Biodosimetry: Model calculations for u.v. water disinfection devices with regard to dose distributions

The increasing importance of disinfection of drinking water by u.v. radiation makes it necessary to determine the u.v. dose which is applied to the water by u.v.-disinfection plants. In Austria a minimum microbicidal dose of 400 Jm⁻² at a wavelength of 253.7 nm is demanded for drinking water, the control of it shall be assured by type testing. A method was developed in using calibrated spores of Bacillus subtilis as biodosimeter which are added to the inflowing water, and after determination of their survival rate in the plant one can deduce the applied dose from it. This procedure is unproblematic as long as all microorganisms receive the same dose on their way through the reactor. But in some cases, and probably this is the normal case, not all microorganisms receive the same dose. It follows that a dose distribution will exist among the test organisms which have passed through the reactor. The dose (reduction-equivalent dose or RED) which is deduced from the survival rate of the microorganisms passing flow-through systems for u.v.-disinfection of wastewater or drinking water in general is different from the arithmetic mean of the dose distribution. The RED depends on the special form of the dose distribution and on the specific shape of the survival curve of the test organisms. The broader the dose distribution and the higher the u.v.-susceptibility of the microorganisms, the lower is the measured RED. But if the survival curve of the microorganisms used would have a shoulder (D_s > D_m), and the dose distribution would overlap with the shoulder the RED may increase. We investigated by calculations and by experiments the influences on the test results obtained by this method.     

Validation of medium-pressure UV disinfection reactors by Lagrangian actinometry using dyed microspheres

Lagrangian actinometry (LA) has been demonstrated to represent an alternative to conventional biodosimetry for validation of ultraviolet (UV) disinfection systems used in drinking water treatment. However, previous applications of LA for this purpose have all involved monochromatic (λ = 254 nm) UV reactor systems. To address this issue, dyed microspheres (DMS) were applied for quantification of dose distribution delivery by field-scale UV reactor systems based on medium-pressure Hg lamp (MP) technology. These MP reactor systems are characterized by polychromatic output. Dose distribution estimates developed by LA for these reactors were reported as equivalent 254 nm distributions. When combined with the UV₂₅₄ dose-response behavior for challenge organisms used in simultaneous or parallel biodosimetry experiments, the dose distribution estimates developed from the microspheres yielded estimates of challenge organism inactivation that were in agreement with measured values. For one of the reactors tested, biodosimetry tests were conducted with two challenge organisms that had different UV dose-response behavior; UV dose distribution estimates from LA yielded predictions of microbial inactivation that were in agreement with measured inactivation responses for both challenge organisms for all test conditions. It is likely that the agreement between LA results and biodosimetry data was related, in part, to the agreement between the action spectra of the microspheres and the challenge organisms. Because LA yields a measure of the UV dose distribution delivered by a reactor, the information from LA assays will eliminate many sources of uncertainty in the design and operation of UV systems, thereby allowing for implementation of UV reactor systems that are less expensive than their predecessors, yet more reliable.     

Biomarker response in the earthworm Lumbricus terrestris exposed to chemical pollutants

Earthworms are important organisms for the soil ecosystem. They are sensitive to toxic chemicals and represent useful bioindicator organisms for soil biomonitoring. Recently the use of biomarkers in earthworms has been increasingly investigated for soil monitoring and assessment purpose. The aim of the preset paper was to analyze the pollutant-induced response of a suite of cellular and biochemical biomarkers in the earthworm Lumbricus terrestris exposed to copper sulphate or methiocarb in OECD soil at the maximal concentrations recommended in agriculture. These responses were compared to lifecycle parameters such as survival, growth and reproduction.Granulocyte morphometric alteration, lysosomal membrane stability, metallothionein concentration, and acetylcholinesterase activity were considered. In either copper sulphate or methiocarb exposure conditions the mean percentage variation of the pollutant-induced molecular and cellular biomarkers was consistent with the whole organism end-point responses. In particular pollutant-induced granulocyte enlargement, detected in either copper sulphate or methiocarb exposed organisms, showed to be a potential general biomarker that may be directly linked to organism health. Compared to the other biological responses to pollutants, it showed high sensitivity to pollutant exposure suggesting its possible applications as a sensitive, simple, and quick general biomarker for monitoring and assessment applications.     

