ABSTRACT
In the complete absence of nutrients, a waterway would be virtually sterile and incapable of supporting a rich community of organisms. In most waste treatment systems, however, the micronutrients are usually plentiful, and the major concern is avoiding rate limitations from lack of the macro-nutrients nitrogen and phosphorus. Nitrogen enters a sewage treatment plant primarily in the form of ammonium and organic-nitrogen forms such as urea and protein. Obviously, real-world situations are often complex, but the nutrients always considered are nitrogen and phosphorus. If wastewater temperatures are not extremely cold, say less than 5 to 10°C, the autotrophic nitrifiers can be grown in the same bioreactor with the heterotrophic microbes used for carbon removal. Once the Phoredox concept was understood, it was a logical step to apply it to processes configured for both phosphorus and nitrogen removal.
