13)Industrial waste Water Treatment


Introduction

Industrial wastewater contains pollutants such as suspended solids, organic matter, oils, toxic chemicals, acids, alkalis and heavy metals. Treatment is necessary before reuse or discharge.

Major Stages

1. Preliminary Treatment

Screening

Removes large floating materials such as:

  • Plastics

  • Wood

  • Rags

  • Large solid particles

Grit Removal

Removes sand, grit and other heavy inorganic particles.


2. Primary Treatment

Sedimentation

Wastewater is kept in settling tanks so that suspended solids settle as sludge.

Oil and Grease Removal

Oil separators or skimming systems remove floating oils and grease.

3. Secondary Treatment

This stage mainly removes biodegradable organic matter using microorganisms.

Activated Sludge Process

Wastewater is aerated in the presence of microorganisms. Organic matter is biologically oxidized.

Organic matter + O₂ → CO₂ + H₂O + New biomass

Trickling Filters

Wastewater passes over a microbial film growing on a suitable support medium.

4. Tertiary/Advanced Treatment

Used to remove specific remaining pollutants.

Methods include:

  • Filtration

  • Activated carbon adsorption

  • Nutrient removal

  • Membrane processes

  • Ion exchange

  • Advanced oxidation

  • Disinfection

Heavy Metal Removal

Heavy metals may be removed by:

  • Chemical precipitation

  • Ion exchange

  • Adsorption

  • Membrane processes

Sludge Treatment

Sludge may undergo:

  • Thickening

  • Digestion

  • Dewatering

  • Stabilization

  • Safe disposal or beneficial use where appropriate

Treatment Flow

Industrial wastewater → Screening → Grit removal → Primary treatment → Secondary biological treatment → Tertiary treatment → Disinfection → Reuse/Discharge

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