water treatment purpose
- drinking
- recreation
- irrigation
- cooling
- habitat
Pollutant
something that effects our desired uses of water
- Organic matter - increases BOD
- Infectious agents
- nutrients - N and P
- Toxics - pesticides, industrial, PCPP, metals
Actual vs Goals
- BOD 250 mg/L vs 15 mg/L
- Suspended solids 220 mg/L
- P 8 mg/L <1 mg/L static <0.05 mg/L moving <0.1 mg/L
- N 40 mg/L <0.1 - 10 mg/L <1 mg/L
Accounts for dilution when teh WWTP discharges into the receiving water
Use base flow to make calculations - based on 7Q10 (lowest 7 day discharge over a 10 year period)
Stream discharge + WWTP discharge / WWTP discharge
Primary treatment
- physical removal of solids
- decrease BOD, N and P via sorption and lowering OM
- screening
- clarifer - settling tank
- decrease velocity
- more particulate settles
- things float
- arms sweep off the oil and grease from the surface
Combined Sewer
- domestic wastewater and stormwater
- combined sewer overflows
- allows for overflow and prevents backups into homes
- Increase the flow rate then decrease the residence time
- less effective
- volume/flow = time
secondary treatment
- decrease BOD
- biological process that uses microbes to consome BOD
- carb + O2 = CO2 + H2O
- activated sludge - rich in microbes
- airate to mix and provide O2
- also decrease N and P due to microbial uptake
- sediement tanks
Sediment tanks
- secondary treatment
- add chemicals to coagulate and induce settling
- settling velocity increases as size increases (aggregation)
- Stokes law - terminal settling velocity
- increase diameter of the particle increases the terminal settling velocity
- also accounts for denisty of the particle, density of water, gravity (effect using centrifuge), visocity of water
Coagulates
Aluminum sulfate
iron chloride
calcium hydroxide
Form metal hydrates
acidic because metal pulls electron density of oxygen in water and loss a proton
Tertiary treatment
- nutrient removal
- wastewater increases OM in water by directly adding OM and by promoting plant synthesis via extra nutrients
- uptake in biomass via bacteria
- Metal ions bind phosphate but does not help nitrate
- use phosphorous hyperaccumulating bacteria
- uptake more P than they need
- luxury uptake
- Acinetobacter
- Denitrification - nitrification
Denitrification - nitrification
- nitrification - organic N to ammonium (decomp) and ammonium to nitrate
- requires O2
- denitrification - nitrate to nitrogen gas
- anaerobic
- in an open pool
- O2 on surface is used immediately and anaerobic conditions are found in the rest of the tube
- supply methanol for food
- Nitrification and denitrification must be seperated
disinfect
NaOCl then discharge
Biosolids
- metals - on surfaces
- nonpolar organics - floating organic grease, organic rich layer at the bottom with bacteria, run water through carbon filter
- biosolids - organic C, N, P, metals, nonpolar organics, water (only 0.1% solid)
- highly concentrated
- land applied as fertilizer
Dewatering
- pressing
- centrifuge
Digesters
- organic C to CO2 and methane
- anaerobic
- methanogenic
- 35C temp
- collect methane to generate heat
- burn methane to make CO2
Greenhouse effect
- UV (short wavelength and high energy) into greenhouse
- re-emitted as IR which is long wave
- glass not transparent to IR and it absorbs IR via an increase in vibrational energy
- glass reflects IR in inside and outside
- net gain of energy inside
Greenhouse Gas
- absorbs IR
- not possible for monatomic or diatomic
- CO2 stores IR in vibrations
- also N2O, CH4, H2O
- water is 1-5% of the atmosphere
- re emit 360 deg
- peak CO2 in winter of N. hemisphere
Blackbody rediation
objects that emit radiation
IR windows
An IR range where water is not absorbing the energy and therefore other gases have a large impact on the amount of energy absorbtion
Relative index of Radiative forcing
normalized to CO2 = 1
accounts for amount of increased IR absorption for an increase in the gas concentration
considers whether the absorption occus in an IR window
no net effect if water is already absorbing 100%
Global Warming Potential
- similar to RIRF but considers the average lifetime fo the gas in the atmosphere
- longer lived gases have a greater contribution
- CFC - chlorofluorocarbons produce radicals and reduce ozone
- high GWP
- SF6 is a dense gas that does not diffuse through plastic
- RIRF of 19,000 and GWP of 22,800
radiative forcing
- positive helps absorb
- negative helps prevent energy from entering
- N2O contribution from agriculture
Global warming feedbacks
- forcing - something that pushes or forces a system in a particular direction
- negative feedback - system responds to a pertubation in the way that maintains conditions
- positive feedback - amplifies change
- need negative feedback to outweigh positive feedback
Arctic Ice
- positive feedback
- ice is reflective and limits energy absorption
- albedo - amount of reflection
- increase ice melting and increase water temperature
- less reflection and more absorbed
- increase water temp, increase ice melt
Warming wetland peat
- tundra
- limited degradation when frozen and high carbon storage
- thaw and release CO2 and more degradation
- also release methane that absorbs heat in atmosphere
- increase temp due to CO2 and increase thaw and CO2 release
