dr Bello

Question 1

what different zones is ozone in and what are its effects in these zones

Answer 1

troposheric ozone, lower atmosphere, secondary air pollutoant, makes up photochemical smogh

stratospheric ozone
screens uv radiation
cfcs destroy it

Question 2

what is photo chemical smog

Answer 2

haze in the atmosphere accompanied by high levels of ozone and nitrogen oxides, caused by the action of sunlight on pollutants.

Question 3

a couple of harmful effects for each pollutant

Answer 3

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

Question 4

three ways to control air pollution

Answer 4

smokestack with precipitator (negative electrode)
smokestack with scrubbers
legislation-reduced sulfur content in gasolibe, emission std for cars

Question 5

what is necessary for high distance travel of pollutants

Answer 5

high volatility, persistance

Question 6

ground water general parameters

Answer 6

constant compostion
high mineral content
low turbidity 
low colour
no do
high hardness

surface water basically opposite

Question 7

three major contaminants

Answer 7

pathogens
sediments
nutrients

Question 8

types of impurities

Answer 8

suspended (settleable non settle-able)
collodial
dissolved

Question 9

two catagories of treatment methods

Answer 9

unit operations (physical)
unit processes )chemical/biological)

Question 10

two types of colloids and their properties

Answer 10

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)

Question 11

three origins of primary charge

Answer 11

lattice imperfections
adsorption of ions
ionisable surface groups (ph dependent)

Question 12

EDL summary

Answer 12

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

Question 13

net resultant force

Answer 13

sum of zeta potential and venderwaals forces

Question 14

zeta potential

Answer 14

net charge between primary chrage and counter charge

Question 15

isoelectric point

Answer 15

when particles are in the presence of enough counter ions they become electrically neutral. hence interaction

Question 16

4 destabilisation methods

Answer 16

double layer compression
ion adsorption and charge neutralization
bridging and adsorption
enmeshment in precipitate (sweep floc)

Question 17

doubkle layer compression

Answer 17

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

Question 18

adsorption and charge neatralisation

Answer 18

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

Question 19

adsorption and bridging

Answer 19

metal salt or polymer
adsorb to surface
charge neatralisation
bridges between molecules
overdosing possible (covers surface without bridging)

Question 20

Enmeshment in precipitate

Answer 20

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

Question 21

what destabilisation should occur when low colloid conc low

Answer 21

low interaction, so get destabilization through sweep floc

Question 22

what destabilisation should occur when colloid conc medium

Answer 22

sufficient interaction before sweepfloc so charge neautralisation

Question 23

what destabilisation should occur when colloid conc high

Answer 23

lost of coagulant, may approach sweef floc conc but dont get any sweep floc

Question 24

what molecule consumes fe and al

Answer 24

PO4

Question 25

what flocculation is from heat movement

Answer 25

perikinetic

Question 26

what flocculation is from external mixing

Answer 26

orthokinetic

Question 27

excess lime treatment process

Answer 27

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

Question 28

selective calcium removal

Answer 28

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

Question 29

advantages disadvantages if ion exchange method

Answer 29

- 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

Question 30

zones of filtration system.

Answer 30

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

Question 31

three types of removal for different size parrticles in filter

Answer 31

diffusion (only applicable to 1um D) interception ( Radius greater than distance between flow streamline and grain) sedimintation (for larger particles)

Question 32

two types of particals when iit comes to sedimentation

Answer 32

discrete (2000 kg/m3) or flocculant (size and velocity fluctuates 130 kg/m3)

Question 33

organisms that use organic carbon vs organsism that derive carbon from co2

Answer 33

heterotrophs, autotrophs

Question 34

oraginsms that use light as energy or derive from chemical reactions

Answer 34

phototrophs, chemotrophs

Question 35

define respiratory metabolism and fermantation metabolism

Answer 35

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

Question 36

aerobic respiartion, vs anoxic respiration

Answer 36

aerobic, uses oxygen as electron acceptor, anoxic uses inorganic compounds such as nitrate

Question 37

difference between strict anaerobes and facultative anearobes

Answer 37

, strict, devoid of oxygen, faculative, grow with or without oxygen .

Question 38

what two processes are responsible for nitrogen removal

Answer 38

aerobic nitrofication, (nh4 into no3) then denitrification (anoxic) no3 into n2

Question 39

if BOD lower than 500, use what

Answer 39

aerobic process (cheap to aerate)

Question 40

if ss smaller than 200 or if larger than 200

Answer 40

if smaller use fixed growth (wont clog) if larger use suspended growth

Question 41

3 stage process in activated sludghe system

Answer 41

transfer food to cell, conversion of food to byproducts and cells, flocculate

Question 42

three types of sedimintation

Answer 42

discrete, flocculate, zone ( increasing ss conc)