Dreamerish*~'s Guide to Water Monitoring and Management (1 Viewer)

[Dreamerish*~]

As requested by Nosadness. Enjoy.

This covers probably most of the water section of Module 3. If anyone has anything to add, post it up.


QUALITATIVE AND QUANTITATIVE

Qualitative: determining the type of substance being measured. For example, detecting the presence of copper ions is a qualitative process.
Quantitative: determining the amount of substance being measured. For example, measuring the concentration of copper ions in a solution is a quantitative process.

QUALITATIVE MONITORING

Qualitative analysis of water is observations (using human senses) of the water's:

• Colour
• Transparency (lacking turbidity)
• Odour
• Taste
• Hardness

QUANTITATIVE MONITORING

Quantitative analysis of water uses chemicals and/or equipment to measure the amount of:

• Concentration of common ions
• Acidity (pH)
• Total dissolved substances (TDS)
• Chemical hardness (hard water is difficult to lather with soap)
• Turbidity (opaqueness, mostly due to suspended clay particles absorbing light)
• Dissolved oxygen (DO)
• Biochemical oxygen demand (BOD)
• Heavy metals (Hg, Pb, Cd)

QUANTITATIVE TESTS

TESTING FOR THE CONCENTRATIONS OF COMMON IONS

Electrical conductivity can be used to measure the concentration of dissolved salts present as ions, called salinity. The units are microsiemens per centimetre (µS cm^-1). Because ionic compounds conduct electricity in solution, the more dissolved salts (ions), the higher the conductivity. Water with an electrical conductivity of less than 280 µm cm^-1 is suitable for irrigation. Concentration of ions can also be measured in ppm or mg L^-1.

Atomic Absorption Spectroscopy (AAS) can be used for determining the concentration of many metallic ions in water samples. It relies on the fact that when electrons of an atom absorb light of a specific wavelength, they gain enough energy to jump to a higher energy level. The atomic absorption spectrometer consists of:

• Cathode Lamp - which is made from the same metal as the one being tested
• Flame or Furnace - into which the sample solution is sprayed, the heat of the flame or furnace makes the metal atoms gaseous
• Filter or Monochromator - which selects the specific wavelength of light to be measured
• Detector - which measures the amount of light recieved (that is, the total amount of light given from the cathode lamp minus the amount of light absorbed by the metal atoms)
• Processor - which calculates the concentration of the metal ion in solution from the amount of light recieved

Basically, when the sample solution is sprayed into the flame or furnace, the electrons in the metal atoms absorb some of the energy from the cathode lamp. The rest of the light passes through to the detector to be measured, and the concentration of the metal ion in the sample is calculated from the amount of light absorbed.

Ion-selective Electrodes (ISE) are also available for determining ion concentrations in water. Similar to pH electrodes which measure specifically H⁺ in water, the ISE measures the concentration of any specific ion. The change in electrode voltage between a reference electrode and the indicator electrode is related to the concentration of the specific ion being measured. The ISE can detect ion concentrations as low as ppb. As with AAS, a series of dilute standards are used to establish a calibration graph.



TESTING FOR ACIDITY

Potable water should have a pH between 6.5-8.5. The acidity of water is tested using acid-base indicators or pH meters. The pH electrode must be calibrated against buffer solutions of known pH.

Once the pH is measured, the concentration of H⁺ in the sample can be calculated by using [H⁺] = 10^-pH.



TESTING FOR TOTAL DISSOLVED SOLIDS (TDS)

By evaporation: Natural water samples contain a wide range of dissolved inorganic salts and organic materials. Salt water in the oceans contain very high levels of mineral ions mainly in the form of sodium and chloride ions. Reservoir water supplies contain variable amounts of dissolved solids. To measure the TDS of water, a sample must first be filtered to remove undissolved particles. A known volume of filtrate is then evaporated and the mass of solid residue remaining is determined gravimentrically.

Eg. Water from an artesian bore was collected and filtered. 500mL of the filtrate was evaporated to dryness in a weighed evaporating basin, then weighed in the basin.

