JAR TEST 1. Select the most effective chemical. 2. Select the optimum dosage. 3. Determine the value of a flocculant aid and the proper dose. Objectives Procedure 1 1. Place an appropriate volume of water sample each of the jars (250 to 1000 mL samples may be used, depending upon the size of the equipment being used). Start mixers and set for 100 r/min. 3 2 1. Add previously selected amounts of the chemical being evaluated. (Initial tests may use wide variations in chemical volumes to determine the approximate range. This is then narrowed in subsequent tests.) Continue mixing for 1 min. Chapter 3 :Water Treatment 51
PROBLEM • Calculate the doses of alum and chlorine being streamed for each 500,000 liters of water in mg/L units based on the data obtained from a water treatment plant. • Calculate the quantity of alum and chlorine (in kg) needed in a day if the treatment plant operates in 24 hours. (1L =4.5kg). • A water treatment plant has 6 units of sedimentation tank to treat 200 million liters water per day. Calculate the dosage of alum (mg/L) needed if the plant required 400 tones alum per year. Chapter 3 :Water Treatment Raw water flow rate 95,000 L/hr Alum flow rate 35 L/hr Chlorine flow rate 20 L/hr Strength of alum 5% Strength of chlorine 0.5% 52
Factors influence Selection of Treatment Plant Location Planning and Environmental Obstruction Factors Plant Design Factor Environment al Factor Location Factor Chapter 3 :Water Treatment The examples of the impact from the treatment plant are: i) Effect of noise when operating the plantsuch as pump, generator or chemical tanks. ii) Dust impact during the construction iii) Dangers of chlorine leakage during shipment iv) The smells of chemicals and sludge v) Effect of sludge and wastewater from the plant to the river nearby Avaibility of land cost of the land and taxes that will incurred on land and plant often dictate where a plant will be located once the supply is identified. In many cases, a treatment facility can be at the point of supply, and where possible raw water can gravitate to the plant from the reservoir or the river. The process and instrumentation diagram and the detailed design criteria are developed by establishing (1) the major process units and theirsize and place in the scheme of design, (2) the kind, amount and application points of chemicals reagent and (3) the monitoring and control of the processes and chemicals. The expansion of plant processesis paid attention to. Space is made available for adding capacity and for the addition of processes. 53
Principle Design of Plant Component Standby Power Supply Level Measurement Valve Selection Piping System Chapter 3 :Water Treatment The three principal application for flow measurement are establishing the flow rate of the process and determining the liquid chemical and gas flow rates of varioussubordinates processes. Flow Measuremen t Level measurement is an essential item in plant operation because the plant operator must be aware of the water level of all the process units, the levels of chemical storage tank and silos, and the pressure of water compressed air lines. To be able to select an appropriate type of valve, all design engineers must have a basic knowledge of the various types of commonly used valves, the characteristic of the fluid that is to be regulated, and the hydraulic characteristic of the piping systemin which the valve is to be installed. (1) raw water and finished waste distribution mains; (2) plant yard piping that connects the unit processes; (3) plant utility, including the fire hydrant lines; (4) chemical lines; (5) sewer lines; (6) miscellaneous pipings, such as drainage and irrigation lines. Power outages will undoubtedly occur for a number of reasons, including damage to the power generation system or power supply system as the result of accidents such as earthquake, or even sabotage. 54
CHAPTER 4 WATER DISTRIBUTION SYSTEM 55
Definition Tank / pool generally used to stabilize the supply on changing of the demand. Tape water / fire hydrant taps to bring the water out of the supply system, especially for fire fighting. Pipe connection - used for various Reticulation pipe pipes that distribute treated water to the supply areas. Delivery pipe pipes that carry treated water from treatment plants or from pump to the tank or from a tank to another tank. Chapter 4 :Water Distribution System Water meters complementary components that are used to measure the quantity of water has flowed through it. Distribution pipe pipes that distribute water to reticulation pipes from the services tank/pool, treatment 56
Characteristics This system is suitable for irregular developed towns or cities. Inthis system water flows in one direction only into submains and branches. The diameter of pipe decreases at every tree branch Advantages Disadvantages Disadvantages Characteristics Disadvantages Characteristics Distribution Characteristics Systems Dead End / Tree Radial Grid Iron Circular / Ring Chapter 4 :Water Distribution System From the mainswater entersthe branches at all Junctions in either directions into submains of equal diameters.At any pointin the line the pressure is balanced from two directions because of interconnected networkof pipes. Advantages Supply to the inner pipes is from the mains around the boundary. It has the same advantages as the grid-Iron system. Smaller diameter pipes are needed. The advantages and disadvantages are same as that of grid-Iron system. Advantages This is a zoned system. Water is pumped to the distribution reservoirs and from the reservoirs it flows by gravity to the tree system of pipes. The pressure calculations are easy in this system. Layout of roads need to be radial to eliminate loss of head in bends. This is most economical system also if combined pumping and gravity flow is adopted. 57
