Abstract
Conventional water resources are not sufficient in many regions to meet the needs of growing populations. Due to cyclical weather cycles, drought, and climate change, water stress has increased worldwide including in Southern California, which serves as a model for regions that integrate reuse of wastewater for both potable and non-potable use. The Orange County Water District (OCWD) Advanced Water Purification Facility (AWPF) is a highly engineered system designed to treat and produce up to 100 million gallons per day (MGD) of purified water from a municipal wastewater source for potable reuse. Routine facility microbial water quality analysis is limited to standard indicators at this and similar facilities. Given recent advances in high throughput DNA sequencing techniques, complete microbial profiling of communities in water samples is now possible. By using 16S/18S rRNA gene sequencing, metagenomic and metatranscriptomic sequencing coupled to a highly accurate identification method along with 16S rRNA gene qPCR, we describe a detailed view of the total microbial community throughout the facility. The total bacterial load of the water at stages of the treatment train ranged from 3.02 × 106 copies in source, unchlorinated wastewater feed to 5.49 × 101 copies of 16S rRNA gene/mL after treatment (consisting of microfiltration, reverse osmosis, and ultraviolet/advanced oxidation). Microbial diversity and load decreased by several orders of magnitude after microfiltration and reverse osmosis treatment, falling to almost non-detectable levels that more closely resembled controls of molecular grade laboratory water than the biomass detected in the source water. The presence of antibiotic resistance genes and viruses was also greatly reduced. Overall, system design performance was achieved, and comprehensive microbial community analysis was found to enable a more complete characterization of the water/wastewater microbial signature.
Highlights
IntroductionHuman society would not exist as it does today
Without clean drinking water, human society would not exist as it does today
Turbidity declined from an average of 3.6 Nephelometric turbidity units (NTU) at Q1 to 1.6 NTU at MFF, to 0.08 – 0.04 NTU at ROF, RO permeate (ROP), and finished product water (FPW)
Summary
Human society would not exist as it does today. Many societies face water scarcity due to increasing population growth and land use. Many communities face a decrease in water quality as demonstrated by increased eutrophication related to agriculture to feed global population growth (Moss, 2011). Within the Southern California region of the United States, all of these pressures have been brought to bear and have resulted in increased water stress. Projects that integrate water reuse via the engineered treatment of wastewater have become more desirable across California, the United States, and the world (Wade Miller, 2006). While inherent reuse is a natural part of the earth’s water cycle, human intervention via new technologies, engineering, and knowledge speeds up this process, making it possible to produce highly purified water directly from wastewater for potable purposes
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