Better Management

of

Nutrients in Sewage

Present Practice

• Present sewage treatment practice involves

oxidation by bacteria in presence of air

followed by bacterial denitrification.

Ammonia and sulphur compounds escape

giving a foul smell.

• Nitrogen in the sewage is lost to the

atmosphere mainly as nitrogen molecules

and to some extent as nitrous oxide.

• Nitrous oxide is 300 times more powerful

green house gas than carbon dioxide. It

contributes to climate change, ozone

depletion and to acid rain. Ammonia and

sulphur compounds contribute to fog

formation.

CLIMATE CHANGE

Hole in the ozone layer UV filter

FOG

Our Relation to Nitrogen

• We fix nitrogen by an industrial process to make

fertilizers and also by growing leguminous

plants.

• We use them to produce food in which nitrogen

is present in proteins. We eat the food.

LEGUMES

• We excrete. Most of the nitrogen excreted is present in urine.

Better Practice

• Separate the solids and make use for biogas

production. Biogas can be used as a source of

energy. Nutrients remaining in residue can be

used as fertilizer.

• Store liquids in a closed tank. The liquids give

off ammonia by natural bacterial

decomposition. By pumping air into the

liquid a major part of the ammonia can be

taken out and made to react with acids to

form ammonium salts. The latter can be used

as fertilizers.

• Suitable sea weeds can be grown in the

remaining liquids to further extract NPK etc

present in the liquid. The weeds can be

composted to make fertilizers. Only common

salt remains in the residual liquid which

should be disposed off suitably.

Seaweed

COMPOST

Advantages

1. Valuable fixed nitrogen and other nutrients

are recovered.

2. Pungent smell of ammonia and bad smell of

sulphur compounds are avoided.

3. Air, soil and water pollution is avoided.

4. Less disposal problem.

5. No health problems as there is no mix up with

industrial waste containing heavy metals etc.

6. Less dependence on natural gradients.

7. No contamination of crops and soil with E coli.

8. Reduced need for manufactured fertilizers.

Thank you for reading