Equipment :

60ml glass sample bottle
Dedicated BR collecting bucket with rope tied securely to the handle.
Latex gloves
Safety glasses

Safety

It is imperative to work with a buddy when using a bucket to sample.

Important

Collect the D.O. sample FIRST.

Take the D.O. water sample from the bucket FIRST before the 500ml bottle sample, so there is less disturbance and oxygen getting into the water.

Try to test between 12noon and 2pm.

The recommended time for testing is between 10am and 2pm, and ideally, between 12noon and 2pm.

Collect from the same place each month.

Check your site guide sheet if you are unsure.

Collect the sample water from a flowing section of the water body in midstream (if possible). Do not collect sample water from backwater or stagnant pools.

Collect in flowing water.

Part 1. Collecting the sample in your bucket.

1. Holding tightly onto the rope, throw the bucket out into a flowing area of the river.

2. Gently jostle the rope until some water enters the bucket.

Pull rope back gently and slowly after each rinse water collection to avoid disturbing and mobilising sediments. To avoid contamination, do not pour the rinse water back into the sampling area as this may disturb and mobilise sediment. Now you are ready to take TEST sample.

3. Rinse bucket three times with the river water to be tested.

4. Again, holding tightly onto the rope, throw the bucket out as far as possible into a well-mixed and flowing area of the river away from the bank.

If sampling from a bridge drop bucket into a well-mixed and flowing area of the river away from the bank.

5. Gently jostle the rope until the bucket sinks slightly until water enters the bucket from just below the top water surface.

The sample should be taken from half the depth of the stream. Be careful not to let the bucket sink to the bottom or stir up bottom sediment.

6. Fill the bucket to about three quarters full and pull it back in with the rope.

Part 2. Collecting the sample in your D.O. bottle

1. Rinse collection bottle 3 times with the water to be tested.

2. Replace lid on sample bottle after rinsing.

3. Turn bottle on its side and lower into the water (lid closed).

4. Lower to half the depth of the stream.

5. Slowly remove lid and allow to fill with water.

6. Turn vertically up to completely fill and release all trapped air.

7. Recap bottle while underwater.

8. Remove from water.

9. Invert bottle to check that there are NO air bubbles.

If air bubbles present, tip out water downstream of where you are collecting your sample and repeat steps 2 to 8.

The black lids have an inverted plastic cone inside which stops air bubbles being trapped within the water sample.

Dissolved oxygen (DO) is a measure of how much oxygen is dissolved in the water - the amount of oxygen available to living aquatic organisms. The amount of oxygen in the water regulates the distribution, activity, movement, and behaviour of all aquatic animals.
The amount of dissolved oxygen in water is dependent upon the water temperature; colder water can carry more dissolved oxygen that warmer water. When in equilibrium with the atmosphere, at this maximum concentration the water is said to be saturated or at 100% saturation of dissolved oxygen. DO is also affected by the presence of algae that can produce oxygen via photosynthesis during the day and consume oxygen via respiration at night. This is why it is important to always test at the same time of day.
DO analysis should be performed immediately and in situ. Therefore, this is test that should be performed on site where possible, however in some cases e. when raining or doing the test in a school room the sample can be fixed on site for further analysis at home or in the school room.