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River Water Testing


​A city has tested the water in a nearby river. The following data were recorded:

pH DO ammonia E. coli
River 7.54 9.4 mg/L 3.8 mg/L 515 colonies/100 mL
Standard 6.5-8.5 4 mg/L 5.0 mg/L 235 colonies/100 mL

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Based on this report, what will the city's residents be most interested in improving?


Decreasing the pH which has been affected by acid rain and which could cause a fishkill.


Decreasing the ammonia which has increased due to industrial waste, and which can cause cancer in humans who use the river as a drinking water source.


Decreasing the DO which is too high for the wildlife that depend on the river for drinking water.


Decreasing the E. coli which is high due to agricultural runoff and combined sewer overflows and which can cause illness in people who swim in the river.


Nothing needs to be changed, since the water testing data shows all variables are within healthy levels.