Analysis of water pollution presentaion by m.nadeem ashraf
SES_311 Introduction to soil and environmentDepartment of Soil & Environmental Sciences Faculty of Agriculture Rawalakot University of Poonch, awalakot. email: firstname.lastname@example.org
Why Water analysis is necessary? To asses water quality To provide pure water to public for drinking To analyse microbial organisms Preventive measure and effective disinfection procedure Sewagw and waste water analysed
Physical assesment• Temperature• Ph• Turbidity• TSS Chemical assesment• Acidity• Alkalinity• COD• Chemical substances Biological assesment BOD Microbiological
Colour in water is due to suspended particles in solution,even pure water is not colorless(pale-green) Colour of water may be caused by Fe,Mn,Cu,metals,Iron. humus,algae,weeds,protozoa etc. Colour can be compared visually or Photoelectrically. Colour is measured with an instrument known as Tintometer. Yellow color indicates the presence of O.M Yellow red color indicates. True color can be estimated by visual comparispon with platinum cobalt standard solution, unit is measured on cobalt scale.
Turbidity in water mainly arises from colliodal material and fine suspended particles. Turbidity can be measured by absorptiometrically(visual methods) and nephelometrically(instrumental methods) Another methods used to measure turbidity is Turbidity Rod which has a platinum needle. Jackon,s turbidimeter which consists of metal stand over which a metal container is placed.
Odour in water are sue to the presence of microscopic organisms or decaying vegetation including algae, fungi, bacteria, H2S, N, P, S compounds.Determination of Odour: For dermination of odour place 250ml of sample in a 500ml wthite mouth erlenmeyer flask & sniff the odour.
Dissolve mineral matters in water produce tastes but not odour. If faint bitter taste may be due to the presence of Sulphate while soapy or inky taste may be due the excess of sodium bicarbonate. Way to remove objectionable taste & odour from water is to pass it through a filter bed containing activated charcoal, if finely divided form of carbon. The enormous surface area enables it to absorb large quantities of impurities.
Surface water differs considerably in temperature b/w winter & summer. Temperature measurment are usefull in detecting an unsuspected suorce of pollution, in calculating alkalinity and in industrial water supplies for heat tranmision calculations.
pH a measure of hydrogen ion activity is used to express the intensity of acidic or alkaline condition of a solution. It is an also important factor in water analysis. pH of a sample can be determine by electrometrically. it involves the measurment of EMF of a cell comprising an glass electrode response to hydrogen ion and refrence electrode. pH meters used for measurement. The desirable pH range for drinking water is 7-8.5
EC is a measure of water’s capacity to convey electric current.its unit is micro Siemns/cm3 Conductivity of water varies directly with temperature and is proportional to its dissolved mineral matter content. It is an important to check the purity of distilled water. Distilled water with conductivity more the 2 should not be used for water analysis.
500ml of a sample is taken in volumetric flask and allowed to filter through a dried and weighed Gooch crucible containing an asbestos mat.The suspended solids retained in the crucible or washed with distilled water to remove chloride. The crucible is finally dried, cooled in a desicator and weighed.the weighed of crucible is equalent to suspended impurities present.
It is the power of water to neutralized hydroxyl ions and is expressed in terms of CaCO3. water attains acidity fron industrial effulents etc. Take 50ml of sample dechlorinated in a 250ml conical flask add 2 drops of methyl orange indicator and titrate with 0.02 N-NaOH solution till faint orange colour. Methyl orange point is a measure of mineral acidity. Amount of sodium hydroxide to reach pH 8.3 (phenolphthaline end point) is a measure of total acidity.
Alkalinity of water is generally due to the presence of carbonate and hydroxide ion. It is measured by titrimetric method.
Calsium in water mainly due to the presence of limestone,gypsum,dolomite. The determination of Ca is required potable water. EDTA titrimetric method and gravimetric method are used for determination of calcium. In EDTA titrimetric method Ca reacts with EDTA in the presence of a selective indicator at a high pH and Mg is allowed to precipitate as its hydroxide. Ca2+ + 2EDTA Ca(EDTA)2
Magnesium salts occur in natural waters,sea waters(130ppm). It is measured by gravimetric method or photometric method. It may also be calculated as the difference between total hardness and Ca hardness as under: Mg(as CaCO3)mg/L =mg/L total hardness as CaCO3 –mg/L calcium hardness as CaCO3.
Ammonia N is present in water in the form of ammonia, nitrates & nitrites. The presence of the substances in water indicates the the presence of organic contamination. The amount of free ammonia is determine by boiling the sample of water. The quantitiy of ammonia in potable water should not be greater then 0.15 ppm. Ammonia is calorimrtrically measured using Nessler,s reagent.
Nitrites are obtained by the oxidation of ammonia, nitrites should never be present in potable water. The presence of nitrites in water can be determine by adding sulphonilic and naphthamine. The permissible limit of Nitrate in drinking water is 10mg/L. The presence of nitrate in water bodies caused mathemoglobinemia. It can be measured by Brucine method.
It is necessary to destroy these chemical substances by digestion with strong acids. Digestion destroys the O.M and brings metallic compounds in suspension to solution.
Arsenic occur in water as a result of mineral dissolution,industrial waste or application of insectisides. The presence of As as 100mg in water cause poisoning,it can cause chronic effect. It can be measured by Gutzeit method.
Cd enters water through industrial wastes,it is toxic and poisoning can cause human kidney. It can be measured in water sample by detected by dinitrophenyl carbazide.
BOD is the measure of the dissolve oxygen required by the microbes in polluted water, it is measured in mg/L. During this process dissolve oxygen is consumed and micro-organism transform the ollutants into non- hazardous compounds. microbes CH2O+O2 CO2 +H2O+M.Org O.M aerobic oxidation
The water sample is first saturated with oxygen and then incubated at constant temperature(20C) for 5- days. This allows the sufficient time for micro- organism in polluted water to affect oxidation of pollutants. After 5-days, the remaining amouny of dissolved oxygen is determined and BOD is obtained by substraction. The 5-day BOD(ppm) analysis is considerd as an accepted stndard test.
Drinking water should have 5-day BOD of less than 1.5mg/L. BOD of raw sewge ranges from 200-400mg/L Major contributor to BOD are chemical industries, pulp and paper and food processig industry. BOD of very clean water is 1mg/L, clean water is 2mg/L and unfit for drinking water is 5mg/L.
COD is a measure of oxygen required to breakdown the organic matter. In BOD breakdown of organic matter is affected by micro organisms but in COD the degradation is affected by some chemical oxidizing agent like Potasium dichromite .
The water sample is treated with an oxidizing agent(K2Cr2O7) which oxidizes most of the polluting substances including those which are resistant to microbial oxidation. The unused potassium dichomite is determine by back titration with a suitable reducing agent like Mohr’s salt. The amount of oxygen used in oxidation can be calculated as:K2Cr2O7 + 4H2SO4 K2SO4+Cr2(SO4)3+4H2O+3(O)
COD in mg/L Status0-5 Very clean water, used for drinking5-20 Fairly clean20-100 Unfit for drinking
Microbiologicalparameters WHO standards EU standardsEscherichia coli Not mentioned 0 in 250 mlEnterococci Not mentioned 0 in 250 mlPseudomonasaeruginosa Not mentioned 0 in 250 mlClostridiumperfringens Not mentioned 0 in 100 mlColiform bacteria Not mentioned 0 in 100 mlColony count 22oC Not mentioned 100/mlColony count 37oC Not mentioned 20/ml