Environmental Engineering Lecture-2

1. Environmental EngineeringLecture-2 Chemical Engineering Department UET Lahore www.engineering-resource.com

2. Synopsis • Water • Water Analysis • General Water Analysis Parameters www.engineering-resource.com

3. Water….. • Water covers 70.9% of the Earth's surface, and is vital for all known forms of life. On Earth, it is found mostly in oceans and other large water bodies, A very small amount of the Earth's water is contained within biological bodies and manufactured products. www.engineering-resource.com

4. Water is Essential for Life • Clean drinking water is essential to humans and other life forms. However, some observers have estimated that by 2025 more than half of the world population will be facing water-based vulnerability. A recent report (November 2009) suggests that by 2030, in some developing regions of the world, water demand will exceed supply by 50%. www.engineering-resource.com

5. Resources of Water • Water appears in nature in all three common states of matter and may take many different forms on Earth: water vapor and clouds in the sky; seawater and icebergs in the polar oceans; glaciers and rivers in the mountains; and the liquid in aquifers in the ground www.engineering-resource.com

6. Hydrology and Hydrosphere • Hydrology is the study of the movement, distribution, and quality of water throughout the Earth. The study of the distribution of water is Hydrography. • The collective mass of water found on, under, and over the surface of a planet is called the Hydrosphere. www.engineering-resource.com

7. Water Cycle The water cycle (known scientifically as the hydrologic cycle) refers to the continuous exchange of water within the hydrosphere, between the atmosphere, soil water, surface water, groundwater, and plants. • Evaporation • Transpiration • Precipitation • Runoff www.engineering-resource.com

8. Physical Properties of Water Water has several physical properties. These properties are: • Water has a high specific heat. Specific heat is the amount of energy required to change the temperature of a substance. Because water has a high specific heat, it can absorb large amounts of heat energy before it begins to get hot. It also means that water releases heat energy slowly when situations cause it to cool. www.engineering-resource.com

9. Water in a pure state has a neutral pH. As a result, pure water is neither acidic nor basic. Water changes its pH when substances are dissolved in it. Rain has a naturally acidic pH of about 5.6 because it contains natural derived carbon dioxide and sulfur dioxide. www.engineering-resource.com

10. Water conducts heat more easily than any liquid except mercury. This fact causes large bodies of liquid water like lakes and oceans to have essentially a uniform vertical temperature profile. www.engineering-resource.com

11. Water molecules exist in liquid form over an important range of temperature from 0 - 100° Celsius. This range allows water molecules to exist as a liquid in most places on our planet. • Water is a universal solvent www.engineering-resource.com

12. Why Waste Water Analysis?? • Estimation of pollution load and their potential damage. • Preliminary assessment for planning and operation of waste water treatment plants. • To find out the amount of toxic components such as cyanide, cadmium, mercury etc.& to evaluate the degree of toxicity. • To find out the substances that cause difficulties in the treatment, such as non-biodegradable organics. www.engineering-resource.com

13. General Water Analysis Parameters • Color • pH • Electrical Conductivity • Turbidity • Solids • Chlorides • Hardness • Sulphates • Dissolved Oxygen • BOD & COD www.engineering-resource.com

14. 1. Color Pure water is colorless. However color is contributed to natural water by many sources. SOURCES: • End products of organic matter degradation are picked up by run-off water. www.engineering-resource.com

15. Algal metabolism such as chlamydomnas excrete yellow substances into the water. • Divalent species of ions of iron & manganese in both ground & surface water. In surface water these ions may convert to Fe(OH)3 and MnO2 as a result of oxidation and ultimately precipitated. • Discharge of untreated & partially treated waste water from textile & drying operation, paper & pulp production, tanneries, food processing, chemical production & slaughter operation may contribute color to the water. www.engineering-resource.com

16. Color caused by suspended matter is called Apparent color. • Color caused by dissolved solids that remains after removal of suspended solids is called True color. • Color intensity is affected by pH value. www.engineering-resource.com