Data:
Mass of evaporating basin = 128.345 g
Mass of evaporating basin + dry residue = 128.728 g

Calculation:
Mass of dry residue = 128.728 - 128.345 = 0.383 g = 383 mg
Therefore TDS = 383 mg/0.5 L = 766 mg L^-1

By using a conductivity meter: Most dissolved solids such as NaCl are ionic salts. The greater the concentration of dissolved salt, the higher the electrical conductivity. Electrical conductivity measurements can be made using a small meter.



TESTING FOR WATER HARDNESS

Although hardness is a qualitative property, the actual hardness of water can be calculated from measurements.

Hard water contains high levels of calcium, magnesium and aluminium ions. See my previous post for the relationship between water quality and the concentration in ppm of these ions.

To test water hardness, soap is used. While soft water forms a lather with soap, hard water does not, because in the presence of calcium or magnesium ions, the soap precipitates out as a "scum":

Ca²⁺ + 2Na stearate (soap) --> Ca (stearate) + 2Na⁺
"Stearate" is used to make the equation more simple. Soap is composed of sodium or potassium salts of long chain alkanoic acids such as stearic acid.



TESTING FOR TURBIDITY

Turbidity is measured in nephelometric turbidity units (NTU).

Nephelometry: A meter is used to measure the percentage of light transmitted through a standard depth of water. As light is passed through the water sample, some is scattered by suspended particles. The remaining light is transmitted. The intensity of the light scattered at 90º allows the turbidity of the water sample to be determined. The nephelometer must also be calibrated using a series of standards.

Gravimetric methods: A measured volume of water is filtered through a preweighed filter paper, which is then dried and reweighed and the concentration of solid calculated.

Secchi Disc: A disc which contains a cross at the bottom. It is lowered into the water being tested, and the moment the cross can no longer be seen, the depth of water is recorded. Similarly, a measuring cylinder with a cross at the bottom can be filled with the water sample until the cross can no longer be seen.



TESTING FOR DISSOLVED OXYGEN (DO)

Oxygen is usually present in concentrations of 6-9 ppm. At concentrations of lower than 5 ppm, aquatic organisms begin to suffocate.

Oxygen-sensitive Electrode: Dissolved oxygen meters are based on electrochemical cells. The most common type of probe uses a gold or platinum electrode and a silver electrode in a KCl electrolyte solution. The voltage applied between the gold/platinum and silver electrodes does not cause electrolysis until oxygen reaches the electrolyte solution. The electrodes and electrolyte are separated from the water being sampled by a plastic membrane that oxygen can diffuse through. The amount of electrolysis is proportional to the amount of oxygen. The DO level is measured by a milliammeter.

Winkler Method: (This may look a little confusing, and I still can't write the equations from memory. Don't worry, we don't need it. As long as we know the oxygen-sensitive electrode method, who gives a toss about Winkler.) The Winkler method is a way of fixing the amount of dissolved oxygen in a sample and determining the DO by titration at a later time.

Manganese (II) ions and hydroxide ions are added to the water sample. The amount of insoluble brown manganese (IV) oxide produced depends on the amount of DO:

2Mn²⁺ + 4OH^- + O_2(aq) --> 2MnO_2(s) + 2H₂O_(l)

Acidified iodide solution reacts with the MnO₂, producing a yellow iodine solution.

2MnO_2(s) + 8H⁺ + 4I^- --> 2Mn²⁺ + 4H₂O_(l) + 2I_2(aq)

The iodine released is titrated against a standard sodium thiosulphate solution from a burette containing starch indicator. The starch indicator forms a blue colour with iodine, and the blue colour disappears at the end point.

2I_2(aq) + 4S₂O₃^2-_(aq) --> 4I^- + 4S₂O₃^2-_(aq)

It can be seen that each dissolved O₂ molecule gives 2MnO₂ which gives 2I₂ which reacts with 4S₂O₃^2-_(aq). Thus for each molecule of thiosulphate used at the end in the titration there was ¹/₄ mole of dissolved oxygen in the original sample.

When water samples are collected from different locations, identical containers, identical sealing systems and the same collection procedures must be used. It is important that the containers are completely filled with water so there is no air space, and that they are kept out of light so algae present cannot add to the oxygen level by photosynthesis.



TESTING FOR BIOCHEMICAL OXYGEN DEMAND (BOD)

BOD is the quantity of oxygen needed by aerobic bacteria to break down all the organic matter in a water sample. The higher the BOD, the greater the pollution in water. This is because organic waste requires oxygen for aerobic decomposition.

