Department of Microbiology, Faculty of Science, Stellenbosch University, Private Bag X1, Stellenbosch 7602, South Africa.
School for Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ 85281, United States; The Biodesign Institute Center for Environmental Health Engineering, Arizona State University, Tempe, AZ 85281, United States.
Sci Total Environ. 2020 Nov 15;743:140717. doi: 10.1016/j.scitotenv.2020.140717. Epub 2020 Jul 8.
Illumina amplicon-based sequencing was coupled with ethidium monoazide bromide (EMA) pre-treatment to monitor the total viable bacterial community and subsequently identify and prioritise the target organisms for the health risk assessment of the untreated rainwater and rainwater treated using large-volume batch solar reactor prototypes installed in an informal settlement and rural farming community. Taxonomic assignments indicated that Legionella and Pseudomonas were the most frequently detected genera containing opportunistic bacterial pathogens in the untreated and treated rainwater at both sites. Additionally, Mycobacterium, Clostridium sensu stricto and Escherichia/Shigella displayed high (≥80%) detection frequencies in the untreated and/or treated rainwater samples at one or both sites. Numerous exposure scenarios (e.g. drinking, cleaning) were subsequently investigated and the health risk of using untreated and solar reactor treated rainwater in developing countries was quantified based on the presence of L. pneumophila, P. aeruginosa and E. coli. The solar reactor prototypes were able to reduce the health risk associated with E. coli and P. aeruginosa to below the 1 × 10 annual benchmark limit for all the non-potable uses of rainwater within the target communities (exception of showering for E. coli). However, the risk associated with intentional drinking of untreated or treated rainwater exceeded the benchmark limit (E. coli and P. aeruginosa). Additionally, while the solar reactor treatment reduced the risk associated with garden hosing and showering based on the presence of L. pneumophila, the risk estimates for both activities still exceeded the annual benchmark limit. The large-volume batch solar reactor prototypes were thus able to reduce the risk posed by the target bacteria for non-potable activities rainwater is commonly used for in water scarce regions of sub-Saharan Africa. This study highlights the need to assess water treatment systems in field trials using QMRA.
Illumina 扩增子测序与溴化乙锭单键（EMA）预处理相结合，用于监测总活菌群落，并随后识别和优先考虑未经处理的雨水和使用大容量批量太阳能反应器原型处理的雨水的目标生物，以进行健康风险评估。分类学分配表明，军团菌和假单胞菌是未经处理和处理后的雨水在两个地点最常检测到的包含机会性病原体的属。此外，分枝杆菌、梭菌严格意义上和大肠杆菌/志贺氏菌在未经处理和/或处理后的雨水样本中在一个或两个地点均具有高（≥80%）检测频率。随后调查了许多暴露情景（例如饮用、清洁），并根据嗜肺军团菌、铜绿假单胞菌和大肠杆菌的存在，量化了在发展中国家使用未经处理和太阳能反应器处理的雨水的健康风险。太阳能反应器原型能够将与大肠杆菌和铜绿假单胞菌相关的健康风险降低到目标社区内所有非饮用水用途的 1×10 年基准限值以下（淋浴除外，大肠杆菌）。然而，未经处理或处理后的雨水的故意饮用风险超过了基准限值（大肠杆菌和铜绿假单胞菌）。此外，虽然太阳能反应器处理降低了基于嗜肺军团菌存在的花园浇水和淋浴相关风险，但这两种活动的风险估计仍超过了年度基准限值。因此，大容量批量太阳能反应器原型能够降低目标细菌对撒哈拉以南非洲水资源匮乏地区雨水常用的非饮用水活动的风险。本研究强调了需要在野外试验中使用定量微生物风险评估来评估水处理系统。