17. Color water is expressed in mg/l in platinum cobalt scale. • Drinking water standard is 20ppm on platinum cobalt scale. • Colored water is unsuitable for drinking, laundering, dying, paper making, food industries, etc. • Colored water will affect the photosynthesis process in marine water. www.engineering-resource.com

18. Color Removal: • Apparent color is removed by simple filtration or ultra filtration. • True color causing organic compounds require chlorine demand and hence more quantity of chlorine is required for disinfection. www.engineering-resource.com

19. 2. pH • pH is the method of expressing the concentration of ionized hydrogen. • It is the logarithms to base 10, of the reciprocal of hydrogen ion conc. in g/L. pH = - log(H+) • Pure water has equal conc. Of hydrogen & hydroxyl ions and has pH of 7 (neutral). www.engineering-resource.com

20. pH of natural water lies in the range of 6.0 to 8.5. • Most of natural water is alkaline due to the presence of carbonates. • pH of natural water changes due to biological activity, temperature, photosynthesis, and industrial disposal. • Waste water with adverse hydrogen ion conc. is very difficult to treat by bacteria. www.engineering-resource.com

21. pH is measured by pH meter. The basic principle of pH meter is potential difference developed b/w two electrodes is directly proportional to hydrogen ion concentration. • pH is one of the important parameter in water treatment. • To maintain anaerobic treatment, pH must be maintained b/w 6.8 to 7.6 in the digester otherwise bacteria will not survive. www.engineering-resource.com

22. 3. Electrical Conductivity • It is the measure of the capacity of the substance or solution to carry an electric current. • It is a parameter for dissolved & dissociated substance. • Its value depend on conc. Of ions, temperature and the migration velocity of the ions. www.engineering-resource.com

23. It indicates the conc. Of dissolved electrolyte present in water sample. • It helps in estimating the total dissolved solids by following empirical relation: • TDS(mg/L) = C * Specific Conductivity • Where C is empirical factor may vary from 0.55 to 0.9 depending on the soluble solids present in water. www.engineering-resource.com

24. Although unionized species are the portion of total dissolved solids but they are not detected by conductivity meter. • Also silica will not be detected by conductivity meter. So this is only the estimation method for TDS. www.engineering-resource.com

25. 4. Turbidity The suspended solids interfering with the passage of light is called turbidity.It is caused by wide variety of suspended matter which differ in size. SOURCES: • Clay • Silt • Organic matter & metals • Microscopic organisms www.engineering-resource.com

26. Turbidity is measured photo metrically by determining %age of light of a given intensity absorbed or scattered. Units are: • NTU (Nephlometric Unit) based on light scattering • JTU (Jackson Unit) based on light absorption www.engineering-resource.com

27. 5. Solids • The term solids refer to the matters either filterable or non filterable that remains as residue on evaporation. • Kinds of solids present in water are: A) Suspended Solids a) Settle able b) Non Settle able B) Filterable Solids a) Colloidal b) Dissolved www.engineering-resource.com

28. Gravimetric methods are used to measure all types of solids. • Solids are generally expressed in mg/L • Filterable solids consists of colloidal & dissolved solids. • Colloidal solids includes particulate matters with an approximate diameter range from 1 mill micron to micron. • Dissolved solids consists of both organic & inorganic salts. www.engineering-resource.com

29. Dissolved solids removable by: • Chemical precipitation • Adsorption • Oxidation • Reverse Osmosis • Ultra filtration • Biological Oxidation www.engineering-resource.com

30. Colloidal solids removable by: • Coagulation Suspended or non filterable solids removable by: • Settle able by gravity settling • Floatation www.engineering-resource.com

31. 6. Chlorides Chlorides is present in all natural waters at greatly varying concentrations. SOURCES: • Leaching through rock & soils • Effluent from chemical industries • Sewage disposals • Irrigation drainage • Sea water in coastal areas • A man discharges 8 to 10 gm per day of NaCl through both urine & excreta www.engineering-resource.com

