r the WWTP outflow undergoes low dilution
in surface water, ozonation of the biologically purified
wastewater should be considered. If 5–10 g/m3
of ozone are used, concentrations of many pharmaceuticals
are reduced below detection limits (38). The
effectiveness of the ozone treatment depends on the
chemical properties of the compound and the background
level of dissolved organic carbon in the wastewater (39). Although ozonation costs only a few cents
per cubic meter of wastewater, the energy expenditure
is 0.1–0.2 kilowatt-hours per cubic meter, which
is significant in comparison with the total energy consumption
of a WWTP. In addition, although initial results
indicate significantly reduced toxicity, oxidation
products formed during ozonation should be further
investigated prior to large-scale application (40).
Treatments such as nanofiltration or activated carbon
adsorption are more cost-intensive than ozonation
and therefore are of interest only if the wastewater
is used for groundwater recharging or directly reused
as drinking water. In addition to these short-term
fixes, the following more sustainable measures should
be considered for the future.