1. SANITARY ENGINEERING

2. Books
It is the branch of public health engineering healing with collection, conveyance and disposal of wastage (garbage, sullage, sewage). The main purpose of sanitary engineering is to maintain such environment as well not affect the public health in general: Following are he various aspects of sanitary engineering: - 1. Collection: The solid and liquid works are collected in specially installed lavatory blocks 2. Conveyance: This includes provision of drainage line for the conveyance of solid and liquid wastes, which are collected. 3. Disposal: The conveyed refure / wastes is treated as the disposed off.

3. Sewerage Definition of Terms
Sewage: It is the waste of foul water of the community conveyed by the sewer. There are three types of sewage:-
- Domestic or Sanitary Sewage: The sewage from residential buildings business centers, institutions, etc. this also contain human body waste (feces & urine) and also saluge water.
- Industrial Sewage: The liquid wastes obtained from industrial Proust such as dying, papermaking, etc, are called industrial sewage.
- Storm Sewage: It is that part of surface run off which is flowing in sewer during of following period of rainfall.

4. Sullage: It is the waste water resulting from personal wasting, bathing, laundry, food preparation and cleaning of atensils. It does not include discharge from hospitals O.T and slighter houses which has high content of organic matters. Sullage is not very foul and can be disposed off in open drain with out treatment.
Garbage: It is used for dry refuse of town containing organic, inorganic solids, semisolids, combustable, noncombustible, putrecible and nonpatrocibe substances. It includes sweeping from houses, streets, markets, public places, garden etc. work paper, leaves, grass, panning of vegetable, deaying fruits etc. with small quantities of snad, cinder, clay and gravel constitute garbage. It is collected separately from sewage and sullage and dispose off separately.

5. Infiltration & Exfiltration: infiltration is the water which has leaked into the sewer from the ground while exfiltration is leakage of water out of the sewer to the ground. Inflow: It is the water entering the sewer from surface source through cradis in manholes, open cleanouts, perforated mainhole cross, and root drain of basement sumps connected to the sewers inflow occurs only during runoff. Sewers. Sewer is a pipe or candiute carrying sewage, sewage are uaually not flowing full (gravity flow). The full flowing sewers are called fore main as the flow is under pressure.

6. Sewer has following types.
- Sanitary Sewer: It is a sewer carrying sanitary and industrial sewage excluding storm sewage. It is also some time called seprate sewer.
- Storm Sewer: It is the one which carried storm sewage including surface runoff and street wash.
- Continued/Combined Sewer: It is the one carrying domestic, industrial and storm sewage combined.

7. ·       Sewerage. It is the science and art of collecting, treating and disposing of sewage. There are three systems of sewerage of sewerage.
o       Separate System
o       Combined System
o       Partially Separate System
o       Separate Sewerage System: In this system the sanitary sewrae and storm water are carried separately in two sets of sewers. The sewage is conveyed to wastewater treatment plant and the storm water is discharge directly into rivers without treatment. The separate system has the following advantages & disadvantages

8. Advantages § The load on treatment plant is less as only sewage is carried to the plant. §The size of sewers are small thus economical. §When pumping is required the system process to be economical. §Natural water is not unnecessarily polluted by sewage.

9. Disadvantages § Cleaning of sewers is difficult due to their small size. § The maintenance costs are high. §The system requires two costs of sewers making it uneconomical. § The self cleaning velocity is not easily achieved. §The storm sewers come in operation in rainy season only. They may be chocked in during dry season by garbage. § Sewage sewers are provided below storm sewer which cause sewer depth and pumping at WWTP. The separate system is suitable when separate outlets for storm water is available and the topography is such at storm water can be dispose off in natural drains.

10. o Combined Sewerage System: in this system the sewage and storm water are carried combinelly in only one set of sewers to the wastewater treatment plant. Before disposal. This system has the following advantages and disadvantages: Advantages § It is easy to clean combine sewers because of large size. § The maintenance cost is reasonable. § It reduces strength of sewage by mixing storm water with sewer. § The system requires one sewer making it economical.

11. Disadvantages § In storm seasons water may overflow and the sewer may damage causing serious health risks. § The combine sewer gets silted and becomes foul in dry days. § The load on treatment plant is high because storm water is also carried there. § The storm water gets polluted unnecessarily. § The system is uneconomical when pumping is need. The system is suitable when space available for laying two sets of sewers is less and when pumping is not required.

12. o Partially Separate Sewerage System:
o  Partially Separate Sewerage System: this system is the comprise between separate and combine system taking advantages of both systems. In this case the sewage and storm water of building are carried by one set of sewers while storm water from roads, streets, pavements, etc are carried by other system of sewers usually open drains. This system has the following advantage and disadvantages.

13. Advantages § It combines the good features of both systems
Advantages § It combines the good features of both systems. § The setting is avoided due to entry of storm water. § The storm water from houses is easily disposed off. § The sewers are of reasonable size. Disadvantages: § Very small of bad features of combined system are there in partially separate system.

14. Method of Disposal of Sewage There are two methods collecting and disposing sewers. o Conservancy System / Method or (dry system) o Water Carriage System / method · Conservancy System: In this system also called dry system different types of wastes / refuses are collected separately and disposed off. · Garbage is collected separately in dustbins and conveyed covered carts or lurris to suitable place. The combustible and non-combustible garbage are sorted out. The farmer is burnt and the later is buried in low lying areas.