Quality and quantitative assessment of the impact of magnetic field and ultra sound on water with different concentration of deuterium

The paper gives results of experimental research of changes of the dimensional spectrum of gigantic heterophase clusters of water with various content of deuterium under the effect of magnetic field. It is found that th magnetic field effect (0.6 T) results in an increase of arithmetic mean diameter of clusters for light, deionized and heavy water respectively by 21, 15 and 10%. One may observe the relationship between the content of clusters and the value and time of action of the magnetic field. Ultra sound effect (44 kHz), on the contrary is conducive to a decrease of the arithmetic mean diameter of clusters of specified waters respectively by 16; 11 and 8%.     

Interspecies correlations of toxicity to eight aquatic organisms: Theoretical considerations

Interspecies correlations allow the prediction of toxicity to a number of other species. However, little attention has been paid to the theoretical considerations of the interspecies relationship based on the differences of bio-uptake and toxic mechanism between species. This study examines the interspecies correlations of toxicity between species of Vibrio fischeri, river bacteria, algae, Daphnia magna, carp, Tetrahymena pyriformis, fathead minnow and guppy based on the theoretical background. The results show that there are good interspecies correlations between marine bacterium and fresh water bacteria or fish and fish. It is suggested that compounds share the same bio-uptake and toxic mechanism of action between the species. On the other hand, poor interspecies relationships were found between toxicities to algae and T. pyriformis or D. magna. It is suggested that compounds have different toxic mechanisms of action between these species. Interspecies relationships can be improved by inclusion of the octanol/water partition coefficient or the energy of the lowest unoccupied molecular orbital. They reflect the difference of bio-uptake or toxic mechanism of action between species for organic compounds. Benzoic acids show very different toxicity contributions to the three species, V. fischeri, D. magna and carp. They can be easily absorbed into the unicellular bacteria, V. fischeri. On the contrary, the skin and lipid content of multicellular organisms, such as D. magna and fish, can strongly inhibit the bio-uptake for ionizable compounds, which results in the different toxic effect between V. fischeri and D. magna or carp. Good correlation coefficients were observed between toxicities to V. fischeri and D. magna or fishes by inclusion of hydrophobic and ionization parameters. V. fischeri or D. magna can serve as a surrogate of fish toxicity for hydrophobic and ionizable compounds studied. Toxic mechanisms of action are discussed based on the theoretical background of the interspecies correlation.     

Microbial toxicity of metal oxide nanoparticles (CuO, NiO, ZnO, and Sb2O3) to Escherichia coli, Bacillus subtilis, and Streptococcus aureus

In this study, the microbial toxicities of metal oxide nanoparticles were evaluated for Escherichia coli, Bacillus subtilis, and Streptococcus aureus in laboratory experiments. The nanoparticles tested were CuO, NiO, ZnO, and Sb₂O₃. The metal oxide nanoparticles were dispersed thoroughly in a culture medium, and the microorganisms were cultivated on Luria-Bertani agar plates containing different concentrations of metal oxide nanoparticles. The bacteria were counted in terms of colony forming units (CFU). The CFU was reduced in a culture medium containing metal oxide NP, and the dose-response relationship was characterized. CuO nanoparticles were found to be the most toxic among the tested nanoparticles, followed by ZnO (except S. aureus), NiO, and Sb₂O₃ nanoparticles. We determined that the intrinsic toxic properties of heavy metals are also associated with the toxicity of metal oxide nanoparticles. Ion toxicity was also evaluated to determine the effects of metal ions dissolved from metal oxide NPs, and the toxicity induced from the dissolved ions was determined to be negligible herein. To the best of our knowledge, this is the first study of the toxicity of NiO and Sb₂O₃ NPs on microorganisms. We also discuss the implications of our findings regarding the effects of the intrinsic toxic properties of heavy metals, and concluded that the apparent toxicities of metal oxide NPs can largely be understood as a matter of particle toxicity.     

Dose-response functions in aquatic toxicity testing and the Weibull model

A linear transformation of the Weibull model for dose-response functions is developed. The transformation is analogous to the probit and logit transformations. Typical dose-response curves in aquatic toxicity testing using macroorganisms and algae are analyzed by the Weibull and probit models, and it is shown that the Weibull model generally provides at least as good a fit to experimental data as the probit model.The expansion of the Weibull model to reflect the survival fraction or yield of organisms under multiple toxicant limiting conditions leads to particularly useful expressions for simple similar joint action (concentration addition with parallel response curves for the individual toxicants) and independent joint action (response multiplication). Explicit water quality criteria are derived based on both formulations. The multiple toxicity models, expanded to include concentration addition with non-parallel response curves for the individual toxicants, are applied to algal assay data for Selenastrum capricornutum exposed to manganese, copper, and lead. The fact that the yield based on response multiplication for the manganese-lead pair is lower than that calculated from concentration addition suggests that water quality criteria based on concentration addition may not always provide safe limits.     