Methods Gravity System Pump System Dual System Chapter 4 :Water Distribution System When some ground suffic iently high above the c ity area isavailable , this can be best utilized for distribution system in maintaining pressure in water mains . Thismethod isalso much suitable when the source of supply such as lake, river or impounding reservoir isat suffic iently higher than c ity. The water flows in the mains due to gravitational forces. Constant pressure can be maintained in the system by direct pumping into mains. Rate of flow cannot be varied easily ac cording to demand unless number of pumps are operated in addition to stand by ones. Supply can be effected during power failure and breakdown of pumps. Hence diesel pumps also in addition to electrical pumpsas stand by to be maintained. During fires,the water can be pumped in required quantity by the stand by units. This is also known as dual system. The pump is connected to the mains as well as elevated reservoir. In the begining when demand is small the water is stored in the elevated reservoir,but when demand increases the rate of pumping , the flow in the distribution system comes from the both the pumping station as well as elevated reservoir. As in this system water comes from two sources one from reservoir and second from pumping station, it is called dual system. This system ismore reliable and economical, because it requires uniform rate of pumping but meets low as well as maximum demand. The water stored in the elevated reservoirmeets the requirements of demand during breakdown of pumps and for fire fighting. 58
Pump Types Component Operation / maintenance The function of pump is to left the water or any fluid to higher elevation orat higher pressure. Pumpsare driven by electricity ,diesiel or steam power. They are helpful in pumping water from the sources,that is from intake to the treatment plant and from treatment plant to the distribution system or service reservoir . Inhomes also pumps are used to pump water to upper floors or to store water in tanks over the buildings. 1.Casing: the impellor is enclosed in the casing, which is so designed that kinetic energy. Of the liquid is converted into pressure energy before it leaves the casing. 2. Delivery pipe 3. Delivery valve 4. Impeller 5. Prime mover 6. Suction pipe 7. Strainer and foot valve Chapter 4 :Water Distribution System 59
WHAT ISVALVE? • Valve is a device that regulates, controls • or directs the flow of a fluid by opening, • closing, or partially obstructing fluid flow. • A valve is a mechanical device that controls the flow and pressure of fluid within a system or Process. • So basically, it controls flow & pressure. Chapter 4 :Water Distribution System 60
TYPES OF VALVES • In piping following types of valves are used depending on the requirements. • The cost of Valve in the piping system isup to 20 to 30%of the overall piping cost. • And the cost of a given type and size of the valve can vary 100%. • It means that if you choose ball valve over butterfly valve for the same function. It can cost you more. So, the selection of valves is essential to the economics, as well as operation, of the processplants. 1. Globe Valve 2. Gate Valve 3. Check Valve 4. Plug valve 5. Ball Valve 6. Butterfly Valve 7. Needle Valve 8. Pinch Valve 9. Pressure Relief Valve 10. Relief Valve 11. Stop Valve Valves Functions Valve serve a various function within the piping system. Such as 1. 2. 3. 4. 5. 6. 7. Stopping and starting a fluid flow. Throttling the fluid flow. Controlling the direction of a fluid flow. Regulating a flow or pressure within the piping system. Relieve pressure or vacuum from the piping system and equipment. Pressure and vacuum relief valve safeguard the processsystem from overpressure and during vacuum condition. : Relief Valves Butterfly Valves Neddle Valves Ball Valves Gate Valves Plug Valves Check Valves Stop Valves Chapter 4 :Water Distribution System 61
Steel 1. No. of joining are less because these are available in long lengths 2. The pipes are cheap in first cost 3. The pipes are durable and strong enough to resist high internal water pressure 4. The pipes are flexible to some extent and they can therefore laid on curves 5. Transportation is easy because of light weight. 1. Maintenance cost is high 2.The pipes are likely to be rusted by acidic or alkaline water 3.The pipes require more time for repairs during breakdown and hence not suitable for distribution pipes 4.The pipes may deform in shape under combined action of external forces HDPE (High Density Polyethylene) 1. Highly elastic 2. Light 3. Strong on the impact 4. Very low internalfriction 1. Difficult to connect 2. Need special equipment 3. Higher cost 4. Necessary adjustments if connected to other pipes. UPVC (Unplasticise Polyvinyl Chloride) 1. Light 2. Elastic 3. Corrosion-resistant 4. Low internalfriction 1. Declined by ultraviolet (UV) 2. Easily leak 3. Expensive and dependent on petroleum prices GRP (Glass Reinforced Plastic) 1. Light 2. Corrosion-resistant 3. Low internalfriction 1. Easily damaged on impact 2. Very careful handling is required 3. Not suitable for high pressure 4. Easily leak Advantages and Disadvantages Pipe Material Pipe Material Advantages Disadvantages Cast Iron 1. Cost is moderate 2. The pipes are easy to join 3.The pipes are not subjected to corrosion 4.The pipes are strong and durable 5.Service connections can be easily made 6. Usual life is about 100 years 1. Breakage of pipes are large 2.The carrying capacity of these pipes decreases with the increase in life of pipes. 3.The pipes are not used for pressure greater than 0.7 N/mm2 4.The pipes are heavier and uneconomical beyond 1200 mm dia. Ductile Iron 1. Corrosion-resistant 2. Strongly on the impact 1. Weight 2. High cost Asbesto s Cement 1. Low cost 2. Free from electrolysis 3. Light 4. Easy to handle - cut etc 1. Weak in bending 2. Easily leak when exposed to excavation machinery 3. Fragile 4. Leakage at the joints Chapter 4 :Water Distribution System 62
