{"id":2966,"date":"2021-11-10T18:44:17","date_gmt":"2021-11-10T18:44:17","guid":{"rendered":"https:\/\/sci-monitoring-cn.com\/?p=2966"},"modified":"2021-11-17T18:51:16","modified_gmt":"2021-11-17T18:51:16","slug":"pathogen-removal-and-high-log-reduction-value-crediting-for-reverse-osmosis-systems-using-continuous-strontium-monitoring","status":"publish","type":"post","link":"https:\/\/sci-monitoring-cn.com\/pathogen-removal-and-high-log-reduction-value-crediting-for-reverse-osmosis-systems-using-continuous-strontium-monitoring\/","title":{"rendered":"Pathogen Removal And High Log Reduction Value Crediting For Reverse Osmosis Systems Using Continuous Strontium Monitoring"},"content":{"rendered":"
Public potable water supplies are being stressed by growing population, cyclical droughts, and climate change. One way to sustainably augment the potable water supply is to recycle (reuse) wastewater. This is performed by using a tertiary wastewater treatment facility followed by advanced water purification (AWP) which includes; Reverse Osmosis (RO), UV\/advanced oxidation and free chlorine disinfection. RO is the core technology of AWP providing a physical barrier to waterborne pathogens and dissolved constituents. Reliable and safe potable reuse requires continuous demonstration of pathogen removal. Since monitoring pathogens directly is prohibitively time consuming, removal is typically demonstrated using total organic carbon (TOC) and electrical conductivity (EC) as a surrogate. TOC and EC offer a maximum achievable log reduction value (LRV) of approximately 2 and 1.5, respectively. Where under controlled conditions measuring actual pathogens, RO systems provide at least a 4-log reduction. Prior research studies show that strontium, a naturally occurring constituent, has a 3.0 \u2013 3.5 LRV for RO systems. Strontium\u2019s higher LRV allows RO systems to receive more accurate treatment credits and allows increased sensitivity to RO membrane breaches.<\/p>
This application evaluates the feasibility of demonstrating continuous RO pathogen removal by measuring strontium using Cooper Environmental\u2019s Xact 920, a continuous multi-metals monitor based-on energy dispersive X-ray fluorescence (XRF).<\/p>
Data presented in this paper was collected over a two-month demonstration in 2021, with the Xact 920 configured to provide continuous 1-hr strontium measurements. The Xact 920 was installed at a pilot AWP facility capable of treating 100,000 gallons per day. The pilot plant was equipped with a 2-stage primary (PRO) and closed circuit secondary (CCRO) RO system which together achieves greater than 90% recovery. One Xact 920 was installed with an automatic switching manifold, allowing switching between four sample locations including; PRO Feed, PRO permeate, CCRO Feed (PRO Brine) and CCRO Permeate. Measuring these four locations allows LRV calculations (Equation 1) for both the primary and secondary RO systems. Figure 1 show the AWP RO treatment process and the Xact 920 sample locations.<\/p>
LRV=Log(Cf<\/sub> )-Log(Cp<\/sub>) Equation 1<\/p> Where:<\/p> LRV = log removal value<\/p> Cf<\/sub> = strontium RO feed concentration<\/p> Cp<\/sub> = strontium RO permeate concentration<\/p>