6 Flashcards
Describe the techniques used in the purification of drinking water from surface water.
Main common ones:
- Coagulation -> Flocculation -> Sedimentation
- Filtration
- Taste and odor control
- Disinfection
Describe the techniques used in the purification of drinking water from groundwater.
Main common ones:
- Iron and manganese removal
- Softening
- Arsenic and nitrate removal
- Disinfection
What is Coagulation?
Process adding and mixing chemical reagents to water to destabilize colloidal and fine solids suspended in water
Fix turbidity
What is flocculation?
Slow stirring promotes agglomeration (clustering) of destabilized particles formed during coagulation.
What is filtration?
Filtering water using fine sand, gravel, and anthracite to remove non-settleable flocs that stayed after coagulation/flocculation/sedimentation.
what is a way to remove odor from water samples
using an activated carbon filter, like charcoal to remove remaining organic contaminants
how can we soften water
by precipitating Ca and Mg out of the water via the addition of phosphate or lime stone
What are the disinfection methods for water?
-Membrane technology
- UV radiation
- Chemical methods: Ozonation or Chlorination
What are the advantages and disadvantages of membrane technology for disinfection methods?
Takes long time but is pretty efficient
What are the advantages and disadvantages of UV light for disinfection methods?
Pros:
- Good against microorganisms
- No need for chemicals
- No residue
- User friendly
- Less space
Cons:
- Low doses might nit work against all microorganisms
- High preventive maintenance (Fouling of tubes)
- Turbidity and total suspended solids block light so it can make this less effective (must be filtered to ensure it will work)
- Not cost effective
What are the advantages and disadvantages of Ozonation for disinfection methods?
Pros:
- O3 generated onsite (convenience)
- Generates radicals in water which can kill bacteria
- Only 10 min of concentrated O3 destroys bacterias and viruses
Cons:
- Energy intensive
- Short-half life and no residual preventive protection
What are the advantages and disadvantages of Chlorination for disinfection methods?
Cl2 in water leads to HOCl which goes into cell walls and oxidizes vital stuff for micro orgs
- Chlorine residual left over
Cons:
- Formation of byproducts like haloacetic acids and haloacetonitriles. Also, chlorinated phenols and halomethanes
which is the best disinfection method
UV, is the best for all things except for cost.
What’s the difference between municipal water and wastewater treatment?
wqater treatment: treating water from natural sources like surface and groundwater
Wastewater treatment: treating water from human waste (water humans have used)
What are the objectives of wastewater treatment?
Remove:
- Dissolved biodegradable organics (BOD)
- Suspended solids
- Pathogenic microorganisms
- N and P if eutrophication is a concern
what is screening
a pre treatment
to remove large object inorder to protect down stream equipment
what is grit removal
a pre-treatment
to remove dirt, sand and stones with other inrog particles
prevent clogging pipes
what is floatation
pre-treatment
to remove fast oils and grease (FOG) via air
what are the three pre-treatments used
screening
grit removal
floatation
what is the objective of the primary treatment of wastewater
to separate solids from wastewater.
they use a sedimentation tank to remove and settable or floatable solids not extracted during pre-treatment
soluble pollutants will remain
how much BOD is removed from primary treatment
30%
what is the purpose of secondary treatment
remove any remaining BOD and COD and TTS (which can be organic or not)
it may also remove some N and P or heavy mental (though this usually needed advanced methods)
how is secondary treatment preformed
via the use of living micro orgs
either aerobic or anerobic
what is the result form using aerobic orgs in secondary treat
they will produce CO@ and energy whike increasing thier bio mass in the tanks
what is the result from using anaerobic orgs in secondary treat
will make CO@ and CH4 while their biomass will likely decrease due to internal organism decay
what is the main goal in the aeration tanks (used for secondary)
to max the # of orgs in the tanks at a given moment
what are the 4 stages of micrbo pop in the tanksn
exponential growth
declining growth
stationary
endogenous phase (internal decay_
what type of device is used fro secondary treatment
aeration tanks to inject ari and accelerate bio degredation
this is very efficient but it is also very costly
what are the top steps of the municipal wastewater treatment plan
inffluent, pre treatment, primary settleing, secondary treatment (biological treat and secondary settling), effluent onto advanced
what are the bottom steps of the municipal wastewater treatment plan
primary sludge from primary settling
excess sludge from secondary settling )which may be returned to the aeration tank
the sludge goes to the anaerobic digester. it can be stabilised and stored then disposed… OR the bio gas emitted can be held in a gas tank and electricity will be produced by a generator
what is the purpose of advanced water treatment
to meet stringent discharge limits
to reclaim or reuse water
what is WW reclimantion
the treatment of WW to resue
and aims to remove nitrogen, phos, TDS and TSS, microorgs and refractory organics (alkenes or alkanes in the water system)
how are refractory organics removed
advanced oxidation processes
what is the advanced oxidation process
a water purification method that removes organic materials from water through reactions using OH radicals
what is the key component of AOP
OH radicals
what are the advantages of AOP
what are the 2 main sources for AOPs
H2O2 + UV and O3 (with water) +Uv
what is sludge
the residues from wastewater in the form of liquid or semi solid that generally has a strong odour.
what are the objective of sludge treatment
volume reduction (of the treated water)
safe disposal of the material
resource and reuse
how is sludge digested
via anaerobic methods. in the absence of oxygen allows for the destruction of pathogens while actively removingwater/ in many cases this save energy too as oxygen does not have to be supplied constantly to sustain the micro orgs
here is sludge disposed
landfills
ocean
incineration
deep weel injections
where is treated water disposed of
rivers, lakes and seas
may be disposed onto land, such as lawn, crops or pastures
or possibly used as a treatment for soils or wetland
where is treated water reused
in fire fighting, cleaning systems, cooling systems
aquifer recharing
growth of aquatic plants for animal consumption