Oxygen Probe: Saturate a measured sample of water with oxygen, measure the dissolved oxygen concentration using the oxygen-sensitive electrode as mentioned before, seal and incubate at 20ºC for 5 days in the dark, measure residual dissolved oxygen concentration, and then calculate BOD.

Winkler Method: (My notes said "Wrinkler", but I'm pretty sure that "r" isn't supposed to be there).

Eg. Samples of river water were collected. The Winkler test was conducted on a 1 L sample of this water at the time of collection. The 1 L sample was then kept at 20ºC in the dark for 5 days and the Winkler test repeated.

Data:
Initial DO of water sample = 7 ppm
Final DO of water sample (after 5 days) = 3 ppm

Calculation:
5 days BOD = 7 - 3 = 4 ppm

This water sample would be considered as moderately clean. There is sufficient oxygen in the water to cope with the oxygen demands of the decomposers.

IDENTIFYING HEAVY METAL POLLUTION

QUALITATIVE TESTS

Precipitation Reactions can be used to detect the presence of the following heavy metal cations in water - I'm giving one precipitation test for each, because these tests are not of great importance:

• Hg⁺ - Forms yellow or red precipitate with NaOH
• Cd²⁺ - Forms white precipitate with NaOH which dissolves in ammonia
• Zn²⁺ - Forms white precipitate with NaOH which dissolves in excess NaOH and also ammonia
• Cr³⁺ - Forms grey-blue precipitate with NaOH which dissolves in excess NaOH but not ammonia
• Al³⁺ - Forms white precipitate with NaOH which dissolves in excess NaOH but not ammonia

As you can see, if uncertain, NaOH is always a good guess.

The Sodium Sulfide Test: A solution of sodium sulfide can be used to get a quick indication of whether or not any heavy metals are present in a sample of water.

The water sample is acidified, then drops of Na₂S solution are added: if a precipitate forms, then one or more of the following cations is present: Pb²⁺, Ag⁺, Hg²⁺, Cu²⁺, Cd²⁺, As³⁺.

If only a very slight amount of precipitate formed from acid solution (or none at all), this solution should then be made slightly alkaline. If a significant amount of precipitate formed under alkaline conditions then one or more of the following cations is present: Cr³⁺, Zn²⁺, Fe³⁺, Ni²⁺, Co²⁺, Mn³⁺, Al³⁺.

Flame tests can also be used, but they are not specifically designed for testing heavy metals.



QUANTITATIVE TESTS

Traditional methods such as gravimetric analyses and titrations have limited use because of the low concentrations involved in environmental water supplies.

Atomic Absorption Spectroscopy (AAS) is widely used for environmental monitoring. AAS technology is based on the fact that the electron in the metal atoms absorb light of a specific wavelength in order to jump to a higher energy level.

An Atomic Absorption Spectrometer consists of:

• Cathode Lamp which is made from the same metal as the one being tested. This is because the lamp has to give light at a specific wavelength which the electrons of the atoms of the metal is known to absorb.
• Flame or Furnace which provides heat in order to vaporise the metal atoms. It also separates compounds into ions (ionises - but use it in the right context) so that metals are present as ions instead of compounds.
• Monochromator which selects only light of the desired wavelength to be passed onto the photomultiplier or processor.
• Computer or Processor which calculates the concentration of metal ions in solution from the amount of absorbance. The light emitted from the cathode lamp is compared to the light recieved by the detector after passing through the vaporised water sample.

Atomic Emission Spectroscopy is also widely used. It has the advantage of being able to analyse for several metals in the one measurement. With AAS, metals must be measured one at a time because each requires a separate lamp.

When atoms are heated to high temperatures, some of the electrons get excited out of their normal energy levels (called ground state) into higher energy levels. However, after a short time, some of the electrons fall back from these higher energy levels to the ground state. As they do this, the excess energy is liberated as light. The energy emitted as an electron falls back to its ground state is the same as that absorbed when it was raised to the excited state.

When the emitted light is broken into various wavelength components, we find that the emissions have occured at just a few discrete wavelengths. The patterns are called emission spectrums, and each element has its own, unique emission spectrum.



