Evaluation of water quality using physico-chemical parameters and coliform bacteria of Mae Kha Canal in Chiang Mai, Thailand

Abstract

Mae Kha Canal is one of Chiang Mai’s most important waterways that nourishes local agriculture, irrigation, and transportation and provides stormwater drainage to prevent floods. Due to the unregulated rapid urbanization of the city and lack of efficient solid waste and wastewater management systems over the past few decades, the canal has been heavily polluted. This study was conducted to evaluate the canal’s water quality through assessment and analysis of the physico-chemical parameters, the presence of coliform bacteria and the riparian zone landscape condition. The water quality parameters were measured across three seasons in the cool dry, hot dry and rainy seasons from 7 sampling sites along the canal. The physico-chemical parameters consisted of water temperature (WT), pH, electrical conductivity (EC), dissolved oxygen (DO), biochemical oxygen demand (BOD5), ammonium-nitrogen (NH4--N), nitrate-nitrogen (NO3--N), orthophosphate (o-PO43-) and total suspended solids (TSS). Results from this study indicate that the canal has poor water quality and is heavily polluted. This was shown by DO, BOD5, ammonium, phosphate, total and fecal coliform bacteria (TCB and FCB) average concentrations that were beyond the limits of the surface water quality standards for Thailand and/ or EPA standards. Similarly, according to water quality based on the chemical index, the results categorized the canal as heavily polluted (17 – 27) to very heavily polluted (0 – 17). The riparian zone condition was also found to be degraded, contributing to the negative impacts on the water quality. Single factor analysis of variance (ANOVA) indicated significant differences (p < 0.05) between sites for EC, DO, BOD5, NH4--N, NO3--N, o-PO43-, TCB and FCB whereas no significant differences (p > 0.05) was found between sites for WT, pH and TSS. Significant differences (p < 0.05) between seasons were found for WT, pH and TSS. CI had a significant difference between sites and non between seasons. Pearson’s correlation analysis of physico-chemical and biological parameters showed BOD5 to have significant correlations with most parameters, having positive significant correlation with NH4--N (r = 0.734), NO3--N (r = 0.448), o-PO43- (r = 0.702), TCB (r = 0.634) and FCB (r = 0.649), and negative significant correlation with DO (r = -0.697) and TSS (r = -0.536). DO also had negative significant correlation with NH4--N (r = -0.649), o-PO43- (r = -0.549), TCB (r = -0.659) and FCB (r = 0.697). CI was negatively correlated to WT (r = -0.543), EC (r = -0.462), BOD5 (r = -0.611), NH4--N (r = -0.507) and o-PO43- (r = -0.521) whereas positively correlated to DO (r = 0.706). Cluster analysis produced three main clusters or groupings of sites based on similarities of physico-chemical parameters and chemical index.