WATER QUALITY: DEFINITIONS, CHARACTERISTICS AND PERSPECTIVES

THE HYDROLOGIC CYCLE AND WATER QUALITYWater - cover of the earth surfaceOver 97% of the total water is not readily usable oceans and other saline bodies of waterOver 2% is inaccessible ice caps and glaciers, atmospheric and soil moistureOnly 0.62% for human fresh water lakes, rivers & groundwater supplies

HYDROLOGIC CYCLEAtmosphereEarths surfaceCondensation Evaporation Evapotranspiration Percolation Surface runoffGround water flow

IMPURITIES IN WATERSurface, or nuclei during condensationLiquid water travels through the remainder of the hydrologic cycle contact with other material in air or earthHuman activities industrial and domestic waste* Impurities can be both in suspended and dissolved form

WATER QUALITYPredicted on the intended use of the waterWater pollution defined as the presence in water of impurities in such quantity and of such nature as to impair the use of the water for a stated purposeStandard method analytical procedures to measure the impact of impurities on water

PHYSICAL PARAMETERS

1. SUSPENDED SOLIDSSOURCESNatural contaminants resulting from the erosive action of water flowing over surfacesResult from human use of water domestic wastewaterContain inorganic (clay, silt) or organic (plant fibers, bacteria)particles, immiscible liquids (oil and grease)

IMPACTAesthetically displeasingProvide adsorption site for chemical and biological agentsMay be degraded biologically or may include diseases-causing organismsMEASUREMENTFiltering the water, drying the residue and filter to a constant weight at 104oC and lastly determine the mass of the residue retained on the filter

FILTERABLE RESIDUE AND NONFILTERABLE RESIDUETerm used in laboratory analysis to represent the SS and DSFilterable residue closely related to DS while nonfilterable residue more closely to SSUSE Measure the quality of wastewater influentMonitor several treatment processesMeasure the quality of the effluent

2. TURBIDITYA measure of the extent to which light is either absorbed or scattered by suspended material in waterNot a direct quantitative measurement of SSSOURCES results from the erosion of colloidal material such as clay, silt, rock fragments, metal oxides from the soil, vegetables fiber, microorganism, soaps, detergent, emulsifying agents

IMPACTAesthetically displeasing opaqueness will appearProvides adsorption sites for chemicals and biological organism that may be harmful or cause undesirable tastes and odorsMay interfere with light penetration and photosynthetic reactions in streams and lakes

MEASUREMENTMeasured photometrically by determining the percentage of light of a given intensity that is either absorbed or scatteredTurbidity is a relative measure, not absolute measures. It is usually expressed as nephelometric turbidity units (NTU) or as metres depth. Other units, formazin turbidity units (FTU) or Jackson turbidity units (JTU)

Turbidimeter using light scattering at sample surface

Turbidimeter using the scattered/transmitted light method

USEMade on clean waters

3. COLORApparent color color of water partly due to suspended matterTrue color color contributed by DSSOURCESYellowish-brown water contact with organic debrisReddish cause by iron oxideBrown/blackish manganese oxideIndustrial waste textile and dyeing operations, food processing

IMPACTUnsuitable for laundering, dyeing, papermaking, dairy productionAffect the market of domestic and industrial companyOrganic compound reduce the effectiveness of chlorine as disinfectantMEASUREMENTComparison with standardized colored materials (unit used TCU)

One unit is equivalent to the color produced by 1 mg/L of platinum in the form of chlorplatinate ionsSpecial spectrophotometric techniques used for industrial waste effluentsUSE used in potable water analysis (true color) indirect measurement of humic substances in the water

4. TASTE & ODORSOURCESMineral, metals and salts from the soil end products from biological reactionsInorganic substances tasteAlkaline material & metallic salts cause a bitter taste to waterOrganic material contributed to both taste and odor

IMPACTConsumer associates T&O with contaminationOrganic substances carcinogenicMEASUREMENTCan be made if the causative agents are knownOrganic cause gas or liquid chromatographyQualitative test threshold odor number (TON)

TON = (A + B)/A

WhereA = volume of odorous water (mL)B = volume of odor-free water required to produce a 200-mL mixtureUSEServes as guideline for potable waterTON of 3 recommended by the Public Health Service

5. TEMPERATUREIMPACT OF TEMPERATUREAffect chemical reaction rateBiological activities higher in higher TPhysical properties e.g viscosity and density affect planktonic microorg.Affect solubilities of gases in waterAlgae growth higher in warm water, causes algae mats secrete oil and dead algae will causes taste & odor prob.

CHEMICAL WATER QUALITY PARAMETERS

1. TDSMaterials remaining in water after SS removalOrganic sources decayed product of vegetation, organic chemicalInorganic sources minerals, metals, gasesProduce undesirable substances in water (color, taste, odor, toxicity problem)Some are essential: distilled water taste flat, readily dissolved added to pure water to reduce its tendency to dissolve pipes and plumbing

2. ALKALINITYThe ability of water to neutralize acids (quantity of ions that can neutralize H+)Ions sources dissolution of mineral substances in soil and atm (CO32-, HCO3-, OH-, NH3 etc)-HPO42- from detergent, fertilizers and insecticide-HS- and NH3- from byproduct of decomposition of organic material

3. HARDNESSAmount of multivalent metallic cation in waterSum of Ca & Mg ions in waterOther ions very little Fe, MnIMPACTSoap consumption higherForm precipitation with soap sticks to surface of sinks, dishwasher, rough skin, stain clothesEconomic loss: fouling of water heaters and boilers