15. · The human and animal wastes (feaces & urine) are collected in panes from lavatories and is then carried by labours in carts of lorries for disposal outside the city where it is buried for manure. The human and animal waste are also called night soil. · The sludge & storm water are conveyed separately by close and open channel and discharge into natural streams. This system is obsolete now and can be used in rural where there is scarcity of water. It is not used now a days because of the following reasons.

16. § Cost. The system has less initial cost but the operation cost is very high because of working labours. § Design of building. The lavatory has to be build separate from residential building which cause inconvience and lack if company. § In sanitary Condition. The sewage is carried once in 24 hours while sewage becomes unsanitary after 5 – 6 hours and attract § Labour problems. If the labour goes on strike the system totally fails. § Land requirement. It requires large area for disposal of sewage thus becoming unconvienent.

17. §   Foul Appearance. It is highly undesireable to allow night soil carts to pass through roads of city.
§  Open drain. Storm water and sullage flowing in open drains cause unhygienic condition in the area.
§   Pollution of Water. The liquid wastes from lavatories may seeps into the ground thus polluting the ground water.
Risk of Epidemic. The sewage is conveyed openly and is not properly disposed off causing risk of epidemic

18. · Water Carriage System
· Water Carriage System. In this system water is used as a medium to carry wastes to the its point of final disposal. The quantity of water si so large (99.9%) that the waste becomes a liquid which is carried by sewers. The garbage is collected as separately as in conservery with sanitary sewage. This is absolute system and is used now a days universally because of following reasons: - § Cost. Through the initial cost of the system is high but he operation cost id very low.

19. § Compact Design. The lavatories can be accomodaetd inside the building which cause compact design of house and convenience. § Hygienic System. The sewage is carried in covered drains thus the risk of and break of epidemic is reduced. § Land Requirement. The land requirement is very low which make the system economical. (for treatment & disposal) § Treatment. Proper treatment of sewage is possible to make the sewage suitable for disposal. The system has only disadvantage of wastage of water, which is used for making the sewage in liquid from (about 99.9% of sewage is water).

20. Design of Sewers Design sewer mean to find the diameter (size) and to scope (gradient) of sewer to carry the given amount of discharge providing a self cleaning velocity. · Velocity in Sewers. The deposition of solids in sewer is undesireable. The velocity of sewage in sewer should be such that there is not setting of solid in sewer for a wide range of discharge. The self cleaning velocity largely depended on the scope or gradient of sewer and the size of suspended solids in sewage and size of sewer and the material of sewer.

21. Minimum Self-cleaning velocities for varies size of sewers are: - Size of sewers (cm) 15 – 25 (30-60) > 60 Min S.C. velocity (cm/s) Self-cleaning velocity for some natural materials are: - Nature of Material Minimum Self Cleaning Velocity Angular stone 100 cm / sec Round pebbles 60 cm / sec Fine Gravels 30 cm / sec Course Sand 20 cm / sec Find sand clay 15 cm / sec

22. Generally the velocity in sanitary sewer shold not be less then 0
Generally the velocity in sanitary sewer shold not be less then 0.6 m/s (2 ft /s ec) and in storm sewer should not be less than 1.0 m/s (3ft/sec) because of high organic area. The upper limit of velocity in set by screening action of a sewage are depend on limiting of sewer. Some of savues are. Nature of Sewers Non Scouring Velocity (cm/s) Eether channel 60 – 120 Brick lined sewer 150 – 240 Cement line sewer 240 – 300 Stone ware sewer 300 – 450 Generally 2.4 m/s is set for sewers

23. Design flow in Sanitary Sewer: To find the design flwo in sanitary sewers the following steps are followed: - 1. Forcast the desing population (P) of the area. 2.Find the sewage flow per day by multiplying population with flow pe day per capita of sewage. The sewage is taken as (70 – 80) % of average water supply. If (8) is average per capita per day water consumption of water then Qavg = Average Sewage Flow = (0.7  0.8) x P x q

24. 1. Select a peaking factor (P
1. Select a peaking factor (P.F) to find the peak sewage flow according to WASA P.F = 4 (for discharge upto m3/sec) P.F = 2 (for discharge >= 5.66 m3 /sec) I.e peak discharge = Q peak = (P.F) (Qavg) Peaking factor M which is the ration of max rate of sewage to average flwo is M = or (22) / 4 + √P 2. Calculate the allowance for industrial and commercial sewage at a rate of 3734 m3 / km2 / day 3. Calcualte infiltration attendance of Cr = Min of average sewage flow as given by WASA Q inf = (0.05 – 0.1) Q avg

25. 1. find the desing sewage flwo by adding peak flow, industrial allowance and infiltration flow Q design = Q peak + Q ind + Q fil * Formula Used Normalyy Mannings’s formula is used for desing of sanitary sewer which is : - V = l / n (R)2/3 √S Where V = Velocity of sewage flow R = Hydraulicc radious S = Slope of sewer n = roughness coefficient the value of n depends on the type of lining of sewer. Some valuew of n are. n = 0.01 (for smooth pipe) n = (for brick masonry) n = (for stone masonry) n = (for earth channels)

26. Some other formula used for designed of sewage flow are  Chazy’s Formula V = C√ RS where C Chazy’s Constant  Kutter’s Formula for value of C C = ( /n /S) Where n = roughness cooefficient  Basin’s Value of C C = / C1 + K / √R Where K = constant depends on nature of sewer  Hazew’s William formula may also be used.

