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How to Run an Experiment
Overview
A This sampling method for testing raw water at the Pilot Plant has been used for several semester's research. Alum or PAC is used as a coagulant , and the dose can be set using process controller. Raw water running through flocculation tank can be sampled at any desired location by placing the tube settlers there. Sampling lines run to turbidimeters from three mobile the tube settlers. The tube settlers mimic sedimentation. Additionally a sampling line runs from the raw water inlet to a turbidimeter. Turbidity data is stored in a excel spreadsheet using process controller.
Alum Coagulant Dosing
Because the pilot plant takes water directly from the stream, environmental conditions change all the time and affect the incoming turbidity to the plant as well as the chemical composition of the particles causing turbidity. It is therefore necessary incredibly important to determine the best alum or PAC dose for each day of testing to ensure the formation of good flocs and collect appropriate data.
Tube Settlers are used to mimic sedimentation before the turbidity of water in the flocculator is measured. They can be moved to different locations along the flocculator in order to examine effluent turbidity at various stages of flocculation.
Data Collection and Analysis
Process Controller was used as our main data collection tool. Excel was then used to analyze the data that was collected. Process Controller is a software package that is used to control the raw water pump, the alum pump and data collection. For the raw water pump Process Controller only controls the on/off status of the pump. When the flocculator is running the raw water pump is turned on and the flow rate is controlled by a valve that can only be changed in increments. The flow rate was calculated by partially draining the flocculator to below the outlet pipe height. The valve was then opened to a noted location and the time it took for the water to rise 5 cm was recorded. To calculate the flow rate increase in the volume of water in the tank was divided by the time it took for that volume to fill in the tank. The volume was calcuated by multiplying the height the water rose in the tank by the cross sectional area of the tank. When this technique was used the head loss over the flocculator was small and did not affect the measurement. If the head loss increases then a new way to measure the head loss will need to be created. The choice of location for the tube settlers was chosen originally to establish general information about how flocs were forming in each individual section of the flocculator.
Use process controller to collect and store data and excel to analyze it.
Procedure
Make a folder in AguaClara data with the date
Example - 6.18.07. This way all information for tests run that day can be saved in a separate file, making data analysis quicker and easier.
Save datalog and statelog in correct folder
Go to the configuration tab, At the bottom under and to the left of Data directory path there is a button with the picture of a folder. Click on the button and choose the folder for the directory (this will save the statelog and the datalog to the chosen folder, if a statelog and datalog already exists for that day it will start a new one in this folder)
Save a copy of the setup
Look in the folder for the last date that data was collected. The most up to date version of the pilot plant setup documentation should be in there. The setup documentation (excel file) is where variables are listed; if you change any of them note it here. This is also where the location of the tube settlers should be noted. Make sure before you change anything you save it in the current date's folder and call it SetUp "date".
Save a copy of process controller method
Save in the folder with the date and call it PC setup. This will allow future users to see what the logic and variables were set to the day of the experiment. If for some reason a variable is changed and not noted this will allow the user to check to see what was used. Also, if for some reason Process Controller isn't working properly and states or set points disappear then this file can be used to re-install themThe states utilized by process controller allow the flocculator to run continuously and data to be collected about how alum dose and changes in Gθ affect flocculation and settled water turbidity With the configuration of the baffles spaced evenly throughout the flocculator G remains constant through the 3 sections. However, by sampling at different locations the volume of the flocculator that the water travels through changes which changes θ and thus Gθ. The tube settlers were placed one at the end of each section. Original Tube settler set-upThis figure shows the configuration that was originally tested and used to collect data. This configuration was chosen to get a general understanding of how each section contributed to floc formation and final settled water turbidity.