Storage Tank / Pool Water Storage Tank Service tank Types of Storage Reservoir Types of Pool / Tank Construction Material General Components of a Pool / Tank Factors of tank material selection The main function of the storage tank is :- Chapter 4 :Water Distribution System 1. to provide treated water storage 2. to minimize disruptions during the burst pipe. 3. to provide treated water storage 4. to cope with the needs of the fluctuating. 5. as a stress breaker tank where the level of differences range in the supply area is divided into a zones. 6. to provide water storage for fire fighting purposes. The amount of emergency storage needed to determine tank size. Balancing tank Balancing tank main function is to receive and collect the treated water from treatment plants and then transfer it to a tank or some services tank. Balancing tank depends on the capacity of the treated water at treatment plants and storage required to balance the inflows and outflowsfrom the reservoir. Service reservoir serves to supply water to the reticulation system. Minimum capacity service tanks and reserve pond in the distribution system should be equal to the reserve for one day. Storage per day is usually sufficient for the needs of fire prevention. Service reservoirs are provided in the water treatment distribution systemfor the following functions: I. II. III. To equalize the variation in hourly demand of water by the consumers to a uniform rate of supply from the source either by gravity or pumping, To maintain the desired minimum residual pressure in the distribution system, To provide the required contact time for the disinfectant added in order to achieve effective disinfection, and Underground reservoir Underground reservoirs, also known as sumps serve as suction sources for pumps. These reservoirs normally are built at the site of a supply source. It is common to design a well pump station where number of well pumps discharges to an onsite reservoir. Balancing reservoir The balancing reservoir has a single connection to serve asinlet as well as outlet. Balancing reservoir isalso called floating reservoir. Only one pipe is connected to the reservoir, which will act as inlet as well asoutlet. In a water supply system with number of service reservoirsone foreach zone, they can be connected to a master balancing reservoir (MBR) so that the proper distribution of water to each of the SRs can be achieved by supplying through independentfeedermains. Service reservoir In case the supply from the source is not continuous for all the 24 hours and only during certain duration by pumping for12 to 20 hours in a day and the water distribution is intermittent for certain specified hours different from the pumping schedule, the supply from the source isstored in a storage reservoir and then supplied to the consumers according to the schedule. Service Reservoir Has Separate Inlet And Outlet Connections. 1. profit/life expectancy 2. strength of the structure 3. resistance to corrosion and abrasion (internal and external) 4. the requirementof total load 5. location and environment ReinforcedConcrete • Reinforced concrete pool is preferred because of low maintenance and life-saving use. • Can be constructed on land or elevated according to the pressure and site conditions. Pre-stress Concrete • In Malaysia, the construction of tanks / ponds using pre-stress concrete only involves the construction on the land only and not for the construction of elevated tanks. GalvanizedPressed Steel(GPS) • Pressed steel tanks are often used as a storage tank and can be built in a short time. • Rarely built on the ground and usually elevated and galvanized. Fiber-Glass ReinforcedPolyester(FRP) • FRP tanks are designed and constructed as a pressed-steel tank. It has an FRP panel and can receive between 1 m3 to 2300m3 of water Steel Fussedwith Glass ( SFG) • This tank is designed with the same FRP and GPS panels from the ‘steel fussed with glass’ material to produce a smooth, low friction, tough and waterproof. Function 63
Non Revenue Water (NRW) Definition Indirect Measurement Leakage Measuring Procedure Factors That Influence Leakage Chapter 4 :Water Distribution System 1. Pressure The conversion or changes in pressure will change the rate of water leakage through a leaking or broken pipes and faulty connections. Increased pressure in the system, even slightly, can cause an increase of burst pipes in short-term. 2. Pressure Fluctuation The pressure isalwaysup and down in cycles may cause pipe failure. 3. Soil Movement The movement of land referred to here is a small movement thatis caused by changes in soil moisture content. 4. Rust In Pipe Corrosion caused by chemical reactions that cause the movement of electric current. Meanwhile, external corrosion is caused by differences in soil water content along the pipe concerned. 5. Quality of Material and Poor Work Quality materials that do not meet the specifications and the work is not monitored properly will cause the water supply system which has a high leakage rate. 6. Soil Characteristic Some of soil is not affecting the pipe condition, but the Lias clay (Tanah liat Lias) or EPIC (alluvium) is very aggressive. 7. 7. Traffic Load Water supply systems should be planted in the ground by a sufficient depth. If itis planted at a less depth, vibration from traffic on it will breakthe water supply pipe. 8. Pipe Age Structural deterioration and exhaustion piping system will increase the the pipe leaking. Non Revenue Water (NRW) could be due to leakage of the distribution system or a pool of water, broken pipes, overflowing water ponds, the use of fire fighting, water theft, damage to water meters;meter reading is unperfected and wash system uses. Indirect measurement may consist three leakage locations or partly, between the boundary in the studied area. Measurements or estimates of water use components will be made without the leakage. Components of water use, other than leakage are: - i. metered usage, M ii. flow under recording, U iii. Permitted use, but not metering as the use of fire and movement of work for maintenance purposes, D iv. Use without leakage, I Formula to find the leaks value are: Leaks = inflow-outflow - (M+U+D+I) Source of leakage is categorized in three areas: - i. Water pool ii. Main pipe iii. Distribution pipe From the study, leakage from the pool and the main pipe is small and if it exists, it can be easily detected. While, the distribution pipe leakage is high and difficult to detect. Water Pool Leakage To determine the rate of leakage from the pool of water, fall of water level in the pool is measured using the internal sensors (sensor depth) by closing all the out valves. First, the valves must be tested to ensure that it does not leak. Measurements will be made for 6 to 24 hours. Leakage from Main Pipe Measurement rate of leakage in the main pipe is different the distributionpipe. This is because the main pipe does not involve a lot of connections. Before the leak test conducted, each connection valve between the two ends of the pipe need to be tested. Valves on both ends must be closed and the water pipes installed in the first bypass valve. 64
