TT (advanced treatment) | Benefits | Obstacles | Recommendations |
a or b (UV) | ・ Efficient disinfection (comprising ARB demobilization) ・ No DBPs 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 | • Toxicity trials recommended ・ DBPs (following the disinfectants utilized) must be controlled |
d (O3/AOP and biological post-treatment) | ・ Efficient disinfection (comprising ARB demobilization) ・ CECs reduction: Elevated throughout ozonationand (solar) photo Fenton, moderate with UV/H2O2 ・ Full-scale evidence on practicability onlyfor O3 | ・ Generation of numerous DBPs (Nnitrosodimethylamine (NDMA), bromate) throughout ozonation • Production of oxidation transformation products throughout AOP and ozonation ・ Partial ARGs reduction | • Toxicity trials recommended ・ NDMA and bromate must be controlled inO3 treatment |
e (GAC and UV) | • Efficient disinfection via UV • Elevated CECs reductionvia GAC ・ Full-scale evidence on practicability | • Poor/no reduction of ARB & ARGs via GACalone ・ 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 eliminationvia PAC ・ Full-scale evidence on practicability forCEC removal by PAC | • Poor/no reduction of ARB & ARGs via PACalone ・ • For UV see above, TT a & b |
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g (NF or RO membrane filtration, with potential pre-treatment with MF or UF membranes) | • Efficient disinfection for bacteria (comprising ARB) and protozoa for all membranes; viruses well removed by UF, NF & RO • ARGs well removed by NF and RO ・ CECs removal from poor (MF, UF) to verygood (NF, RO) following membrane type • RO and partially also NF reduce salinity ・ For post UV-C see TT a & b | • Poor/no reduction of ARGs at full-scale byMF (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 ifthe risk of unknowns and spills is considered high ・ Consider high UV doses if NDMA can be suspected in the membrane effluent (e.g. following prior chloramination) |