Activity 5 - Primary treatment: sedimentation and settler tank

Jaime Sierrra and Alvaro Rivas
23/10/2018

• Aim of the study:

This part is the primary treatment of the sewage water treatment plant process, which is the one in charge of the sedimentation of the clay in settler tanks, separating this one from the water to have it clean. To do the experiment we were based on the Hjulstrom diagram:

After looking the Diagram, we started comparing different clays to finally put them into water with the objective of separating the clay from silt. Then we could know and observe the properties of each clay that we worked with.
Also to help in the experiment we created our own settler tank to filtrate the water with clay.

• Materials: 

Settler tank built

1. Three Beakers
2. Plastic bottle
3. Filter paper
4. Small rocks
5. Sand
6. Three different types of clay:
1. one from abacus, 
2. one which case was green 
3. one blue(that were the names we used to refer to each one)

• Methodology:

In order to check which material was really clay and which was silt, we mixed each material with water in 3 separated beakers. After 24 hours we could observe that the abacus and green types were completely deposited and that the blue type was still mixed with water. We chose the blue type to further experiment with the settler tank.

In order to built the settler tank, we first take the bottle and we cut it in two pieces. After we make some holes in the cap bottle to make sure that the water can pass through.

Then we need to put the paper filter between the bottle cap and the bottle to retain the sand. After this we need to add another filter to separate the sand from the small stones and finally another filter.

• Result and discussion:

We have observed that the filter that we have made, it works as expected.

When we filter the water with clay, we could see how the water is changing the color gradually.

Also, it´s easy to observe, that when we clean the filter with clean water, as we can see the images below, the amount of clay that remained in the filter and a cleaner water.

Comparing our filter with others, our filter with just a single pass, the water has a lighter color so it´s much better than the others but it takes more time to filter the water, but it does not mean that the result is worse.

• Conclusions:

Concerning the three types of clay, our conclusion is that the blue type is really clay and, therefore, it does not deposit with time. However, the other two types are silt.

The result that we have obtained from our experiment is not perfect but we can improve it. If we add a new fabric layer on top of everything and in the bottom of the bottle to put a carbon filter the efficiency of our filtration will improve.