WATER DISTRIBUTION SYSTEM PIPES USING HAZEN WILLIAMS FORMULATION. a. Delivery pipe size b. Distribution pipe size c. Dead-end reticulation pipe Easily Pipe Design Before the design of distribution system pipe sizes can be implemented, pipe layout and all fixtures required should be calculated in advance. The selection of plumbing system for a town or housing scheme should take into account cost and 100 1128 10 9 Q 1.85 d H 4.87 L = where: HL = head loss (m) Q 3 = flow rate (m /hr) d = pipe diameter (mm) Example 1 Dead-end system One type of dead-end distribution system is proposed to supply water to a city such as in Figure 1 below. Using loss data and formulasprovided, estimate the size of the pipe for the ABand BC to the head by over15.0 m. Data have been given : q = 175 litre/capita/day Q design = 3Q average pressure = 15 m distance AB = 700 m distance BC = 550 m Loss formula : (Hazen Williams) 100 112810 9 Q 1.85 d HL 4.87 = where: HL = head loss (m) Q = flow rate (m3/hr) d = pipe diameter (mm) effectiveness of the services. Formula Hazen- Wiliams Method of calculating the size of the pipe isdivided into two, namely,to the deadend and not the dead-end system (grid, ring and radial). Chapter 4 :Water Distribution System 65
Chapter 4 :Water Distribution System Pipe References Total of populatio n Design flow (m3/hr) Size Pipe estimate d (mm) Loss Surface level (m) Hidrau l Level (m) 66 Head user (m) Each 1000 metre (m) Lengh t (m) Actual (m) A = 185.5 -168 AB 7350 175 7350 3 24 60 60 = 44.7 litre/sec = 160.8 m3/hr 200 16.9 700 16.9 700 1000 = 11.8 A = 168 B = 154 A = 185.5 B = 185.5 – 11.8 = 173.7 =17.5 ≥ 15 m Satisfied... OK B = 173.7 -154 = 19.7 ≥ 15 m Satisfied... OK BC 3100 175 3100 3 24 60 60 = 18.8 litre/sec = 67.6 m3/hr 150 13.8 550 13.8 550 1000 = 7.6 C = 146 C = 173.7 – 7.6 =166.1 C = 166.1 – 146 = 20.1 ≥ 15 m Satisfied... OK
Exercise 1 State the function of storage tank and balancing tank Exercise 2 Explain briefly FOUR (4) classification of Non Revenue Water (NRW) cause. [CLO1] (10 marks) Exercise 3 Water distribution network system can be divided into four types. Explain briefly different TWO (2) type water distribution network system with the help of diagram. 67
CHAPTER 5 Sewerage System 68
Sewerage System Combined Partially Chapter 5 :Sewerage System Separate separate system of sewerage there are two collection systems or pipe network; 1. for collecting domestic sewage as sanitary sewerage system and 2. for collecting storm water as storm water drainage system. Combined system of sewerage both sewage discharge and the storm runoff are collected and conveyed through a common collection system. system part of the storm water especially collected from roofs and paved court yards of the buildings is admitted in the same drain along with sewage from residences and institutions, etc. 69
Combined sewerage System Advantages Disadvantages Condition Chapter 5 :Sewerage System • Advantages • In an area where rainfall is spread throughout a year, there isno need of flushing of sewers, as self cleansing velocity will be developed due to more quantity because of addition of storm water. • Only one set of pipe will be required for house plumbing. • In congested areas it is easy to lay only one pipe rather than two pipes as required in other systems. • Disadvantages • Not suitable for the area with small period of rainfall in a year, because dry weather flow will be small due to which self cleansing velocity may not develop in sewers,resulting in silting. • Large flow is required to be treated at sewage treatment plant before disposal, hence resulting in higher capital and operating cost of the treatment plant. • When pumping is required this system is uneconomical. • During rains overflowing of sewers will spoil public hygiene. Conventional gravity sewers are large networks of underground pipes that convey blackwater, greywater and, in many cases, stormwater from individual households to a (Semi-) Centralized Treatment facility, using gravity (and pumps when necessary). 70
Separate sewerage System Advantages Disadvantages Condition • Disadvantages • Self cleansing velocity may not developed at certain locationsin sewers and hence flushing of sewers may be required. • - This system requires laying two sets of pipe, which may be difficult in congested area. • This system will require maintenance of two sets of pipelines and hence maintenance cost is more. • Advantages • Assewage flows in separate pipe, hence the quantity to be treated at sewage treatment plant is small, resulting in economy of treatment. • Thissystem may be less costly as only sanitary sewage is transported in closed conduit and storm water can be collected and conveyed through open drains. • When pumping is required during disposal, this system is economical due to less flow. Separate sewerage consists : i- municipal wastewaters (blackwater from toilets,greywater Ii- industrialwastewater) Iii. surface run-off (rainwater and stormwater). The separate collection prevent the overflow of sewersystems and treatment stations during rainy periods and the mixing of the relatively little polluted surface run-off with chemical and microbial pollutants from the municipal wastewater. Chapter 5 :Sewerage System 71
• Advantages • Economical and reasonable size sewers are required. • Work of house plumbing is reduced as rain water from roofs, wastewater from bathrooms and kitchen, etc. are combined with discharge from water closets. • Flushing of sewers may not be required as small portion of storm water isallowed to enter in sanitary sewage. Partially Combined orSeparate System Advantages Disadvantages Condition Chapter 5 :Sewerage System Disadvantages Increased cost of pumping as compared to separate system at treatment plants and intermediate pumping station wherever required. In dry weather selfcleansing velocity may not develop in the sewers. The storm water from the other places iscollected separately using separate storm water conduits. 72
