Winkler’s method (unmodified) was followed for the estimation of dissolved oxygen. The water samples collected for dissolved oxygen estimation were treated with manganous sulphate solution, alkaline iodide solution and acidified with concentrated sulphuric acid on the spot. The treated samples were transferred to the laboratory and the remaining steps of analysis were done. No noticeable change occurred in the treated samples within 24 hours. The quantity of dissolved oxygen, thus estimated, was expressed in milligram of oxygen per liter of water (mg/l).
BIOCHEMICAL OXYGEN DEMAND (BOD)
The sample of BOD bottles were filled with water and immediately transported to the laboratory and left for incubation in 20oC for five days. Dissolved oxygen (DO) content of BOD bottle water sample was determined after five days by following the Winkler method (unmodified). The value of BOD was obtained by subtracting final dissolve oxygen (FDO) from initial dissolve oxygen (IDO).
When the DO content was almost negligible or showing a condition of total anoxia, the BOD was determined by dilution method (APHA 1989).
good.....................
ReplyDelete