Question

Q8. As an Engineer, you are requested to implement a small wastewater treatment plant for your apartment that comprise of 52 flats. Explain the different steps or stages involved in the wastewater treatment process.

Answer 1

I divided the answer in 2 parts. First part describe how to implement an waste water treatment plant in any community. Second part describe the steps involved in waste water treatment.

Part 1 :

Implementation

of waste water treatment plant:

Step 1: calculation of total input waste water : this calculation can be done using the supply data of water to community. Normally 80% of water supplied to community converts into waste water.

Step 2: design of different waste water treatment units based on input waste water discharge

Step 3: reuse or recycling: the sludge produced during waste water treatment is rich source of nutrients required by plants. This this sludge could be used for slude farming of manure.

Step 4: sludge treatment units : the sludge generated from waste water treatment could be dangerous when disposed off without suitable treatment. Thus tertiary treatment process is used for conditioning & treatment of sludge.

Step 5: based of discharge coming from community, septic tanks or imhoff tanks could be as an whole effective and economical waste water treatment plant unit. Septic tank is it self a small treatment plant which is used in small towns or societies producing small discharge.

PART 2:

steps and stages involved in waste water treatment process :

Waste water treatment is divided into 3 stages :

1. Primary process

2. Secondary process

3. Tertiary process

1. Primary process :

In primary process, rough treatment is done like sieving out coarse material, oils & inorganic materials. Following treatments are done :

A. Sieving through fine & coarse messes.

B. Removal of oil from detritus tanks

C. Removal of inorganic particles using grit chambers.

(A, B & C all are recognised as preliminary processes)

D. Removal of suspended solids using primary settling tanks.

2. Secondary treatment :

In secondary treatment, suspended organic impurities are removed using following steps :

A.Removal of suspended organic compounds using activated slude process ( suspended growth system) or using trickling filter process (attached growth system)

B. Seperation of slude from treated waste water using secondary sedimentation tanks.

3. Tertiary treatment :

Tertiary treatment is done to treat sludge generated from secondary treatment process. This process can be done by

A. Chemical treatment of slude using chemicals

B. Sludge conditioning and densification.

C. Anaerobic slude digestor ( sludge digestion chambers)

D. Aerobic sludge digestor.

4. Disposal :

A.Treated waste water can be disposed in rivers, land or sea.

B. Treated sludge could be used as manuer or can be disposed in slude drying beds, soak pits etc.

Thankyou :-)