Treatment Plant for Waste Water - Assignment Example

Module 1- Water and sewerage systems Treatment plant for waste water History Wetalla water reclamation and Toowoomba sewer facility was constructed in 1926. The construction of the biological nutrient reduction was undertaken in 1996. In 2006, the solar and bioreactor drying hall was constructed. In order to make use of current technology and to handle the escalating population in Toowoomba, the process of upgrading the facility has been on the upward trend. The three main processes of treatment used at Watella treatment plant include chemical, BNR and mechanical processes as shown below; From the above diagram, the treatment process begins by collecting the sewage from the town in a PTA. It is then screened for girts and solids. The biological nutrient reduction process follows in the bioreactor. 3 zones are used to carry out this process. They include; 1- Removal of oxygen gas (anaerobic) 2- Removal of nitrogen gas (anoxic) 3- Conversion of ammonia into oxygen (Aerobic) The clarifier serves the purpose of separating liquid through the process of converting bacteria into RAS. Any pathogen left in the effluent is removed by disinfecting the effluent with Chlorine gas in the contact tank. The process of treating the effluent ends and the final product goes to the Gowrie creek. The solar hall and the aerobic digester are used to collect around 5% of the liquid that escapes from the bioreactor. The water content of the liquid that escapes from the bioreactor is 85% but when it comes out of the solar hall it contains more than 60% sludge (solid). The purpose is to reduce the size and solidify the stuff so that it get be removed easily. Information regarding the capacity of the plant is given below; The daily plant maximum capacity is 100ML The plant has a design capacity of 33 ML The operating volume of plant in a normal operating day is 25ML The aeration tank has a biomass concentration of 3500-400mg/L The rate of wasting in a day is 25ML 2 days is the approximate detection time of hydraulic in the reactor tank 20 days is the sludge age The plant for water treatment The plant for water treatment in Toowoomba is made up of three huge supply systems. The plant capacity is 68ML. The normal condition of the plant operation is 20-25ML per day while the maximum condition for operation in the plant is 740 per day. The subsequent section gives details about the supply/storage system of the plant. Included here is the maximum water release, rate of intake and the capacity of the pumps in different locations. 1- Cress Brook dam This length of this dam is 278 meters with clay score walls. In order to provide the best quality and cheapest water for treatment, the dam has 7 intakes. The dam has 2.75ML/sec Perso spillway and it empties its water into the western part of the dam. The dam has an 83GL Cressy storage. It has a lift of 286metres and 278 meters to Pechey and jockey respectively. The cress dam has two pumps. The first and the second pumps have capacities of 500L/s and 550L/s respectively. At the off peak period, the cost is £200 per ML. 2- Perseverance dam This dam has a length of 286 meters. The approximate area of the dam is 222 Ha with 5 intakes. The dam has a 32GL storage capacity. The dam has a 301 meters lift and 410L/s pump capacity. At the off peak duration, the dam has a £110 per ML in cost. 3- Cooby Dam The dam has a storage capacity of 23GL. The dam releases more than 1.8 ML/s of water and it has 3 intakes. The dam has three pumps with different capacities such as 200ML/s, 160ML/s and 60ML/s. At the off peak duration, the dam has a cost of $280 per ML. The process of treating water begins by screening water from the dams before the actual process of treatment is undertaken. This is followed by the closure of flash mixer coagulants. 