The application of membrane filtration in the production of drinking and process water is
steadily increasing. The use of spiral wound membranes for nanofiltration (NF) and reverse
osmosis (RO) is often hampered by biofouling which leads to operational problems such as an
increase in normalized pressure drop (NPD) and a decrease in production rate (Ridgway and
Safarik, 1991). Biofouling can be limited by pretreatment of the feed water of the membrane
installation, but this approach increases the total investment cost of the water treatment process.
Another option is to use periodical cleaning in place (CIP) for biofouling control, in which the
negative effects of biofouling are (temporarily) reversed.
For a cost-effective application of membrane filtration in practice, extensive knowledge
is required of the influence of cleaning methods on biomass removal. Partly due to the
complexity of biofouling the determination of the optimal CIP strategy is based on "trial and
error". Furthermore, data from scientific literature in many cases gives incomplete information
about the interactions between the feed water quality, the type of membrane, the resulting type
of membrane fouling, the cleaning method and the effect of membrane cleaning on the
membrane process. An important step in elucidating the effect of membrane cleaning processes
is to develop a protocol for a systematic analysis. Two approaches can be followed for evaluating
the effects of a cleaning procedure: the use of operational parameters (Graham et al, 1989);
and, the application of a test procedure under standardized conditions in the laboratory or in a
pilot set up (Whittaker et al, 1981).
Indications of effective cleaning procedures for biofouling control were obtained from a
systematic approach to evaluate CIP procedures from both literature and full-scale membrane
plant experience. In some cases, biofouling was effectively controlled with mixtures of
complexing agents, surface active components and denaturating agents. Apart from this, the
effect of a hydraulic action, e.g. by using air-water flushing, proved to be very promising in
biofouling control (Cornelissen et al, 2007). The biomass removal efficacy of the air-water
flushing strategy was verified with a newly developed laboratory test procedure and described in
this paper. Includes 6 references, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 270 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 4 |
| Published : | 03/01/2007 |
