The effect of the individual chart with variable control limits on the river pollution monitoring

This study performs a model to evaluate the river water quality monitoring system. The standard River Pollution Index which includes dissolved oxygen (DO), biochemical oxygen demand (BOD₅), suspended solids (SS), and ammonia nitrogen (NH₃-N) is collected from years 2006 to 2010 for monitoring of river water quality. Furthermore, control chart technology can monitor the river pollution and signal the aggravation of water quality. This study proposes an individual control chart with variable control limits (VCL individual chart) and verifies this chart can quickly signal the mean change of both normal can skew populations in statistical performances. In addition, this study also presents a real case that VCL individual chart is applied on monitoring the water quality of Taiwan’s river. This case shows the VCL individual chart controls successfully the river pollution, and this chart is very suitable to apply monitoring the water quality of rivers.