MONITORING EUTROPHICATION

Eutrophication is the presence of excessive nutrients (especially nitrates and phosphates) in a water system, which causes algae and other aquatic organisms to grow out of control. This is called algal bloom. These aquatic plants grow out of control, using up all the dissolved oxygen in the water, leaving other aquatic life with insufficient oxygen to survive. When all the oxygen is used up, the aquatic plants undergo anaerobic decomposition, taking up what's left of the dissolved oxygen in decomposing, leave the body of water and its inhabitants dead.

Eutrophication can be monitored and measured by measuing the total dissolved oxygen levels and biochemical oxygen demand. These tests were discussed in the above section.

At the dissolves oxygen concentration of:

• 6-8 ppm, the water is healthy
• 4-6 ppm, there is moderate pollution
• 2-4 ppm, there is heavy pollution
• <1 ppm, the water is "dead"

FACTORS WHICH AFFECT CONCENTRATION OF IONS IN WATER

The Pathway from Rain to Water Body: Rain contains just a few ions - just small concentration of carbonate (from dissolved CO₂) and some Na⁺, Cl^- and SO₄^2- ions from sea spray that winds carry into clouds. When rain runs off bushland into streams, it picks up small amounts of nitrates and phosphates from natural nutrients on the surface and perhaps small amounts of Ca²⁺ and Mg²⁺ from decomposing materials.

If, however, rain water soaks into the ground and flows through underground aquifers and then into a stream, it will contain increased amounts of these (and more) ions by dissolving them from the soils and rocks it flows through.

If water perculates down to deep underground aquifers, heavy metals and other metal ions may be absorbed.

The pH of Rain: Water from acidic rain is better able to leach certain cations such as calcium, magnesium and iron from the soil it passes over.

The Nature and Amount of Human Activity in the Catchment: Land clearing generally leads to more water rapidly running across the land into streams. This results in more dissolved Na⁺, K⁺, Ca²⁺, and more.

Aguicultural pursuits often lead to fertiliser run-off. This increases the concentration of nitrates and sulfates.

Discharges into the Water: Discharges of raw and/or treated sewage increases the concentration of many ions, particularly nitrates and sulphates. Even good sewage treatment can increase the TDS of the water by 200 ppms or more.

Storm-water runoff in urban areas can similarly increase the concentration of a variety of ions.

Industrial effluents, if carefully monitored and controlled, can discharge heavy metal ions into water bodies, such as lead, mercury and cadmium.

Leaching from Rubbish Dumps: When rain and storm water flows over and seeps through poorly designed rubbish dumps, it dissolves many harmful substances such as cadmium from nickel-cadmium batteries, mercury and lead from other batteries, zinc from old galvanised iron and anions such as nitrate and phosphate from decaying organic wastes are carried into streams.



PURIFICATION PROCESS OF WATER

• Screening: Water is passed through a sieve-like device which removes large objects such as twigs and fish.
• Aeration: Water is sprayed into the air in order to absorb more oxygen. The oxygen ionises iron compounds present in water, eliminating yellowness and metallic taste. Note: Aeration is not used in the Sydney water purification process. You can write it in the exam but you need to state that we don't use it.
• Flocculation: There are suspended particles in water which are too fine to settle to the bottom of the tank. Hence flocculants such as FeCl₃ are added, attracting the suspended solids and thus coagulating into larger particles which are heavier and easier to settle out.
• Sedimentation: The coagulants are allowed to settle to the bottom of the tank, where they are collected and extracted.
• Filtration: The water is passed through large sand and gravel filters. When the water emerges, it should be clear.
• Chlorination: Chlorine is added to disinfect the water by killing microorganisms such as E. coli. Ammonia is added to produce chloramines, which maintain the disinfection action of the chlorine.
• pH Adjustment: Buffers (such as carbonates and hydroxides) are added to achieve and maintain the ideal pH of 7.0 - 8.5.
• Fluoridation: Fluorine is added to raise the fluoride level to 1 ppm. At this level, tooth decay can be prevented.

EFFECTIVENESS

Due to the Giardia and Cryptosporidium scare in Sydney in 1998, it was realised that our sand filters are somewhat ineffective in removing microorganisms. However, Sydney water is always clear, free of metallic tastes, and soft. Our purification processes are effective in most aspects. Possible alternatives for sand filters include membrane filters or ozone sterilization. However, these are quite costly. A more economical solution would be better catchment management.