Type of Sewer Pipe Brick Sewer Steel Sewers Cement Sewer Cast iron (CT)Sewer Asbestos Cement (AC) Sewer Plastic Sewers Chapter 5 :Sewerage System • Types of sewer like Asbestos Cement (AC) Sewers are manufactured from a mixture of cement and asbestos fiber. • AsbestosCement (AC) Sewers are suitable for carrying domestic sanitary sewage. • Asbestos cement sewer isbest as vertical pipe for carrying sullage from upper floorsof multistory buildings (in two pipe system of plumbing). These typesof sewer (Brick Sewers)are made at site and used for construction large size sewer. BrickSewersare very useful for construction of storm sewer or combined sewer. Nowadaysbrick sewers are replaced by concrete sewer. Brick sewers get deformed and leakage may take place. A lot of labour work is required. i. PCC - for dia upto 60 cm Suitable for small storm drains. Not durable . ii.RCC - for dia >60 cm They may be cast in situ or precast, resistant to heavy loads, corrosion and high pressure.These are very heavy and difficult to transport. These typesof sewer are High strength and durability water tight. Cast Iron sewers can with stand high internal pressure and can bear external load. Cast Iron sewers are suitable for the following conditions. -When the sewage is conveyed under high pressure -When the sewer line is subjectto heavy external load e.g. under railway line, foundation wall etc, below highways -When there is considerable difference in temperature -These types of sewer (steel sewers) are Impervious,light, resistant to high pressure,flexible, suitable when; - The sewage is carried under pressure - The sewage has to be carried across a river under water - The sewer has to crossunder a railway track - They are generally used for outfall and trunk sewers Nowadays PVC sewers are used for carrying sewage. Plastic sewers are resistantto corrosion. -lightin weight, smooth and can be bent easily. -having high co-efficient of thermal expansion and cannot be used in very hot areas. 73
Criteria for Pipe Selection Facilities for get the supply, delivery and installation Connection method Water sealing capabilities Resistance rustiness - corrosion and abrasion inside and outside The strength of pipe structural The value of the coefficient of friction / roughness Previous experience Life expectancy Chapter 5 :Sewerage System 74
Shallow Manholes A manhole is a masonry or reinforced cement concrete (R.C.C) chamber constructed for providing access to the sewer for the purposes of inspection, testing, cleaning and removal of obstructions from the sewer line. -Shallow manholesare the one which are about 0.75 to 0.9m in depth. -They are constructed at the start of a branch sewer. These are also known as inspection chambers. Normal Normal manholes are those which are about 1.5m in depth. -They are contrasted either in square (1mx1m) or rectangular (0.8m x 1.2m) in cross-section. -The section of such manholes isnot changed with depth. Itisprovided with heavy cover at itstop. Deep manholes Deep manholes are those which are deeper than 1.5m. The size of such a manhole is largerat the bottom, which is reduced at the top to reduce the size of manhole cover. Chapter 5 :Sewerage System 75
Infiltration in Sewer Pipe Infiltration isgroundwater that enters sanitary sewer systems through cracks and/or leaks in the sanitary sewer pipes. Groundwater can enter these cracks or leaks wherever sanitary sewer systems lie beneath water tables or the soil above the sewer systems becomes saturated. Cracks or leaks in sanitary sewer pipes or manholes may be caused by age related deterioration, loose joints, poor design, installation or maintenance errors, damage or root infiltration. Chapter 5 :Sewerage System 76
Corrosion in Sewer Pipe Chapter 5 :Sewerage System 77
Sewer Pipe Design Procedure Preliminary investigation Zoning Design period Treatment plant Sewer layout Chapter 5 :Sewerage System a. provide information on estimated costs for reviewing the reasonableness of a project b. work granulation map must have at least aerial photographs c. preliminary design is based on the estimated flow, contours of land, the road location or pipeline routes, and the position of the sewage produced from the d. from this information, the estimated quantity of pipes of different sizes can be made simultaneously with estimates of excavation, restoration of roads and sewer pipe components which required. Sewage quantity estimation a. The quantity of sewage is depend with the seasons, days and hours. For example, the flow volume during the day would be more than night, and this makes it difficult to determine the average daily flow rate and maximum flow rates. b. Sewer must be designed so that they can carry a maximum flow rate in flow ⅔ full for diameter more than 75cm, and the flow of ½ full for sewers less than 75cm in diameter. The flow factor for this method : a. 6 is used for all sewer which carries a flow rate of the population less than 10,000 people b. 4.5 for the culvert which carries the discharge population of more than 10,000 people a. Sewer channel system should be designed to meet current and future needs. b. The need to come means that the needs of the contemporary if not too wide and not beyond the existing provisions. c. time limit does not exceed 30 years. a. The layout of the sewer pipe should be at the shortest distance to the treatment plant so that infrastructure costs can be minimized. b. Most of sewer pipeline route is parallel to the back door of the terraced house, on the curb next to the main channel, or on the front side of the road if no curb and within individual lots for attached housing, with no road at the back. Sewage is not entirely liquid, but also contains some of the solid, especially for combined sewer pipe system. The velocity of sewage flow in the sewer pipe must be sufficient to ensure that no solids will settle out and create piles of silt, resulting in clogged pipes. 78 a. Distribution area, or zonation should be made in advance depending on the extent and condition of the surface areas, or housing schemes where his sewer-channel system to be designed. b. Construction of treatment plants will be over design if the area is too large or the density is too low. c. For areas where the population intensity are evenly distributed, it is more economical, if the area is divided into several zones with high population density.