32. When chlorides concentrations of 250 mg/L is present along with sodium ions, a salty taste can be observed. • Chlorides can only be removed by reverse osmosis and electrolysis. www.engineering-resource.com

33. 7. Hardness • Hardness is a measure of the ability of water to cause precipitation of insoluble calcium & magnesium salts of higher fatty acids from soap solutions. • Principal hardness causing cationsare calcium, magnesium, strontium, iron & manganese ions associated with carbonates, bicarbonates, chlorides & sulphates. www.engineering-resource.com

34. In general hard waters are originate in areas where top soil is thick and limestone is present. • Hardness is classified with respect to the metallic cations and the anions associated with metallic ions. With respect to metallic actions: • Calcium hardness • Magnesium hardness www.engineering-resource.com

35. With respect to anions associated with metallic ions: • Carbonate hardness • Non-carbonate hardness www.engineering-resource.com

36. 8. Sulphates Sulphates occur in natural water at conc. Up to 50 mg/L. SOURCES: • Rain water especially in areas of air pollution. • Leaching through soils. • Released during degradation of proteins Standardfor drinking water is 200 ppm. www.engineering-resource.com

37. 9. Dissolved Oxygen (DO) • Amount of oxygen gas dissolved in a given volume of water at a particular temperature and pressure. • The presence of oxygen is essential for the survival of aquatic life. • It plays an important role for the metabolic pathways of aerobic bacteria and other microorganisms which are responsible for the degradation and stabilization of organic constituents in waste water. www.engineering-resource.com

38. A rapid fall of DO level in river waters is one of the first indication of organic pollution. • DO level depends on physical, chemical & biological activities. • Major inputs of dissolved oxygen to natural waters is from atmosphere & photosynthesis reaction. • DO level in water should be 5-8 mg/L www.engineering-resource.com

39. The solubility of oxygen in waters on depends on temperature, pressure, altitude & chloride conc. • The solubility of atmospheric oxygen decreases with increase in temperature. • The solubility of oxygen is lesser in salt containing water than in clean water. www.engineering-resource.com

40. 10. Biological Oxygen Demand (BOD) • Biochemical oxygen demand is a measure of the oxygen utilized by microorganisms during biological oxidation of organic matter contained in the liquid waste under a specified conditions. Organic matter + O2 CO2+ new bacteria+H2O www.engineering-resource.com

41. On average basis, the demand for oxygen is directly proportional to the amount of biodegradable in waste water under aerobic conditions. • BOD is a direct measure of oxygen requirement and indirect measure of biodegradable organic matter. www.engineering-resource.com

42. Biochemical is a slow process and theoretically takes an infinite time to go to completion. • Within 20 days oxidation is 95 to 99% complete and within 5 days it is 60 to 70% complete. • BOD is an empirical test in which water conditions such as temperature, oxygen conc. Or type of bacteria play a decisive role. www.engineering-resource.com

43. 11. Chemical Oxygen Demand (COD) • Chemical oxygen demand is the oxygen required for chemical oxidation of organic matter by strong chemical oxidant (K2Cr2O7) under acidic conditions. • Degree of oxidation depend upon the type of substance, pH value, temperature, reaction time & conc. Of oxidizing agent. www.engineering-resource.com

44. Advantages: • Major advantage of the COD test is the short time required for evaluation. COD test is conducted in approximately 3 hours while BOD is conducted in 5 days. • COD test is much more useful for estimating strength of certain industrial wastes of both organic & inorganic which contained toxic chemicals. www.engineering-resource.com

45. Disadvantages: • COD test does not differentiate b/w biological oxidizable & biologically inert organic matter. • Some amino acids, ketones or saturated carboxylic acids, benzene, pyridine etc. are not oxidized by dichromate. • Some oxygen is consumed by inorganic substances such as nitrites, chlorides, sulphates, reduced metal ions, etc. So, test is a poor measure of strength of organic wastes unless these factors are considered. www.engineering-resource.com