Amendments for the in situ remediation of contaminated sediments: Evaluation of potential environmental impacts

Active sediment caps represent a comparatively new technology for remediating contaminated sediments. They are made by applying chemically active amendments that reduce contaminant mobility and bioavailability to the sediment surface. The objective of this study was to determine if active cap amendments including organoclay, apatite, and biopolymers have the potential to harm benthic organisms. Methods included laboratory bioassays of amendment toxicity and field evaluations of amendment impacts on organisms held in cages placed within pilot-scale active caps located in Steel Creek, a South Carolina (USA) stream. Test organisms included Hyalella azteca, Leptocheirus plumulosus, Lumbriculus variegatus, and Corbicula fluminea to represent a range of feeding modes, burrowing behaviors, and both fresh and saltwater organisms. In addition to the laboratory and field assays, chemical extractions were performed to determine if the amendments contained harmful impurities that could leach into the ambient environment. Laboratory bioassays indicated that 100% apatite had minimal effects on Hyalella in freshwater and up to 25% organoclay was nontoxic to Leptocheirus in brackish water. Field evaluations indicated that pilot-scale caps composed of up to 50% apatite and 25% organoclay did not harm Hyalella, Lumbriculus, or Corbicula. In contrast, organisms in caps containing biopolymers died because of physical entrapment and/or suffocation by the viscous biopolymers. The extractions showed that the amendments did not release harmful concentrations of metals. These studies indicated that apatite and organoclay are nontoxic at concentrations (up to 50% and 25% by weight, respectively) needed for the construction of active caps that are useful for the remediation of metals and organic contaminants in sediments.     

Changes in the non-protein thiol pool and production of dissolved gaseous mercury in the marine diatom Thalassiosira weissflogii under mercury exposure

Two detoxification mechanisms working in the marine diatom Thalassiosira weissflogii to cope with mercury toxicity were investigated. Initially, the effect of mercury on the intracellular pool of non-protein thiols was studied in exponentially growing cultures exposed to sub-toxic HgCl₂ concentrations. T. weissflogii cells responded by synthesizing metal-binding peptides, named phytochelatins (PCs), besides increasing the intracellular pool of glutathione and γ-glutamylcysteine (γ-EC). Intracellular Hg and PC concentrations increased with the Hg concentration in the culture medium, exhibiting a distinct dose-response relationship. However, considerations of the PCs-SH:Hg molar ratio suggest that glutathione could also be involved in the intracellular mercury sequestration. The time course of the non-protein thiol pool and Hg intracellular concentration shows that PCs, glutathione and γ-EC represent a rapid cellular response to mercury, although their role in Hg detoxification seems to lose importance at longer incubation times. The occurrence of a process of reduction of Hg(II) to Hg° and subsequent production of dissolved gaseous mercury (DGM) was also investigated at lower Hg concentrations, at which the PC synthesis doesn't seem to be involved. The significant (P < 0.01) correlation between the cellular density in solution and the production of DGM suggests that this diatom is capable of directly producing DGM, both in light and dark conditions. This finding has been confirmed by the absence of DGM production in the culture media containing formaldehyde-killed cells. Finally, the relationship between these two different pathways of Hg detoxification is discussed.     

An analysis of the combined effects of organic toxicants

This paper presents a basic database for the joint actions of 44 binary mixtures of various organic toxicants on Escherichia coli. The multiple toxicity behaviors observed from the E. coli organisms were analyzed and compared with previous works based on the Microtox tests. The two kinds of tests produced quite different responses, in terms of the joint action mode and the sum of toxic units, to various organic mixtures. However, detailed analyses with the considerations of the chemical's mechanisms of toxicity and the slope of toxicant's dose-response curve have revealed several general criteria for the prediction of combined effects of organic toxicants. First, for both reactive and non-reactive toxicants, either additive or less than additive (antagonistic) joint actions will be observed for chemicals of the same mechanism of toxicity. Second, the mixture of reactive toxicants with different mechanisms is the only category of organic mixtures associated with frequent observations of synergism. Third, greater-than-additive (synergistic) effects are inherently associated with toxicants having flat dose-response curves. Less than additive effects are, however, mainly related to a chemical's display steep dose-response curves. Model analyses indicate that the observed synergistic effects are due to response addition or response multiplication joint actions. Hence, most of the synergistic joint actions are non-interactive in nature and are governed by the dose-response relationships of individual toxicants.     