4. FLUORIDEAppears in groundwater in few geographical regionsToxic in high conc, beneficial in low conc1 mg/L help prevent dental cavities, stronger teeth>2 mg/L discoloration of teeth (mottling)Higher conc bone fluorosis

5. METALSNONTOXIC METALIf exist in small amount Zn, Fe, Mn, AlCa and Mg hardness ionsNa most commonTOXICMining and industrial industryAr, Ba, Cd, Pb, Hg goes up food chain, greatest danger to top of chainMEASUREMENT by AAS

6. NUTRIENTSNitrogen is often the limiting nutrient in ocean waters and some streamsCan exist in numerous forms, but most common are nitrate, nitrite, ammoniaSources are primarily from fertilizers and acid deposition

Phosphorus is typically the limiting nutrient in lakes and algae growth is linked to phosphorus inputsProblemsTaste and odor in drinking waterCan be toxic, especially to farm animalsFoulingDiurnal DO cyclesSources fertilizers and detergentsCan exist in a variety of chemical forms, so total P is normally measured

7. ORGANICSSoluble in waterObtained from natural sources and human activitiesCategories of dissolved organicBiodegradableNonbiodegradable

7.1 BIODEGRADABLE ORGANICSConsist of organics that can be utilized for food by naturally occurring microorg within a reasonable length of timeOrganic material exist in dissolved from - starches, fats, proteins, alcohols, acids, aldehydes and estersMicrobial utilization involved oxidation (more efficient) and reduction

BOD the amount of O2 consumed during microbial utilization of organics (how much available O2 is used by bacteria to decay organic matter in the water)BOD test: determine the O2 consumed from a sample placed in an airtight contained in controlled environment fro selected time.Standard 300 ml bottle, incubated at 20oC, 5 days in dark room (prevent algae growth produce O2)

BOD CALCULATION

Where DOi= initial DO (mg/L)DOf= final DO (mg/L)P= decimal fraction of sample in 300 mL bottle

BOD FROM SEWAGE TREATMENT PLANT IN MALAYSIA (2006)

StateNo. of STPTotal PEFlow (m3/day)BOD Load (kg/day)Selangor2,5635,908,4501,329,401332,350.31Perak1,3431,300,430292,59773,149.19Johor10101,198,417269,64467,410.96Negeri Sembilan928931,458209,57852,394.51Kedah755556,637125,24331,310.83Melaka725570,192128,29332,073.30Pulau Pinang6502,149,001483,525120,881.31Pahang486314,83070,83717,709.19WP Kuala Lumpur2992,571,877578,672144,668.08Terengganu22475,18416,9164,229.10Perlis3616,1563,635908.78WP Labuan3239,2658,8352,208.66WP Putrajaya972,83316,3874,096.86Total9,06015,704,7303,533,563883,391.08

Example 1: Determining BOD5The BOD of w/water is suspected to range from 50 to 200 mg/L. Three dilutions are prepared to cover this range. The procedure is the same in each case. First the sample is placed in the standard BOD bottle and is then diluted to 300 mL with organic-free, oxygen-saturated water. The initial DO is determined and the bottles tightly stoppered and placed in the incubator at 20oC for 5 days, after which the DO is again determined.

Given:

Wastewater, LDOi (mg/L)DOf (mg/L)0.0059.26.90.0109.14.40.0208.91.5

7.2 NONBIODEGRADABLE ORGANICSome organics materials are resistant to biological degradation tannic and lignic acid, cellulose,phenolsPolysaccharides (strong bond) and benzene (ringed struct) are also nonbiodegradable e.g detergent compound ABSInsecticide, herbicide, pesticide accumulate to top food chain, can cause extinction of animal species

BIOLOGICAL WATER QUALITY PARAMETERAll members of biological community are water quality parametersPATHOGENOrganism capable of infecting, or transmitting disease to humanUsually require an animal host for growth and reproductionCan be transported by natural water systemsInclude bacteria, viruses, protozoa and helminths (parasitic worm)

1.1 BACTERIADiseases causes by bacteria gastrointestinal disorder, cholera, typhoid

1.2 VIRUSES

Diseases disorder of the nervous system, poliomyelitis, infectious hepatitis

1.3 PROTOZOA

Diseases dysentery, malaria

1.4 HELMINTHS

Serious case of liver, intestine and urinary system

WATER QUALITY REQUIREMENTSVary according to the proposed use of the waterRepresent a known/assumed need & based on prior experience of the water userWQS set by government

WATER QUALITY STANDARDSStandards

RIVER WATER QUALITY MONITORINGBODCODAmmonical nitrogenpHDOSSOptional heavy metals and bacteria

WATER QUALITY INDEXGive info on water quality conditions & trendsTo measure the degree of water pollution and a tool in water quality classificationReflect changes in physio-chemical quality of surface water & indicator of ecological changeEasiest method to explain the pollution level of water esp to public using ranges between excellent, good, medium, bad and very bad

WQI - continuousIs used to relate a group of variables to a common scaleVaries with changes in parameters values that would be indicative of changes in the quality of watersWQI system and parameters vary from country to countryMeasures general water quality conditions and does not reflect the presence of toxic compounds or specific toxic conditions

TUTORIAL2.4, 2.8, 2.24, 2.31, 2.43 and 2.44