Impact of particles on UV disinfection of water and wastewater effluents: A review

Particles in water sources may be classified in various groups such as living vs. non-living, nano vs. sub-micron to micron sized and mineral vs. organic. Living particles for example comprise of bacteria, viruses, protozoa and algae while non-living particles include mineral particles, organic particles, cell debris and macromolecules. Particles in water sources may be dispersed as single entities or associated with multiple particles in flocs or aggregates. Particles may be further characterized by their chemical nature, size distribution, density, absorbance, scattering find typical gross measurements such as turbidity and suspended solids. Although ultraviolet (UV) irradiation is principally accepted as a primary disinfection technology for use in water and wastewater effluent, still research is needed to understand the extent to which particles in water may hinder the UV treatment efficacy by interacting with microbial pathogens. Both of the phenomena: (1) particles physically associated with microorganisms in a clump or aggregate and (2) particles not physically associated with microorganisms however interact by shielding, absorbing, scattering or blocking UV light, are integrated in the term "particle-microbe interactions". This review covers the impact of the interaction between microorganisms (mainly bacteria) which are the target for UV disinfection and particles in water and wastewater effluents on the efficacy of UV disinfection.