Mumbai university > Civil > SEM 8 > Industrial Waste Treatment

Marks: 10M

Year: Dec 2014, May 2013

An acidic waste can be neutralize by following methods:

• Mixing the waste by the waste from other industry.

• Passing the acidic waste through the beds of lime stone.

• Mixing the acidic waste with the lime slurry

• Adding proper proportion of caustic soda and soda ash.

• Mixing the waste by the waste from other industry: Mixing of waste can be accomplished within a single plant operation or industry or between neighboring industry plants. Acidic and alkaline waste may be produced individually within one plant and proper mixing of these wastes at approximate time can accomplish neutralization.

• Mixing the acidic waste with the lime slurry : This method is effective method, slacked lime stone is used and so 7-15% of lime slurry reaction. The reaction is as follows:

  $CaCO_3 + H-2SO_4 --------\gt CaSO_4 + CO2 + H_2o$

  Calcium sulphate is formed continuously but it is carried away with waste. It is less expensive than limestone method. Since by product is carbon dioxide gas which escapes away which further causes erosion of wall of treatment vessel within a treatment plant.

• Adding proper proportion of caustic soda and soda ash: This treatment is more effective than lime treatment. Reaction is fast but it is costly. Required less volume of tank. Requires lesser volume of agents since these neutralization agents are more powerful than lime or limestone. Another advantage is that the product is soluble and do not increase the hardness of receiving water.

Effects of acidic waste:

• Most fresh water lakes, streams and ponds have a natural pH in the range of 6 to 8. Acid deposition has many harmful ecological effects when the pH of most aquatic systems falls below 6 and especially below 5.

• This causes a severe effect on aquatic life.

• They not only affect the secondary treatment process but also corrodes pipes and pumps of treatment units.

• It also causes the foaming of water at the surface which is very dangerous for the survival of the water bodies.

• Therefore, stream water cannot be used without treatment.