Post on 23-Dec-2015
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!