MICROSCOPIC MEMBRANE FILTERS

Microscopic membrane filters can be used to remove fine particles and micro-organisms from water that cannot be removed by the normal treatment.
Membrane filters are made of thin polymer sheets with fixed pore sizes. The commonly used polymers are PVC, polycarbonate, polypropylene, polyester and polysulfone. The polymer sheets are folded or wound around a central, rigid core to form a cartridge that can be replaced as required. Other microfiltration membranes consist of fine hollow capillaries that are housed inside a filtering unit. Here the filtered particles are trapped on the outside of the capillaries and the filtrate passes through the centre of the capillary. Water that is to be filtered is made to flow across the surface of the membranes rather than at right angles to prevent clogging.

The filters can be cleaned by back-flushing. Air is blown from the clean side to dislodge trapped particles which are then washed away by the dirty water on the outside.

Membrane filters are widely used for filtering both drinking water and treated sewage. For drinking water, membrane filters can remove virtually all particles larger than 0.2 nanometres including Giardia and Cryptosporidium. Primary and secondary sewage treatment removes about 90% of BOD and 90% of suspended solids from raw sewage. Membrane filtration is widely used in industry, particularly for beverage preparation (including bottled water).

However, no filters can remove substances that are actually dissolved in the water such as phosphates and nitrates and heavy metal ions.



LOCAL TOWN WATER SUPPLY

CATCHMENT AREA

Warragamba Dam is Sydney's major water reservoir. Most Australian cities rely predominantly on large reservoirs located on rivers within protected catchment areas. Sydney Water and the newly created Sydney Catchment Authority are the organisations reponsible for ensuring the quality of most of the water for domestic consumption in NSW.



POSSIBLE SOURCES OF CONTAMINATION

• Agricultural activities
• Poor sewage and stormwater management
• Uncontrolled bushfires
• Mining
• Development of roads
• Forestry
• Salts and metallic ions from natural weathering and erosion

TESTS AVAILABLE TO DETERMINE TYPES AND LEVELS OF CONTAMINANTS

For details, see above.

Chemical Tests:

• Sodium sulfide testing
• Atomic Absorption Spectroscopy (AAS)
• Atomic Emission Spectroscopy
• Flame tests
• Precipitation tests

PHYSICAL AND CHEMICAL PROCESSES TO PURIFY WATER

For details, see above

Physical methods:

• Screening
• Sedimentation
• Filtration

Chemical methods:

• Chlorination
• Flocculation
• Fluoridation
• pH adjustment

CHEMICAL ADDITIVES IN WATER

• Chlorine - to disinfect the water by killing micro-organisms such as E. coli.
• Various hypochlorites (OCl^-) - same reason as previous.
• Ammonia - to produce chloramines, which maintain the disinfection action of chlorine.
• Buffering chemicals - such as carbonates and hydroxides, in order to achieve and maintain the required pH (7 - 8.5).
• Fluoride - to achieve the fluorine level of 1ppm. This level prevents tooth decay.
• Oxygen via aeration - if you count it as an additive, it is to oxidise iron salts (which make the water yellow and taste metallic).
• FeCl₃ or Al₂(SO₄)₃ - act as flocculants which cause small suspended particles to coagulate.

 

[kami]

Hmm...I have some other stuff that I used in my research assignment - though some of its a bit beyond the HSC exam I think, so it should only be used if you're doing an extremely extensive research assignment(mine was 7,000 words...*shakes fist at teacher*) or you have too much time on your hands

• Metal pollution of water
Guidelines are set for the levels of heavy metals such as Mercury, Lead and Cadmium that are found in water for health reasons. Chemists closely monitor the level of heavy metals that is present in the waterways. This is done in the following ways:

1. Lead, Cadmium
1. Flame Atomic Absorption Method: Sample is aspirated into a flame and atomized. The amount of light emitted is measured.
o Detection Limits: Detection range may be extended 1)downward by scale expansion or by integrating the absorption signal over a long time, and 2)upward by dilution of sample, using a less-sensitive wavelength, rotating the burner head, or by linearizing the calibration curve at high concentrations.
o Metal Wavelength Detection Limit Optimum Range
o Cd 228.8 nm 0.002 mg/l 0.5 - 2.0 mg/l
Pb 283.3 nm 0.05 mg/l 1.0 - 20 mg/l
o Interferences: Chemical interference by a lack of absorption by atoms that are bound in molecular combination by the flame.

