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Water Quality Index Research Methodologies: BOD
[BOD Research Background]
HOW TO DO A FIVE-DAY
BOD TEST
- Begin by determining the amount of dissolved oxygen in the stream water by using a Hach Dissolved Oxygen (DO) test kit as described on the "How to do a Dissolved Oxygen Test" page. Record this
amount.
- Clean and rinse the 60ml D.O. sample bottle. Carefully. refill the sample bottle with stream water. Stopper the bottle. Be sure there
are no air bubbles in the sample.
- Wrap the bottle completely with aluminum foil.
- Place the bottle in a dark room at about 20oC or 68oF (room temperature) for five days (120 hours).
- At the end of the five day period, measure the amount of dissolved oxygen left in the water by using the Hach DO test kit.
- Subtract the DO value obtained on day five from that obtained on day one. The difference is the five-day BOD.
EXAMPLE:
Day one DO level equals 14 mg/l
Day five DO levels equal - 6 mg/l
5-day BOD equals 8 mg/l*
*Report this number as your five-day BOD.
Use the rough standards below too begin interpret your
findings.
1-2 mg/l BOD | Very clean water, little biodegradable
waste |
3-5 mg/l BOD | Moderately clean water, some biodegradable
waste |
6-9 mg/l BOD | Many bacteria, much biodegradable
matter |
10 or more mg/l BOD | Very bad; someone may be dumping
biodegradable wastes into the water.
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