Recirculating media filters providing wastewater treatment at rural schools with ammonia discharge limits
Buchanan, J. R.  2013.  Proceedings National Onsite Wastewater Recycling Association, 22nd Annual Technical & Education Conference, Millennium Maxwell House Hotel, Nashville, Tennessee. November 17-20.

Morgan County is located on the northern Cumberland Plateau in Tennessee. The Board of Education of this rural county has three schools that use individual wastewater treatment systems with discharge permits. Two of these schools have fixed-film bioreactors that recirculate effluent between the aerobic and anaerobic chambers, and the third has an activated-sludge system. All three systems utilize ultraviolet light for disinfection. Originally, these systems had numeric limits for BOD and fecal coliform, and ammonia was monitored by quarterly sampling. During the next permit cycle, the Tennessee Department of Environment and Conservation added numeric ammonia limits to these permits. These aerobic treatment technologies provided excellent oxygen-demand removal, but were regularly in violation of the ammonia limit. It took a combination of solutions to recover the nitrification process (and thus reduce the ammonia concentration) at these locations. The first approach was to reduce the use of quaternary ammonia sanitizers and to add alkalinity to the influent. Next, the mixed-liquor (biomass) in the aerobic zone of the activated-sludge plant renewed. Lastly, the accumulated solids in the recirculation tanks were pumped out from the media filter systems. When observing these systems in operation, it became clear that flow equalization needs to be incorporated into the design of wastewater treatment systems that serve schools. Much of the daily flow comes in a four-hour period during school days, and then in a two-hour period during sporting events. It was found that these systems are more likely to be in permit violation during times of peak flow.