My thought was maybe other things go down the drains that alter the chemistry? Cheap bleach vs expensive bleach? Hummus? Shampoo? Or maybe just a meat rich diet

My thought was maybe other things go down the drains that alter the chemistry? Cheap bleach vs expensive bleach? Hummus? Shampoo? Or maybe just a meat rich diet vs a more vegetarian diet of the poor folks. He also said that in the pumping stations there are thousands of frogs and toads that have fallen into the road side drains and have been swept down the sewers. They get chewed up in the pumps.