dr Bello Flashcards
what different zones is ozone in and what are its effects in these zones
troposheric ozone, lower atmosphere, secondary air pollutoant, makes up photochemical smogh
stratospheric ozone
screens uv radiation
cfcs destroy it
what is photo chemical smog
haze in the atmosphere accompanied by high levels of ozone and nitrogen oxides, caused by the action of sunlight on pollutants.
a couple of harmful effects for each pollutant
sulfur dioxide and particular material- irritate respiroty tract, inability to exchange oxygen
nitrogern oxides-airway restriction
carbon monoxide-binds with iron hemoglobin , death
ozone- burning eyes etc, asthma
three ways to control air pollution
smokestack with precipitator (negative electrode)
smokestack with scrubbers
legislation-reduced sulfur content in gasolibe, emission std for cars
what is necessary for high distance travel of pollutants
high volatility, persistance
ground water general parameters
constant compostion high mineral content low turbidity low colour no do high hardness
surface water basically opposite
three major contaminants
pathogens
sediments
nutrients
types of impurities
suspended (settleable non settle-able)
collodial
dissolved
two catagories of treatment methods
unit operations (physical) unit processes )chemical/biological)
two types of colloids and their properties
hydrophobic -negative-dispersion stabilised by electrostatic repulsion- charge due to metals clays etc-thermodynamically unstable (will aggregate slowly)
hydrophillic- slight charge but dispersion stabilised by hydration (attraction to water) - biological generally-thermodynamically stable (react spontaneously to form colloids)
three origins of primary charge
lattice imperfections
adsorption of ions
ionisable surface groups (ph dependent)
EDL summary
attracts counter ions creates gradient (but cannot attract same amount of counter ions) EDL formed via attraction of oppositely charge counter ions by primary surface charge then diffusion of counter ions away from surface
net resultant force
sum of zeta potential and venderwaals forces
zeta potential
net charge between primary chrage and counter charge
isoelectric point
when particles are in the presence of enough counter ions they become electrically neutral. hence interaction
4 destabilisation methods
double layer compression
ion adsorption and charge neutralization
bridging and adsorption
enmeshment in precipitate (sweep floc)
doubkle layer compression
addition of indifferent charged ions (do not react with colloids)
increases ionic strength
compresses EDL
van derwaals negate repulsion
no risk of OD
no relationship between coag conc and colloid conc
adsorption and charge neatralisation
charged counter ions wiith affinity for colloids get adsorbed and reduce charge
larger and more positive ions are best
can result in over dosing (surface charge reversal)
proportional to colloids conc
adsorption and bridging
metal salt or polymer adsorb to surface charge neatralisation bridges between molecules overdosing possible (covers surface without bridging)
Enmeshment in precipitate
al2(so4) or Fecl3 colloids serve as site for precipitation relationship is inverse lower PH more charge per al and fe higher ph more likely to form polymers
what destabilisation should occur when low colloid conc low
low interaction, so get destabilization through sweep floc
what destabilisation should occur when colloid conc medium
sufficient interaction before sweepfloc so charge neautralisation
what destabilisation should occur when colloid conc high
lost of coagulant, may approach sweef floc conc but dont get any sweep floc
what molecule consumes fe and al
PO4
what flocculation is from heat movement
perikinetic
what flocculation is from external mixing
orthokinetic
excess lime treatment process
first stage, rapid mix, only lime, ph increase (removes carbonate hardness from ca and mg)
remove excess lime to lower PH
second stage
only soda ash added, rapid mix, NCH reaction. use recarbonation to lower Ph to 8.5-9.5
selective calcium removal
reduce lime and co2 dosage
no need for first stage recarbonation
magnesium conc in bypass will be the same as in raw ater, finnished water should have mg at 40mg/l as caco3
advantages disadvantages if ion exchange method
- effective for CH and NCH
- flash mixers, flocculation basin, and sediment basin not required
- doesn’t take long
bad because sodium ions in treated water
disposal of brine
fouling might occur
zones of filtration system.
1 lag phase, (back wash water passes from under fill)
2 pre rippening, becomes poorer quality from back wash still inside
3 second pre rippening, further deteriorates from back wash above medium
4 ripening
5effective filtration
6breakthrough
7 spent phase
three types of removal for different size parrticles in filter
diffusion (only applicable to 1um D)
interception ( Radius greater than distance between flow streamline and grain)
sedimintation (for larger particles)
two types of particals when iit comes to sedimentation
discrete (2000 kg/m3) or flocculant (size and velocity fluctuates 130 kg/m3)
organisms that use organic carbon vs organsism that derive carbon from co2
heterotrophs, autotrophs
oraginsms that use light as energy or derive from chemical reactions
phototrophs, chemotrophs
define respiratory metabolism and fermantation metabolism
respitory, generate energy by enzyme mediated electron transport from an electron donor to external electron accpetor,
fermentation, does not involve the participation of external electron acceptor
aerobic respiartion, vs anoxic respiration
aerobic, uses oxygen as electron acceptor, anoxic uses inorganic compounds such as nitrate
difference between strict anaerobes and facultative anearobes
, strict, devoid of oxygen, faculative, grow with or without oxygen .
what two processes are responsible for nitrogen removal
aerobic nitrofication, (nh4 into no3) then denitrification (anoxic) no3 into n2
if BOD lower than 500, use what
aerobic process (cheap to aerate)
if ss smaller than 200 or if larger than 200
if smaller use fixed growth (wont clog) if larger use suspended growth
3 stage process in activated sludghe system
transfer food to cell, conversion of food to byproducts and cells, flocculate
three types of sedimintation
discrete, flocculate, zone ( increasing ss conc)
