Impact of a nitrified biofilter on NDMA formation

An emerging process to control bromate formation is to add chloramines upstream of the ozone contactor (Buffle et al., 2004). As part of this process, ammonia can be transformed?via nitrification?on a biologically active filter (Yun et al., 2009). In previous demonstration-scale testing, a nitrified biofilter resulted in an increase in the formation of N-nitrosodimethylamine (NDMA) during post-chloramination (Krasner et al., 2010). It was hypothesized that soluble microbial products (SMPs) from the nitrifiers were a source of NDMA precursors. In other research, laboratory-generated SMPs from activated sludge were found to contribute to the formation of NDMA (Krasner et al., 2008). In addition, in the demonstration-scale tests, there was more formation in the biofilter effluent at pH 9 at 5°C than at 25°C. However, it was not understand why this phenomenon occurred.