Filtration Methods for Improving Drinking Water Quality

Professor discusses the process of filtration as a means to reduce turbidity in drinking water.

Coagulation and sedimentation are first used, but if the turbidity is still too high, filtration is needed. There are three common methods of filtration: slow sand filtration, rapid sand filtration, and membrane filtration. Slow sand filtration is best for small communities as it has a biofilm on the top layer of sand that removes particles. Rapid sand filtration has a higher filtration rate but requires backwashing if blocked. Membrane filtration has four types, each of which can intercept particles of a certain size. Microfiltration intercepts particles larger than 1 micron, ultrafiltration intercepts particles larger than 10 nm, nanofiltration intercepts particles larger than 1 nm, and reverse osmosis only allows water molecules to pass through.

In summary, filtration is an effective means of reducing turbidity in drinking water. The type of filtration used will depend on the size of the community and the level of filtration needed. Slow sand filtration is suitable for small communities, while rapid sand filtration and membrane filtration are better suited for larger communities.

Review questions:

• What is the purpose of filtration in drinking water treatment?
• What are the three common methods of filtration?
• What are the four types of membranes used in membrane filtration and what size particles can they intercept?