Page 23 - GS58346 Tasik Chini

Biochemical oxygen demand (BOD) and chemical oxygen demand (COD)

level in Tasik Chini

• Biochemical oxygen demand (BOD) a slightly more refined measure of water quality constituents

than COD. BOD measures the amount of organic components that can be biologically degraded in

water. COD and BOD are measured in mg oxygen/L of water. COD is always equal to or greater
BOD. The ratio of BOD to COD is the percent of the organic materials in water that can be

degraded by natural micro-organisms in the environment.

• Mean BOD value at Chini Lake was 1.50 ± 0.92 mg/l, which ranged from 0.09 - 4.20 mg/l. The
mean value of COD was recorded 21.53 ± 7.51 mg/l and the values ranged from 7.00 - 42.00

mg/l. Raised COD level indicates higher pollution in that definite area (Varunprasath and Daniel

2010) and strong positive correlation between BOD and COD indicates the presence of
biologically active organic matter.

• High levels of COD in water often correlate with threats to human health including toxic algae

blooms bacteria from organic wastes.
• High COD levels decrease the amount of dissolved oxygen available for aquatic organisms.

Dissolve oxygen in Tasik Chini

• Dissolved oxygen (DO) will measure of oxygen dissolved in water. The results of water quality

trends clearly show that the majority of water quality parameters were quite high during wet

season compared to dry season. Water quality analysis shows that in the dry season, DO level
was low. (Gasim et al., 2008).

• A dissolved oxygen level that is too high or too low can harm aquatic life and affect water quality.

Dissolved oxygen is absolutely essential for the survival of all aquatic organisms ( not only fish but
also invertebrates such as zooplankton, etc).