Bacterial aerosol emission rates from municipal wastewater aeration tanks

Abstract

In this report we describe the results of a study conducted to determine the rates of bacterial aerosol emission from the surfaces of the aeration tanks of the Metropolitan Water Reclamation District of Greater Chicago John E. Egan Water Reclamation Plant. This study was accomplished by conducting test runs in which Andersen six-stage viable samplers were used to collect bacterial aerosol samples inside a walled tower positioned above an aeration tank liquid surface at the John E. Egan Water Reclamation Plant. The samples were analyzed for standard plate counts (SPC), total coliforms (TC), fecal coliforms, and fecal streptococci. Two methods of calculation were used to estimate the bacterial emission rate. The first method was a conventional stack emission rate calculation method in which the measured air concentration of bacteria was multiplied by the air flow rate emanating from the aeration tanks. The second method was a more empirical method in which an attempt was made to measure all of the bacteria emanating from an isolated area (0.37 m2) of the aeration tank surface over time. The data from six test runs were used to determine bacterial emission rates by both calculation methods. As determined by the conventional calculation method, the average SPC emission rate was 1.61 SPC/m2/s (range, 0.66 to 2.65 SPC/m2/s). As determined by the empirical calculation method, the average SPC emission rate was 2.18 SPC/m2/s (range, 1.25 to 2.66 SPC/m2/s). For TC, the average emission rate was 0.20 TC/m2/s (range, 0.02 to 0.40 TC/m2/s) when the conventional calculation method was used and 0.27 TC/m2/s (range, 0.04 to 0.53 TC/m2/s) when the empirical calculation method was used.(ABSTRACT TRUNCATED AT 250 WORDS)

The assessment of airborne bacterial contamination in three composting plants revealed site-related biological hazard and seasonal variations

“…The upwind sites were located about 100 m upwind of the plants to collect a background (ambient) air sample for bacterial analysis. These samples were used as a check to ensure that no unusually high levels of bacteria were being blown across the sampling area (Sawyer et al 1993). The downwind sites monitored the air flow coming from the treatment locations and were located in a range of 50-100 m from the plants.…”

Activated sludge and other aerobic suspended culture processes

“…Results supported the use of SBR technology for the removal of indicator organisms and treatment of domestic wastewater. Emissions of total coliforms, fecal coliforms, fecal streptococci, and standard plate count bacteria were measured in aerosols from the aeration basin at a municipal wastewater treatment plant (Sawyer et al, 1993). Two methods, a conventional volumetric method and an empirical method, were used to calculate the bacterial emission rate.…”

Detection and quantification of enteric pathogens in aerosols near open wastewater canals in cities with poor sanitation

“…In the case of sanitation-related pathogens -where primary exposure is generally ingestion rather than inhalation -studies in high-risk, extramural (outdoor) settings in the USA and in other highincome countries have revealed that bioaerosols containing enteric microbes are common near point sources of concentrated fecal waste. Studies have primarily focused on ambient air surrounding wastewater treatment plants [32][33][34][35][36][37][38][39][40][41][42][43] and in the context of land application of biosolids [44][45][46][47][48][49][50][51][52][53][54] ; several studies have examined bioaerosols surrounding composting facilities 55,56 , meat markets 57 , impacted urban sites [58][59][60][61][62][63] , and concentrated animal feeding operations [64][65][66] .…”

“…Studies in high-risk, extramural (outdoor) settings in the USA and in other high-income countries have revealed that bioaerosols containing enteric microbes are common where concentrated fecal waste and one or more mechanisms for aerosolization exist. Enteric microbes in aerosols have been best characterized in ambient air surrounding wastewater treatment plants 27–37 and in the context of land application of biosolids 38–48 ; several studies have examined bioaerosols surrounding composting facilities 49,50 , meat markets 51 , urban areas 52–54 , and concentrated animal feeding operations 55–57 . The majority of such studies are based on detection of fecal indicator bacteria including members of the coliform group 54,58 , partly because the presence of important enteric pathogens is unexpected outside high-burden settings.…”