Water quality is the physical, chemical andbiological characteristics of water The vast majority of surface water on theplanet is neither potable (fit for drinking) nortoxic Approximately 25% of the world’s populationhas no access to potable water
Free from pathogenic organisms Clear Not saline Free from offensive taste or smell Free from compounds that may have adverseeffect on human health Free from chemicals that cause corrosion ofwater supply systems
Contaminants that may be in untreatedwater include:◦ microorganisms (viruses and bacteria)◦ inorganic contaminants (salts and metals)◦ pesticides and herbicides◦ sediments◦ organic chemical contaminants from industrialprocesses and petroleum use◦ radioactive contaminants. Water quality depends on the local geologyand ecosystem, as well as human uses(sewage dispersion, industrial pollution, useof water bodies as a heat sink)
COLOUR: May be due to the Presence of organic matter,metals(iron, manganese) or highly colouredindustrial waste Desirable that drinking water be colorless The Guideline value is up to 15 true colorunits(TCU)
Mainly due to organic substances, ,Biologicalactivity, industrial pollution Taste buds in the oral cavity specially detectinorganic compounds of metals likemagnesium, calcium, sodium, copper, ironand zinc Water should be free from objectionable tasteand odour.
Caused by suspended matter High level turbidity shield and protectbacteria from the action of disinfectingagents Desirable limit-5NTU(Nephlometric turbidity unit)Should be below 1 NTU when disinfection ispracticedPermissible limit-10NTU
It is the measure of hydrogen ionconcentration pH<7 cause corrosion of distribution pipesand elevates the level of lead pH>8 cause decrease in efficiency ofchlorination disinfection process Desirable limit 6.5-8.5. Beyond this limit thewater will affect the mucous membrane andwater supply system
Determine types of organisms that can livein water Affects how much oxygen water can hold◦ Warm water holds less oxygen Thermal Pollution (increased watertemperature)◦ decreasing oxygen supply◦ killing fish juveniles which are vulnerable to smallincreases in temperature◦ affecting ecosystem composition.
CHLORIDES Causeso Dissolution of salt deposito Discharge of effluentso Intrusion of sea water Acceptable limit - 250 mg/litre
Increasing level of nitrate is due to:o Agricultural fertilizers, manure, animal dung,nitrogenous material ,sewage pollution (blue baby diseases to infants) Maximum permissible limit 45 mg / litre
Fluoride is released into water bodiesmainly during manufacture & use offertilizers Long term consumption above permissiblelevel can cause –o Dental fluorosis (molting of teeth)o Skeletal fluorosis Acceptable limit – 1.5 mg / litre
One of the earth’s most plentiful resource High iron causes brown or yellow staining oflaundry, household fixtures Iron promotes growth of “Iron Bacteria”, whichderives their energy from the oxidation offerrous iron to ferric iron. Ferric ions give an objectionable “reddishbrown” color to the water. Acceptable limit – 0.3 mg / litre
Arsenic is introduced into water through thedissolution of minerals and ores, fromindustrial effluents and from atmosphericdepositions. High arsenic causes various type ofdermatological lesions, muscular weakness,paralysis of lower limbs, can also cause skinand lung cancer A provisional guideline value for arsenic indrinking water of 0.01 mg/litre is established
Present as mineral in soil and rocks of earth Industries:Battery – Lead & NickelTextile - CopperPhotography – SilverSteel production – Iron
BACTERIOLOGICAL INDICATOR: Coliform Organisms:o Includes all aerobic & facultative anaerobic,gram negative, non-sporing, non- motilerods capable of fermenting lactose at 35-37deg C in less than 48 hours.o If the coliform organisms are present in awater sample, the assumption is the probablepresence of intestinal pathogens
Faecal streptococci:o Finding of faecal streptococci in water isregarded as important confirmatory evidence ofrecent faecal pollution of water Clostridium perfringes:o The presence of spores of Cl.perfringes in anatural water suggests that faecal contaminationhas occurred, and their presence, in the absenceof coliform group, suggests that faecalcontamination has occurred at remote time.
Species of protozoa known to have beentransmitted by the ingestion of contaminateddrinking water include Entamoeba histolytica,Giardia spp. And rarely, Balantandium coli. These organisms can be introduced intowater supply by human or animal faecalcontamination
Visible effects ReasonIron taste, change in colour afterexposure to atmosphere, change incolour of cloths,utensils Oily appea-rance on top of water bodyIronSoap not lathering HardnessBrownish black streaks on teeth FluorideGrowth of Algae Nitrate,phosphateFish kills Low pHLess DOSalty taste Chloride
Intended to protect public from waterbornediseases Elements of Surveillance Program are:o Sanitary surveyo Samplingo Bacteriological surveillanceo Biological examinationo Chemical surveillance
On the spot inspection & evaluation by aqualified person of entire water supply Purpose – detection & correction of faults&deficiencies. It is essential for adequate interpretation oflaboratory results
Samples for physical & chemical examination:o Collected in a clean glass stoppered bottle made of neutral glass ofcapacity not less than 2 litres Samples for bacteriological examination:o Collected in clean sterilized 200-250ml bottle made of neutralglass provided with a ground glass stopper having an overlappingrimo When samples is to be collected from a TAP in regular use , thewater is first run to waste for 2 min & then water is collectedo In case of TAPS not in regular use, it is first sterilized with a blowlamp or with an ignited piece of cotton soaked in methylated spirit
o For collecting samples directly from rivers, lakes, tanksetc. a bottle with a string attached to the neck which isfully wrapped in paper and sterilized should be used. TRANSPORT AND STORAGE OF SAMPLESo Where immediate commencement of examination is notfeasible samples should be kept in ice until it is taken foranalysiso Particulars regarding the date and time of collection anddispatch, source of water, particulars of recent rainfall andfindings of the sanitary survey should be also be suppliedwith the sample.
Presumptive Coliform test: Multiple tube method:o Based on estimating most probable number(MPN) ofcoliform organisms in 100ml of water.o The test is carried out by inoculating measuredquantities of the sample water(0.1,1.0,10,50ml)ontotubes of McConkey`s Lactose Bile Salt Broth withbromcresol purple as an indicator.o The tubes are incubated for 48 hours. From thenumber of tubes showing acid and gas, an estimateof the MPN obtained from statistical table
Membrane filtration technique:o Measured Vol. of the sample is filtered through amembrane specially made of cellulose ester.o All bacteria present in water are retained on the surface ofmembrane and by inoculating the membrane face upwardson suitable media, it is possible to count the colonies COLONY COUNT:o Colony counts on nutrient agar at 37 deg C and 22 deg Care frequently used in bacteriological examination of watero Colony count provide an estimate of general bacterialpurity of water.
“Planktons” produce objectionable tastes & odours inwater. Degree of pollution is assessed qualitatively &quantitatively by noting the type & number of organismsprevailing in waterCHEMICAL EXAMINATION: Basic tests for pH, turbidity, chlorides, ammonia etc areperformed Complete chemical analysis would also include analysis fortoxic metals, pesticide, persistent organic chemicals andradioactivity.
TEXTBOOK OF PREVENTIVE AND SOCIALMEDICINE(22nd edition)- K.PARK WATER QUALITY PARAMETERS-ABDUNNASAR,UK WATER QUALITY-JAMES M.EBELING INTERNET: WIKIPEDIA www.authorstream.com www.slideshare.com