chapter-4- Water Carriage Sanitation System

Introduction to water carriage sanitation system. This is a lecture PPT presentation on water carriages sanitation systems

1. CHAPTER - 4 INTRODUCTION TO WATER CARRIAGE SYSTEM By Tesfay T.

2. Introduction Sewer is an under ground pipes or conduits which carry sewage to points of disposal. Sewage is the mainly liquid waste containing some solids produced by humans which typically consists of; Washing water Faeces Urine Laundry waste Other material from household and industry Sewerage system: is the entire system used for collection, treatment and disposal of Liquid waste. This includes pipes, manholes, and all structures used for the above mentioned purposes.

3. Sanitary engineering mainly concerns with the cleanliness of the cities. The sanitary engineering activities at any projects may be divided into four stages, namely: Collection Conveyance Treatment and Disposal of solid and liquid waste Conti…..

4. Types and sources of wastewater Two main categories: 1. Sanitary Wastewater (Dry-whether flow) Wastewater from residential, commercial, institutional and industrial sources. 2. Storm water Runoff (Wet-whether flow) Wastewater resulting from rainfall running off streets, roofs, and other impervious surfaces. Conti…..

5. Water carriage system In this system, the waste water is carried with the help of water through underground pipes (sewers). Water Carriage system may be divided in two: Sewerage Systems Septic Tank Types of Sewerage Systems These are broadly classified as follows Separate system Combined system Partially separate system

6. 1. Separate system Provides two separate systems of sewers , one for the conveyance of sanitary or dry weather flow, and the other for rain water runoff.

7. cont’d…. Conditions to Adopt Separate System Flat topography and Hard subsoil condition. Limitations of available fund. Uneven Rainfall:- not all year round but concentrate for a short period. Appropriate when a centralized treatment facility is available. Separate Outlets for sewage and storm water. Pump requirement to lift sewage. Gradient of sewer.

8. Cont’d…. Advantages Size of sewers are small Sewage load on treatment plant is small. River or stream waters are not polluted Storm water can be discharged into streams or rivers without any treatment In case pumping of sewage is required it is economical D isadvantages Sewers being small, difficult to clean, likely to choke frequently Maintenance cost is more because of two sewers. Storm water sewer used only in rainy season – can be dumping place of garbage in dry period and get choked . In busy lanes laying of two sewers is difficult.

9. 2. Combined system P rovides only one sewer to carry both the dry weather flow as well as the rain water runoff to a centralized treatment facility .

10. cont’d….. Suitable Conditions for Adopting Combined Sewer Rainfall continues evenly throughout the year. Restriction of space, when area is restricted combined system is desirable. If an existing storm water sewer is to be converted into combined sewer; and if only if sanitary sewage is small compared to that of rainfall. Appropriate when both sanitary and storm water need treatment.

11. Cont’d….. Advantages Large sewer size; easy to clean and less probability of choking Strength of sewage is reduced due to dilution of sewage by storm water. Reasonable maintenance cost The system requires only one set of sewer making economical D isadvantages Load on treatment plants unnecessarily increased due to storm water. Overflow of sewers during heavy rain may create unhygienic condition. In dry season it becomes difficult to maintain proper flow as the sewers are large. Unnecessary pollution of storm water. Uneconomical when pumping is needed

12. Single sewer laid but in small rain period it is used for both but as amount of storm water is increased storm water is collected by open channel and drained to river or stream. Thus, the load on the treatment plant is controlled and kept within the capacity of the treatment plant. 3. Partially separate system Advantages Size of sewer not very large since it takes only part of storm water. Combines advantages of the two systems (Separate/Combine) No silting problem. Problem of disposing of storm water from residence is simplified. Load on TP is controlled and kept within the capacity of the TP. D isadvantages Flow velocity may be low during dry period. Storm water increases load on treatment plants and pumps. There are possibilities of over-flow.

13. WASTEWATER QUANTITY ESTIMATION Why we need to measure wastewater flow? Key issues:

14. Estimating Quantity of Dry-weather flow The sewage discharge which has to pass through a sewer must be estimated as correctly as possible; otherwise the sewers may either prove to be inadequate , resulting in their overflow, or may prove to be of too much of size, resulting in unnecessary wasteful investments. The quantity of sewage affected by the following factors: Rate of water supply Population growth Types of area to be served (industrial, commercial, residential,…) Infiltration/exfiltration of ground water to sewers.

