Real-Time Online Monitoring for Assessing Removal of Bacteria by Reverse Osmosis

Abstract

Rigorous monitoring of microbial water quality is essential to ensure the safety of recycled water after advanced treatment for indirect and direct potable reuse. This study evaluated real-time bacterial monitoring for assessing reverse osmosis (RO) treatment for removal of bacteria. A strategy was employed to monitor bacterial counts online and in real time in the RO feed and permeate water using a realtime continuous bacteriological counter. Over the course of 68 h pilot-scale testing, bacterial counts were monitored in real time over approximate ranges from 1 × 10 3 to 4 × 10 4 and from 4 to 342 counts/mL in the RO feed (ultrafiltrationtreated wastewater) and permeate, respectively. The results indicate that the bacteriological counter can track the variations in bacterial counts in the RO feed and permeate. Bacterial concentrations were confirmed by epi-fluorescence microscopy for total bacterial counts. A high correlation (R 2 = 0.83) was identified between the online bacterial counts and epi-fluorescence counts in the RO feed; a negligible correlation was observed for RO permeate. In this study, we evaluated a real-time bacteriological counter (i.e., counts per milliliter every second) to ensure continuous removal of bacterial contaminants by RO treatment.

Integrity of reverse osmosis membrane for removing bacteria: new insight into bacterial passage

“…Further details of the real-time instrument can be found elsewhere. 16 Conductivity of RO feed and permeate was analyzed using Orion Star™ A322 Conductivity meters (Thermo Fisher Scientific, Waltham, MA, USA).…”

“…11,14 This is because of the protocol for ensuring pathogen removal using rather conservative surrogate performance indicators: removal of total organic carbon (TOC) and/or electrical conductivity (EC). 9,15 Fujioka et al, 16 have recently demonstrated the potential of continuously measuring bacterial removal by RO through real-time counting of bacterial number in RO feed and permeate. Although the direct counting method was expected to help ensuring bacterial removal considerably greater than conventional methods, their study identified bacterial removal of lower than 3-log (99.9%).…”

Online assessment of sand filter performance for bacterial removal in a full-scale drinking water treatment plant

“…It is important to note that the frequency of backwashing at the full-scale plant during this 132 study period was once every three days, however, throughout the year it can vary depending on the increase in turbidity or the head loss of the filters. To reduce the background interference from dissolved organics (humic acid-like organic matter) that are not counted but can mask autofluorescence of bacteria, an online sample dilution method that was previously reported in literature (Fujioka et al, 2018) was applied. Before analysis, the filter influent and effluent underwent 50-and 3-fold dilution using the pure water, respectively (Fig.…”

“…Another online bacterial counting technique that has recently emerged is a real-time bacteriological counting technology, which is also based on simultaneous light-scattering and autofluorescence measurements (Pepper and Snyder, 2016;Fujioka et al, 2018). This technology utilizes the combined autofluorescence emitted from riboflavin and nicotinamide adenine dinucleotide -hydrogen (NADH) in bacterial cells to identify them in water.…”

Evaluating changes to Ralstonia pickettii in high-purity water to guide selection of potential calibration materials for online water bioburden analyzers

“…As a result, there is a need for real-time feedback on counts of viable bacteria in purified water systems to facilitate informed, timely decision making. Newly available online instrumentation is proposed to fulfill this need of real-time bioburden detection [6, 9, 17], with the added potential to detect viable, but nonculturable bacteria that would otherwise be missed by culture-based methods [21]. Online water bioburden analyzers (OWBAs) commonly probe the HPW with a 405 nm laser, which yields detection of bacteria through the combination of bacterial scattered light and endogenous autofluorescence, which is excited by the violet light (observation of scattered light only would suggest non-biological particulate matter) [6].…”