Determination of Chemical Oxygen Demand (COD) Concentration in Domestic Wastewater Using UV-Vis Spectrophotometry Method Based On The Effect Of Reflux Time And Preservation Time

The purpose of determining Chemical Oxygen Demand (COD) in samples domestic wastewater is to determine the effect variations reflux process time which set 0, 30, 60, 90, and 120 minutes as well with testing are 3, 7 days. Determination LOD LOQ using a UV-Vis Spectrophotometer was also carried out regression equation y = 0.0003x + 0.0066 coefficient determination (R2) 0.998 values ​​respectively 40.0416 mg O2/L 133.4721 O2/L. preservation on COD levels statistically, namely normality test (Kolmogorov-Smirnov Test) homogeneity (Levene ending two-way ANOVA probability or significance value inlet outlet 0.000 < 0.05 ( ). Reflux affects levels, longer time, higher more stable levels. Preservation decrease greater