HOW TO CALCULATE PARAMETERS FOR CIRCULAR SHAPE SEWER Formulas calculating the velocity a) Chezy Formulas V = C mi m =A/P = d/4 Where: V = Flow velocity (m/s) C = Chezy Constant m = Hydraulic min depth (m) i = Sewer slope n – rougness coefficient b. Manning Formulas n 2 m 3 i 1 V = Chapter 5 :Sewerage System 79
EXERCISE 1 Determine flow velocity in sewer channels of circular section made from cast iron with a diameter of 25 cm and spread with a slope of 1:35. n = 0.013 and C =45.50 Use the method below :Chezy Formulas and Manning Formulas EXERCISE 2 Calculate the flow velocity in sewer channels made of cast iron with a diameter 25cm and spread over the slope 1:40, C= 227. Assume the flow is full. n =0.013 Chapter 5 :Sewerage System 80
Example 1 : sewer pipe made of clay has 15cm diameter with A manning coefficient, N =0.014 and has grown into the ground with A slope of 1:90. 1.Calculate the sewage velocity through it. Assume the flow is full. 2. Ifthe self-cleaning the pipe is 1.0 M/S, calculate the slope of the sewer pipe. i n 2 m 3 1 V = Chapter 5 :Sewerage System 81
SOLUTION Chapter 5 :Sewerage System 82
Example 2 A housing scheme consists of four rows of terraced houses where each line is there are 20 units in which the number of occupants per unit is about 6 people. By using the manning formula, calculate the required sewer diameters for this housing scheme by making the assumption of flow in sewers are full. Then indicate whether the flow velocity is appropriate or not. Design criteria required are as follows culvert slope =1:40 water requirement per capita =250 liters / person / day flow-rate factor:6 for the population <10,000 people 4.5 for the population >10,000 people self-cleaning velocity >0.45 M / S roughnesscoefficient =0.014 Chapter 5 :Sewerage System 83
Chapter 5 :Sewerage System 84
Chapter 5 :Sewerage System 85
CHAPTER 6 Sewage Treatment 86
Purpose of Sewage Treatment 1. Protect public health. 4. Preserve the best uses of the waters. 5. Protect adjacent lands. 3. Protect aquatic life. 2. Protect public water supplies. Chapter 6 :Sewage Treatment Parameter Unit Standards A B Temperature C 40 40 pH Value - 6.0-9.0 5.5-9.0 BOD5 at 20C mg/l 20 50 COD mg/l 50 100 Suspended Solids mg/l 50 100 Mercury mg/l 0.005 0.05 Cadmium mg/l 0.01 0.02 Chromium,Hexavalent mg/l 0.05 0.05 Arsenic mg/l 0.05 0.10 Cyanide mg/l 0.05 0.10 Lead mg/l 0.10 0.5 Chromium, Trivalent mg/l 0.20 1.0 Copper mg/l 0.20 1.0 Manganese mg/l 0.20 1.0 Nickel mg/l 0.20 1.0 Tin mg/l 0.20 1.0 Zinc mg/l 1.0 1.0 Boron mg/l 1.0 4.0 Iron (Fe) mg/l 1.0 5.0 Phenol mg/l 0.001 1.0 Free Chlorine mg/l 1.0 2.0 Sulphide mg/l 0.50 0.5 Oil and Grease mg/l Not Detectable 10.0 Effluent that is discharged upstream of a water supply intake should meet Standard A, while effluent that is discharged downstream has to meet Standard B. These standards are set by the Environmental Quality Act 1974. Effluent Standard 87
Characteristics of Sewage Physical Chemical Biological Total Solid Substances Turbidity Tempertaure colour odor Nitrogen Compounds Dissolved Gases Chemical Oxygen Demand (COD) Biochemical Oxygen Demand (BOD) pH Phosphorus Alkalinity Bacteria Fungi Algae Virus Protozoa Chapter 6 :Sewage Treatment 88
Pollution in Water Surface water Chemica l Suspended matter Microbiology Nutrients Groundwater Oxygen depleting Chapter 6 :Sewage Treatment Surface waters are the natural water resources of the Earth. They are found on the exterior of the Earth’s crust and include oceans, rivers and lakes Microorganismsthat live in water feed on biodegradable substances. When too much biodegradable material is added to water, the number of microorganisms increase and use up the available oxygen. Thisis called oxygen depletion. When oxygen levels in the water are depleted, relatively harmless aerobic microorganisms die and anaerobic microorganisms begin to thrive. Humans often use aquifers as a means to obtain drinking water, and build wells to access it. When this water becomes polluted it is called groundwater pollution. Groundwater pollution is often caused by pesticide contamination from the soil and it can infect our drinking water and cause huge problems. Nutrients are essential for plant growth and development. Many nutrients are found in wastewater and fertilizers, and these can cause excess weed and algae growth if large concentrations end up in water. This can contaminate drinking water and clog filters. This can be damaging to other aquatic organisms as the algae use up the oxygen in the water, leaving none for the surrounding marine life. Microbiological water pollution is usually a natural form of water pollution caused by microorganisms. Many types of microorganisms live in water and cause fish, land animals and humans to become ill. Microorganisms such as: Bacteria, Viruses and Protozoa. Serious diseasessuch as cholera come from microorganismsthat live in water. The suspended particles eventually settle and cause thick silt at the bottom. This is harmful to marine life that lives on the floor of rivers or lakes. Biodegradable substances are often suspended in water and can cause problems by microorganisms present. increasing the amount of anaerobic Toxic chemicalssuspended in water can be harmful to the development and survival of aquatic life. Industrial and agricultural work involves the use of many different chemicals that can run-off into water and pollute it. Metals and solvents from industrial work can pollute rivers and lakes. These are poisonous to many forms of aquatic life and may slow their development, make them infertile or even result in death. Pesticides are used in farming to control weeds, insects and fungi. 89
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Sewage Treatment Processes Preliminary treatment Primary treatment Secondary treatment Advanced waste treatment Disinfection Sludge treatment 1 2 3 4 6 5 Provides for the removal of large debris & heavy inorganic materials that could damage plant equipment or would occupy treatment capacity without being treated. Removes settleable and floatable solids (may not be present in all treatment plants). Removes BOD and dissolved and colloidal suspended organic matter by biological action.Organicsare converted to stable solids, carbon dioxide and more organisms. Uses physical, chemical, and biological processes to remove additional BOD, solids and nutrients (not present in all treatment plants). Removes microorganisms to eliminate or reduce the possibility of disease when the flow isdischarged. Stabilizes the solids removed from wastewater during treatment, inactivates pathogenic organisms, and reduces the volume of the sludge by removing water. Purposes Chapter 6 :Sewage Treatment 91
