PRESENTATION ON

WATER CHEMISTRY

Madhur Devkota

Bikalp Acharya

Environmental Engineering

D R I N K I N G W AT E R Q U A L I T Y

Background

1. Rural India has more than 700 million people residing inabout 1.42 million habitations spread over 15 diverseecological regions.

2. 85 % of rural population in India is solely depended on groundwater, which is depleting at a fast rate.

3. India has 16% of the world’s population and 4% of its freshwater resources.

4. Ninety 2% groundwater extracted is used in the agriculturalsector, five and 3 % respectively for industrial and domesticsector.

Water Quality Problems

1. Excessive extraction of ground water make water critical criticalduring summer months in many parts of the country.

2. 70 million people in 20 states are at risk due to excess fluoride andaround 10 million people are at risk due to excess arsenic inground water.

3. Ingress of seawater into coastal aquifers as a result of over-extraction of ground water has made water supplies more saline,unsuitable for drinking and irrigation.

4. It is estimated that around 37.7 million Indians are affected bywaterborne diseases annually, 1.5 million children are estimatedto die of diarrhoea alone and 73 million working days are lost dueto waterborne disease each year.

Water Pollution

Polluting Agents*

(Public Health Services)

Contribution of each Polluting Agents

Water Quality Surveillance

Critical Parameters to be tested for assessing water quality

Alkalinity* –

Sources – i) salts of weak acids (CO3-2, HCO3

-, OH-….)ii) *Algae consuming CO2 *

Impact – i) Induces bitter taste, unpalatableii)Foul pipes and water system appurtenances

Acceptable Limit Limit for Rejection Result

200 mg/L 600 mg/L 512 mg/L

Hardness –defined as concentration of multi-valent metallic cation in soln

Sources – i) dissolved Ca++ & Mg++ and their salts

ii) Other ions Fe++, Mn++, Al+3 (in small quantities)

iii) Area where top-soil is thick & lime stone formation are present

Impact – i) Consumes soap*

ii) Scale formation in boilers and pipes*

Acceptable Limit Limit for Rejection Result

75 mg/L 110 mg/L 20 mg/L

Arsenic –

Sources – i) Natural source:volcanic ash, weathering of arsenic containing minerals and ores

ii) Artificial source: Smelter emission*, Mining wasteWood preservatives such as Chromated copper arsenateArsenic bearing fertilizers, Deposition from coal combustion

Impact – i) Hinders aquatic lifeii) Increases risk of cancer* and other various acute diseases*

Cases- High Arsenic contamination in Ground water in West Bengal* and Bangladesh*

Acceptable Limit Limit for Rejection

0.05 mg/L 0.05 mg/L

Instrument used

SpectrophotometerAbsorption vs. Concentration

graph

Chloride –

Sources – i) Nonpoint source: a) Natural*b) Agriculture*c) Residential and Urban*

ii) Point source *

Reagent Used for test- Indicator: K2CrO4; Titrant: N/70 AgNO3 soln

Impact – i) >250 mg/L the taste is saltyii) Evapotransportation increase salinity makes crops difficult

to absorb water *

Application- Used as a tracer*

Acceptable Limit Limit for Rejection Result

200 mg/L 600 mg/L 36 mg/L

Total Coliform –

Sources – i) Contamination of animal feces in soil & ground water

ii) Agricultural runoffiii) Effluent from septic systems or sewage

discharges

Reagent Used for test- Beef Extract, Lactose & Peptone

Impact – Most coliform bacteria do not cause illness however…*i) Positive fecal coliform results fecal pollutionii) Stomach and intestinal illness*iii) Waterborne pathogenic*

Acceptable Limit Limit for Rejection Result

0 1 coliform colonyper 100 ml

460 per 100 ml (in waster water)0 per 100 ml (in tap water)

Instrument Used

Autoclave- for sterilizingbroth for 3hrs

Incubator- for incubation of organism at 35oC

pH–

Cause of pH change–

i) Depletion of CO2 in water increases pH

ii) High pH in lake during summer *iii) Increases due to increase of carbon-based mineral

molecules suspended in the solutioniv) Is decreased by Acid rain

Impact – i) corrosive effects of acidityii) high or low pH harm fish by denaturing cellular

membranes.iii) as the pH approaches 5, non-desirable species of

plankton and mosses may begin to invade at bottomiv) aesthetic problems dur to low pH* & high pH

Acceptable Limit Limit for Rejection Result

7-8.5 6.5-9.2 7.63

Instrument Used–

pH meter

Fluoride –

Reagent Used for test- SPANDS solution, Zirconyl-acid reagent, referencesolution, sodium ardenate solution

Health Impact – i) Immediate symptoms include digestive disorders, skindiseases, dental fluorosis.

ii) Fluoride in larger quantities (20-80 mg/day) taken over a periodof 10-20 years results in crippling and skeletal fluorosis which issevere bone damage.

Affected states – Andhra Pradesh, Assam, Bihar, Chattisgarh, Gujarat, Haryana,Jharkhand, Karnataka, Kerala, Madhya Pradesh, Maharashtra,Orissa, Punjab, Rajasthan, Tamil Nadu, Tripura, Uttar Pradesh,West Bengal

Instrument Used– Spectrophotometer

Iron –

Reagent Used for test- Conc HCl, Hydroxylamine solution, Ammoniun acaetate, sod. acetate soln, phenanthroline soln, stock iron soln

Health Impact – i) A dose of 1500 mg/l has a poisoning effect on a child as it can damage blood tissues.

ii) Digestive disorders, skin diseases and dental problems.

Affected states – Arunachal Pradesh, Assam,Bihar, Chattisgarh, Jharkhand, Jammu andKashmir, Karnataka, Kerala, Manipur, Meghalaya, Mizoram, MadhyaPradesh, Maharashtra, Nagaland, Orissa, Punjab, Rajasthan, Sikkim,Tripura, Tamil Nadu, Uttar Pradesh, West Bengal, A&N Islands, Pondicherry

Acceptable Limit

Limit for Rejection

Result

0.3 mg/L 1 mg/L 0.3 mg/L

Turbidity –

Sources – presence of iron, chlorine, suspended particles.

Instrument used for test- Nephelometer

Impact-1. Aesthetic value2. High turbidity may be an indication of Iron and other impurities

Instrument Used– Nephlometer

THANKYOU !!