27. DESIGN PROCEDURE The following steps should be followed. 1
DESIGN PROCEDURE The following steps should be followed. 1. Calculate the design flow as already explained 2. Select value of self cleaning velocity and compute area of pipe (sewer) by A = Q / v and the diameter. 3. find the slope of sewer by Mannings formula. V = l / n (R)2/3 √S 4. Check the velocity it should be greater then minimum self cleaning velocity.

28. DESIGN OF STORM SEWER Storm sewer carried water produced as surface run off aduring and following a period of rainfall. All of the rainwater does not appear as surface runoff. Some water is absorbed by soil as infilteration and the remaining flow as surface runoff. The runoff and soil properties and direction of storm etc. To computer the design flow of a storm sewer the surface runoff must be found. Various formulae are used among while the rational formula is most widely used.

29. Rational formula. It was suggested by Lloyed Daview who related the storm flow to the following parameters. 1. Rainfall intensity (i) (mm/hr) or (inch / hr) computed from available data 2. The catchment area (A) 3. A coefficient representing the combined affect of ponding, perculation and evaporation. © also called runoff coefficient. The amount (volume) of which falls upon data (A) per unit time under a rainfall intensity (i) is Qm = iA And the design discharge for a storm sewage is Q = C * (Qppt) where C = runoff coefficient .: Q = CiA is the rational formula

30. The value of C for various soils are given in tables but the value of C is not constant and changes (increase) with increase in direction of rainfall as the infiltration decrease. For impervious soil C = 0.175(t)1/3 or C = t/(s + t) For previous singases C = o.3t / (20 + t) Where t = direction of rainfall in inimeter. For computer area the average value of C is C = (C1A1 + C2A2 + ……… CnAn) / EA Where A1 A2 are the catchment area with runoff coefficient of C1 C2 …. Cn and EA is the total area.

31. Time of Concentration: - It is a time required for max runoff rate to develop at a point in sewerage line. It is the time required for storm water to runoff the farthest point of the area to reach the point for which max run off is to be estimated. Time of conc. = Time of inlet + time of flow Time of inlet is the time required for water to flow over the surface of ground to the sewer inlet. It depends on size, shape and slope of area ranging from 3 min (paved surface) to 20 min (cities)

32. Time of Flow: It is the time taken by storm water to flow from one inlet to the other. It depends upon length, size and shape and smoothness of a sewers and id found as T = L/V where t = time of flow L = length of pipe(sewer) V =velocity of flow Importance. The importance lies in the fact that act of all storms ofequal frequency of occurance, the storm which have duration equal tot eh time of conc. Produces max flow in sewers. Duration less than conc time produces less flow max discharge.

33. SEWER APPURTENANCE
Sewer appurtenances are the devices in addition to conducts that essential to or assists on the proper operation of sewerage they consists of main holes, drop main holes, lamp holes, flush tank, street inlets, regulators, siphons, junctions, outlets, grease traps, pumping station Now we discuss some of then in details. a) MAIN HOLES: It is an opening connecting ground surface with a hole in the sewer for the purpose of permitting a man to enter and come out of the sewer as a mean of access for inspection and maintenance of sewer.

34. Purpose of maintenance: 1
Purpose of maintenance: 1. They are used to carryout inspection, cleaning and removing obstraction in the sewer line. 2. The allow flowing of sewer or changing the direction of sewer or alignment of sewer or both. 3. They allow the escape of unsccessable gares through perforatied covers and thus help ventilation of sewage. 4. They facilitate the laying of sewer line in conventional langthes

35. Location of manholes: 1. There is change in grades of sewer 2
Location of manholes: 1. There is change in grades of sewer 2. There is change in alignment 3. There is a change in size of sewer 4. At junction of two or more sewers 5. Manholes are also provided in straight alignment of sewers at regular interval, depending upon diameter of sewer. It ranges from 90m to 150m( )(e.g. 75m for 60cm, 120m for 90cm, 150m for 120cm)

36. Types of Main holes. Depending upon depth at which sewers are provided holes may be classified as:- a. Shallow Manhole (b) Normal Manholes (c) Deep Manhole a. Shallow Manhole. It is provided at shallow depth “75 – 90 cm” (2’ – 3’). It is provided at the beginning of branch sewer or at a point not subjected to heavy traffic. It is provided with a light cover at its top. It is also called inspection chamber.

37. b. Normal Manhole: It is provided in sewers at depth of 150cm heavy covers ot its top. It is usually of square shape. c. Deep manhole: They are provided in sewers at depth greater than 150 cm with heavy cover at top. The size is gradually increase and a facility for going down is provided.

38. Characteristics of a Good Manhole 1. It is structurally stable 2
Characteristics of a Good Manhole 1. It is structurally stable 2. It allows free flow of sewage in a smooth manner. 3. It should provide safety to workers. 4. The walls and floor of manhole should be impervious. 5. If the inlet and outlet sewers are of different sizes. The crown of sewers should be kept at same levels by slope. The invert (bottom) the water will back flow in smaller when the large is running full.

