What folks need to understand about septics is that the only thing they do to nutrients is put them into solution. Then, we put that water in the ground. If we're lucky, the plants growing over the drainfield suck em up. If not, they move with the water wherever it goes. If your drain field is close to water it gets there quicker.

The nutrients are not a problem, per se, IF we managed the Canal for planktivores. If we made sure that there were enough beasts that ate the algae. But, we gotta harvest those clams and oysters and mussels and fish whose fry eat algae and so on and so on and so on. Choices have consequences.