EPA Raises Biodiesel Manadate for Refiners

Sounds like it contains elements of the biologic filtration for aquariums. The Sludge uses a range of bacteria and other microbes to break down organic matter and urea. Ammonia is a major waste product of the process, and where the bacteria aquarium hobbyists should be aquainted step in. Converting the ammonia into nitrite and then nitrate. This all happens aerobically.

At a water treatment plant, the water high in nitrate is pumped to an anaerobic area. There bacteria eat the nitrate and give off the nitrogen, which gets driven off by agitation. Skip the anaerobic step, and you could use the nitrate rich water for algae. Depending on layout of the treatment plant, it could be simple to do.