Wastewater Treatment

ByShantanu ManeVaidehi Dharkar

Viral Shah

What is Wastewater?

• Water is used for many purposes.

• Water that has beenused and contains domestic, industrial, institutional andcommercial waste products is called wastewater.

Where does wastewater come from?

• Residences (kitchen, bathroom)• Commercial Institution• Industrial Institution (usually requires specialized

treatment process)

What is wastewater treatment?

• Usually refers to sewage treatment or domestic wastewater treatment.

• Process of removing contaminants from wastewater, both run-off and domestic.

Goals

• To produce a waste stream.• To produce solid waste (sludge).• Then discharge or reuse them back into the

environment.

Why do we need to treat wastewater?

• Wastewater treatment is important to remove constituents or contaminants that could harm people or the environment.

• Common constituents in domestic wastewater are:

-Organic Solids -Nutrients -Pathogens

Where is wastewater treated?• All sources of

wastewater in a Sewage Service Area are connected to sewers, which join together to form a network called a collection system.

• The collection system leads to a Water Pollution Control Plant (WPCP).

How does it get there?• Water flows downhill

because of gravity, so the WPCP is usually located at a low point in the service area.

• If the force of gravity isn’t enough, pumping stations are used to boost wastewater through forcemains (pressurized sewers) to the WPCP.

Stages of wastewater treatment:

Preliminary Treatment:

• Mechanical screens remove materials like rags,sticks, etc.

• Grit removal processes remove grit, sand andgranular materials.

Primary Treatment:

•Typical materials that are used during primary treatment include -fats, oils and greases (a.k.a FOG) -sand, gravel and rocks -larger settle-able solids including human waste -floating materials

Methods used in primary treatment:

Sand catcher Primary sedimentation

Secondary Treatment:

•Biodegradable organic matter is removed by microorganisms (biomass).•This is considered the second stage of wastewater treatment.

Methods/Approaches of Secondary Treatment:

• Secondary treatment is usually accomplished by a process called suspended growth biological treatment.• The term “suspended” is used because the biomass floats freely in the liquid. • Other approaches are: -Fixed Film System -Lagoon System

Tertiary Treatment:•Removal of disease causing organisms from wastewater.•3 different disinfection processes:

Chlorination UV light radiation OzonationUV light radiation OzonationChlorination

Advanced Treatment:

•Quaternary and sometimes tertiary treatment are classed as advanced treatment.•Advanced treatment is not always required.•Technologies include membrane filtration and reverse osmosis.

Sludge

What is sludge?

• Sludge is solid material removed from primary sedimentation tanks and secondary clarifiers.

• Other sludge components may include chemical precipitates and backwash solids from tertiary filters or other processes.

Sludge Processing - Thickening

• Raw sludge is usually more than 95% water!

• Thickening the sludge reduces water and increases sludge solids concentration from 3% to 8%.

Sludge Processing - Stabilization

• Stabilization is a process that reduces pathogens and sludge odours.

• Bio-solids are stabilized.• Biological stabilization is called digestion.• Aerobic digestion is a suspended growth process with oxygen

present for stabilization.• Anaerobic digestion involves the decomposition of organic

and inorganic matter in the absence of oxygen.

Sludge Processing - Dewatering

• Dewatering reduces the water content of bio-solids to the 20% to 30% range.

• At this dryness level it is often called sludge cake.

Sludge Processing – Bio-solids

• Bio-solids are incorporated into the soil. Available nutrients are taken up by plants for growth.

• If land application is not possible, bio-solids may be disposed of in a landfill, composted or incinerated.

• Further processes exist to convert bio-solids to a marketable fertilizer.

What can effluent be used for?

•Discharged into a stream, river, bay, lagoon or wetland.•Used for the irrigation of a golf course, green way or park.•If it's sufficiently clean it can be used for groundwater recharge.

Conclusion

• Wastewater treatment is a great technique to make optimum use of water.

• Water which would simply be thrown away is put to good use.

• Reduces contamination of clean water sources.

Thank you!