Ammonium removal from primary and secondary effluents using a bioregenerated ion-exchange process

Abstract

A new process for ammonia removal from sewage effluents is presented. The process uses an ion exchange material, zeolite, both as the separator of NH4+ from the wastewater and also as the carrier for a nitrifying biomass. The process is carried out in a single reactor operating in two modes: an adsorption mode in which the zeolite column acts as a typical ion exchanger and a bioregeneration mode in which the bacteria attached to the zeolite oxidizes the NH4+ to NO3–. The separation between carbonaceous removal and NH4+ removal enables the exclusive selection of nitrifiers at high concentrations attached to the zeolite, thus achieving high bioregeneration rates. This paper summarizes three years of research on the process and focuses on the operation with actual secondary and primary effluents. Process operation showed: (1) no bed clogging occurred due to suspended solids accumulation; (2) residual BOD from the adsorption phase resulted in only minimal heterotroph competition and thus, no fall in the rate of bioregeneration; (3) only a small deterioration in exchange efficiency due to zeolite biofilm coverage as compared to the ion exchange efficiency of “virgin” zeolite. Results show that both secondary and primary effluents can be successfully treated by the process.