39. Components of Manholes: Every manhole consists essentially of following components. 1. Manhole cover and pane 2. Access Shaft 3. Walls 4. Working Chamber 5. Steps or ladder 6. Invert and Foundation.

40. Manhole Cover: A manhole is provided with a frame on top which is firmly embedded in pavement. A cover with (500-60)(20” – 24”) mm clear opening is placed on the top of frame. The weight of the frame (70-270) kg ( ) and should have an arrow in the direction of flow. Access Shaft. The portion if hole starting from cover and going towards the full dia (1-1.25)m of manhole is called access shaft which is in the shape of a cone. The height if a shaft ranges from (0.9 to 1.5)m

41. Walls. Walls of manhole may be made of brick, stone or R. C
Walls. Walls of manhole may be made of brick, stone or R.C.C of which brick wall are common. Min thickness of wall is 9” (230cm) for 4m deep manhole. The wall should be properly designed. Working Chamber. The lower portion of manhole with vertical walls is called W. C. it should be of such dia as to carryout different operation by an operator. The usual size is 1.25m. Steps or Ladder. Steps are provided for a man to go in or come out of the hole. They are made of cast iron and are laced at a vertical distance of ( mm) c/c.

42. Invert & Foundation. Bottom of manhole is made of concrete and is called invert. It is stopping towards the channel of channels, which are continuation of sewer lines. The channels are some time made of spl of sewer pipe. The channel depth should be equal to the dia, so that sewage don’t spread at the bottom of the manhole curves, change in direction, grades and junctions are provided invert. The invert and manhole sets on a sufficiently strong on R.C.C foundation.

43. b. Drop Manhole A manhole constructed to provide a cannel a high level branch sewer and low level main sewer with amount of disturbance. Purpose: there are tow main purpose of a drop manhole 1. It avoids unnecessary step gradient of branch surplus thus saving a large quantity if earth work. 2. it provides convenience of working in the main hole as the discharged from the branch sewer is near the bottom of the

44. Construction details A typical drop manhole is shoen in the adjoining figure which is very similat to the ordinary manhole. The only difference is that of vertical drop pipe of branch sewer. A pplug is provided at the point where branch sewer intersect the manhole so that branch sewer can be inspected and cleaned easily by removing plug the section of branch sewer between vertical drop manhole and manhole is called inspection arm. If the drop is less than 0.6m, it is achieved by a sloping sometimes instead of vertical drop a pipe indireda t 45o is called a ramp.

45. c. SEWAGE PUMPING STATION Nead of pumping
c. SEWAGE PUMPING STATION Nead of pumping. Pumping of sewage is required for:- 1. Natural slope is not available for transport of sewage by gravity flow. 2. There is some obstruction is passage of sewage flow 3. The receiving stream for sewage is higher than sewage outlet. 4. Gravity flow is desired in an above ground treatment plant. 5. The basement is locality are deep.

46. Components of Pumping Station: A place where pumps are located is called pumping station. A typical pumping station is shown in the figure having the following components: - 1. Bar screens 2. Wet well /sump well 3. Dry well / pump room 4. Motor Room 5. Other appurtenance

47. 1. Bar Screens. Sewage usually contains floating material; which must be removed prior to pumping, as they are dangerous to the pumps. This is done by bar screening at the inlet of wet well. 2. Wet Well. The sewage coming is first accumulated in a pit or well called wet well. It may be square, rectangular or circular in shape, and is made of masonry or concrete. The wall at inlet side is made sloping to prevent accumulation of solids. Two walls are after provided interconnected by gats for cleaning and maintenance operation. A manhole is provided on the top of it.

48. Chapter No. II

49. QUALITY OF SEWAGE
Sewage is the wask or foul water of a community conveyed by a sewer. It may be pure (domestic in origin) or it may contain some industrial and storm sewage. In order to know about the line of treatment, the composition of sewage must be known. The characteristics of sewage are determined by various tests. A typical composition of sewage is shown below. Sewage Water (99.9%) Solids (0.1%) Organic Solid (70%) Inorganic Solids (30%) Protien (65%) Carbohydrate (25%) Fats (10%) Salts Grits Metalic

50. Characteristics of Sewage Following characteristics / properties of sewage are foundduring the analysis of sewage. a. Physical characteristic b. Chemical characteristics c. Biological characteristics a. Physical Characteristics They include the colour, odour, turbidity, solids and temperature of sewage.

51. Colour. The colour of sewage shows the water it is fresh or septic (Stale). The colour of fresh sewage is varying from yellowish grey to light brown (earthy) while that of septic sewage is dark brown or black due to oxidation of organic matters. Odour. The smell of a fresh sewer is oily or soapy while the septic sewage develop and objectionable colour odour of H2O. special odours are imparted due to the presence of some industrial sewage

52. Turbidity. Turbidity is the indirect measure of suspended solids present in sewage. Sewage is very turbid in nature (cloudy) and contains reconizeable size such as fieces, greese, fruits skins, soap, match sticks, pias of fruit etc. Solids. Sewage contains a very small amount of solids (0.1%) and suspension and dissolved state. Roughly in 100 parts of total solid, 50 parts are in dissolved form, 25 parts are in suspension and 25 parts are in settleable stage.

