Conclusions
The results of this study show that direct filtration (i.e.
without pre-ozonation) of WWTP effluent through biological
activated carbon can significantl
reduce the DOC concentration by 35e60% which potentially
limits the formation of disinfection by-products if water is
chlorinated before discharge or reuse as well as bacterial
regrowth in the distribution system in the latter case;
reduce the concentrations of a wide range of PPCPs by more
than 90%, most of them down to levels below 10 ng L1
which lowers the potential risk of environmental and/or
human health impact;
reduce the baseline toxicity equivalent concentration, which
is a measure of all chemicals present including PPCPs and
small natural organic molecules, by 28e85% but less than the
individual chemicals quantified by chemical analysis because
transformation products formed during the biodegradation
process and natural compounds may also contribute to the
mixture toxicity measured with the bioassay.
On the contrary, under similar conditions, sand filtration
showed limited improvement of water quality. Moreover, the
long term study of the BAC filters showed steady performance
which suggests that EfOM and PPCPs are biodegraded, the filters
could therefore potentially be used for many years without
replacing the media. BAC filtration could be implemented as an
advanced treatment in WWTP to reduce the impact of the
effluent discharged into the environment and/or to produce
a water of a higher quality for reuse. In the meantime, further
investigations are necessary to fully understand the mechanisms involved in EfOM and PPCPs removal, particularly the role
of adsorption, and to clearly identify the key parameters that
have to be taken into account for the design of full-scale filters
(e.g. initial DO concentration, EBCT).