Question

I am diluting wastewater (ww) with creek water. Say I have an initial concentration of 10% wastewater in a bin. I have 1 liter wastewater and 9 liters creek water. I keep pouring 1 liter aliquots of creek water into this bin to further dilute. My trash bin only holds a volume of 50 liters, but I need to keep diluting. If I take out half of the total volume in my bin (to have only 25), but I keep adding 1L, how do I know what my ww concentration is when I add the subsequent 1L of creek water to the mixture?

Answer 1

If the initial concentration of the waste water is 10%, and the bin contains 1 liter of 10% waste water, then when the 50 liter bin is full, 49 liters of creek water should have been added. At this point the concentration of the waste water should be 0.2% (2% of 10% waste water) in the bin. When 25 liter is taken out after mixing well, the concentration of the waste water in the remaining diluted water should be the same 0.2%. When one more liter of creek water is added, the dilution calculation should take only the remaining 25+1 liter into account. So the final concentration of waste water in 26 liter of total water mixture should be 0.1923%