Community size expansion that affects water quality in the Phetchaburi River

Abstract

Rapid expansion of community size especially, along the river is a crucial cause of water pollution. This research aims to study the relation of community size expansion affecting water quality in the Phetchaburi River and propose guidelines for urban wastewater treatment based on consideration of satellite imagery interpretation of the community size along Phetchaburi River during 1995-2017 and water quality information such as BOD TCB FCB in wet season and dry season. The areas of study were divided into 3 zones namely, upstream, midstream and downstream. It was found that the biggest community was located in the midstream zone because it was a traditional community which originally located along the river. The greatest community size expansion was found in the downstream zone (8.82 km²) followed by the upstream zone (5.71 km²) and the midstream zone (4.83 km²). Considering an annual averaged water quality value per 1 km² of the upstream, midstream and downstream zone, it was found that the averaged BOD was 6.22, 0.05 and 6.17 ml/l respectively. The averaged TCB was 19,210, 1,258 and 9,841 MPN/100ml respectively. The averaged FCB was 2,132, 1,099 and 3,977 MPN/100 respectively. The results presenting good quality in the midstream zone was due to how Mueang Phetchaburi Municipality created a collecting wastewater system and send the wastewater through pipe lines to a wastewater treatment system. However, the upstream and the downstream have greater community size expansion and do not provide a central domestic wastewater system or wastewater treatment and release wastewater into the river. Such action affects water quality in the Phetchaburi River. Therefore, it is suggested for communities exceeding 0.25 km² that guidelines for central domestic wastewater system and domestic wastewater treatment suitable for the community size should be provided before releasing wastewater into natural resources.