53. The dissolved and suspended solids create the necessity of sewage treatment as they contain harmful constituents. There are two harmful effects of solids in water body where sewage is discharges: i. They obstruct light to reach the plant life with in the water body. ii. they obstruct also the free flow dissolved oxygen which is necessary for equatic life. Temperature. Temperature os sewage is slightly more than the temperature of ware because of the presence of industrial sewage. The temperature changes when sewage become septic because of chemical process. The lower temperature indicates the entrance of ground water into sewage.

54. a. Chemical Characteristics Sewage contains both organic and inorganic chemicals. The organic chemicals are present in carriage water while the inorganic chemicals are present in ware discharge into sewers or products of decomposition of sewage. They may be separated into fats, carbohydrates, proteins, acids etc. Nitrogen and phosphates may pollute water bur are also necessary in biological treatment process. The sewage in initially alkaline in nature but becomes acidic (buffered) due to the of inorganic bacteria. The pH is initially high and drops to the sewage becomes septic but increase again with the treatment process. The industrial sewage is unusual in its chemicals constituents. Sewage also contained various gares like H2S, CO2, CH4, NH4 etc which are formed due to the decomposition of organic matters present in sewage.

55. a. Biological Characteristics Domestic sewage contains enoumous amount of bacteria like other microorganisms such as algae, fungi, protozoa. The bacteria in raw sewage may be expected to range for to per ml. ther bacteria are responsible on the decomposition of complex compound to table compounds with the help of some intracellular & extra cellular enzymes. The bacteria in sewage sewage be either pathogenic or nonpathogenic, pathogenic bacteria comes discaers and originate from discharge of disease suffering people and animals. Also non- pathogenic bacteria are harmless to health The sources of bacteria are faecal matters(night soils) urine, industrial wastes, discharge from slaughteres houses, stables etc. depending this mode of action bacteria may be divided into the following three catergories.

56. 1. Aerobic Bacteria. They carry their activities in the presence of oxygen and die in its absence. 2. Anaerobic Bacteria. Those which works in the absence of free oxygen. 3. Facultative Bacteria. Those bacteria, which carries their activities in the present as well as absence of oxygen. The first two types are very important in treatment of sewage in W. W. T. P.

57. Aerobic Process Aerobic bacteria utilize free oxygen as an electron acceptor. The oxygen is present naturally, absorbed from atmosphere or supplied artificially in the form of air bubbles by aerator. The products of aerobic process are CO2, H2O, NH3, SO4-2, NO3- and some main bacteria. The energy is evolved as a heat or is consumed by the new cell masses and a stable effluent is resulted which do not undergo any further decomposition. The treatment units like oxidation pond, aeration tank, trickling filter, contact bed, intermittent filter, etc use the aerobic process.

58. Anaerobic Process (Putrefaration) Anaerobic bacteria oxidize organic matter utilized electron acceptance organics and more bacteria. The cell production is low because a large part weighd which give the colume of total solids and is expressed as mg per litre of sample.

59. b. Suspended & dissolved Solids Tests A known volume of sewage sample is taken and is passed through a filter glass filter of size about 1 micron. The residue on the filter is arid and weighed which given the amount of suspended solids. The filtrate is evaporated to dryness and the cut of the residue is calculate as the dissolved solids. If any two of the three (T.S, O,S,S.S) are known the third can be found for. T.S - S.S + D.S

60. c. Settleable Solids Test the suspended solids may be settle able and non settleable. The settleable solids are those which settles under gravity and are a rough measure of sludge removed by primary sedimentation tank. To fine the amount of settleable solids a cone shaped container called imhoff cone is used. The capacity of inhoff cone is 1 liter. The sample is put of the cone and is allowed for 60 min to stay. The settlesable solids goes to the bottom of the tank and is measured as volume at the bottom of the cone. To find the exact quantity the liquid is decented off and the solids at eh bottom are weighed. The sewage sample should be thoroughly mixed before test. It is usually expressed as ml/ml of sewage.

61. Biochemical Oxygen Demand (BOD) The amount of oxygen required by aerobic bacteria to decompose / stabilize the organic matter present in sewage at a standard temperature of 20oC for a period of 6 days. It is written as BOD or BOD205. BOD is the measure of organic matter of sewage and show the polluting strength of sewage. For domestic sewage 5 days BOD represents approximately 2/3 of demand for complete decomposition. Organic Matters + O  CO2 + H2O, etc

62. Importance of BOD. The BOD of sewage is very important to know because it tells use about. à The line a extent of treatment à Amount of dilution required for safe disposal à Efficiency of W.W.T.P and load of W.W.T.P BOD Lab Tests. There are various methods for daumination of BOD in lab. Special electronic portable instruments are available to determine BOD in the filled. There are two common laboratory method.

63. BOD Lab Tests. There are various methods for daumination of BOD in lab
BOD Lab Tests. There are various methods for daumination of BOD in lab. Special electronic portable instruments are available to determine BOD in the filled. There are two common laboratory method. 1. Direct Method 2. Dillution / Analytical Method In direct method the sample is kept in contact with a definite amount of air or O2 in a specially prepared vessel. The BOD is then measured manometrically. The dilution method is the most accurate and authentic method available.

