Preliminary Assessment of Spring Water Sources as Raw Water using the Weighted Arithmetic Water Quality Index in Batu City, Indonesia

Abstract

Assessing raw-water quality is essential for ensuring a safe drinking-water supply, particularly in municipalities that rely on natural springs. This study evaluated the physicochemical and microbiological quality of six spring-water sources supplying Perumda Air Minum Among Tirto in Batu City, Indonesia. Water samples were collected in December 2024 from Ngesong, Banyuning, Gemulo, Torong Belok, Darmi, and Kasinan. Physicochemical parameters were assessed against Indonesia's Ministry of Health Regulation No. 2 of 2023 and incorporated into the Weighted Arithmetic Water Quality Index (WAWQI) calculations, while Escherichia coli and total coliforms were evaluated separately. Turbidity ranged from 0.02 to 0.05 NTU, total dissolved solids from 118 to 288 mg L⁻¹, and hardness from 62 to 169 mg L⁻¹ as CaCO₃. Banyuning exhibited deviations in pH (6.46) and color (15 TCU), while Gemulo and Darmi recorded the highest nitrate concentrations (11 mg L⁻¹). All springs were classified as having excellent physicochemical water quality under the adopted WAWQI framework, with values ranging from 0.776 to 4.060. Nevertheless, total coliforms were detected in all sources (7–80 CFU/100 mL), whereas E. coli was only identified  at Ngesong (20 CFU/100 mL) and Darmi (1 CFU/100 mL), indicates recent fecal contamination which requiring immediate disinfection prior to distribution. It is importance of combining physicochemical WAWQI assessment with independent microbiological monitoring to guide source protection and municipal raw-water management.