2. Electrothermal Atomic Adsorption Spectrometry: The high heat of a graphite furnace atomizes the element being determined.
o Detection Limits: Use a larger sample volume or reduce the flow rate of the purge gas to increase sensitivity.
o Metal Wavelength Detection Limit Optimum Range
o Cd 228.8 nm 0.1 ug/l 0.5 - 10.0 ug/l
Pb 283.3 nm 1.0 ug/l 5.0 - 100 ug/l
o Interferences: Interferences by broadband molecular absorption; and chemical (formation of refractory carbides) and matrix effects.

3. Inductively Coupled Plasma (ICP) Method: Ionization of an argon gas stream by an oscillating radio frequency. High temperature dissociates molecules, creating an ion emission spectra.
o Detection Limits:
o Metal Wavelength Detection Limit
o Cd 226.50 nm > 4.0 ug/l
Pb 220.35 nm > 40.0 ug/l
o Interferences: Spectral interference from light emissions originating elsewhere (other than the source). Physical interference from changes in sample viscosity and surface tension.

4. Cd Dithizone Method: Cadmium ions react with dithizone to form a pink/red color that can be extracted with chloroform. Extracts are measured photometrically.
o Detection Limits: Detection limit is 0.5 ug/l Cd in a 15 ml final volume with a 15 cm light path.
o Interferences: Interference if [Pb]>6 mg/l, [Zn]>3 mg/l, or [Cu]>1 mg/l.

5. Pb Dithizone Method: Lead is mixed with an ammoniacal citrate-cyanide solution and extracted with dithizone in chloroform to form a cherry-red Pb dithozate.
o Detection Limits: Detection limits are > 1.0 ug/l Pb in a 10 ml dithizone solution.
o Interferences: At pH 8.5 to 9.5, dithizone complexes with bismuth, stannous tin, and monovalent thallium.

2. Mercury
1. Cold Vapor Atomic Adsorption Method:
o Detection Limits: Choice method for all samples with [Hg] < 2ug/l.
o Interferences: None.

2. Dithizone Method: Mercury ions react with dithizone solution to form an orange solution that is measured in the spectrophotometer.
o Detection Limits: Most accurate for samples with [Hg] > 2ug/l.
o Interferences: Copper, gold, palladium, divalent platinum, and silver react with dithizone in acid solution.

Also with eutrophication the variables and methods that the government uses are summarised here(I'll put it inna table a bit later):
Variable Recommended procedure
Chlorophyll: Spectrophotometry
Phytoplankton counts: Sedimentation and enumeration using an inverted microscope
Total phosphorus: Phosphomolybdate colorimetry
Kjeldahl nitrogen: Digestion and colourimetry
Nitrate: Cadmium reduction
Nitrite: Colourimetry
Total Suspended Solids: Filtration
Dissolved Oxygen: Winkler (titration) method or O² sensitive electrode



And here are some links on water stuff:
www.premiers.nsw.gov.au/our_library/archives/sydwater/5threp/r5chapter5.html
www.australianwaterservices.com.au/WaterProspect.htm
www.premiers.nsw.gov.au/our_library/archives/sydwater/3rdrep/rep3ch3.htm
www.waterquality.crc.org.au/consumers/Consumersp9.htm
www7.health.gov.au/nhmrc/publications/synopses/eh19syn.htm
www.sydneywater.com.au/EnsuringTheFuture/WaterSchool/
www.dwaf.gov.za/IWQS/eutrophication/NEMP/NEMP_implementation.htm
www.water.ncsu.edu/watershedss/info/hmetals.html

 

[Dreamerish*~]

Also with eutrophication the variables and methods that the government uses are summarised here(I'll put it inna table a bit later):
Variable Recommended procedure
Chlorophyll: Spectrophotometry
Phytoplankton counts: Sedimentation and enumeration using an inverted microscope
Total phosphorus: Phosphomolybdate colorimetry
Kjeldahl nitrogen: Digestion and colourimetry
Nitrate: Cadmium reduction
Nitrite: Colourimetry
Total Suspended Solids: Filtration
Dissolved Oxygen: Winkler (titration) method or O2 sensitive electrode

Whoah, that is so cool. Thanks Kami.

