 3,000 MPN/100 mL upstream to 15,000 MPN/100 mL mid- and downstream. While basic parameters are stable, the combination of low DO, elevated Nitrate and Cadmium, and overwhelmingly high Fecal Coliform counts renders the river unsuitable for Class C uses and poses a grave public health risk.