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Flashcards in Water Kwal-E.T. Deck (25)
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For chemical disinfection of water the following disinfectants can be used:
- Chlorine (Cl2)
- Chlorine dioxide (ClO2)
- Hypo chlorite (OCl-)
- Ozone (O3)
- Halogens: bromine (Br2), iodene (I)
- Bromine chloride (BrCl)
- Metals: copper (Cu2+), silver (Ag+)
- Kaliumpermanganate (KMnO4)
- Fenols
- Alcohols
- Soaps and detergents
- Kwartair ammonium salts
- Hydrogen peroxide
- Several acids and bases

For physical disinfection of water the following disinfectants can be used:
- Ultraviolet light (UV)
- Electronic radiation
- Gamma rays
- Sounds
- Hea

Read more: http://www.lenntech.com/processes/disinfection/what-is-water-disinfection.htm#ixzz3b3w9enTn


Palatable water

Considers the presence of chemicals that are not a threat to human health, affected by chloride, colour, corrosivity, iron, manganese, taste and odour, dissolved solids, tubidity


Potable water

considers the presence of harmful chemicals, affected by microbials, organic chemicals (disinfection by-products), inorganic chemicals (cadmium, copper, lead, mercury), radionuclides.


sources of drinking water

groundwater: shallow wells, deep wells
surface water: rivers, lakes, reservoirs


Groundwater Characteristics

High in hardness, mineral content and metals
Low in variability, suspended sediments, turbidity, colour, dissolved oxygen, and cracking taste.


Surface Water Characteristics

Low in hardness and mineral content.
High in all other parameters of concern.


Sources of pollution

Point sources - discharges from industries and spills into surface water or groundwater.

Diffuse sources - runoff at multiple sources, varies substantially with use of the land
- agricultural, urban, commercial, special (golf courses)
There is minimal regulation


Oxygen Demanding material

Organic materials convert oxygen to co2

High oxygen levels necessary for healthy ecology
-trout requires 5-8 mg/L D.O.
-aesthetic problem at less than 1mg/L



Problems: aesthetic, taste and odour, toxicity (especially to farm animals), fouling, diurnal D.O cycles.

Phosphurus is typically the limiting nutrient in surface waters.

Sources - fertilisers, detergents, can exist in a variety of chemical forms so total P is normally measured.



Nitrogen is often the limiting nutrient in estuarine and ocean waters

It can exist in numerous forms, but nitrate (NO3-), nitrite (NO2-), ammonia (NH3) are most commonly measured

Sources include fertilisers and acid deposition.


Eutrophication remedial actions

Reduce nutrient input, focus is on Phosphurus due to the 1:10 ratio of P:N required for algal growth.


Dissolved Solids / Salts

May be present as any number of ions
- cations, Na +, K +, Mg 2+, Ca 2+
-anions, Cl-, SO4 2-, HCO3 -

-Freshwater less than 1500 mg/L TDS
-Brackish water 1500 - 5000 mg/L TDS
-Saline more than 5000 mg/L
-Sea water 30-34 g/L TDS


Salty Sources

minerals, deicing, evaporative losses, irrigation, industrial discharges, sea water intrusion.

Effects: limits use for drinking, crop damage and soil poisoning


Suspended Solids

-organic or inorganic particles in water, measured by filtering and weighing.
-distinguished from colloids which are particles that do not settle readily

Problems: sedimentation, oxygen demand, transport mechanism for (metals, organics + pathogens), aesthetics

Sources: storm water and wastes, erosion,


Pathogenic Organisms

human and animal diseases live outside the body for a period of time,
carriers excrete organisms in large quantities, water contaminated by excretia,
organisms transmitted by contact with the water.


Microbial treatment

-physicl (filtration and coagulation) and chemical (chlorine) techniques to remove pathogens.
-effective physical treatment defined by turbidity


Disinfection By-Products

-Produced from chemical interactions between chlorine and natural organic substances (carcinogenic)
-Trihalomethanes (THMs) organohalogens where 3 of the 4 atoms of methane are replaced chlorine, bromine, iodine.


Toxic and Hazardous Substances

Heavy metals, VOCs, SOCs, inorganic elements, acids/ bases, chlorination by-products, combustion by products, pesticides, surfactants, endocrine disruptors, petroleum additives, hydrophobic organic compounds.



-occurs naturally in rock and soil
-released to groundwater under certain conditions
-health effects include heart diseases, skin cancer, nervous system, kidney disease
-problem in bangladesh
-drinking water standard being lowered



-occurs naturallyin rock and soil
-released under acidic conditions
-effects tast, odour and colour
-precipitates stain materials, clog treatment systems and pipes.


Other inorganic chemicals

lead - red blood cells, nervous system & kidneys
copper - nausea and vomiting
fluoride - fluorisis of teeth
nitrate - red blood cells in infants
asbestos - pulmonary fibrosis, lung cancer


Water quality discharge parameters

-D.O. 4 - 7 mg/ L for fish, BOD less than 30mg/L
-pH between 6.5 to 8.5
-temperature below 32 celcius
-low in total coliforms and other toxic substances


Upland waters

derived from moorland springs and rivers, low in minerals and solids, high in dissolved organic matter - although seasonably variable and very high at start of rainy season.

Treatment drivers:
-reduction in organic matter to control colour and disinfection by product formation
-removal of metals such as aluminium, iron and manganese.


Lowland waters

fed by upland lakes and groundwater, receive sewage and industrial effluents, seasonal changes in wq, rapid changes following rainstorms (increase turbidity, DOC, reduced alkalinity, conductivity and pH)

Treatment drivers:
-removal of pesticides, algal toxins, disinfection by-products, nitrate and bromate
-slow moving waters are normally bacteriologically unsafe due to a wide variety of waterborn bacteria and viruses.
-high nutrient loadings lead to widespread algal growth



High dissolved solids, percolation through deep layers on minerals, typically hard and alkaline, low suspended sediment bacteria and organic content. minimal seasonal variation.

Treatment drivers:
-inorganics that leach from rocks
-surface water ingress can add lowland source pollutants (pesticides, nitrate)