Typ. domestic wastwater TN concentrations reange between 20-85 mg/l with a medium value of 40 mg/l.  A 50% TN concentration, therefore,  must reduce concentration beflow  20 mg/l if permit discharge standards are to be meet. In my professiional judgement, no TL-2 system is designed to meet  this standard and could not be used in the Cheaspeake Bay area without additional treatment processes added after the system. 

A significant number of water sources in the affected area may lack sufficient alkalinity to achieve 50% TN removal. The most common BAT to supply alkalinity is the use of chemical treatment of either the wastewater or water source to meet process demands. VHD, in my opinion,  has greatly underestimated the construction and o+m cost s associated with the proposed standard by ignoring the variability in water sources in the Cheasapeake Bay watershed.