first colloquim up to page 99 Flashcards
what is the oxidizability of water
use the permanganate method
units mg/l (mg of o2 per litre of water)
the oxygen necessary for the oxidation of organic substances in 1 L of water
bulgarian instituion: water oxidizability should be no more than 5mg 02/L
principle of detemrintion: mix kmno4 and sulphuric acid and it will turn into kso4
ammonia in water
produced when nitrogenous organic matter is destroyed by microbiological activity, very common in groundwaters. and also water polluted by sewage or fertilisers
indicator of FRESH organic polution
instituiton_ no more than 0.5mg/l
determination: its a colorimetric method and you use nesslers reagnet. add it to the water and will change colour from pale yellow to brown depending on how much ammonia is present
nitrIte NO2
is unstable intermediate in the nitrogen cycle
in natural water its present in small amounts
higher amounts in sewage and insdustrial wastes, polluted waters
its an indicator of RECENT organic pollution of water
instituiton_ no more than 0.5mg/l
determintion: colimeteric method with the reagent Griess-illosvay. the 2 will react to form coloured complex directly proportional to the amount of nitrate . (red pink)
nitrate
the most highly oxidized form of nitrogenous compounds
commonly present in surface and ground waters as it is the end product of aerobic decomposition of organic nitrogenous matter.
signifcant sources come form chemcial fertilisers from cultivated land etc.
is in indicator of OLD organic pollution of water
in water can cause a problem especially for babies as it can affect hb levels forming methaemoaglobonemia - “blue baby syndrome’. bacteria in babies GIt convert nitrate into nitrite which reacts with hb to form methemoglobin leading to cyanosis
instiruton: no more than 50mg/L
determination:
Mercks test, nitrate ions are reduced to nitrite by reducing agent. nitrite ions react with aromatic amine to form a diazonium salt resulting in a red-violet azo dye. the nitrate is measured semi quantitivaly by vision
chloride
we have organic and non organic chlorides
present in natural waters
high amount indicates pollution
high amounts corrodes metal pipes and harmful to most trees and plants.
institution: no more than 250 mg/l. usual content is about 20-40 mg/l
determination: use silver nitrate, colour changes from bright yellow to orange red
sulphate
high levels caused by industrial waste and nine drainage and also the breakdown of sulphur containing compounds
high amounts can be tasted and causes a laxative effect
institution: no more than 250mg/l
determination: colorimetric method with bacl2. barium becomes barium sulphate
coliform organisms and how to test?
include all aerobic and facultative anaerobic organism. use as an indicator for sanitary control of food and water.
Coliform bacteria are defined as rod-shaped Gram-negative non-spore forming bacteria which can ferment lactose with the production of acid and gas when incubated at 35–37°C.
fecal coliform bacteria normally present in intestines example e.coli therefore if found in water it suggests fecal contamination
testing is the multiple tube fermentation method/MPN method. it is presumptive because you can’t confirm for sure that its detected coliform bac, could be due to other factors. you use a lactose broth with bromocresol purple as the indicator incubated at 37 degrees for not more than 24 hours. a positive reaction is if you get gas produced or an acidic reaction.
use 100ml of water
to confirm definitely:
place onto endos medium with methyl red. coliform colonies are usually coloured pink to dark red with green metallic, surface sheen.
can also use gram staining, e.coli is non spore forming,rod
can also use biochemical test of Hiss,
put it on medium with lactose and oxidase. after 24 hours 37 degrees, test should be lactose positive and oxidase negative
why are coliform organisms chosen as indicators of fecal pollution rather than waterborne pathogens?
