TT (advanced treatment)

Benefits

Obstacles

Recommendations

a or b (UV)

・ Efficient disinfection (comprising ARB [30] demobilization)

・ No disinfection by-products (DBPs) [31] [32] generation contrasted to chemical disinfection

・ Poor/no CECs elimination

・ Partial elimination of ARGs

・ Compliance with local residual bacterial density standards should be evaluated

c (chemical disinfection)

・ Efficient disinfection (comprising ARB demobilization)

・ Poor/no reduction of CECs and ARGs

・ Generation of DBPs [33] [34] [35]

・ Toxicity trials recommended [36] [37]

・ DBPs (following the disinfectants utilized) must be controlled [38] [39] [40] [41]

d (O₃/AOP and biological

post-treatment)

・ Efficient disinfection (comprising ARB demobilization)

・ CECs reduction: Elevated throughout ozonation and (solar) photo Fenton [42] , moderate with UV/H₂O₂

・ Full-scale evidence on practicability only for O₃

・ Generation of numerous DBPs (N nitrosodimethylamine (NDMA), bromate)

・ throughout ozonation

・ Production of oxidation transformation products throughout AOP and ozonation [43] [44] [45]

・ Partial ARGs reduction

・ Toxicity trials recommended

・ NDMA and bromate must be controlled in O₃ treatment

e (GAC and UV)

・ Efficient disinfection via UV

・ Elevated CECs reduction via GAC

・ Full-scale evidence on practicability

・ Poor/no reduction of ARB & ARGs via GAC alone

・ For UV see above, TT a & b

・ Reducing adsorption capacity with elevating bed volume must be considered

f (PAC and UV)

・ Efficient disinfection via UV

・ Elevated CECs elimination via PAC

・ Full-scale evidence on practicability for CEC removal by PAC

・ Poor/no reduction of ARB & ARGs via PAC alone

・ For UV see above, TT a & b

g (nanofiltration (NF) or reverse osmosis (RO) membrane filtration, with potential pre-treatment with microfiltration (MF) or ultrafiltration (UF) membranes)

・ Efficient disinfection for bacteria (comprising ARB) and protozoa for all membranes; viruses well removed by UF, NF & RO [46]

・ ARGs well removed by NF and RO [47]

・ CECs removal from poor (MF, UF) to very good (NF, RO) following membrane Type [48]

・ RO and partially also NF reduce salinity [49] [50]

・ For post UV-C see TT a & b

・ Poor/no reduction of ARGs at full-scale by MF (for UF some reduction is expected)

・ Poor CECs elimination for MF and UF

・ Elevated energy needs for NF and RO

・ Formation of a substantial concentrate waste stream by NF and RO

・ For post UV-C see TT a & b

・ Effect of membrane features on disinfection, ARB, ARG, and CEC reduction has to be carefully taken into account in design

・ Consider AOP instead of UV disinfection if the risk of unknowns and spills is considered high

・ Consider high UV doses if NDMA can be suspected in the membrane effluent [51] (e.g. following prior chloramination)