Most people don't think of this as they kill bugs around their house. But the chemicals go somewhere, and how many people think if a little will kill 'em, a lot will kill them better! Waste plants are not made to remove pesticides. They scoot righht on through and into the water killing larvae, bugs, zooplankton. All of which are necessary in the food chain. It is even worse in places like CA where the big bad pilots douse agricultural products from the air. Of course they never overspray and hit waterways. Particularly the rice farms on the river's edge. Yes, northern CA is basically one big rice field until it turns into fruit orchards, nut orchards and olive orchards.
and here is a novel approach to sewage treatment. I wish it were used more.
I actually was trained in making what John Todd called Living Machines and they were very cool. Banana trees growing in Rhode Island in sewage in winter and fruiting. Trouble is they can't be designed as an engineer designs, but require an artists touch. making things live. not designed to live. It is a subtle difference. There is synergy in an ecosystem that just isn't designed in. For example, aquaitc mint (mentha aquiatica) grows well, and kills pathogens through root excretions, other plants take up copper, Nebraska rush kills pathogens, as do willows. And there is little money to be made at it.
More is the pity.
I don't know why hydroponic greenhouses don't utilize wastewater effluent to grow things like tomatoes, that would stay way above ground and never touch the sewage. Hell, find me a sludge pile that doesn't still have tomato seeds in it that will grow. or even using aquaculture.