In late summer, 2014, the city of Toledo had issues with their water, due to an

Question

In late summer, 2014, the city of Toledo had issues with their water, due to an algae bloom near the water intake. This phenomenon has become more prevalent in the past decade, due in part to increased concentrations of phosphorous in waste water.

The following table shows the annual inputs of phosphorous to Lake Erie:

                                                          Tons/year

Source

       Lake Huron                                  2,240

       Land drainage                              6,740

       Municipal waste                       19,090

       Industrial waste                          2,030

                                                            30,100

Outflow                                               4,500

Retained                                            25,600

Convert the retained phosphorous to concentration in micrograms per liter, assuming Lake Erie contains 1.2 x 1014 gallons of water and that the average phosphorous retention time is 2.60 years;

What percentage of the input comes from municipal water?

What percentage of the input comes from detergents, assuming they represent 70% of the municipal waste?

If 10ppb of phosphorous triggers nuisance algal blooms, would removing 30% of the phosphorous in the municipal waste and all of the phosphorous in the industrial waste be effective in reducing the eutrophication (unwanted algal blooms) in Lake Erie?

Would removing all of the phosphate in detergents help?

Explanation / Answer

25,600 tons of phosphorous is retained every year which is equal to 25,600*9.072*108  mg
Lake Erie contains 1.2*1014 gallons of water which is equal to 1.2*1014*3.78541 L
Concentration of retained phosphorous in lake = (25,600*9.072*108mg / 1.2*1014*3.78541 L)
Concentration of retained phosphorous in lake, mg/L = 0.05112 mg/L
Percentage of input that comes from municipal water = (19,090 / 30100)*100 = 63.42%
Removing 30% of the phosphorous in the municipal waste and industrial waste would
not be effective in reducing the unwanted algal blooms because this may sum upto
few mg/L which will be very much higher than 10ppb. The detergents coming from land
drainage, municipal wastes due to cleaning and washing would remove greater % of phosphate
but not all.

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