The measurement of aerosolized endotoxin from land application of Class B biosolids in Southeast Arizona.

The purpose of this study was to determine aerosolized endotoxin concentrations downwind of a biosolids land application site. Aerosol samples were collected from biosolids land application sites, tractor operation, and an aeration basin located within an open-air wastewater treatment plant. Aerosolized endotoxin above background concentrations was detected from all sites, at levels ranging from below detection up to 1800 EU m-3 of air. Biosolids loading operations resulted in the greatest concentrations of endotoxin (mean 344 EU m-3). As downwind (perpendicular to wind vector) distance increased from sources (2-200 m), levels of endotoxin decreased to near background (without biosolids application) concentrations. Overall, the detected levels of aerosolized endotoxin were within past proposed aerosolized endotoxin limits (250-2000 EU m-3) by other occupational exposure studies. Occasionally, peak concentrations were found to be above these limits. Sites in which soil was being aerosolized resulted in greater concentrations of endotoxin with or without biosolids, which suggested that the majority of endotoxin may in fact be of soil origin. This study evaluated the presence of aerosolized endotoxin from the land application of biosolids and showed that these levels were within ranges for concern suggested by other studies and that this area of research needs further investigation.

A national study on the residential impact of biological aerosols from the land application of biosolids.

AIMS: The purpose of this study was to evaluate the community risk of infection from bioaerosols to residents living near biosolids land application sites. METHODS AND RESULTS: Approximately 350 aerosol samples from 10 sites located throughout the USA were collected via the use of six SKC Biosamplers. Downwind aerosol samples from biosolids loading, unloading, land application and background operations were collected from all sites. All samples were analysed for the presence of HPC bacteria, total coliform bacteria, Escherichia coli, Clostridium perfringens, coliphage, enteroviruses, hepatitis A virus and norovirus. Total coliforms, E. coli, C. perfringens and coliphage were not detected with great frequency from any sites, however, biosolids loading operations resulted in the largest concentrations of these aerosolized microbial indicators. Microbial risk analyses were conducted on loading and land application operations and their subsequent residential exposures determined. CONCLUSIONS: The greatest annual risks of infection occurred during loading operations, and resulted in a 4 x 10(-4) chance of infection from inhalation of coxsackievirus A21. Land application of biosolids resulted in risks that were <2 x 10(-4) from inhalation of coxsackievirus A21. Overall bioaerosol exposure from biosolids operations poses little community risk based on this study. SIGNIFICANCE AND IMPACT OF THE STUDY: This study evaluated the overall incidence of aerosolized micro-organisms from the land application of biosolids and subsequently determined that microbial risks of infection were low for residents close to biosolids application sites.

Estimation of bioaerosol risk of infection to residents adjacent to a land applied biosolids site using an empirically derived transport model.

AIM: The purpose of this study was to develop an empirically derived transport model, which could be used to predict downwind concentrations of viruses and bacteria during land application of liquid biosolids and subsequently assess microbial risk associated with this practice. METHODS AND RESULTS: To develop the model, coliphage MS-2 and Escherichia coli were aerosolized after addition to water within a biosolids spray application truck, and bioaerosols were collected at discrete downwind distances ranging from 2 to 70 m. Although coliphage were routinely detected, E. coli did not frequently survive aerosolization. Data on aerosolized coliphage was then used to generate a virus transport model. Risks of infection were calculated for various ranges of human virus concentrations that could be found in biosolids. CONCLUSIONS: A conservative estimate at 30.5 m (assumed to be nearest adjacent residences) downwind, resulted in risks of infection of 1 : 100,000, to the more realistic 1 : 10,000,000 per exposure. Conservative annual risks were calculated to be no more than 7 : 100,000 where as a more realistic risk was no greater than 7 : 10,000,000. Overall, the viral risk to residences adjacent to land application sites appears to be low, both for one time and annual probabilities of infection. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrated a simple approach towards modelling viral pathogens aerosolized from land applied liquid biosolids, and offers insight into the associated viral risk.

Bioaerosols from the land application of biosolids in the desert southwest USA.

This study evaluated bioaerosol emissions during land application of Class B biosolids in and around Tucson, Arizona, to aid in developing models of the fate and transport of bioaerosols generated from the land application of biosolids. Samples were collected for 20 min at distances between 2 m and 20 m downwind of point sources, using an SKC BioSampler impinger. A total of six samples were collected per sampling event, which consisted of a biosolid spray applicator applying liquid biosolids to a cotton field. Each application represented one exposure. Samples were collected in deionised water amended with peptone and antifoam agent. Ambient weather conditions were also monitored every 10 min following initiation of sampling. Concurrently with downwind samples, background (ambient) air samples were collected to compensate for any ambient airborne microorganisms. In addition, biosolids samples were collected for analysis of target indicator and pathogenic organisms. Soil samples were also collected and analysed. Significant numbers of heterotrophic plate count (HPC) bacteria were found in air samples collected during the biosolid application process. These could have arisen from soil particles being aerosolised during the land application process. Aerosolised soil may contribute significantly to the amount of aerosolised microorganisms. Soil particles may be able to more readily aerosolise, due to their low density, small particle size and low mass. Aerosolised HPC bacteria found during biosolids land application were similar to those found during normal tractor operation on non-biosolids applied fields. Coliforms and coliphages were not routinely detected even though they were found to be present in the biosolids at relatively high concentrations, 10(6) and 10(4)/g (dry weight) of biosolids respectively. This could be due to the die-off rate of aerosolised Gram-negative bacteria or sorption to the solid portion of the biosolids. Low numbers of aerosolised coliphages may likewise be due to sorption phenomena. We theorise that only organisms in the aqueous phase of the biosolids were available to desorb and be aerosolised. Animal viruses, which were not detected in the biosolids, were likewise not detected in the aerosol samples. Clostridium perfringens was detected in only a small percent of aerosol samples although it was detected during all weather conditions; other microorganisms were detected during more favourable environmental conditions (relative humidity >10%). Despite the fact that many of these organisms were present in the biosolids at significant concentrations, their presence in bioaerosols generated during the land application of biosolids was limited to only a small percentage of samples. Bacteria as well as viruses may sorb to biosolids, which contain a high percentage of organic matter, and desorption during land application of biosolids may not readily take place; therefore, these microorganisms may not be readily aerosolised.

Evaluation of electrochemically generated ozone for the disinfection of water and wastewater.

Effective wastewater treatment is critical to public health and well-being. This is especially true in developing countries, where disinfection of wastewater is frequently inadequate. People who live in these areas may benefit from wastewater disinfection using ozone. This study evaluated the ability of a new electrochemical process of ozone generation, which produced ozone continuously at high pressure and concentration by the electrolysis of water, to disinfect tap water and secondarily treated wastewater. Inactivation of Klebsiella terrigena, Escherichia coli, MS2 bacteriophage and poliovirus 1 was evaluated first in reverse osmosis (RO) treated water. Inactivation of K. terrigena (6-log), E. coli (6-log), MS2 (6-log) and poliovirus 1 (>3-log) was observed after 1 min of ozonation in a 1 L batch reactor. Experiments were then performed to assess the microbiological impact of disinfection using ozone on secondarily treated municipal wastewater. The effect of ozonation on wastewater was determined for total and faecal coliforms, bacteriophages and heterotrophic plate count (HPC) bacteria. Electrochemical ozone generators provided an effective, rapid and low-cost method of wastewater disinfection. Based on the results of this research, electrochemically generated ozone would be well suited to remote, small-scale, disinfection operations and may provide a feasible means of wastewater disinfection in developing countries.