64. Principle of BOD test. The BOD of a sample is determined from the different of dissolved oxygen at zero day and 5 day. The dissolved oxygen is determined by the fact the oxygen oxidizes Mn + to lighter state of valency in the presence of an alkali, which is capable of oxidizing I-1 to iodine (I2) under acidic condition. Thus the amount of free iodine released in equivalent to dissolved oxygen originally present. The iodine is measured with standard sodium thsulphate solution and is interpreted interms of D.O Mn (OH-)  Mn(OH)2 2Mn(OH)2 + O2  2MnO2 + 2H2O MnO2 + 2I-1 _ 4H+  Mn++ + I2 + 2H2O

65. Apparatus BOD Bottle, Pipette, Pipette filter, Incubator Titration app
Apparatus BOD Bottle, Pipette, Pipette filter, Incubator Titration app. Reagents: 1. Manganese Sulphate ml/sample 2. Alkali iodide azide (NaNo3 _ KI + NaOH) ml/sample 3. Conc. Sulphuric acid (H2SO4 conc.) ml/sample 4. Standard Sodium thiosulphate solution N 5. Starch Indicator mg/litre

66. Test Procedure: 1. Take tow BOD bottle and fill half with distelled water. 2. Add about 3ml of sewage to each with held of pipette and filter to get diluted sample. 3. the bottle are then filled with dustilled water completely and the stopper are fixed and the excess water is spilled 4. one bottle is placed in the incubator for 5 days at a controlled temperature of 20oC 5. to other BOD bottle add 2ml of MnSO4 with help of pipetter and filter.

67. 1. About 2ml of alkali iodide azide solution is added to this which changes the colour to brown, indicated the presence of O2. 2. add 2 ml of conc. H2SO4 and shake which changes its colour to that if mustered oil (clear brown) 3. take 200 ml of this in a conical glass and add 1ml of starch indicator to it which changes its colour to black. 1. the flash is placed below burette containing standard sol. of sodium thiosulphate and titrate until the colour disappears

68. 1. the reading of buretter shown the value of dissolved oxygen (D
1. the reading of buretter shown the value of dissolved oxygen (D.O) at zero day. 2. After 5 days the dissolved oxygen of other sample is found in the same way. 3. Determine the BID in mg/l from the formule. BOD (mg/l) = Less of oxygen * dilution factor = ((DO)0-(DO)5) * (volume of BOD bottle/ Volume of sewage used) = ((DO)0-(DO)5) * 300

69. Precautions. The dilution water shouled be carefully manufactured
Precautions. The dilution water shouled be carefully manufactured. It should contain a mixture of salti providing all track mutrients necessary for a biological activity plus a phosphate buffer to maintain a nutral PH. This water is aerated with oxygen before mixing it with the sewage to saturate it with O2.

70. Draw backs 1. The test only measure biodegrable organics 2
Draw backs 1. The test only measure biodegrable organics 2. it required large time of 5 days 3. this test was designed by British Royal Commission of Sewage Disposal assuming rivers taking less than 5 days to reach sea, which is not the situation in Pakistan 4. The toxic element should be pre-treated which change the results. 5. the stoiosiometric validity is last after to soluble organic the fully utilized.

71. BOD Removal Kinetics The rate at which the organic materials are oxidize by bacteria is a fundamental parameter in the design of biological plant. It has been found experimentally that the rate of organic removal (exertion of BOD) can be considered to approximate into first order kinetic i.e. rate of organic removal (BOD removal) at any time is proportional to amount of organics (BOD) present is the system Mathematicaly dL/dt –L  dL/dt = -KL – O Where L = BOD at any time t and K = first order reaction rate contant for BOD removal also

72. called the deoxidization constant expressed as 1/sday (day-1)
called the deoxidization constant expressed as 1/sday (day-1). It Lo is the BOD at t = 0 and Lt is the BOD at any time at then integrating e Eq 1.

73. This equation is called after BOD model
This equation is called after BOD model. If a graph is draw b/w Lt and t we get a curve as shown. Now to find the BOD removal at anytime (t) Yt = (BOD)t = (BOD)uit – (BOD) present/removing Yt = Lo – Lo exp (-Kt) = Lo (t – exp(-kt))

74. DEOXYGINATION CONSTANT (K) The value of K depends upon the temperature of sewage. It value at 20oC are K20 = 0.23 for natural log system (bae = 0.10 for log with base 10 It value at any temperature T can be computed as: KT = K20(Q) (T-20) Where Q is a contant called arhinious constant and its unit is: Q = when T > 20oC Q = when T < 20oC The ultimate BOD at any temperature T is (Lo) = (Lo)20 (0.02T + 0.6)

75. CHEMICAL OXYGEN DEMAND (C. O
CHEMICAL OXYGEN DEMAND (C.O.D) The COD test determine the amount of oxygen require for chemical oxidation of the organic matter by using a strong oxidizing agent. This test is important because the BOD test required very much time (5 days minimum) while COD requires only two to three hours (2-3) and given a good picture of organic matters and some inorganic matters. The value of COD is like than BOD (almost amble) because of oxidation of materials such as facts and linings, which are only slowly biodegrable

76. Procedure: A measured amount of potassium di chromate (K2Cr2O7) is added to the sample in the presence of sulphuric acid and is boiled for 2 hours. It is then cooled and the amount of K2Cr2O7) is remaining is measured by titration with ferrous ammonium sulphate. The dichromate gives a measure of O2 required for oxidation of organic matters.

