Potable water treatment

waqua

potable water treatment

the process by which lake or river water is made drinkable by humans

What are the 6 steps of potable water treatment?

Coagulation, flocculation, sedimentation, filtration, disinfection, and distribution

1.Coagulation

Coagulation is the first step in water treatment. Chemicals with positive charges are added to the water to help bind together dirt and other small particles.

Why is water mixed quickly in the coagulation process?

Water is mixed quickly so cations can stick to the anions. Without cations, the negative charges of anions would repel each other rather than clumping and settling out.

What are the chemicals that are commonly used in the coagulation process?

Specific types of salts, aluminum, or iron.

2.Flocculation

Flocculation is the gentle mixing of water to form larger, heavier particles called flocs. Often, additional chemicals are added during this step to help the flocs form.

What speed is the tank being stirred in? Why?

The tank is stirred slowly so the coagulants and dissolved solids combine to create flocs without being torn apart by high mixing speeds

3.Sedimentation

Sedimentation separates out solids from the water. Flocs are heavier than water, so they settle to the bottom of the water during this step.

What is formed from sedimentation?

Sludge is formed and must be removed, which impacts the cost of the water treatment plant.

4.Filtration

After the flocs have settled to the bottom of the water, the clear water on top goes through many filters. These filters have different pore sizes and are made of different materials. The filters remove germs, bacteria, dissolved particles, etc.

What removes bad smells from the water in the filtration process?

Activated carbon filters remove bad smells.

What are some other ways of filtration that are used?

Ultrafiltration and reverse osmosis.

Ultrafiltration

Ultrafiltration puts water through a filter with very small pores, only letting water and other small molecules through.

Reverse osmosis

Reverse osmosis is a membrane separation process that physically removes contaminants from water. This process forces water at a high pressure through semipermeable membranes. Water that does not pass through the membrane is known as concentrate or reject and retains the higher molecular weight substances, including many unwanted contaminants.

When is reverse osmosis most commonly used?

Water treatment plants often use reverse osmosis when treating recycled water or salt water for drinking.

5.Disinfection

Disinfection is often the last step. Disinfection is to remove the remaining viruses, bacteria, and parasites from the water .

What are the common types of chemical disinfectants?

Chlorine, chloramine, chlorine dioxide, UV treatment.

A similar process called fluoridation (or pH adjustments) also occurs. What does this do?

Water treatment plants often adjust water pH and add fluoride after the disinfection step. Adjusting the pH improves taste and reduces corrosion (breakdown) of pipes. Adding fluoride to drinking water keeps teeth strong and reduces cavities.