Just what I was missing. I'd usually just shove in the normal textbook tests without really knowing if we actually use them.

 

[kami]

Whoah, that is so cool. Thanks Kami.

Just what I was missing. I'd usually just shove in the normal textbook tests without really knowing if we actually use them.

Haha, your welcome.
The only reason I bothered to dig that stuff up is because my class would get docked a mark in our research assignment for every hsc related text we quoted in our bibliography...*shudders*
There is also another method that they used for testing for eutrophication if anyone is interested? Its very innacurate and generally not used anymore though.

 

[currysauce]

You should include the EDTA titration method for testing for water hardness...

Ca(2+) + EDTA(4-) ---> Ca EDTA (2-) (colourless)

Mg(2+) + EDTA(4-) ---> Mg EDTA (2-) (colourless)

Only problem with this method is it doesn't discriminate between the two cations

 

[Haku]

nice thread, good that you made it. was waiting whole night on the 30th since u were making it than...but was not put up. Anways i went to perisher blue to go skiing the every next day so only came back and so happy to read this thread.

thanks Dreamerish

though it would be nice if u called it "Dreamo's ....."

 

[wanton-wonton]

Haven't read it yet, but it looks darn good.

 

[~*pixie_poo*~]

wow.. thanks!

 

[Sirius Black]

thanks for ur notes

1.Electrical conductivity can be used to measure the concentration of dissolved salts present as ions, called salinity. The units are microsiemens per centimetre (µS cm-1). Because ionic compounds conduct electricity in solution, the more dissolved salts (ions), the higher the conductivity. Water with an electrical conductivity of less than 280 µm cm-1 is suitable for irrigation. Concentration of ions can also be measured in ppm or mg L-1.

2.By using a conductivity meter: Most dissolved solids such as NaCl are ionic salts. The greater the concentration of dissolved salt, the higher the electrical conductivity. Electrical conductivity measurements can be made using a small meter.

these two methods looked the same -does that mean the test for common ions = test for TSD?

 

[Dreamerish*~]

1.Electrical conductivity can be used to measure the concentration of dissolved salts present as ions, called salinity. The units are microsiemens per centimetre (µS cm-1). Because ionic compounds conduct electricity in solution, the more dissolved salts (ions), the higher the conductivity. Water with an electrical conductivity of less than 280 µm cm-1 is suitable for irrigation. Concentration of ions can also be measured in ppm or mg L-1.

2.By using a conductivity meter: Most dissolved solids such as NaCl are ionic salts. The greater the concentration of dissolved salt, the higher the electrical conductivity. Electrical conductivity measurements can be made using a small meter.

these two methods looked the same -does that mean the test for common ions = test for TSD?

I suppose so, but TDS can also be measured by evaporation.

 

[jennylim]

<<<<<<<<<<<<<<3 to dreamerish!!! dreamerish for president!!!!!! hahaha thank you so much darling, that was my worst topic

 

[Abtari]

great notes dreamerish!

thanks a bunch

 

[rnitya_25]

thanks heaps dreamerish, i was actually just revising that topic, monitoring water quality, before i came online, so all the more help. thanks a great deal! all the best with chem for you, even though you don't even need it!!!!!!!

 

[*yooneek*]

how sweet you are dreamerish!
<3
thanks for all your hard work
!

 

[kevinle]

thanx dreamisher
those note r really good

 

[wccchick]

thanks heaps - a real help!

 

[Riviet]

This guide has truly been useful in cross-referencing with my own notes/summaries.

 

[sando]

whats a healthy level of TDS in a river ??

 

[Riviet]

whats a healthy level of TDS in a river ??

Streams and rivers that flow through undisturbed bushland typically have TDS of less than 100 ppm. If they flow through farming areas, the TDS often rises to 200-300 ppm which is still relatively healthy. Drinking water for humans should have a TDS of less than 500 ppm. A TDS greater than 1000 ppm indicates a seriously degraded waterway and is really only useful for irrigation.

 

[s2indie]

That is so freaking awesome. Thankyou.
This is definitely my weakest area in this topic.
Thankyou.