77. PROBLEMS

78. SEWAGE TREATMENT
Sewage treatment is the combination of physical and biological processes with chemical processes occasionally applied additionally to bring the sewage to such a quality such that it is not harmful to human health and environment. Some of these processes are as follows: -

79. 1. Physical Process / Operations. a. Fereaning b. racking c
1. Physical Process / Operations. a. Fereaning b. racking c. Comminution d. Grit Removal e. Primary Sedimentation f. Secondary or final sedimentation 2. Biological Processes a. Attached Growth Process (1) Contact Beds (2) Intermittent Filter (3) Tackling Filter b. Suspended Growth Processes (1) Oxidation ponds (2) Activated Sludge Process (3) Aerated Lagoons (4) Stablization Process

80. 3. Chemical Processes a. Removal of Pathogens by chlorination distifaction b. Removal of typical wastes of some industry

81. OBJECTIVES OF TREATMENT The sewage is treated before its final disposal because of following resons / objectives: - a. To kill pathogenic bacteria present in sewage which may result in water bom disease like cholera, typhoid, dyserity etc. b. To avoid unhygienic condition in the area because of highly fouled sewage. c. To protect aquatic life from harmful effect of sewage directly discharge in the water body (river or sea)

83. c. Grit Removal Grits are heavy inorganic solids such as sand, metal fragments. Egg shells of sp gravity ranging from 2 – they come excessive wear during different treatment stages and therefore must be removed. From newtons’s law of sitting velocity: For particles S with Sp. Gravity 2.65 and size 0.2mm Vs = 2.1cm/s Vh= 23 cm/sec The sewer velocity for organic solids with sp gr =1.1 Vh = 5.6 cm/sec Thus the grid chamber should have following characteristics

84. 1) Surface overflow rate (sitting velocity) is 2
1) Surface overflow rate (sitting velocity) is 2.1cm/sec 2) The horizontal velocity should be greater then 5.6 and less then 23 cm/sec 3) To assure clean removal of grit Vh should be near 23 cm/sec 4) Length for chamber is governed by tragectry of slowest sitting psrticle and velocity of flow. 5) Detertain period is 1 min and the grit removal capacity is l/106l 6) Min depth of tank is 30 cm and length is 16 time depth

85. Grit Disposal Grit of a properly designed and operated chamber is free from organic matter which may be used as landfill. If grit contain organic in high proportanat it is designed by burial of work as a measure. * A grit chamber may be horizontal flows vertical flow and manually, hydraucillay of mechanically cleaned . standby units are supplied for emergency.

87. d. Detritious Chamber They are installed to remove fewer partices which are left by grit chamber. They have a depth of (2.5 – 3.5) m with a detention period of (3-4) min and flow velocity of (20-40) cm/sec e. Skimming Tank It is used to seprate grease and other floating matters which may adversely effect the efficiency of treatment facilities. Grease may tends to plug trickling filters and coat the biological flow in the activated sludge process. The skimming are rectangular, eluptical or circular in shape and design in such a way to reduce organic sections. The floating matters may be collected by continuous mechanical processes or by hand manually. They have buffered entrance & submerged out let.

88. Design Criteria. Horizontal Velocity (5-25)cm/sec (ro period deposition of organic) Retention Time <= 15 min (steel) Depth of tank = 1m

89. B. PRIMARY TREATMENT Primary treatment is a plain sedimentation process to remove suspended organic solids from the sewage. Chemicals are sometimes used to remove timely devided and collided solids or to precipate phosphorous. The purpose of primary treatment is: -

90. 1) To reduce the strength of sewage to the extent of (30- 55)% 2) To remove settleable solids by (80-90)% 3) To reduce BOD by (30-35)% 4) To make the sewage fir for further treatment process 5) To prevent closing of filters.

91. Primary sedimentation tank also called primary clarifier located just after grit chamber. It may be of rectangular, circular or square shape. The principle and construction details are same as that of plain sedimentation tank of W.T.P. some design specification of primary sed. Tank are: -

92. 1. Hydraulic loading rate (surface over flow rate) sitting velocity
1. Hydraulic loading rate (surface over flow rate) sitting velocity. Vs = (0.3 –0.7) mm/sec (1-2.5 m/hr) 2. Detention time / retention time td= (1-2) hours 3. From sitting velocity and detention time the depth of tank ‘s’ D = (1-5)m (3’ – 16’) 4. BOD removal (20-40)% 5. Suspended solid removal (30-60)% 6. Mon no of tank provided = 2 7. Sewage accumulation = 2.5 kg of wet solids / m3 of flow 8. Design formula Vs = Q/As Vs=8/18v (

94. For rectangular tank L:B = 4:1, average depth =3
For rectangular tank L:B = 4:1, average depth =3.5 m bottom slope 1:12 towards sewage accumulation (usually % of seprate speed.