- present in great amounts in the small intestine. they are foreign to potable waters and so their presence is evidence for fecal contamination
- easily detected by culture methods
- survive longer than the other pathogens which tend to die out more rapidly than them
EPA approved method for coliform bacteria (36)
membrane filter method
has a cellulose membrane , water freely passes through but not e.coli. after the water is incubated at 35 deg for 24 hours in a special media. if present you will see metallic green sheen
then newest is MMO-MUG test
use media containing ONPG and MUG
after incubation bacteria break down ONPG causing clear media to turn yellow
coliert test
very fast
has several advantages over traditional methods due to its reliability
has up to 12 months shelf life
in a sachet into 100 ml water shake til dissolved and incubate at 35-37 degree and yellow colour is positive
enterococci in water
most of the species are of fecal origin and can generally be regarded as specific indices of human fecal pollution
institution: 0 per 100 ml of water
c. perfringens
institution: 0/100ml of water
also occur regularly in feces but in smaller amounts then e.coli
spores are resistant in water for long time and resist chlorination which is normally used to kill them
prescenes of c.p indicate fecal contamination has occurred and their presence without choliform group means it occurred in the past
pseudomonas aeruginosa
commonly found in poo, soil etc but cannot be used as a measure of fecal contamination cos its not just limited to that
affects taste and odour
its detection is only for drinking water in bottles and institution is 0/250ml
colony count (39)
done on nutrients agar at 22 and 37 most frequently used
most bacteria which are capable of growth in potable water grow better at 22
organisms that grow best at 37 are less able to grow in potable water
CC not a good indicator of risk to health but useful for assessing the effectiveness of water treatments ( pre + post).
examples of ground water and its treatment
well and springs
may need no other treatment other than just disinfection
components of typical water purification system in order
storage and sedimentation
coagulation and flocculation
filtration
disinfection
coagulation and flocculation
key processes for reducing the naturally occurring organic matter and turbidity which can seriously affect the efficiency of disinfection
have coagulants based on iron and aluminium - they are good because they form charged complexes with enhanced adsorption qualities . coagulants have a positive charge which neutralize the negative charge of the dissolved and suspended particles in the water. when they react the particles stick together so now they can be more easily removed
storage and sedimentation
larger particles are heavy and settle to the bottom
storage is relatively slow, for storage speed use coagulation and flocculation.
flocculation
colloids ( things like bacteria and stuff which are too light to settle to the bottom) come together to form larger particles called flocs by addition of a chemical called flocculants like aluminium and iron .
flocs have to be removed by either sedimentation or if the flocs are very light you can use fine air bubbles to carry them to the surface (air flocculation) where they are skimmed off. they can also be removed by filtration
filtration
2 types important as 99% bacteria are removed by this method
- biological or slow sand filters
- mechanical or rapid sand filters
disinfection
last step
the only step that guarantees the defenses of water the others are not guaranteed.
in the absence of the others it is enough
can use chemical or physical methods to disnecft
chemical:
disinfection is synonymous with chlorination
can be applied as gas,chloramine or perchloron. gas is the first choice cos its cheap, quick and easy
when added you form HCL and hypochlorous acid. HOCL is a weak acid and dissocates.
the mamin action of cl is due to HOCL.It wkrs best when the ph is around 7
values of free chlorine in water
0.3-0.4 mg/l after a contact period of 30 mins
methods for determination of resiudal chlorin in water
orthotolidine test
add agent to chlorinated water it runs yellow and intensity depends on concentration of cl.compare with a standard colour scale
OR
use a spectrophotometer using indicator tablets
ozonation
powerful oxidising gas
eliminates smell, tatse, colour and removes chlorine too!
has a strong vriucidal effect
ozone does not produce a stable residual meaning it works at the time but after there is . nothing to prevent re-growth
physical methods of disinfection
- Uv- effective against most microorganisms including virus interferes with DNA
- ultrasound -
small scales methods are
- boiling - has to be done for 5-10 mins. the taste of water however is affected but its not harmless. disadvantages offers no residual portection just like ozone.
physical methods of disinfection
- Uv- effective against most microorganisms including virus interferes with DNA
- ultrasound -
small scales methods are
boiling
water needs to brought to a rolling boil for 5-10 mins, kills bacteria and some spores and cysts, taste is altered but its harmless. disadvantage: no residual protection like ozone.
