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After the rejection of the three options listed above, we re-considered the use of a float value to monitor the surface level of the alum solution. This should make dosing less variable and may help find a better solution to the orifice problem. Originally, we eliminated this design because we did not want to include small, hard-to-fabricate components into the design. Yet, this seemed like the only potentially successful option at the time, and still currently. Also, we are looking into the addition of a flocculation component; yet, this can be thoroughly researched and considered more next semester.
Add more info. about new Our current design eliminates the alum and chlorine doser components, as we decided to utilize a "batch" system instead. More information about this dosing system can be found below under the section entitled "Final Design Schematic." In the Point-of-Use Design Calculations for this new design, the head loss through the system is calculated.
and current final design of the point-of-use unit. Comment on how we omitted the alum doser and chlorine doser in the design (and how we will use "batch" system instead). Also, comment on why this schematic actually works: need 2-3 inches of water above foam based on graph in file.
Final Design Schematic (as of currently)
Because there were many problems with the alum/chlorine doser designs, a "batch" dosing system was used instead of a continuous system. In In this system, the user will manually add alum into the holding tank and chlorine into the distribution tank, while stirring the mixtures together. Influent Influent water dosed with alum from the holding tank flows into the filter column and is filtered through the depth of foam in the column. The The height of the foam in the column will be ten inches; this was chosen empirically based on previous experimental results from Summer 2010, which indicated that a ten inch height would result in the least effluent turbidity. Heights Heights greater than 10 inches generally performed about the same, providing diminishing returns. The The diameter of the column will be four inches to give the operator easy access to the contents inside for the purposes of cleaning and maintenance. After After the water is filtered through the column, it enters a flow accumulator designed to maintain constant flow through the unit. A A float valve can be utilized to monitor the level of water in the flow accumulator and, thus, control flow through the system. If If we decide to forego forgo these parts, the unit may be cheaper to construct, and the variable flow would then be determined by the height difference from the water surface in the foam column to the highest location of the exit tubing through which filtered water travels to the distribution tank. From From the flow accumulator, the water flows into the distribution tank where it is manually dosed with chlorine to deactivate any residual pathogens. The The water is then ready for distribution.