15. WASTEWATER QUANTITY ESTIMATION Generally, The remaining 20%-25% is quantity of water which do not join the sewer system. They includes: The water used for drinking Water used for clothe washing-evaporated during drying Water used for sprinkling and gardening of roads, parks gardens and others. Variation in rate of sanitary sewage Rate of sewage flow is not constant. It varies hour to hour, day to day and season to season. Therefore , maximum and minimum flow should be considered during design of sewer pipes , it should have the capacity to carry max. flow and there should be no deposition in the sewers at min. flow.  

16. Flows Water demand Sewage produced 0 4 8 12 16 20 24 Time in hours Generally the waste water discharge curves closely parallel the water consumption curve but with time lag of a few hours. Conti….

17. When rain fall takes place, apart of it infiltration or peculate into the ground surface which the remaining flow over the ground depend up on permeability of the ground, its surface condition. The amount of water flowing over the ground surface, pavement, house roofs… is commonly called Run off or Storm water flow. The quantity of storm water is affected by: Catchment area Slope of the catchment area Permeability of the ground Intensity of the rainfall Duration of the rainfall Compactness of catchment area climatic conditions Estimating the Peak storm water Discharge

18. Generally quantity of storm water can be estimated either by Rational method or Empirical formula Rational method: Most commonly used method to estimate quantity of storm water Q = quantity of run off water in m 3 /s A = drainage area in hectares I = Intensity of rainfall in mm/ hr C = Coefficient of run off The method is useful for smaller catchment up to 400 hectares   Estimating the Peak storm water Discharge

19. Estimating the Peak storm water Discharge a) catchment area the drainage surface area in hectares, measured in a horizontal plane. b) Runoff coefficient T he impervious factor of runoff , and the ratio of runoff to precipitation . The value of C increases as the imperviousness of the area increases.

20. WASTEWATER QUANTITY ESTIMATION A.A, Gurdi -shola area, August 6, 2014 Adi-haki sub road

21. Estimating the Peak storm water Discharge Hydrologic Response-Pre- Development 45 - 50% Recharge 10-15% Runoff 40% Evaporation

22. Hydrologic Response-Post- Development 30 % Evaporation 55 % Runoff 15 % Recharg e 10% or greater impervious cover enough to impact stream channels Estimating the Peak storm water Discharge

23. Estimating the Peak storm water Discharge If a given catchment area consists of various types of surfaces for which different runoff coefficient applicable , then the average runoff coefficient is calculated as:

24. Table 1: Values of Run-off coefficient (C) for various Surfaces Conti….

25. c) intensity of rainfall (I) Expressed in cm/hr is the rate at which the rain falls in cm during particular time. The value of I can be determine from the IDF curve using time of concentration( t c ) & frequency of the storm . Conti….

26.   Conti….

27. Estimating the Peak storm water Discharge

28. Time of concentration the time it takes for runoff to travel from the most hydraulically distant point in the catchment to the outlet. Time of concentration is made up of Inlet time or overland flow time - Time taken for rain water to run over roof and road surfaces etc. along gutters, channels and drains prior to reaching sewer Estimating the Peak storm water Discharge where Ti – inlet time, hrs L = length of overland flow from the critical pt to the entrance of the drain, km H = total fall of level from the critical point to the entrance of the drain in metres

29. Channel flow time or gutter flow time - Time of flow through sewers to point at which rate of flow is assessed Difference between the two: Inlet time has to be estimated or found by experiments, being dependent upon unknown factors Channel flow time can be calculated to a reasonable degree of accuracy , being dependent on gradient and hydraulic mean depth of the sewers. Where; L = length of the drain V = velocity in the drain T C = T i + T f Conti…..

30. For example, at inlet point number 7 in the figure below, the various flow times to that point are as follows: Cont…..

31. Estimating the Peak storm water Discharge II. Empirical Formulae For the design of drains having larger catchments (say above 400 hectares or so), Various empirical formulas have been suggested by various investigators; based on local conditions only , and can be adopted only when certain specific requirements are specified. i) Burki -Ziegler formula (earliest and developed by a Swiss Engineer) Q = 296 CIA (S/A) 1/4 ii) McMath’s formula (USA/St Luis local condition Q = 292 CIA (S/A) 1/5 iii)Fannings formula Q = 3125 A 5/8

32. The drainage area of one sector of a town is 12 hectares. The classification of the surface of this area is as follows : If the time of concentration for the area is 30 minutes, find the maximum runoff. Example #1

