scholarly journals Long-Term Stability of Low-Pressure Reverse Osmosis (RO) Membrane Operation—A Pilot Scale Study

Water ◽  
2018 ◽  
Vol 10 (2) ◽  
pp. 93 ◽  
Author(s):  
◽  
Keyword(s):  
Reverse Osmosis ◽  
Low Pressure ◽  
Pilot Scale ◽  
Term Stability ◽  
Long Term Stability ◽  
Ro Membrane

Preservation of reverse osmosis membranes with non oxidizing biocides – comparison with SMBS

2011 ◽  
Vol 11 (3) ◽  
pp. 342-351 ◽  
Author(s):  
K. Majamaa ◽  
U. Bertheas ◽  
F. Finlayson ◽  
R. B. Levy
Keyword(s):  
Reverse Osmosis ◽  
Brackish Water ◽  
Storage Time ◽  
Sea Water ◽  
Temperature Dependent ◽  
Current Standard ◽  
Term Stability ◽  
Sodium Metabisulphite ◽  
Long Term Stability

Sodium metabisulphite (SMBS) is the current standard preservation chemical used in RO plants during shut down. It is a cheap and efficient preservative, but its tendency to oxidize easily has several drawbacks. The use of a non-oxidizing biocide instead could solve some of the issues currently seen with the SMBS, but little has been reported about membrane compatibility and preservation efficiency in the long-term mode. Long-term membrane preservation trials have been executed with three different non-oxidizing biocides: DBNPA (2,2-dibromo-3-nitrilopropionamide), CMIT/MIT (5-chloro-2-methyl-4-isothiazolin-3-one (CMIT) and 2-methyl-4-isothiazolin-3-one (MIT), OIT (2-octyl-2H-isothiazol-3-one) as well as SMBS as the reference chemical. The suitability of these chemicals in this application was confirmed using both new Brackish Water Reverse Osmosis (BWRO) and used membranes with various membrane chemistries (Nanofiltration (NF), BWRO, Sea Water Reverse Osmosis (SWRO)). The preservation trial with new membranes confirmed the long-term stability of the product when stored in the biocide solution while the trial with used elements is closer to realistic plant conditions and validated the efficiency of the biocide against biofouling in the long-term. These results show that the biocides can be equivalent preservatives to SMBS and that the application is economically feasible. The used active concentrations for biocides are storage time and temperature dependent and this should be taken into account when first applying them in the field.

scholarly journals Development and characterisation of a low pressure transfer standard in the range 1 Pa to 10 kPa

ACTA IMEKO ◽  
2018 ◽  
Vol 7 (1) ◽  
pp. 80 ◽  
Author(s):  
Frédéric Boineau ◽  
Sébastien Huret ◽  
Pierre Otal ◽  
Mark Plimmer
Keyword(s):  
Low Pressure ◽  
Differential Capacitance ◽  
Full Scale ◽  
Relative Uncertainty ◽  
Transfer Standard ◽  
Term Stability ◽  
Long Term Stability ◽  
Gauge Pressure ◽  
Uncertainty Contribution

We describe a transfer standard for low absolute and gauge pressure in the range 1 Pa to 10 kPa. This transfer standard is composed of three differential capacitance diaphragm gauges (CDGs) of full-scale 130 Pa, 1.3 kPa and 13 kPa respectively and one absolute 130 kPa resonant silicon gauge (RSG). The objective for the relative uncertainty contribution (<em>k</em>=1) of this standard during a comparison is a few tens of ppm at 10 kPa to a few hundred ppm at 1 Pa. It relies on a good long-term stability of the calibration slope of the RSG used, between 5 kPa and 10 kPa, disseminated to CDGs in absolute mode and subsequently in gauge mode. The methods to assess such uncertainty and the preliminary characterisation of the transfer standard are presented.

scholarly journals Effect of the Characteristic Properties of Membrane on Long-Term Stability in the Vacuum Membrane Distillation Process

Membranes ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 252
Author(s):  
Yuki Suga ◽  
Ryousuke Takagi ◽  
Hideto Matsuyama
Keyword(s):  
Production Cost ◽  
Retention Factor ◽  
Pilot Scale ◽  
Membrane Distillation ◽  
Water Production ◽  
Vapor Flux ◽  
Term Stability ◽  
Long Term Stability ◽  
Vacuum Membrane Distillation

Membrane distillation (MD) is a technology that can treat feed solutions with higher osmotic pressure, as well as produce high-purity water. However, the water production cost of the MD process is expensive. In this study, to decrease the water production cost, we attempted to evaluate the effect of membrane characteristics on the long-term stability of a vacuum MD (VMD) system. We fabricated four different types of polyvinylidene difluoride hollow fiber membranes, and operated a VMD system with 3.5 wt% NaCl aqueous solution at 65 °C as a feed under 11 kPa of air gap pressure. Consequently, in the proposed VMD system, it is found that the liquid entry pressure (LEP) is the most important factor. When LEP was higher than 0.37 MPa, the pilot-scale module was very stable for long-term operations, and the vapor flux was approximately 19.3 kg/m2·h with a total salt retention factor of over 99.9% during the 300-h operation.

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