The Analysis Study on The Self-Purification Capacity of Klampok River, Assessed from Organic Parameter of Dissolved Oxygen (DO) And Biochemical Oxygen Demand (BOD) (Case Study: Segment Sidomukti Village, Bandungan Sub District – Poncoruso Village, Bawen Sub District)

Klampok River is a river that is geographically located in Semarang District. It flows from Sidomukti Village, Bandungan Sub-District to Pringsari Village, Pringapus Sub-District. The fact that population growth and a large number of human activities such as household chores, agricultural (husbandry) and industrial works have eminently impacted on the quality of Klampok River's water, it has motivated this research to be conducted. Generally, river has its inherent capacity to purify itself on certain defilement condition. The main aim of this study is to determine (discern) the ability of Klampok River's to self-purify based on DO and BOD parameter by using Streeter-Phelps method to obtain oxygen sag curve and Qual2KW program to simulate the water quality. In this study, the value of deoxygenation constant K= 0, 226 and the reaeration constant R= 0, 162 on segment 2 and K= 0, 226 and R=0, 217 on segment 3 would be gained. Based on that result, we found the purification constant fs= 0, 717 on segment 2 and fs= 0, 956 on segment 3, in which segment 2 functions as active decomposition zone and segment 3 as recovery zone.