Assessment of pressure decay test for RO protozoa removal validation in remote operations

Zhang, Jianhua; Cran, Marlene; Northcott, Kathy; Packer, M; Duke, Mikel; Milne, Nicholas; Scales, Peter J.; Knight, A; Gray, Stephen

doi:10.1016/j.desal.2016.02.031

Cited by 15 publications

(9 citation statements)

References 7 publications

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“…The study concluded that this method was sensitive in detecting breaches but was not practical for full-scale systems because the entire element array must be drained prior to the test. Other examples have demonstrated the use of automated PDT on RO systems for direct potable reuse applications [ 13 , 34 ]. In practice, the main aim of the PDT for RO in most cases is to determine an LRV for relatively large protozoa and this only requires low pressures.…”

Section: Direct Integrity Monitoringmentioning

confidence: 99%

“…Moreover, this technique, that has similarities to the VDT, has the potential to induce mechanical failures such as telescoping in spiral wound elements. Telescoping can occur during a PDT as a result of the charging and discharging of compressed air from an RO element [ 13 ] although this can be prevented by the use of anti-telescoping devices [ 35 ].…”

Section: Direct Integrity Monitoringmentioning

confidence: 99%

“…In reality, however, NF and RO membranes are not complete barriers to these contaminants [ 6 ] and over time the integrity of membrane systems may be compromised due to a range of breaches that can develop in the system. Membrane breaches can occur as a result of: damage to the membrane layer as a result of chemical or biological degradation and particulate abrasion; delamination of the skin layer from the supporting layer; telescoping; and failures of O-rings, gaskets, connectors and other fittings [ 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. In addition to these ‘in service’ failure modes, manufacturing defects such as incomplete glue-lines can affect the integrity of membrane elements and depending on the quality control processes employed, these are usually detected before membranes are shipped to customers.…”

Section: Introductionmentioning

confidence: 99%

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Current and Emerging Techniques for High-Pressure Membrane Integrity Testing

et al. 2018

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Ideally, pressure driven membrane processes used in wastewater treatment such as reverse osmosis and nanofiltration should provide a complete physical barrier to the passage of pathogens such as enteric viruses. In reality, manufacturing imperfections combined with membrane ageing and damage can result in breaches as small as 20 to 30 nm in diameter, sufficient to allow enteric viruses to contaminate the treated water and compromise public health. In addition to continuous monitoring, frequent demonstration of the integrity of membranes is required to provide assurance that the barrier to the passage of such contaminants is intact. Existing membrane integrity monitoring systems, however, are limited and health regulators typically credit high-pressure membrane systems with only 2 log10 virus rejection, well below their capability. A reliable real-time method that can recognize the true rejection potential of membrane systems greater than 4 log10 has not yet been established. This review provides a critical evaluation of the current methods of integrity monitoring and identifies novel approaches that have the potential to provide accurate, representative virus removal efficiency estimates.

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Section: Direct Integrity Monitoringmentioning

confidence: 99%

Section: Direct Integrity Monitoringmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Current and Emerging Techniques for High-Pressure Membrane Integrity Testing

et al. 2018

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“…Twenty different TrOCs were detected in the product water, and this included fire retardants (2), pharmaceuticals (2), fragrances (5), antioxidants (1), sterols/stanols (2), fatty acid methyl esters (2), and other miscellaneous organic chemicals (6). Less than half of these compounds were detected more than once and all at very low concentrations (sub-μg/L and close to their limits of reporting).…”

Section: Trace Organic Compounds (Trocs)mentioning

confidence: 99%

“…The membrane integrity was monitored by both conductivity and PDTs. The PDT was conducted based on the method described by Zhang et al [6]. The RO PDT was used to achieve the required LRV for protozoa and a protozoa LRV of 2 across the RO membranes was claimed.…”

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confidence: 99%

Small Scale Direct Potable Reuse (DPR) Project for a Remote Area

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Duke

Northcott

et al. 2017

Water

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An Advanced Water Treatment Plant (AWTP) for potable water recycling in Davis Station Antarctica was trialed using secondary effluent at Selfs Point in Hobart, Tasmania, for nine months. The trials demonstrated the reliability of performance of a seven barrier treatment process consisting of ozonation, ceramic microfiltration (MF), biologically activated carbon, reverse osmosis, ultra-violet disinfection, calcite contactor and chlorination. The seven treatment barriers were required to meet the high log removal values (LRV) required for pathogens in small systems during disease outbreak, and on-line verification of process performance was required for operation with infrequent operator attention. On-line verification of pathogen LRVs, a low turbidity filtrate of approximately 0.1 NTU (Nephelometric Turbidity Unit), no long-term fouling and no requirement for clean-in-place (CIP) was achieved with the ceramic MF. A pressure decay test was also reliably implemented on the reverse osmosis system to achieve a 2 LRV for protozoa, and this barrier required only 2-3 CIP treatments each year. The ozonation process achieved 2 LRV for bacteria and virus with no requirement for an ozone residual, provided the ozone dose was >11.7 mg/L. Extensive screening using multi-residue gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS) database methods that can screen for more than 1200 chemicals found that few chemicals pass through the barriers to the final product and rejected (discharge) water streams. The AWTP plant required 1.93 kWh/m 3 when operated in the mode required for Davis Station and was predicted to require 1.27 kWh/m 3 if scaled up to 10 ML/day. The AWTP will be shipped to Davis Station for further trials before possible implementation for water recycling. The process may have application in other small remote communities.

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