Preliminary treatment 1 Processes Purposes Screening Chemical addition Pre-aeration Grit removal Shredding The purpose of screening is to remove large solids, such as rags, cans, rocks, branches, leaves, roots, etc., from the flow before the flow moves on to downstream processes. As an alternative to screening, shredding can be used to reduce solids to a size that can enter the plant without causing mechanical problems or clogging. The purpose of grit removal is to remove the heavy inorganic solids that could cause excessive mechanical wear. Grit is heavier than inorganic solids and includes, sand, gravel, clay, egg shells, coffee grounds, metal filings, seeds, and other similar materials. to achieve and maintain an aerobic state (to freshen septic wastes), strip off hydrogen sulfide (to reduce odors and corrosion), agitate solids (to release trapped gases and improve solids separation and settling), and to reduce BOD. to improve settling, reduce odors, neutralize acids or bases, reduce corrosion, reduce BOD, improve solids and grease removal, reduce loading on the plant, add or remove nutrients, add organisms, and aid subsequent downstream processes. Chapter 6 :Sewage Treatment 92
2 Purpose Primary treatment Process Overview The purpose of primary treatment (primary sedimentation or primary clarification) is to remove settleable organic and floatable solids. Normally, each primary clarification unit can be expected to remove 90 to 95% settleable solids, 40 to 60% TSS, and 25 to 35% BOD. Sedimentation may be used throughout the plant to remove settleable and floatable solids. It is used in primary treatment,secondary treatment, and advanced wastewater treatment processes. In primary sedimentation, wastewater enters a settling tank or basin. Velocity is reduced to approximately 1 ft/min. Solids that are heavier than water settle to the bottom, while solids that are lighter than water float to the top. Settled solids are removed as sludge and floating solids are removed as scum. Wastewater leaves the sedimentation tank over an effluent weir and on to the next step in treatment. Detention time, temperature, tank design, and condition of the equipment controlthe efficiency of the process 1.Primary treatment reduces the organic loading on downstream treatment processes by removing a large amount of settleable, suspended, and floatable materials. 2.Primary treatment reduces the velocity of the wastewater through a clarifier to approximately 1 to 2 ft/min, so that settling and floatation can take place. Slowing the flow enhances removal of suspended solids in wastewater. 3.Primary settling tanks remove floated grease and scum, remove the settled sludge solids, and collect them for pumped transfer to disposal or further treatment. 4. Clarifiers used may be rectangular or circular. In rectangular clarifiers, wastewater flowsfrom one end to the other, and the settled sludge is moved to a hopper at the one end, either by flights set on parallel chains or by a single bottom scraper set on a traveling bridge. Chapter 6 :Sewage Treatment 93
Secondary treatment 3 Trickling filter Rotating Biological Contactor (RBC) Activated sludge Oxidation pond Chapter 6 :Sewage Treatment • • In operation, wastewater is distributed evenly over the surface of the trickling filter media. As the wastewater flows over the surface of the media the organisms in the slime remove the organic matter from the flow. • • • • • • The organisms aerobically decompose the solids producing more organisms and stable wastes, which either become part of the zoogleal slime or are discharged back into the wastewater flowing over the media. The wastewater continues through the filter to the under drain system where it is collected and carried out of the filter. At the same time air flows through the filter (bottom to the top or top to bottom depending on temperature). Oxygen is transferred from the air to the wastewater and slime to maintain the aerobic conditions. Periodically the slime on the media becomes too heavy and portions will be released. This material known as sloughing is carried out of the filter with the wastewater flow and is removed in the settling tank following the filter. te The surface of the disk is covered with a biological slime similar to that on the media of a trickling filter. RBC units are usually installed in a conc rete tank so that the surface of the wastewater passing through the tank almost reaches the shaft. Thismeans about 40%of the total surface area of the disks isalways submerged. The shaft continually rotates at 1 to 2 rpm, and a layer of biological growth 2 to 4 mm thick is soon established on the wetted surface of each disk. The organisms in the slime assimila (remove) organic matter from the wastewater for aerobic decomposition. The disk continues to rotate, leaving the wastewater and moving through the air. Additional settling of solids and biological treatment of organic matter in the water o ccurs. Some of the feacal coliform in the water is also removed. Italso can provide additional clarification, BOD removal and disinfection. The oxidation pond is very similar in design to the stabilization pond. Activated sludge refers to biological treatment processes that use a suspended growth of organisms to remove BOD and suspended solids. • • • • • • Primary effluent (or plant influent) is mixed with return activated sludge to form mixed liquor. The mixed liquor is aerated for a specified length of time. During the aeration the activated sludge organisms use the available organic matter as food producing stable solids and more organisms. The suspended solids produced by the process and the additional organisms become part of the activated sludge. The solids are then separated from the wastewater in the settling tank. The solids are returned to the influent of the aeration tank (return activated sludge). 94
SLUDGE Pre-treatment Pre-treatment consists of various physical and mechanical operations, such as screening, sieving, blast cleaning, oil separation and fat extraction. Pre-treatment allows the removal of voluminous items, sandsand grease. Primary sludge Primary sludge is produced following primary treatment. This step consists of physical or chemical treatments to remove matter in suspension (e.g. solids, grease and scum). The most common physical treatment is sedimentation. Sedimentation is the removal of suspended solids from liquids by gravitational settling. Sedimentation is usually considered first because it is a simple and cost-effective method. Secondary sludge Secondary sludge is generated from the use of specially provided decomposers to break down remaining organic materials in wastewater after primary treatment. The active agents in these systems are micro-organisms, mostly bacteria, which need the available organic matter to grow. Mixed sludge The primary and secondary sludge described above can be mixed together generating a type of sludge referred to asmixed sludge. Tertiary sludge Tertiary sludge is generated when carrying out tertiary treatment. It is an additional process to secondary treatment and is designed to remove remaining unwanted nutrients (mainly nitrogen and phosphorus) through high performance bacterial or chemical processes.These treatments are necessary when a high level of depollution is required. Sludge Treatment Thickening Digestion Dewatering Sludge Disposal Landfill Incineration Chapter 6 :Sewage Treatment Composting A few sewage works compost sludge by the process of ‘windrowing’. The process generates heat and a rise in temperature in the composting material causes pathogen destruction. The final product may be suitable for amenity use. Ocean dumping Dumping waste in the ocean, estuaries, or inland lakes is regulated by emission standards for abating pollution of the oceans. The concept of an infinite ocean (a mile and a half deep on the average around the world) has given way to the reality that the ocean is a limited and valuable resource. Spray Irrigation Spray irrigation is a modification of the system used in agriculture for irrigating crops.However,the objective is the disposal of liquid rather than providing moisture and nutrients to harvestable crops. After pretreatment and grease removal, this system sprays wastewaterthrough a sprinkler system onto land that is planted with special grasses. landfills are the ultimate disposal location for dried (dewatered)sludge, and this disposal method can be economically depending on the haul distance from the wastewater treatment plant to the landfill. In considering the location, design, operation and maintenance ofsludge disposal lagoons and landfills, environmental engineers must consider the sludge loading criteria, possible health effect through groundwater pollution, the potential for heavy metal accumulation in the soil and groundwater, the possibility of fertilizer nutrients like nitrogen and phosphorus reaching the surface water, and general nuisance developments. incinerators produce the maximumsolids and moisture reductions. The equipment required depend on whether the unit is a multiple hearth or fluid bed incinerator. Generally, the system will require a source of heat to reach ignition temperature, solids feed system and ash handling equipment. It is important to note that the system must also include all required equipment (e.g., scrubbers) to meet the air pollution control requirements. In operation, solids are pumped to the incinerator. Thickening is a first step to reduce sludge water content. Sludge reaches 10 to 30 % dryness, and can still be pumped. Note that the sludge removal and pumping facilities and the method of operation also affect the solids content. Various existing techniques are presented below. Sludge thickening (or concentration) is a unit process used to increase the solids content of the sludge by removing a portion of the liquid fraction. Sludge dewatering is used to reduce volume by removing the water to permit easy handling and economical reuse or disposal. Dewatering processes include sand drying beds, vacuum filters, centrifuges, filter presses(belt and plate), and incineration. i. ii. iii. iv. reduce its water content, stabilize its organic matter and reduce the generation of odours reduce its pathogen load, reduce its volume and global mass. Several treatments can be applied to sludge to achieve this. These are described in a following part of this report. One of those transformsthe sludge in a way that it is considered as a new type of sludge usually referred to as “digested sludge”. After watertreatment, additional treatments9n5eed to be performed on sludge in order to:
Individual Wastewater Treatment Unit Septic tank Imhoff tank Septic tanks are prefabricated tanks that serve as a combined settling and skimming tank and as an unheated– unmixed anaerobic digester. Septic tanks provide long settling times (6 to 8 hours or more), but do not separate decomposing solids from the wastewater flow. When the tank becomes full, solids will be discharged with the flow. The process is suitable for small facilities (i.e., schools, motels, homes, etc.), but due to the long detention times and lack of control, it is not suitable for larger applications. Septic Tank receives raw sewage, allow it to settle, and pass the relatively clear liquid to the adsorption field, which is the next stage of treatment. The two-story or Imhoff tank is similar to a septic tank in the removal of settleable solids and the anaerobic digestion of solids. The difference is that the two story tank consists of a settling compartment where sedimentation is accomplished, a lower compartment where settled solids and digestion takes place, and gas vents. Solids removed from the wastewater by settling pass from the settling compartment into the digestion compartment through a slot in the bottom of the settling compartment. The design of the slot prevents solids from returning to the settling compartment. Solids decompose anaerobically in the digestion section. Gases produced as a result of the solids decomposition are released through the gas vents running along each side of the settling compartment. Figure : Imhoff Tank Source: http://www.sswm.info/category/implementation-tools/wastewatertreatment/hardware/site-storage-and-treatments/imhoff-tank Chapter 6 :Sewage Treatment 96
REFERENCES FOR E-BOOK • Academy of Sciences Malaysia (2015).Study on the Current Issuesand Needs for Water Supply and Wastewater Management in Malaysia. Vol. (2). • Chhipi-Shrestha, G., Hewage, K. & Sadiq, R. (2017). Fit-for-purpose Wastewater Treatment: Conceptualization to Development of Decision Support Tool (I). Science of the Total Environment, 607-608, 600-612. • Cui, Q., Fang, T., Huang, Y., Dong, P., & Wang, H. (2017). Evaluation of Bacterial Pathogen Diversity, Abundance and Health Risk in Urban Recreational Water byAmplicon Next-generation Sequencing and Quantitative PCR. Journal of Environmental Sciences, 57, 137-149. • Debra, S. (2000). General Microbiology Laboratory Manual. Penerbit Universiti Teknologi MARA. Shah Alam. • Department of Environment, Interim National Water Quality Standards for Malaysia. DOE, Kuala Lumpur, Malaysia (2008). • Indah Water Konsortium (2018).Sewage Treatment Plant. Public Sewage Treatment Plants in Malaysia. Accessed on 30th Apr 2018 at www.iwk.com.my/do-you-know/sewage-treatment-system. • Karia and Christian (2012). Wastewater Treatment Concepts and Design Approach. Eastern Economy Edition. New Delhi. • Luigi, R., Fiorentino, A., & Anselmo, A. (2013).Advanced Treatment of Urban Wastewater by UV Radiation: Effect on Antibiotics and Antibiotic-resistant E. coli strains.Chemosphere, 92, 171-176. • Masters, G.M. & Ela, W.P. (2014). Introduction to Environmental Engineering and Science. Pearson New International Edition -3rd Edition.Pearson; England. • Metcalf & Eddy (2014). Wastewater Engineering Treatment and Reuse. Fifth edition Vol. 1 & 2). McGraw Hill;New York, United States. • Mohd-Aizat, A., Mohamad-Roslan, M.K., & Wan Nor Azmin Sulaiman (2013). Water Quality Index of Selected Station at Rasau River, Ayer Hitam Forest Reserve, Puchong, Selangor. International Journal of Water Research, 1(2), 37-42. • Rukeh, R.A., & Agbozu I.E. (2013). Impact of Partially Treated Sewage Effluent on the Water Quality of Recipient Epie Creek Niger Delta, Nigeria using Malaysian Water Quality Index (WQI). J. Appl. Sci. Environ. Manage, 17(1): 5-12. 97
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