The effect of geometrical microstructure of solid surfaces on the kinetics of water vapour condensation process

Alternating environmental conditions not only influence the long-term performance of construction materials but also the overall energy consumption. Humidity in building partitions has particularly strong effect. Condensation of water vapour and subsequent absorption of water adversely affect thermal properties and, if persistent may lead to the severe deterioration of building envelop.This paper presents the results of a non-contact dynamic study of the condensation process. The investigations give a clear evidence of the strong relationships between the rapid growth of water vapour condensate and the roughness of the surface. Experimental results confirmed that the kinetics of condensation process depends very much on the geometrical characteristics of surfaces—their roughness. It is proposed by the authors to adopt for analysis of the process two parameters—mean arithmetic deviation of profile R_a and mean spacing of profile S_m. Critical value of free Gibbs enthalpy, critical radius of nucleus on surfaces of complex microstructure as well as rate of condensate growth during the second stage of condensation process have been expressed as functions of R_a and S_m.     

A reliability-based methodology for considering corrosion effects on fatigue deterioration in steel bridges - Part II: Case study of Neka Bridge -

The methodology presented in Part I is examined on Neka Bridge, a railway, truss bridge in northern Iran. The study includes: considerations of climate and air pollution, extraction of the stress-time histories from the FE model, prediction of future traffic volumes in a probabilistic manner and assessment of the effects of MR&R actions on the deterioration profile. PDF of D is determined using Monte Carlo simulations, and the reliability profile is calculated from the performance function. The study shows that for a target reliability of 2.0, the fatigue life of the bridge is reduced by either 29% or 31% if dose-response function or qualitative-based y-t function is used, respectively.     

The Simultaneous Bioremoval of Cr(III) and Dye by Immobilized <Emphasis Type="Italic">Phanerochaete Chrysosporium</Emphasis>

To attain better removal efficiency and higher toxic resistance, the alginate was used to immobilize Phanerochaete chrysosporium BKM-F-1767 in this study. And according to the characteristics of tannery wastewater, inhibitory effect of Cr(III) to the decolorization was investigated and adsorption kinetics of Cr(III) by the immobilized P. chrysosporium had been established. Furthermore, the Acid Violet 7 and Basic Fuchsin contributed as the experimental dyes in the paper, the removal studies were performed at an initial pH of 4.5. The combined effects of Cr and dyes on the simultaneous removal properties were determined in a batch system at different levels of Cr and dyes. Moreover, the dose-response relationship and a kinetic equation describing the simultaneous removal properties had been established. The results have proved that the immobilized P. chrysosporium has the ability to treat the tannery wastewater.     

Comparative chronic toxicity of homo- and heterocyclic aromatic compounds to benthic and terrestrial invertebrates: Generalizations and exceptions

The aim of the present study was to elucidate consistent patterns in chronic polycyclic aromatic compound (PAC) toxicity to soil and sediment inhabiting invertebrates. Therefore we examined our experimental dataset, consisting of twenty-one chronic effect concentrations for two soil invertebrates (Folsomia candida and Enchytraeus cripticus) and two sediment invertebrates (Lumbriculus variegatus and Chironomus riparius) exposed to six PACs (two homocyclic isomers, anthracene and phenanthrene; two azaarene isomers: acridine and phenanthridine; and two azaarene transformation products, acridone and phenanthridone). In order to determine if effect concentrations were accurately predicted by existing toxicity-K_ow relationships describing narcosis, chronic pore water effect concentrations were plotted jointly against logK_ow. Fifteen of the twenty-one effect concentrations (71%) were above the lower limit for narcosis, showing that narcosis was the main mode of action for the majority of the tested homo- and heterocyclic PACs during chronic exposure. Toxicity of all tested compounds to soil organisms was accurately described by the toxicity-K_ow relationship. However, for the sediment invertebrates exposed to some of the tested heterocyclic PACs deviations from narcosis were identified, related to specific physicochemical properties of the test compounds and/or species specific sensitivities. It is concluded that existing toxicity-K_ow relationships describing narcosis in some cases underestimate chronic PAC toxicity to sediment inhabiting invertebrates.     