33. Example #1 Use to calculate rainfall intensity. Where, i is the rainfall intensity, generally expressed in mm/ hr and t is the concentration time in minutes. Solution: Using rational formula, we have First average C value = 0.4425 Then i value, = 1cm/ hr = 0.1475m 3 /s  

34. Example #2  

35. Example #3 A storm drain system consisting of two inlets and pipe is to be designed using rational method. A schematic of the system is shown. Determine the peak flow rates to be used in sizing the two pipes and inlets. Rainfall intensity (mm/hr) as a function of t is:

36. Conti…. Area A and B contribute to inlet-1 Take largest tc = 12 min A = 10+9 = 19 hectare C = ((10*0.2)+(9*0.3))/19 = 0.25 I= 30/(12+5)0.7 = 4.13mm/hr Q = CIA/360 = 0.25*4.13*19/360 = 0.055m3/sec.

37. Conti….. Size Inlet 2: Flow from area C contributes Take tc = 8 min A = 8Hecr C = 0.4 I = 30/(8+5)0.7 = 4.98 mm/hr Q = CIA = (0.4*4.98*8)/360 = 0.0443 m3/sec

38. Conti….. Size pipe 2: Flow from all areas Take tc = 12+1 = 13 min A = 10+9+8 = 27 Hectares C=(10*0.2+9*0.3+8*0.4)/27 = 0.29 I = 30/(13+5)0.7 = 3.97 mm/hr Q = CIA/360 = (0.29*3.97*27)/360 = 0.0865m3/sec

39. Hydraulic design of Sewers The hydraulic design of sewers and drains , means finding out their sections and gradients, is generally carried out on the same lines as that of the water supply pipes. However , there are two major differences between characteristics of flows in sewers and water supply pipes.

40. The water supply pipes carry pure water without containing any kind of solid particles, either organic or inorganic in nature. The water supply pipes carry water under pressure , and hence, within certain limits, they may be carried up and down the hills and the valleys. To avoid silting of sewers, it is necessary that the sewer pipes be laid at such a gradient , as to generate self cleansing velocities at different possible discharges. The sewer pipes carry sewage as gravity conduits , and are therefore laid at a continuous gradient in the downward direction up to the outfall point, from where it will be lifted up, treated and disposed off. Conti.....

41. Freeboard in Sewers Sanitary sewers are designed large enough to carry the maximum sewage discharge while flowing half full for sewers less than 0.4m dia. two-third for sewers between 0.4m to 0.9m dia. or three fourth full for sewers greater than 0.9m dia. The main reason that why we are provided free board is; - Low estimates of flows made due to wrong data obtained - Large scale infiltration of water from underground through cracks or open joints in sewers. -Unforeseen increase in population or water consumption and the consequent increase in sewage production.

42. Flow velocity in the sewer Chezy’s formula Constant (C) is very complex. Depends on size, shape and smoother roughness of the channel, the mean depth etc. C can be calculated by using Bazin’s formula. where V=  is the mean velocity [m/s], C= i s the Chézy coefficient [m ½ /s], R= is the hydraulic radius (~ water depth) [m], i= i s the bottom slope[m/m].

43. 2. Bazin’s formula Where, K= Bazin’s constant R= hydraulic radius C   = 157.6[1.81 + ( K / R 1/2 )] Sr. No. Inside nature of the sewer K values 1. Very smooth 0.109 2. Smooth: bricks & concrete 0.290 3. Smooth: rubble masonry 0.833 4. Good, earthen material 1.540 5. Rough: bricks & concrete 0.500 6. Rough earthen material 3.170

44. 3. Manning’s formula 1885 V = velocity of flow (m/s) n = Manning coefficient  R = hydraulic radius (m) S = slope of the water surface * The value of “n” is calculated by kutter’s formula

45. 4. Kutter’s formula Where C = Chézy's roughness coefficient   S = Friction slope   R = Hydraulic radius (m,)   n = Kutter's roughness (unit less)   k 1 =Constant (23.0 SI,)   k 2 =Constant (0.00155 SI,)   k 3 = Constant (1.0 SI,)

46. 5. Hazen – William’s formula where: V is velocity k is a conversion factor for the unit system k = 0.849 for SI units) C is a roughness coefficient R is the hydraulic radius S is the slope of the energy line (head loss per length of pipe )

47. 6. Crimp and Burge’s formula Where, V = 83.47 R 2 / 3 S 1/ 2 V = velocity of flow (m/s)  R = hydraulic radius (m) S = slope of the water surface

48. Minimum Velocity The flow velocity in the sewers should be such that the suspended materials in sewage do not get silted up; i.e. the velocity should be such as to cause automatic self-cleansing effect. The generation of such a minimum  self cleansing velocity   in the sewer, at least once a day, is important, because if certain deposition takes place and is not removed, it will obstruct free flow, causing further deposition and finally leading to the complete blocking of the sewer.

