On-site membrane cleaning

The techniques and chemicals described in Chapter 13.2 apply directly to on-site or Clean-In-Place (CIP) membrane cleaning. 

A two-stage, 500-gpm RO skid can be cleaned is about 2 days. Off-site cleaning can take a couple of weeks to turn around the membranes. 

Cleaning is less efficient than with off-site cleaning. Typically, cleaning operations are limited to one cleaner per pH (e.g.. 

Initial capital outlay will need to include a cleaning skid. 

On-site personnel must store and handle the cleaning chemicals as well as the wastewater that is generated. 

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Off-Site Membrane Cleaning On-Site Membrane Cleaning (CIP) ... 

Chapter 13.2 discussed techniques and chemicals used for cleaning of RO membranes. This section discusses the merits of on-site verses off-site membrane cleaning. Table 15.4 summarizes the advantages and limitations of on-site and off-site membrane cleaning. 

Table 15.4 Merits of on-site versus off-site membrane cleaning.

The spurred impetus has been given to developing non pollutant vehicles, and consequently, the clean cars driven by the fuel cells loading proton exchange membranes (PEMFC), which based upon Nafion, have been surprisingly developed. A promising less pollutant and economical system is also expected, which will be the on site cogeneration system of electric power and the hot water supply with use of fuel cells combined with city gas pipe-lines. 

On-site, dissolved oxygen is commonly measured using a membrane electrode of the polarographic type in a flow-through cell. The zero is commonly set using a saturated solution of sodium sulphite and the 100% saturated environment by holding the probe close to the surface of clean water. Below 1 ppm, electrodes provide only a qualitative measure of D02 due to slow electrode response (Wilkin et al., 2001). 

Off-site cleaning costs more than on-site cleaning. Quotes should be obtained form specific vendors, but pricing can be as high as 150 or greater per membrane 8-inch diameter module. 

This observation is surprising given literature reports that steam adsorbs strongly on Pd membranes [17] and also causes inhibition of the Ha flux when present in the feed gas stream at lower temperatures. The enhancement due to the steam sweep stream could be due to a cleaning effect where the steam reacts with CO or carbon present on the permeate side of the membrane to form CO2 as we have observed that the Pd-Cu membrane is a catalyst for the WGS reaction. Carbon dioxide is less strongly bound to the surface of the membrane than CO that would free additional sites for the formation of molecular hydrogen. The He sweep could have a similar... 

The ability to repeatedly regenerate the flux after the cleaning procedure is a good indication that the formed-in-place membrane is stable and can be used over an extended length of time. In the unlikely event of an irreversible fouling, the membrane can be cost-effectively and easily reformed on-site with a minimum of downtime. 

Since all membranes eventually foul, a cleaning cycle is necessary to restore flux and operability. Many membrane systems have limited abilities to be regenerated due to restrictions in the chc ce of cleaning chemicals. Hie formed-in-place membrane is compatible with a wide rai e of chemical cleaning methods, enabling in-place regeneration of flux. In situatimis where the membrane becomes irreversibly fouled, the formed-in-place membrane can be stripped and reformulated on-site. 

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