Question

1. Briefly describe each of the 5 steps of water treatment
   1. Aeration
   2. Coagulation (flocculation)
   3. Sedimentation
   4. Filtration
   5. Disinfection

Answer 1

Answer:-

a) Aeration: It is the first step of water purification treatment. Aeration brings water and air in close contact by pumping air into the water tank. Aeration promotes microbial growth into the water. Those microbes feed on the organic materials and forms flocks which can be easily settled out. After that the water is transferred to a settling tank where after the settlement water is separated from the "activated sludge" flocks.

b) Coagulation (flocculation): It is an important part of wastewater treatment. Coagulation is a chemical process which involves neutralisation of charge. In coagulation some chemical coagulant like Aluminium sulfate(allum) is added which will promote the clumping of fine into larger floc after which it will be easy to separate them from water. Flocculation is a physical process. In flocculation due to the addition of clarifying agent the colloid come out of the suspension in the form of floc and then separated from the water.

c) Sedimentation:- In this process the main role play the gravitational force. In large tanks the water is kept for 24 hours. The large and heavy particles automatically comes down of the tank. This way the non-dissolving heavy particles can be isolated from the water. This process only isolated non-dissolving heavy particles.When sedimentation done the water from the upper surface slowly pumped out to the next tank.

d)Filtration:- The water came from sedimentation is then filtered. It can be done by many ways like strainer or sand layers or by multiple layers. The minute particles which are not sedimented , this particles can be separated by this process. Water is run through by sand layers or strainers and the liquid came is about 80% pure.

e) Disinfection:- It is the final step of water treatment. This process is to kill the germs, pathogen and other bacteria. Oxidizing process is common as disinfection as by this process nutrition in water will destroyed so that germs can't grow. Chemically disinfection is also important. Chemicals like bleaching powder, chlorine, O3 (ozone gas) , Halogens, Alcohol can be used for treatment. Physical disinfection like UV rays, Radiation, Gamma ray, Ultrasonic sound, Heat are also used in steps.

After all this steps ultimately water is treated and it is safe for use.