Monitoring of river and marine water quality at Sarawak baseline

Abstract

The water quality for the shorelines of Kuching, Samarahan, and Betong divisions was assessed based on the primary and secondary data which was then compared to the National Water Quality Standards and Marine Water Quality Criteria and Standards for Malaysia. The Water Quality Index (WQI) and Marine Water Quality Index (MWQI) were generated where applicable. The results reveal that the baseline river monitoring locations portrayed slight pollution with WQI ranging from 60 to 80 except for Sg. Seblak station with polluted water quality, registering WQI of 42. Most of the baseline marine water monitoring stations recorded excellent to moderate MWQI apart from Btg. Samarahan and Sg. Sarawak stations with MWQI of 40, which might be due to the urban population of the Kuching city and Samarahan area. Moreover, MWQI of 48 was recorded at the estuary of Sg. Tabo and Sg. Buntal. The primary data revealed that the marine water samples had a dissolved oxygen (DO) concentration between 4.58 and 6.88 mg/L. The heavy metal ions and oil and grease parameters were below the detection limit. Hence, no industrial-related effluent was detected at the estuary and coastal waters along the shoreline of Kuching, Samarahan, and Betong. The present study concluded that the main pollutants along the shoreline of Kuching, Samarahan, and Betong include ammoniacal nitrogen (NH3–N), nitrate nitrogen (NO3–N), and phosphate (PO4). The high levels of NH3–N, NO3, and PO4 are attributed to the wastewater discharges originating from coastal settlements and commercial establishments, nutrient runoffs from large-scale agricultural activities, and aquaculture activities. In contrast, the secondary data revealed the presence of faecal pollution originating from untreated or partially treated sewage and sullage discharged by coastal settlements and commercial establishments.