bleaching powder:
usually contains chlorine
chlorij tablets
costly
iodine:
for emergency disinfection of water . 2 drops of ethanol solution of iodine will suffice fr 1 L of water . need about 20-30 mins for effective . only small scales because its costlt, and will affect thyroid activity
kmon4
no longer recommended. it may kill chlorae virus but is of little use against other disease organisms,
definition of air pollution
introduction of harmful materials in high concentrations into the air causing damage to organisms.
types of air pollutants
natural: volcanic activity, wind soil erosion, plant pollen, ocean sands (not as important as man made)
human activity: burning fossil fuels, transport, forest fires
mechanical method filtration CBA page 48
CBA
main air pollution pollutants
nitrogen oxide
co co2
sulfur dioxide
hydrogen sulfide
effects of air poll
skin diseases
eye diseases
respiratory diseases, bronchitis,asthma lung cnacer
acid rain
global warming
determination of gaseous and aerosol pollutants
need to consider the breathing zone
2 ways of taking samples
- long term- 2 parallel samples lasting 30 mins with a constant speed of aspirated air
- short- at least 3 samples lasting 10 mins aspiration
if the working process requires the worker to move the investigation of air pollution is done by taking personality samples
2 methods for collection samples
- absorption
- grab sampling using a container
determination of carbon dioxide
MPV (maximum permissible value) . + 0.07-o.1%
for the normal working environment is 9000mg/m3
use barium oh to determine conc forming barium carbonate. the volume of co2 is determined by the change in titer og of ba0h
CO determination (55)
forms carboxyhb
maximal permissible concentration is 10.g/m3.
working environment max concentration is 200mg/m3
principle:
iodine pentoxide is used acts a reducing agent and iodine is liberated.changes colour from white to brown green.
microclimate
defined as a general influence of its physical parameters - temp,relative humidity,infared radiation, air velocity . these factors determine the thermal setting of a room, hospital room, office etc
essential conditions for the use of thermometer
- the air should have free access to the BULB of the thermometer
- the thermometer should be protected against radiant heat
types of thermometer
- maximum thermometer ( mercury)
- minimum thermometer ( alcohol)
- 6 maximum and minimum thermometer
- dry bulb thermometer
- globe thermometer
organoleptic properties of water mcqs
taste colour odour turbidity
which compounds affect the organoleptic qualites of water
chlorides
sulfates
iron
relative humidity and how to
the amount of moisture in the air compared to what the air can actually hold at the same temperture
if exceeds 65 it is uncomfortable and sticky so to fix you i will need better ventilation. RH below 30% is also uncomfortable as it can be very drying of the nasal mucosa
How to measure relative humidity
can use direct (hygrometery) and indirect (psyhcometry). psychometry is more accuarte
hygrometery is based on the property of hygroscopic materials such as hair to increase their size in more humid conditions and to decrease in less. the have to be corrected with psychometer as their accuracy is easily disturbable.
assman psychometer (71)
Portable instrument designed to give accurate measurement of the wet and dry bulb temperature of the air
air is drawn inn By a clockwork fan the instrument consists of two mercury thermometers (wet and dry) . the dry measures the air temp. the bulb of the wet is covered is covered with a muslin cloth wetted with distilled water. Evaporation of water from the muslin lowers the temperature of the mercury and the difference between the wet and dry thermometer indicates the amount of water present and you can use the table to calculate
air motion constiuents
wind speed
wind direction
wind rose
what we measure wind speed with and wind direction
anemometer
measure in meters per second
permissible value for inside 0.2-0.4 m/s
direction is measured with a wind bane
wind rose is a flower like diagram. v important for the building of of houses and industrial places.
hospitals, houses, school -above wind zone
plants and factories - under wind zone
figure is formed by marking on the coordinates formed by the 4 cardinal points. diagram is sharp towards the direction from where the winds predominate.
kata thermometer 73 and how it works CBA
an alcohol thermometer
is sensitive to low air velocities (indoors) so is largely used as a anemometer .
