| Popis: |
Groundwater aquifers and surface waters currently used as drinking water and irrigation sources are in danger of over exploitation, leading to potable water scarcity in many regions of the world. On-site treatment and reuse of recycled wastewaters such as graywater for non-potable purposes has the ability to enhance water sustainability by alleviating demands on potable water supplies, which is particularly valuable in arid regions or in times of severe draught. However, given the inevitable downstream human contact, graywater represents a waterborne pathogen transmission and amplification pathway if human exposure to reused water is practiced without adequate treatment. Enteric pathogens are currently thought to be one of the most significant public health risks to water reuse. (1) Thus, previous studies sought to predict enteric pathogen presence in graywater through the use of fecal indicator bacteria (FIB) to indicate human fecal contamination and possible pathogen presence. However, FIB are known to grow in stored graywater, (2) do not correlate well with pathogens, (3) and may not accurately predict risks from pathogens transmitted via respiratory/oral and dermal pathways. (4) Therefore, new metrics to measure and predict microbial risk in graywater recycling systems is necessary for advancement of these systems.Due to potential pathogen presence, it is recommended that graywater undergo biological treatment and disinfection prior to reuse if downstream human contact is expected. U.S. graywater guidelines (2012) suggest using fecal coliforms of 0/100mL as the most conservative disinfection surrogate for reuse. (5) However, their quantities at different stages of treatment may vary due to re-growth, (6) causing inaccurate readings of the microbial log removal. Therefore, there is also a need for better microbial surrogates that can be used during graywater treatment to indicate process performance and pathogen reduction. Technologies such as high throughput DNA sequencing and quantitative polymerase chain reaction (qPCR) can assist with identifying novel surrogates potentially suited to evaluate pathogen removal in these systems.In this investigation, we utilize high throughput pyrosequencing and qPCR to identify and quantify select bacterial and human surrogates and pathogens in industrial laundry graywater sourced from the University of Cincinnati’s athletic facility. Pyrosequencing and qPCR revealed that laundry water microbiota was dominated by the skin-associated bacteria Staphylococcus, Corynebacterium, and Propionibacterium (6.5, 5.7, 5.4 log10 copies/100mL respectively). While human mitochondrial DNA (HmtDNA) was less abundant (2.8 log10 copies/100mL) it showed strong positive correlations with these three genera (r = 0.45, P = 0.002) as well as the opportunistic pathogen Staphylococcus aureus (r = 0.54, P = 3.2 x 10^-4). Further, HmtDNA closely followed a first order exponential decay model (R² = 0.98), remaining detectable in stored laundry graywater for up to six days at 20°C. Based on consistency, abundance, and persistence in graywater, this research identifies HmtDNA and skin-associated bacteria such as total Staphylococcus as potential molecular surrogates for measuring microbial log removal in future graywater treatment evaluations. |
