Linear FLow Orifice Meter
Access to clean water is a human right that is unattainable by many people. The Agua Clara project is working to design and build water treatment plants in Honduras, which is among the poorest countries in the world. Major emphasis is placed on the integration of the plants into the communities effectively. Careful consideration is made regarding the specific requirements for each community. In the neighborhoods with the greatest need for water purification technologies there is often an intermittent flow of electricity. Current water treatment designs control chemical dosing and flow rates with electrically powered pumps and sensors. The intermittent electricity supply combined with the current system design would result in intermittent supply of ?treated water,? water sent intermittently through pipelines is no longer considered pure because during shut-down the pipelines will form a vacuum pressure pulling surrounding material into the pipe space contaminating future water flows. The Agua Clara design requires no input of electricity for operation of the plant. Water flows through the plant from high elevation to low elevation; elevation change is the energy source for the water treatment. The water is treated through 4 processes. The first step in water treatment is a grit chamber which removes the large objects such as branches from the water flow using a large spacing metal grid. Water is then treated with a coagulant, aluminum hydroxide, and sent through a flocculation tank. The coagulant binds to the foreign particles (contaminants) in the water and creates flocs, similar to a snowflake. The flocs increase in size as they move through the flocculation tank. Sedimentation follows the flocculation stage, the large flocs are settled out and the clean water is drawn of the top of the sedimentation tank. As a final measure the purified water is treated with chlorine to kill any bacteria remaining the water and provide a residual chlorine concentration for disinfection during transport. My research is focused on the dosing of aluminum hydroxide to the water. Currently the operator of the plant manually adjusts the flow rate of aluminum hydroxide as the flow rate through the treatment plant changes. Automation of the process is required to more rapidly and reliably meter alum to the inflow. The automation process is designed using an entrance tank, riser pipe, and float system. The contaminated water flows into the entrance tank the through a riser pipe and then empties into the flocculation tank. A system of floats and lever arms change the flow rate of alum based on the height of the water in the entrance tank. The height of water in the entrance tank is based on the outflow of water through orifices in a riser pipe located in the entrance tank. The height in the water in the entrance tank with a single outflow orifice is correlated to the square root of the flow rate according to the orifice equation. This relationship makes metering aluminum hydroxide through a float system nearly impossible. Linearization of the head of the water in the entrance tank as a function of flow rate is the goal of my project. If the pattern of orifices on the riser pipe can be situated to create a linear relationship between water height in the entrance tank and the flow rate through the plant then the float system can easily adjust the alum flow rate.
agua clara; LFOM; Linear Flow Orifice Meter; aguaclara
dissertation or thesis