can record velocities as low as 1ms
IR-75
present in sunlight
can cause heat stress form a high temperature radiant source and can damage skin and eyes
2 measurement sources . one is based on Thermal detection that responds to all wavelengths the thermopile and the Bolometer And the other is based on photometric detection such as the photodiode which is only is responsive to certain parts of the spectrum
methods for complex microclimate evaluation (78)
too complex for flashcard
subjective methods:
- questionnaire using 7 bale scale of bedford
- effective temperature index- combines ingle value of the effect of temperature,humidity, movement of internal air etc. the concept it that saturated air which wsd till will induce the same feeing of warmth or cold in the given conditions e.g if ET was 30 deg it implies that the subjective sensation of it will be the same as a saturated atmosphere of 30 deg with no air movement.
thermal comfort zone: 17.1-21.7
2 scales used for clothed people and those who are stripped to the waist
uses 3 variable: dry bulb temp and wet bulb temp and air velocity
- CET-an index of thermal comfort
an improvement from ET. instead of dry you use a globe thermometer which is used to measure radiant heat. CET looks at 4 factors: temp,velocity,humidity and radiant heat
CET same method as ET but subistite globe for dry
- Fanger’s comfort criteria
combined 4 physical factors (temp, humidity,mean radiant temperature and velocity ) and 2 personal variables (clothing and activity level) into an index that can be used to predict thermal comfort. the value corresponds to a scale of ASHRAE. A 7 point scale
objective methods
- resulting temp
- WBFT-
phsiological methods:
a. look at pulse frequency
b. blood pressure
c. vegetative index of kerdo - if sympathetic predominates VI id + and if parasympathetic predominates then VI is -
d) skin temp
thermal comfort (78)
condition of mind which expresses satisfaction with the thermal environment
it’s considered with other factors such as air quality,noise level light etc
thermal comfort has an effect on our work performance
it can only be maintained when heat produced by the body is equaled to the heat lost from bofy
what should the thermal temp of the skin be for thermal comfort
33.2 +-1 degrees
skin temp criteria
- skin temp difference- comfortable difference is 2-4, narrowing suggest overheating and vice versa
- skin temp symmetry- not exceed 0.5
- skin temp gradinet
types of ventilation
exhaust: by exhaust fans driven by electricity . as the air is extracted a vacuum is created which introduces fresh new air into the room. the type is usually provided in large halls and auditoriums . you can adjust by altering the speed of the fan
plenum ventilation: fresh air is blow into the rom by centrifugal fans to create a positive pressure and displace the ventilated air. the system is of limited utility.
balanced ventilation: combination of other 2 . the blowing fan must balance the. when this system is employed the natural system of ventilation is entirely dispensed off.
hygienic requirements for heating
- to maintain a constant temp
- horizontal temp diff must be 1-2 degrees and the vertical 1-3.5
- temp surface of the heating apparatus is no more than 80 c
- heating appliances should nt generate an air velocity more than 0.6 m/s
- heaters should generate no noise
- heaters do not emit harmful substances into the air
temperature of the walls
90
- 5 m from floor
- 2 m from floor
- 2 from opposite wall
- 5 from windows
What do we divide the physical factors of the atmosphere into
Meteorological - air temp, humidity, ionzation of the air, atmospheric electrricity
and factors originating in space- sun radiation and heliomagenteic factort
air ionization
An indicator of a purity the concentration of positive ions increases in polluted areas or in indoor air and negative ions predominates in mountains woody areas near the sea and waterfalls
effect on uv on body
Short has a bacteriocidal affect middle has a mild bacteriocidal and also an anti-Ricket affect and long because cataracts and skin erythema and skin cancer
effects of IR on body
affects retina iris etc and long term exposure cause catarcts
It’s more difficult to acclimatize too
hot weather Takes about 12-14 days where is cold takes 10 days
nephelomtery
Measure the turbidity of water
Determination of lead aerosols l
aerosols lead reacts with sodiumrodisonate to produce lead rodistanate a pink red colour
measuring IR
Split into two one is based on thermal detection and one is based on photometric detection the actinometer LIOT -N it is an instrument for measuring infrared from industrial sources