49. Self clearing velocity To calculate minimum velocity of flow following formula is used. V= where, V= minimum velocity of flow in m/s. k= size of solids in sewage varying between 0.06mm f= Darcy’s coefficient of friction (normally 0.03)

50. e s = Void ratio of solid material flowing in sewage, varies between e= Void ratio of liquid in sewage g= gravitational acceleration cont. d s = dia of solid particles in mm

51. Maximum Velocity The smooth interior surface of a sewer pipe gets scoured due to continuous abrasion caused by the suspended solids present in sewage. It is, therefore, necessary to limit the maximum velocity in the sewer pipe. This limiting or non-scouring velocity will mainly depend upon the material of the sewer .

52. Hydraulic element of Circular Sewer Circular sewer sections are the most widely used. The advantages of circular sections over all other shapes should be: They can be manufactured most easily and conveniently A circular sewer provides the maximum area for a given perimeter, and thus providing the maximum hydraulic mean depth when running full or half full, and hence the most efficient section at these flow conditions. the cheapest and most economical . A circular section, being of uniform curvature all round , offers less opportunities for deposits

53. A) A circular sewer section running full Cross sectional area: Wetted perimeter: Hydraulic mean depth: Velocity of flow: Discharge: Q= AV D

54. B) Circular sewer section running partially full Depth at partial flow Proportionate depth ; cross sectional area: proportionate area: wetted perimeter : proportionate perimeter: hydraulic mean depth : d D θ

55. proportionate HMD: velocity of flow: proportionate velocity: assuming roughness coefficient n doesn’t vary with depth: Discharge: q = a.v Proportionate discharge:

56. Table:1 Proportionate Values of Hydraulic Elements for Circular Sewers when flowing partially full

57. Table 2: Hydraulic Particulars of Circular Sewers, accounting Variations of n with depth

58.   Example #1

59. Conti…..

60. Example #2 Design an outfall circular sewer of the separate system for a town with a population of 100,000 persons with water supply at 180litre/head/day . The sewer can be laid at a slope of 10 in 10,000 with n=0.012 . A self-cleansing velocity of 0.75m/sec . is to be developed. The dry weather flow may be taken as 1/3 of maximum discharge. Solution: Population = 100,000 Average rate of water supply = 180 liters/person/day 1st: calculate quantity of sewage, Q, assume 80% of water supply released as waste water,

61.   Conti…..

62.   Conti…..

63. Conti…..

64. Sewer Appurtenance Drop manhole Lamp hole Catch basin Manhole Street inlet Grease and oil trap Flushing tanks Inverted siphon Ventilating shaft Storm regulator

65. Manholes are openings on the sewer line through which one can enter the sewer line and make necessary inspection and repairs. Placed at changes in: • direction • pipe size • grade and elevation • at junctions • at intervals of 90 - 150 m

66. Street Inlets or Gullies Inlets are gullies or openings on the road surface at the lowest point for draining rainwater from roads , and admitting it into the underground storm water sewers (drains) or combined sewers.

67. Septic Tank is a combined sedimentation and digestion tank , where sewage is held for some period (years) and the suspended solids settle down to the bottom.

68. Septic tanks are constructed of brickwork, stone masonry, or concrete or other suitable materials Concert or steel cover should be provided on the top of septic tank. Manholes should be provided in the cover for inspection and cleaning of the tank. A vent pipe should be installed for the discharge of gases away from the houses . The length of the tank should be kept 2-4 times its width

69. Schematic of conventional septic tank Inspection opening 150 mm diameter Inlet At least 75 mm At least 20mm Access opening near side wall at least 600 mm diameter Inspection opening 150 mm diameter Liquid level 20% of Liquid depth Water line 40% of Liquid depth Scum clear space (75 mm, minimum) Sludge clear space (300 mm, minimum) 20% of Liquid depth (150 mm, minimum) Scum Clear space Sludge Sludge Outlet 40% of Liquid depth Liquid depth First compartment 2/3 length second compartment 1/3 length Total length equals two to 3*width

70. Conti…..

71. Conti….. Advantages Gives the users the convenience of a WC. They are best suited for isolated rural areas, and for isolated hospitals, buildings A proper functioning septic tank can considerably reduce solids and BOD from sewage Disadvantages High cost. Reliable and ample piped water required. Only suitable for low-density housing. Regular de- Sludging required and sludge needs careful handling. Permeable soil is required.