Accumulation de quelques metaux lourds (Cd,Cu, Pb et Zn) chez l'eperlan (Osmerus mordax) preleve sur la rive Nord de l'Estuaire du Saint-LaurentHeavy metal accumulation (Cd,Cu, Pb and Zn) by smelt (Osmerus mordax) from the North shore of the St Lawrence estuary

Heavy metals in trace amounts are normal constituents of marine organisms. At sufficiently high concentrations, heavy metals are toxic to living organisms and so it is important to know by how much their concentration may be increased before effects on marine or estuarine populations can be detected or commercial species become unsuitable as food. A method of removing metals is by storage in a particular tissue. Several different sites for storing metals were investigated and concentrations of Cd, Cu, Pb and Zn were examined in muscle, liver and gonads of the smelt (Osmerus mordax) from the North shore of the St Lawrence estuary. Copper and zinc are constituents of several enzymes and are absolutely essential for normal growth and development, while cadmium and lead are not known to have necessary physiological function. A modified wet digestion procedure was used to prepare biological samples for the determination of trace elements by flameless atomic absorption spectrophotometry procedure, using calibration standards made up in a matrix of similar acidity (Table 1). NBS reference material bovine liver was analyzed along with the samples and the results were within the specified tolerance (Table 2). Analyses were reported on a dry weight basis (Table 3) and the correlations with total body weight were determined by regression analysis. Copper (range 0.3–3.3 μg g^?1) and zinc (range 19–38 μg g^?1) in muscle fillets were found to be negatively correlated with total body weight (Fig. 1). Apparent decreasing concentrations in these two metal levels in muscle sample with increasing body weight were possibly due to factor such as dilution with growth. Growth may dilute metal concentrations in an organism if tissue is added faster than metal. Livers and gonads contained greater levels of the four metals than somatic muscle. Liver metal concentrations of Zn (range 29–108 μg g^?1) and Cd (range 0.06–0.37 μg g^?1) increased with total body weight. All equations fit data at P < 0.01 (Fig. 2). Positive correlations between size and metal concentrations suggest that net uptake may occur. Inessential, slowly exchanging metals such as Cd appear to reflect an uptake which tend to become a cumulative process (age dependence of concentrations). The occurrence of insignificant correlation between liver concentrations of Cu (mean value: 4 μg g^?1) and environmental concentrations of this metal was consistent with equilibration. Since fish are known to possess the metal binding protein metallothionein, a sequestering agent, detoxification of these metals in fish liver may be by sequestration rather than elimination. Increasing metal concentrations in liver may represent storage of sequestered products in that organ. In the gonads, no significant relationship exists between total body weight and trace metal contents. Results of t-test indicated that females had significantly greater Cu and Zn concentrations, but no significant difference existed between males and females for Cd concentrations (Figs 3 and 4). Thus, the relation between concentration and total body weight appears to be specific as to the species, tissues analyzed and environmental conditions. The comparison of metal concentrations in fish to assess variations in contamination levels requires understanding the relationship between metal concentration and body size within each population.     

Using SWAT, Bacteroidales microbial source tracking markers,and fecal indicator bacteria to predict waterborne pathogen occurrence in an agricultural watershed

Developing the capability to predict pathogens in surface water is important for reducing the risk that such organisms pose to human health. In this study, three primary data source scenarios (measured stream flow and water quality, modelled stream flow and water quality, and host-associated Bacteroidales) are investigated within a Classification and Regression Tree Analysis (CART) framework for classifying pathogen (Escherichia coli 0157:H7, Salmonella, Campylobacter, Cryptosporidium, and Giardia) presence and absence (P/A) for a 178 km² agricultural watershed. To provide modelled data, a Soil Water Assessment Tool (SWAT) model was developed to predict stream flow, total suspended solids (TSS), total N and total P, and fecal indicator bacteria loads; however, the model was only successful for flow and total N and total P simulations, and did not accurately simulate TSS and indicator bacteria transport. Also, the SWAT model was not sensitive to an observed reduction in the cattle population within the watershed that may have resulted in significant reduction in E. coli concentrations and Salmonella detections. Results show that when combined with air temperature and precipitation, SWAT modelled stream flow and total P concentrations were useful for classifying pathogen P/A using CART methodology. From a suite of host-associated Bacteroidales markers used as independent variables in CART analysis, the ruminant marker was found to be the best initial classifier of pathogen P/A. Of the measured sources of independent variables, air temperature, precipitation, stream flow, and total P were found to be the most important variables for classifying pathogen P/A. Results indicate a close relationship between cattle pollution and pathogen occurrence in this watershed, and an especially strong link between the cattle population and Salmonella detections.     

