Wastewater101 not needed Flashcards
What is municipal wastewater?
Sewage
Volume of wastewater per person per day?
225 to 450 L
Whats ICI stand for?
Industrial, commercial, institutional flow
What is the waste treatment plant at a low point?
Because pipes are often gravity fed. May be pumps to boost.
What is infiltration?
When water seeps into cracks in the pipes.
What are combined sewer systems?
Where wastewater is mixed with stormwater.
What are common constituents in domestic wastewaters?
- Organics
- Solids
- Nutrients
- Pathogens
What are the three means of removing wastewater contaminants?
Physical
Chemical
Biological
What hours are peak for volume of wastewater?
Morning and night.
What are tested parameters?
Total nitrogen Total ammonia nitrogen Total phosphorus Total suspended solids BOD - indicates organic material in wastewater CBOD
What does the clarifier do?
Removes some of the suspended solids and organic matter.
What is the most widely used form of wastewater treatment?
Primary sedimentation. Particles settling at the bottom of the tank. Settled particles called primary sludge.
What helps speed up sedimentation?
Chemicals called coagulants. They cause flocculation so they settle faster.
What happens to the sludge?
Scraped from the bottom of the tank into a hopper. Then pumped from the tank for processing. Usually water is removed before further processing.
How is biodegradable organic matter removed? (second treatment - secondary clarifier)
Microorganisms.
Wastewater and biomass are mixed, what is this called?
Mixed liquor.
What do microorganisms need to work?
DO. That is why there are aeration.
What is secondary clarification for?
Separating the mixed liquor suspended solids. Similar process to the primary clarification.
What happens to secondary sludge?
Called RAS, returned activated sludge. Contains many living things. Sent back to aeration basin to maintain high biomass. Rest of biomass is removed WAS so conc doesn’t get too high.
Another reason coagulants are added?
To remove phosphorus.
Another method for removing phosphorus?
Enhanced biological phosphorus removal. Phosphorus accumulating organisms (PAOs) grow more easily than others.
Two processes that nitrogen can be removed?
Nitrification and denitrification. Only little by organic matter breakdown.
What is the third stage of wastewater treatment?
Removal of the residual suspended solids following secondary treatment. This is done by filtration through granular media/material. Chemicals added prior to convert dissolved into particles.
How is the third stage maintained?
Backwashing. This water go earlier in the cycle.
When is disinfection involved?
Second or third part.
How is chlorine disinfection applied? How does it work?
Gas or liquid.
Danages the cell and or DNA or organisms.
Chlorine removed by process called dechlorination.
What are examples of advanced filtration?
Membrane filtration. Reverse osmosis. Also potentially the tertiary treatment.
What is stabilisation in terms of sludge?
Reduces pathogens and sludge odours.
What are biosolids?
Stabilised sludge.
What is digestion?
Biological stabilisation.
How much does dewatering remove the water content?
to the 20-30% tot water left