55mL/L of Poly aluminum Chloride is then used at the beginning and LT 25 is applied at the end. The purpose of this step is to ensure maximum form flocs and PH factor. The next process occurs in the flocculation chamber where floc agglomeration is undertaken. A 20 minute hydraulic detention occurs in the flocculation chamber. The next step is sedimentation which is a physical process. In the sedimentation basin, hydraulic detention takes approximately 40 minutes. The second last step is filtration which is the clarification process. It involves the removal of minute floc particles from the stream flow. Before backwash, the head loss in the filter is zero and this is due to control that occurs in the system. Disinfection is the last step and it involves the removal of dangerous microorganisms from the water. Chloride gas is the main disinfecting agent used in Toowoomba plant for water treatment. Module 2- Structural non-destructive testing The property of concrete used at the dam is measured in three ways. First, through the use of semi-destructive test. Second, through the use of non-destructive test, and, third, through the use of destructive structural test. Semi-destructive tests During this testing process, destruction of a small portion of the structure is undertaken. An example of this test is the core cutter test. During the non-destructive test, a number of equipments are used such as the ultrasonic pulse velocity, rebound hammer and the kolectric microcovrmeter. The named equipments are used to measure a given sample of concrete. During the destructive test process, destruction of the concrete sample is undertaken. Examples of tests carried out during this test process include tensile strength test, compressive strength test and flexural strength test. Rebounds hammer (Schmidt) The spring principle is used with this equipment because it provides the rebound force. The rebound force is controlled by properties such as mass (ρ), young modules (E) and the hardness of the surface. Hitting the sample of the concrete and then reading the value of the rebound (R) is the procedure used in the spring principle. The concrete compressive strength that corresponds to R is taken using some graphs. The results presented below summarize the above explained procedure; Table 1 Results of Rebound hammer test Hitting the floor (-90 ᵒ) Reading R value 34 32 f’ (MPa) 37 34 Hitting the front wall (0 ᵒ) Reading R value 44 32 35 41 32 46 f’ (MPa) 50 26 33 44 26 54 Hitting the left side wall (0 ᵒ) Reading R value 38 32 37 36 38 39 f’ (MPa) 39 26 37 34 39 40 Hitting the right side wall (0 ᵒ) Reading R value 43 46 f’ (MPa) 48 54 Hitting the back wall (0 ᵒ) Reading R value 42 39 42 39 42 f’ (MPa) 46 40 46 40 46 From the table above, it is clear that there is variation of the compressive strength of the sample of concrete in different positions. This results from the crack, void or hardness of the surface of the concrete. The variation ranges from 26MPa to 54 MPa. However, 40MPa is the approximate compressive strength. Equipment for Ultrasonic Pulse Velocity testing The main principle under which this equipment operates is that ultrasonic pulses are sent by the equipment and it tracks the movement of sound through the media. The signal transmitted ranges from 20 to 150 KHz and the equipment has both the receiver and transmitter which are located in between the concrete sample. The purpose of this equipment is to give the indication of concrete homogeneity because it helps in the detection of cavities and voids and it gives the proper estimation of the depth of the cracks of the surface. As shown in the table 2 below, the sample is divided into a grid showing the concrete sample properties. For every sample grid position, the time taken to move the signal from the transmitter to the receiver is shown in the table below; Table 2 Pundit test results FRONT WIDE WALL SIDE WALL 1 2 3 4 5 6 7 8 S A 34.5 35.2 33.2 35.5 33.6 35.4 1 87.5 B 33.5 35.5 32.6 33.5 33.5 35.5 2 88.6 C 32.1 31.2 32.5 36.5 33.1 36.6 3 86.7 D 34.6 36.1 32.3 33.0 33.1 35.9 4 88.2 E 34.7 32.7 33.5 34.4 34.0 34.7 5 88.5 F 32.3 32.2 33.9 33.2 37.2 34.2 34.4 6 90.0 G 31.2 36.0 34.2 33.7 34.5 36.7 7 88.9 H 30.4 33.4 33.0 33.7 8 86.4 I 31.5 33.2 33.2 36.3 9 86.5 J 33.7 32.3 32.9 33.9 10 87.1 K 31.9 33.2 33.8 35.3 11 87.7 L 32.1 33.3 34.7 33.1 12 87.4 It is evident from the table above that in the grid shaded (E6) there is a void potential. Additionally, a shallow crack can also be seen around grid B2. The connection of the receiver and transmitters in E row and A row is made in order to show the position of the crack. Table 3 below shows the results; Table 3 Crack position position A1 + E1 A2 + E2 A3 + E3 A4 + E4 A5 + E5 A6 +E6 A7 + E7 A8 + E8 t (μs) 46.4 43.5 43.3 43.4 50.6 53.5 53.7 43.8 The crack can