The purpose was to determine extent that individuals near spray irrigation sites are exposed to microorganisms in wastewater aerosols. Report covers Phase II - a monitoring effort from May 1976 to April 1977 of a spray irrigation site utilizing unchlorinated secondarily-treated wastewater from biofiltration treatment process. Objectives included an in-depth pathogen screen of wastewater, establishing the relationship between pathogen levels and traditional indicator organisms, monitoring microorganisms in air within 600 meters of the spray source, and development/validation of a microbiological dispersion model for predicting pathogen aerosol concentrations. Effluent was monitored for microbiological, chemical, and physical characteristics; extensive microorganism and dye aerosol samples were collected (77 aerosol runs). Enteroviruses were detected in air, but at a very low concentration. Conclusions: There is considerable underestimation of pathogen aerosol levels when using traditional indicators to predict human exposures to enteroviruses. Microbiological dispersion model may be used with minimal monitoring to estimate exposure. There is little correlation between wastewater levels of traditional indicators and pathogens. Microbiological wastewater aerosols are generated by spray irrigation, do survive aerosolization and can be transported to nearby populations.