95. C. SECONDARY TREATMENT The secondary treatment is required to remove the sollubel and collidal organic matters which rmain after primary treatment. As it is mostly a biological prouis also called biological treatment. In this treatment the bacteria present in sewage (and other microorganisms) are allowed to use the organic matters as their fod and oxidize them to stable compounds like water, gases (CO2, NH3, CH4, H2S, etc) and new cells. The process may occur naturally at slow rate, biological treatment is done to inuse the rate of reaction by having a large no of organisms in a small container.

96. There are two types of process in biological treatment of sewage. a
There are two types of process in biological treatment of sewage. a. Attached Growth Process b. Suspended Growth Process

97. a. Attached Growth Process They are biological treatment processes in which microortanisms responsible for the conversion of organic matters in waste water to gases and celltissue are attached to some inert medium such as rocks, slages, specially designed plastic materisls etc. they are also called fixed file processes. The efficiency of these process depends on the area of inert material available for growth. Some of process are 1. Contact beds, 2. Intermittent sand filter, 3. Trickling filter, 4. Rotating biological contactor

98. a. Suspended Growth Processes They are biological treatment process in which microorganisms responsible for the conversion of organic matters to gases and new cells are kept in suspension naturally or mechanically. Ex 1. Activated sludge process, 2. Aerated Lagoon, 3. Oxidation Ponds, 4. Sludge digestion system, etc. In the following para we discuss some of the biological treatment process which are very important.

99. TRICKLING FILTER Trickling filters also known as percolating or sprinkling filter is like a well having depth upto about 2m and filled with some granueller media. The sewage is sprinkled over the media which percolates through filter media and is collected by cinder drainage system. The first T.F was developed in England in 1893 int eh form of contace beds or contact filters which were water tight basin filled with broken stone. The sewage was allowed from top and contact with the filter media for a short time. The bed was then allowed to drain and allowed to rest before the cycle was repeated. E.g. for a cycle of 12 hours, 6 hours are used for operation and 6 hours for resting and old T.F have the flowing limitations.

100. 1. Relative high incidence of cloggings 2. Long rest period 3
1. Relative high incidence of cloggings 2. Long rest period 3. Relatively low and slow loading rate MODERN T.F. To overcome the above drawbacks a T.F was introduced having of bed of highly permeable dta to which microorganisms were attached and sewage perculated or trickles and hance the name T.F. the filter media consists of rocks. Varying in size from (25-100mm) (1” – 4”). The depth of rock varies from 0.9 – 2.5m (3’-8’), avenging 1.8m(6’). A rotating arm (distributing) is provided of blocks or half round type tiles. The air is also provided through under drainage system for ventilation of filter.

101. WORKING: The settled sewage for P. S
WORKING: The settled sewage for P.S.T is sprinkled intermittently over filter body to allow absorption of air during stoppage period. When sewage trickled down a microbial layer developes on the surface or rock which is called sline layer, which is moistly consisted of bacteria. The sewage is oxidize by the bacteria producing effluent in the form of water gases and new cells. Setteled Sewage + Oxygen  Oxidized effluent _ Biomass As the process grows on, the microbial filter grows, the internal layer of bacteria come upon a shortage of food and thus die. Some off the bacteria in slime layer are thus wasted away due to the hydraulic action of flowing water. These cells exert a high BOD of sewage and must be removed before the effluent is finally discharged.

102. RECIRCULATION:. To increase the loading rae of T
RECIRCULATION: To increase the loading rae of T.F the sewage is recirculated by pumping. Some of recirculation flow diagram are shown below:

103. The recirculation changes from plant to plant about 14(steel) the procedure has no effect so the efficiency of T.F. Recirculation has following advantages. 1. It allows continous dosage regardless of fluctuating on sewage flow and thus keep the bed working. 2. It dilutes the influent with better quality water and thus making it fresh and reduces odour. 3. It increase the biological solids in the system and continous seeding with sloughed (removed) solids. 4. It maintain a uniformrate of organic & hydraulic loading. 5. Ir removes worn out films thus reducing film thickness and reduce filter fly problems.

104. 1. It increase the efficiency by reducing the BOD bed, generally
1. It increase the efficiency by reducing the BOD bed, generally. Note always efficient if sewage is already diluted. * Recirculation ratio range as form 0.5 – 1.0 but commonly by (0.5 – 13) are used.

105. DESIGN OF T.F. T.F is usually designed by NRC (National Research Council) formula which is based on the data collected at military basis with in U.S in world war-II. It may apply to single stage and double stage T.F. For a single stage T.F or for first sage of a 2 stage T.F. (Ci – Ce)/Ci = 1/( √Qci/Vf) where Ci = influent BOD in mg/l Ce = effluent BOD in mg/l Q = flow of sewage in m3/min V = Volume of filter in m3 F = recirculation factor = 1 + r / ( r)2

106. Where r is the ration of recirculation flow to sewage for R = Qr /Q For 2nd stage of two stage T.F (Ce-Ce’) = 1/( /1-(Ci+Ce/Ci) √QCe/V’f’) where Ce’ = effluent BOD from 2nd stage V’ = volume of end stage filter F’ = recirculation factor of 2nd stage

107. HYDRAULIC LOADING RATE: The ratio the raw sewage flow to the surface area of the T.F is called hydraulic & loading rate or surface overflow rate denoted by Vs or Vp. For zero circulation rate Vp = Q/As (m3/me/day)