Dose—response of Escherichia coli in ozone demand-free phosphate buffer

The intention of this investigation was to determine the mean response of E. coli at predetermined ozone dose levels. By using replicated, randomized, independent batch experiments, precise estimates of the response could be obtained. Particular care was taken in preparing the bacteria and glassware to eliminate effects caused by extraneous ozone demand. A total of 57 batch experiments were conducted at bench-scale using ozone doses of 4.4, 11.45, 200 and 800 μg l⁻¹ at contact times of 30, 60 and 120 s.

The logarithm of the E. coli survival ratio was plotted as a function of applied ozone dose, utilized ozone and contact time. Contact time was found to have some effect for intermediate doses of ozone, but the effects were small relative to those associated with the utilized ozone dose. It was also found that the disinfection reaction was not first-order with respect to the surviving bacteria concentration and two distinct stages were observed; an initial rapid inactivation stage followed by a slower inactivation stage.

Regression analysis of the E. coli response on the logarithm of the dose parameter is typical of dose-response models for water and wastewater disinfection. However, this model form was inadequate when fitted to the data of this study as a result of a significant tailing effect in the log-log dose-response plots. It was postulated that the observed dose-response could be explained by chemical kinetic theory and that the dose-response was affected by the disinfection reaction rates which were dependent upon the surviving number of bacteria and the residual ozone concentration.

For practical application, it was found that an adequate dose-response model for 0–99.99% reduction of E. coli could be developed using the logarithm of utilized ozone as the dose function.     

A real-time RT-PCR method to detect viable Giardia lamblia cysts in environmental waters

Currently, USEPA Method 1623 is the standard assay used for simultaneous detection of Giardia cysts and Cryptosporidium oocysts in various water matrices. However, the method is unable to distinguish between species, genotype, or to assess viability. Therefore, the objective of the present study was to address the shortcomings of USEPA Method 1623 by developing a novel molecular-based method that can assess viability of Giardia cysts in environmental waters and identify genotypes that pose a human health threat (assemblage groups A and B). Primers and TaqMan^® probes were designed to target the beta-giardin gene in order to discriminate among species and assemblages. Viability was determined by detection of de-novo mRNA synthesis after heat induction. The beta-giardin primer/probe sets were able to detect and differentiate between Giardia lamblia assemblages A and B, and did not detect Giardia muris (mouse species) or G. lamblia assemblages C, D, E and F (non-human), with the exception of Probe A which did detect G. lamblia assemblage F DNA. Additionally, DNA or cDNA of other waterborne organisms were not detected, suggesting that the method is specific to Giardia assemblages. Assay applicability was demonstrated by detection of viable G. lamblia cysts in spiked (assemblage B) and unspiked (assemblage A and B) reclaimed water samples.     

几何平均温差在供热系统调节中的应用

由于传统的算术平均温差在换热器的近似计算中相对误差较大,导致根据它得到的供热系统调节参数不仅精度差,而且需要修正。本文将几何平均温差引入热网的集中调节公式进行计算,详细讨论了一、二级网联合调节的各种方案中计算参数的合理性和相对误差,指出了几何平均温差在计算中的优势。     

Distribution and disinfection of bacterial loadings associated with particulate matter fractions transported in urban wet weather flows

Urban runoff is a resource for reuse water. However, runoff transports indicator and pathogenic organisms which are mobilized from sources of fecal contamination. These organisms are entrained with particulate matter (PM) that can serve as a mobile substrate for these organisms. Within a framework of additional treatment for reuse of treated runoff which requires the management of PM inventories in unit operations and drainage systems there is a need to characterize organism distributions on PM and the disinfection potential thereof. This study quantifies total coliform, Escherichia coli, fecal streptococcus, and enterococcus generated from 25 runoff events. With the ubiquity and hetero-dispersivity of PM in urban runoff this study examines organism distributions for suspended, settleable and sediment PM fractions differentiated based on PM size and transport functionality. Hypochlorite is applied in batch to elaborate inactivation of PM-associated organisms for each PM fraction. Results indicate that urban runoff bacterial loadings of indicator organisms exceed U.S. wastewater reuse, recreational contact, and Australian runoff reuse criteria as comparative metrics. All monitored events exceeded the Australian runoff reuse criteria for E. coli in non-potable residential and unrestricted access systems. In PM-differentiated events, bacteriological mobilization primarily occurred in the suspended PM fraction. However, sediment PM shielded PM-associated coliforms at all hypochlorite doses, whereas suspended and settleable PM fractions provide less shielding resulting in higher inactivation by hypochlorite.