Facultative Anaerobe Bioselector – Aerobic Digester
Application / Industry: Municipal Wastewater Treatment
Customer Name: Carbondale Wastewater Department, Carbondale, CO
Consulting Engineer: SGM Engineering, Glenwood Springs, CO
Process Fluid: Municipal Waste Activated Sludge
Process Treatment Method: Aerobic Digesters No. 5
Challenge
The Carbondale, Colorado, Wastewater Treatment Facility needed to optimize its sludge management process while achieving significant odor reduction. The staff wanted to operate one of its digester tanks in an ON/OFF blower cycling mode to enhance the development of facultative anaerobe bacteria in the process fluid, which thrives in conditions of low dissolved oxygen and in processes where oxygen supply is varied. These bacteria are the most stable 
available in nature for wastewater treatment and when in high populations will not produce hydrogen sulfide gas. Carbondale wanted the mixing system designed for 100% operational time, allowing for field adjustment to a blower cycling mode for development of the facultative bacteria.
Solution
Tideflex® Technologies engineers designed a maintenance-free Coarse Bubble Mixing and Oxygen Supply System that allowed operators to utilize ORP (Oxygen Reduction Potential) probes to monitor the environmental state of the process fluid and adjust blower run times accordingly. The ability of a mixing system to operate on an ON/OFF basis was critical in development of the facultative anaerobes. Diffuser systems that cannot be operated with the blower off will result in full system clogging of the diffuser piping.
Results
Carbondale plant operators were able to develop a high-density population of facultative bacteria in this tank, resulting in the total elimination of discharge odors. These bacteria are also best for nutrient reduction and de-nitrification as these are the same bacteria utilized in Nutrient Removal Systems in the primary bioreactors. Since Tideflex® Check Valve Diffusers prevent clogging and are maintenance-free, operators were able to cycle the blower to produce varying ORP states without experiencing any mechanical problems in operation. At start-up, during operation, and after stabilization of the facultative colony, waste sludge process fluid discharged no hydrogen sulfide gas or odors. Carbondale has implemented several other Tideflex® systems in adjacent process vessels utilizing ORP monitoring to minimize the blower operational run times.