be noticed clearly between cells 5 to 7. Kolectric micro Covermeter The reinforcement cover of the concrete determines the durability of its structure. The covermeter serves several purposes that includes; estimation of the thickness of the cover of a reinforced structure that exists; orientation and location of rebar and providing the approximate diameter of the bar. Using this equipment, the properties of the concrete sample can be provided in three readings. The equipment is used following a given procedure such as scanning the sample of concrete and locating the steel using three methods namely sharp sound, high intensity reading and the use of flickering light. The covermeter is used to scan the concrete sample and the results obtained are as shown below; It is evident from the figure above that estimation of the thickness and the location of the three steel bars has been done. The steel is estimated to be 27mm in thickness. The location of the steel bars is shown from top to the bottom. The bottom end of the third bar is hard to estimate due to the instrument’s limitation. Concrete beam Casting: 3rd Module The purpose of this module is to enhance practical experience on reinforcement cage fabrication for casting cylinders and beams. The following sections shall be contained in the beam; The calculations for the length and the volume of the above dimension are as follows; 3 small cylinders and 1 big cylinder with diameters of sizes d=100, h=200, and dia=155, h=305 respectively. The cylinders shall be 0.004714 and 0.005757m3 in volume respectively. Additionally, the beam mould shall have a volume of 0.035m3 calculated as follows; Beam mould= L x B x D = 1400 x 250 x100. The required concrete shall therefore have a total volume of 0.044m3. The required number of bags of cement shall be 5 bags because each bag has 0.0085m3. 2 L of water will be used for every bag of cement. The approximate liters of water will be 10 litters for use with 5 bags of cement. The bottom bars requires 10mm and the top bars require 4mm as shown in the figure above. The main reinforcement should be 1650mm in length while the stirrup should be 700mm in length. 14 nos. are required for the stirrup. For the purpose of casting the concrete beam the following detailed activities have been undertaken; 1- The main reinforcement should be cut and bend The 10mm and 4mm steel bars stated above are cut into 1650mm in length. The appropriate tools will be used to cut the steel bars. In order to provide a 25mm cover, the bars are bended on both sides and the above figure shows the final shape of the bars. 2- Stirrups are cut and bend A similar procedure is performed on the stirrups. The prepared stirrups are 14 in number. Every step of making the stirrup should be clearly executed to ensure that every stirrup made fits into the mould. 3- Cage marking The shear links, main steel and the stirrup are collected together and the stirrups are spaced at a 100mm distance. Ties are used to stabilize the cage and keep the steel in place. 4- Mould cleaning The dimension of the mould is 1400x250x100. In order to eliminate any dust within the mould, special oil used for moulding is used as well as cleaning the cylinders used for testing. 5- Concrete casting An electric mixer with a 20kg cement capacity (3bags) is used. 6.8 liters of water and 3 bags of cement are used for the first mixer and 5.1 liters and 2 bags of cement are used for the second mixer. 6- Slumping This is a test carried out to measure the workability of the concrete mix. The value of slump test is 55mm. 7- Mould filling 3 small and 1 big cylinders as well as beam mould are filled with concrete. 8- Concrete compaction Until signs of water show at the surface, compaction should be thoroughly carried out using the vibrator. Care must be taken because increased vibration reduces the water content in the concrete. 9- Information After casting the beam, marking of the top part of the beam and group information is undertaken. 10- Cleaning The purpose of cleaning is to enhance the cleanliness of the lab by washing the tools and the mixer with water after all other procedures are completed. Testing of the beam: Module 4 In the above part, testing of the reinforced beam has thoroughly been explained. The support of the beam is done at the midspan. Read More