| Summary: | A perennial increase in river pollution over the Kereh River, Penang, Malaysia, is reported due to an increase in untreated swine wastewater discharge from pig farming activities. The fact that the river receiving the untreated swine wastewater is shallow and narrow exacerbates the situation. In Kampung Selamat, Tasik Gelugor, Penang, Malaysia, 77 pig farms with over 186,390 pigs have been causing an unresolved river water quality issue in the Kereh River, Penang, Malaysia, for nearly four decades. This issue escalated into massive public interest and posed adverse environmental pollution. This study aims to statistically assess and identify the sources and conditions of the aforementioned polluted river. Measured river water quality data from 2010 to 2019 were obtained from the Department of Environment (DOE) Malaysia, covering the condition of the river for the last decade. Initially, the data were segmented into three regions: the river's upstream, middle, and downstream. The data were analyzed using the geospatial technique, statistical tests (Shapiro-Wilk and Kruskal-Wallis tests) and multivariate statistical methods, including cluster analysis (CA) and principal components analysis (PCA). Subsequently, temporal and spatial patterns of river water quality were analyzed to evaluate the pollution status and identify the potential pollution sources along the river. The spatial-temporal analysis study revealed that the lower part (downstream) of the river is significantly polluted, as evident by the dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammoniacal nitrogen (NH3–N), and phosphate (PO4) revealed in the said analysis. Therefore, it can be concluded that the Kereh River is depleted of dissolved oxygen and rich in organic content and nutrients, especially in the downstream region, resulting in the river being classified as a dead river based on national water quality standards. The findings may provide some guidance or inspiration for relevant authorities and pig farmers on the workable action plan that can be opted to overcome the pollution while enhancing the quality of this river. © 2022 The Authors
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