72. Design of septic tank

73. Table 1: Recommended infiltration capacities

74. Table 2: Sludge accumulation rates ( litres per person per year)

75. Table 3: Value of the sizing factor F

76. Example-2 Design a septic tank for a household having five occupants in a medium density housing area in which the houses have full plumbing . Only WC wastes go to the septic tank , and paper is used for anal cleaning . The ambient temperature is more than 10°C throughout the year. Design also soak pit away required in porous silty clay to dispose of the effluent from the septic tank.

77. CHAPTER – FIVE NON-WATER CARRIAGE SANITATION SYSTEM

78. Old and outdated system of disposal. Mostly used in villages / undeveloped urban areas. Night soil stores on site by providing different latrine.

79. 1. Open defecation

80. 2. Simple Pit Latrine

81. Chapter 6 Water supply and urban drainage project preparation

82. Water supply project preparation Data collection Geological data Hydrological data Sanitary conditions of the area Topography of the area Legal data of lands Public opinion

83. Factors to be considered Population Per capita requirement Public services Existing water supply Sources of water Conveyance of water Quality of water Treatment works Pumping units for treated water Reservoir Distribution system Economy and reliability

84. Project Drawings Topographical map. Site plan Contour map Flow diagrams. Detailed drawing

85. 102 Project Estimates The cost of various parts of the water-supply schemes may be taken approximately as follows for guidance. Item Cost of the item expressed as percentage of the total scheme pumping stations 18% reservoirs 6% treatments plants 10% distribution system 50% intake and water works buildings 2% supply 9% water meters and other contingencies 5%

86. Water supply project report the project report should deal with the following points Introduction (General Background, Objective, Scope of the Guideline, Review of previous guidelines, Structure of the guideline ). Service Area and Target Years (phasing and Economic lives) Target Population (Base population, growth rate and projection method) Water Consumption Analysis (Domestic water demand, non-domestic water demand, unaccounted water, variations of water use) Water Sources , Adequacy, Reliability and Quality

87. 104 cont….. Design of water supply facilities (Intakes, treatment plant design, transmission mains and collector lines, distribution networks, pipe material selection, alignment and depth of pipelines, hydraulic design of pipelines) Reservoir sizing (service reservoir, transfer reservoirs) Auxiliary Buildings Electromechanical design (pumps, generating sets, transformers) Contents of the design report Standards and specifications, bill of quantity (works, materials) Environmental impact assessment Mitigation results  how to reduce the risk Tender document preparation

88. Preliminary studies for the design of conventional sewerage system Contour maps, and longitudinal profiles. Geotechnical investigation( type of soil). Hydrological investigation( water table). Metrological data( rain,….). Detailed map of the area showing streets, buildings, levels of buildings entrance … etc Detailed cross section for the streets showing the underground service (water pipes, electricity cables, gas pipes, telephone,…..). Water supply and consumption study. Identification of industrial, commercial institutional and domestic areas. Identification of collection points of sewage and possible locations of pumping stations and point of final collection. Population forecast studies. Expected Development of the area (Master planning)

89. Chapter 7 Software's For Water Supply And Urban Drainage Projects

90. Water supply network modeling Water distribution network schematization Demand allocation Enter required input data Control system (pump, valve and reservoir) model analysis Decisions to be made (pressure and velocity)

91. Soft ware used for water supply system Arc GIS and Auto CAD integrated with water software to prepared the input data Epanet Water cad Water Gems V8i Water Cad v8i Ky pipe H2o net

92. Epanet Alignment

93. Start Water Cad

94. Sewerage network modeling Sewerage network schematization Storm water and sanitary unit load allocation Enter required input data model analysis Decisions to be made (calibration and validation)

95. Soft ware used for urban drainage system Arc GIS and Auto CAD integrated with water software to prepared the input data Storm cad Sewer cad sewer Gems V8i sewer Cad v8i Civil storm SWMM

96. Sewer Gems V8i analysis

97. Network Alignment and Discharge Allocation

98. Manhole and conduit out put result sample

99. The end Thank you