Effluent Treatment Plant – GB Construction

Industrial waste water ( Effluent ) treatment describes the process used for treating waste water produced by industries as an undesirable by-product. After treatment, the treated waste water may be reused or released to a Sanitary sewer or to a surface water in the environment.

FEATURES:

To remove all inorganic & organic through physical, chemical and biological process
To clean industry effluent and recycle it for further use.
To reduced the usage of fresh/potable water in industries.
To cut expenditure on water procurement.
To meet the standards for emission or discharge of environmental pollutants from various industries set by the government and avoid hefty penalties.
To safeguard environment against pollution and contribute in sustainable development

Design of ETP:-

The design and size of the ETP depends upon:

Quality and quality of the industries discharge effluent.
Land availability.
Monetary consideration for construction, operation & maintenance.

Treatment Levels & Mechanisms of ETP:–

Treatment Levels:

Preliminary
Primary
Secondary
Tertiary ( or advanced )

Treatment Mechanisms:

Physical
Chemical
Biological

Preliminary Treatment Level:

Purpose: Physical separation of big sized impurities like cloth, plastics, wood logs, paper, etc.Common physical unit operations at Preliminary level are:

Screening : A screen with openings of uniform size is used to remove large solids such as plastics, cloths etc. Generally maximum 10mm is used.

Sedimentation: Physical water treatment process using gravity to remove suspended solids from water.

Clarification: Used for separation of solids from fluids.

Tertiary / Advanced Treatment:

Purpose :- Final cleaning process that improves wastewater quality before it is reused, recycled or discharged to the environment.

Mechanism:- Removes remaining inorganic compounds, and substances, such as the nitrogen and phosphorus. Bacteria, viruses and parasites, which are harmful to public health, are also removed at this stage.

Methods:-

Alum : Used to help remove additional phosphorus particles and group the remaining solids together for easy removal in the filters.
Chlorine contact tank disinfects the tertiary treated waste water by removing microorganisms in treated waste water including bacteria, viruses and parasites.
Remaining chlorine is removed by adding sodium bisulphate just before it’s discharged.

Primary Treatment Level:

Purpose: Removal of floating and settleable materials such as suspended solids and organic matter.

Method: Both physical and chemical methods are used in this treatment level.

Chemical unit process:

Chemical unit processes are always used with physical operations and may also be used with biological treatment process.
Chemical processes use the addition of chemicals to the waste water to bring about changes in its quality.
Example: pH control, coagulation, chemical precipitation and oxidation.

pH Control:

To adjust the pH in the treatment process to make wastewater pH neutral.
For acidic wastes ( low pH ): NaOH, Na2Co3, CaCO3 or Ca(OH)2.
For alkali wastes ( high pH): H2SO4, HCL.

Chemical coagulation and Flocculation:

Coagulation refer to collecting the minute solid particles dispersed in a liquid into a larger mass.
Chemical coagulants like AL(SO4)3 { also called alum } or Fe2(SO4)3 are added to wastewater to improve the attraction among fine particles so that they come together and form larger particles called flocks.
A chemical flocculent ( usually a polyelectrolyte ) enhances the flocculation process by bringing together particles to form larger flocks, which settle out more quickly.
Flocculation is aided by gentle mixing which causes the particles to collide.

Secondary Treatment Level:

Methods: Biological and chemical processes are involved in this level.

Biological unit process:

To remove, or reduce the concentration of organic and inorganic compounds.
Biological treatment process can take many forms but all are based around microorganisms, mainly bacteria.

Aerobic Processes:

Aerobic treatment processes take place in the presence of air ( OXYGEN ).
Utilizes those microorganisms ( aerobes ), which use molecular/free oxygen to assimilate organic impurities i.e. convert them into carbon dioxide, water and biomass.

Anaerobic Processes:

The anaerobic treatment processes take place in the absence
Utilizes microorganisms (anaerobes) which do not require air (molecular/ free oxygen ) to assimilate organic impurities.
The final products are methane and biomass.