There is a dry cleaner in a shopping center that my wastewater plant serves. I have a BNR plant that nitrifies the ammonia in an aeration basin and then denitrifies the Nitrates in an anoxic zone. The alkalinity and DO are monitored closely in both processes. I will be testing the effluent for MBAS . I have been keeping the processes very stable and still I get mixed Nitrate results in the effluent. One week it will be 2 ppm and the next week it may be 12 ppm under the same conditions.