With more than 30 years of experience multiple options exist for removal of nitrogen and phosphorus from wastewater. Communities that were exempt from nutrient removal for many years must now comply with imposed nutrient limits, and in areas where technology-based nutrient limits have been in place communities are now faced with more stringent mass-based limits that are becoming more difficult to meet as their populations increase. Recent efforts in the industry have been focused on getting more out of existing plants, or in many cases where land is not available, in intensifying existing processes to increase capacity and/or level of treatment. This paper will discuss some of these methods and the general direction in which biological nutrient removal is developing to address these new challenges.

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