Pathogen Filtration, Heterogeneity, and the Potable Reuse of Wastewater

Abstract

Filtration is commonly employed in water and wastewater treatment to remove particles and reduce the concentration of microbial pathogens. All physical models of packed-bed filtration are based on a proportional relationship between particle removal per unit depth of bed and the local particle concentration, dC/dz = -C/l, where l is the filtration length scale. Although l is known to vary with time and filter depth for heterogeneous suspensions or "dirty" beds, this paper demonstrates that the filtration rates of even seemingly monodisperse particle suspensions under clean-bed filtration conditions cannot be described with a single filtration length scale. A new model is derived for particle filtration that accounts for heterogeneity at two different spatial scales. Heterogeneity at the scale of the pathogen and/or collector (microscale heterogeneity) leads to a slow power-law decay of contaminant concentration with distance, instead of the fast exponential decay predicted by the standard model. Heterogeneity at the filter scale (macroscale heterogeneity) provides another level of complexity that can be evaluated once microscale heterogeneity effects are characterized. This model for microscale and macroscale heterogeneous particle filtration is verified by filtration experiments on a recombinant analogue of the waterborne pathogen Norwalk virus.

Transport of multiple Escherichia coli strains in saturated porous media

“…The observed power-law distributions in i α are in agreement with observations made by other researchers (Lutterodt et al, 2009b, Brown and Abramson, 2006, Tufenkji et al, 2003, Redman et al, 2001, 2001a. The large variations in i α give rise to the power-law distribution (Lutterodt et al, 2009b) and may be due to variations in cell surface properties giving rise to differential affinity of cells for the collector grain surfaces as explained by others (Simoni et al, 1998, Baygents et al, 1998.…”

“…However, often, the required reductions in bacterial concentrations at estimated target distances are not achieved. The failure of the filtration theory to accurately predict bacteria transport distances has been ascribed to variations in bacteria sticking efficiencies (Albinger et al, 1994, Tong and Johnson, 2007, Foppen et al, 2007a, b, Lutterodt et al, 2009a, b, Dong et al, 2006, Li et al, 2004, Redman et al, 2001, 2001aAlbinger et al, 1994. Recent research has indicated that the cell affinity for collector surfaces varies within (Lutterodt et al, 2009a, b,chapters, 2&3) and among (Lutterodt et al, 2009a,b, chapters 2 and 3, Bolster et al, 2009 bacteria strains.…”

Processes in microbial transport in the natural subsurface

“…Baygents et al [10] and Glynn et al [46] observed a bimodal distribution of surface charge density in selected bacterial strains, providing experimental support for this hypothesis. Redman et al [95,96] proposed a multiscale (fractal) distribution of filtration length scales arising from microscale heterogeneity in surface properties of microbes and collectors, and provided experimental support for the model based on column experiments of virus transport. Mailloux et al [74] estimated a field-scale distribution of apparent collector efficiencies from observations at various distances in the NC flow cell at the South Oyster site.…”

Taxonomic Precision of Different Hypervariable Regions of 16S rRNA Gene and Annotation Methods for Functional Bacterial Groups in Biological Wastewater Treatment

“…This group of bacteria will hereafter be referred to as the operational group. In addition, the occurrence and abundance of bacterial pathogens in activated sludge is also a concern, since it may be highly correlated with occurrence of pathogens in effluent discharged into receiving water [9,10,11].…”