Spatio-temporal variations of airborne bacteria from the municipal wastewater treatment plant: a case study in Ahvaz, Iran

The study of bioaerosol dispersion in wastewater treatment plants (WWTPs) has received considerable attention. This study aimed to investigate the seasonal changes and spatial distributions of airborne bacteria around different parts of Ahvaz WWTP, the capital city of Khuzestan Province, Iran, over 4 months in the cold and warm seasons. Samples were collected from 2 and 10-m intervals of grit chamber (GCh), primary sludge dewatering basin (PSDB), aeration tank (AT), as well as 60-m upstream (US) and downstream (DS) of the WWTP. Further, bacteria in the indoor air of administrative building (AB) of WWTP were investigated. Bioaerosols were collected by passive sampling method. The total bacteria count was 105.3 +/- 98.5 CFU/plate/h. The dominant bacteria stood 2 m away from the AT with an average 244.2 +/- 73.1 CFU/plate/h in the warm season while they were the lowest with an average 43 +/- 11.4 CFU/plate/h in the 10-m distance of the GCh in the cold season. According to the sequencing results, the dominant bacterial species includedBacillus pumilus(26.7%),Staphylococcus arlettae(23.2%),Kocuria turfanensis(13.6%) andAlicycliphilus (9.2%), respectively. There was a positive relationship between the release of bacteria, temperature and wind speed. However, there was a significant negative correlation between total bacteria concentration and humidity. There are accumulative perils to WWTP workers and neighbors exposed by persistent exposure to airborne bacteria. Therefore, AT should be paid more attention as a dominant source of airborne bacteria emissions, especially in the warm season.