Karra Styliani, Katsivela Eleftheria
Laboratory of Environmental Chemistry and Biochemical Processes, Department of Natural Resources and Environment, Technological Educational Institute of Crete, Romanou 3, Halepa, GR 73133 Chania, Greece.
Water Res. 2007 Mar;41(6):1355-65. doi: 10.1016/j.watres.2006.12.014. Epub 2007 Feb 2.
Measurements were conducted at a Mediterranean site (latitude 35 degrees 31' north and longitude 24 degrees 03' east) during summer, to study the concentration of microorganisms emitted from a wastewater treatment plant under intensive solar radiation (520-840 W/m2) and at elevated air temperatures (25-31 degrees C). Air samples were taken with the Air Sampler MAS 100 (Merck) at each stage of an activated-sludge wastewater treatment (pretreatment, primary settling tanks, aeration tanks, secondary settling tanks, chlorination, and sludge processors). Cultivation methods based on the viable counts of mesophilic heterotrophic bacteria, as well as of indicator microorganisms of faecal contamination (total and faecal coliforms and enterococci), and fungi were performed. During air sampling, temperature, solar radiation, relative humidity and wind speed were measured. The highest concentrations of airborne microorganisms were observed at the aerated grit removal of wastewater at the pretreatment stage. A gradual decrease of bioaerosol emissions was observed during the advanced wastewater treatment from the pretreatment to the primary, secondary and tertiary treatment (97.4% decrease of mesophilic heterotrophic bacteria, and 100% decrease of total coliforms, faecal coliforms and enterococci), 95.8% decrease of fungi. The concentration of the airborne microorganisms at the secondary and tertiary treatment of the wastewater was lower than in the outdoor control. At the same time, the reduction of the microbial load at the waste sludge processors was 19.7% for the mesophilic heterotrophic bacteria, 99.4% for the total coliforms, and 100% for the faecal coliforms and the enterococci, 84.2% for the fungi. The current study concludes that the intensive solar radiation, together with high ambient temperatures, as well as optimal wastewater treatment are the most important factors for low numbers of microbes in the air.
在夏季，于地中海地区（北纬35度31分，东经24度03分）进行了测量，以研究在强烈太阳辐射（520 - 840瓦/平方米）和高温（25 - 31摄氏度）条件下，一家污水处理厂排放的微生物浓度。在活性污泥废水处理的每个阶段（预处理、初沉池、曝气池、二沉池、氯化处理和污泥处理设备），使用MAS 100空气采样器（默克公司）采集空气样本。采用基于嗜温异养细菌活菌计数以及粪便污染指示微生物（总大肠菌群、粪大肠菌群和肠球菌）和真菌的培养方法。在空气采样期间，测量了温度、太阳辐射、相对湿度和风速。在预处理阶段的曝气沉砂池中，观测到空气中微生物的浓度最高。在从预处理到一级、二级和三级的深度废水处理过程中，生物气溶胶排放量逐渐减少（嗜温异养细菌减少97.4%，总大肠菌群、粪大肠菌群和肠球菌减少100%），真菌减少95.8%。废水二级和三级处理时空气中微生物的浓度低于室外对照。同时，在污泥处理设备中，嗜温异养细菌的微生物负荷降低了19.7%，总大肠菌群降低了99.4%，粪大肠菌群和肠球菌降低了100%，真菌降低了84.2%。当前研究得出结论，强烈的太阳辐射、较高的环境温度以及优化的废水处理是空气中微生物数量较少的最重要因素。
