Effluent Treatment Plant

Prepared by-1.Mashuk Rahman Khan2.Logic Karmaker3.Lamia Mahpara4.Fahim Ahamed5.Saifur Rahman

Prepared for- Md. Monirul Islam (MrL)

An Effluent Treatment Plant is a physical plant which is generally used to alter the properties of wastewater.

Also known as Wastewater treatment. Several physical, chemical and biological processes are used to remove any toxic materials present in the wastewater. After the properties of the wastewater are changed, the remaining water is known as Effluent. The Effluent can be discharged into the environment for re-use. Common by-products of the process are screenings, grit, sewage, sludge and odorous gases. The by-products are also treated in the plant.

Common sources of Wastewater-

Iron and Steel IndustryFood IndustryPulp and paper industryNuclear IndustryOrganic Chemicals Industry Residential Wastewater

Steps used in wastewater treatment-

Pre-TreatmentPrimary Treatment Secondary TreatmentTertiary TreatmentDisinfectionOdor Control

Pre-TreatmentPre-Treatment removes all materials that can be easily collected from the raw sewage before they damage or clog the pumps and sewage lines of primary treatment clarifiers. Commonly removed objects during Pre-Treatment-trash tree limbsleavesbranchesother large objects.

ScreeningDuring Pre-treatment, the influent in sewage water passes through a bar screen to remove all large objects like cans, rags, sticks, plastic packets etc. carried in the sewage stream.

Grit RemovalPre-treatment may include a sand or grit channel or chamber, where the velocity of the incoming sewage is adjusted to allow the settlement of sand, grit, stones, and broken glass.

Primary Treatment

In the primary sedimentation stage, sewage flow through large tanks known as Primary Sedimentation tanks.

The tanks are used to settle sludge while grease and oil rise to the surface and are skimmed off.The design of the tank should be such that it removes a high percentage of the floatables and sludge.

Primary treatment can reduce the biodegradable organics of the incoming wastewater by 20-30% and the total suspended solids by some 50-60%.

Secondary (biological) treatment

The dissolved organic matter that escapes primary treatment, are removed. Microbes present in the plant, consume the organic matter as food, and convert it to carbon dioxide, water, and energy for their own growth and reproduction.

Secondary treatment degrade the biological content of the sewage derived from human waste or food waste.

Aerobic biological processes are used.

Secondary treatment technologies include-

The basic activated sludge process the variants of pond and constructed wetland systemstrickling filters other forms of treatment which use biological activity to break down organic matter.

Two types of Secondary sedimentation-

Fixed-film systems include trickling filters, bio-towers, and rotating biological contactors where the biomass grows on media and the sewage passes over its surface.

Suspended-growth systems include activated sludge, where the biomass is mixed with the sewage and can be operated in a smaller space than trickling filters that treat the same amount of water.

Tertiary TreatmentRemoves the pollutants that were not sufficiently removed in the secondary treatment-SolidsNitrogenPhosphorusMetals

Tertiary Treatment provides a final treatment stage to the effluent before it is discharged into the sea or oceans or land.

Nitrogen Removal-Nitrogen is removed through the biological oxidation of nitrogen from ammonia to nitrate (nitrification), followed by denitrification, the reduction of nitrate to nitrogen gas.

Phosphorus Removal achieved by-Chemical Precipitation (with the help of salt or aluminium)The help of bacteria (with a process known as enhanced biological phosphorus removal)

Disinfection

Disinfection is done to reduce the number of micro-organisms present in the water that is to be reduced back into the environment.Disinfection is done by- Chlorination Using UV rays Ozone disinfection (Ozone oxidizes most organic material it comes in contact with, thereby destroying many pathogenic microorganisms)

Odor Control The odor of the water is controlled by-Carbon ReactorsContact Media with bio-slimesSmall doses of chlorineCirculating fluids to biologically capture and metabolize the noxious gases.Addition of iron salts, hydrogen peroxide or calcium nitrate.

Other treatments that can be present in industrial wastewater treatment plants-

An API oil-water separator for removing separate phase oil from wastewater. A clarifier for removing solids from wastewater. A roughing filter to reduce the biochemical oxygen demand of wastewater.A carbon filtration plant, to remove toxic dissolved organic compounds from wastewater.

Conclusion

Some global estimates by United Nations Development Programme(UNDP) and UN-Habitat –

•90 % of all wastewater are released into the environment.•In many developing countries the bulk of domestic and industrial wastewater is discharged without any treatment.•In Latin America about 15 percent of collected wastewater passes through treatment plants.•In Venezuela, 97 percent of the country’s sewage is discharged raw into the environment.•Only few cities in sub-Saharan Africa have sewer-based sanitation systems, let alone wastewater treatment plants.

•Developing countries should plan on investing in more of wastewater treatment plants.

•Countries all around the world should start planning to build Effluent Treatment plants.

Any Questions?