8.2 Evaluation of the cleaning process reveal the mechanism
For research purposes, the measurements do not need to be quick, easy to handle and non-
invasive.Visual inspection is an off-line method and can range from ordinary photos
to follow the course of cleaning, but also together with dyes for specific elements and
microscopic techniques to enhance the details and resolution.Using Scanning electron
microscopy (SEM) structural changes of the fouling, such as the swelling of the protein
deposit, can be revealed.By monitoring
and analyzing the effluent during cleaning over time, important information is obtained; such
as when the protein and mineral content is released in comparison to each other and to the
current parameters used for the cleaning process.UV-absorbance can be used in cleaning studies to investigate the effluent concentration of
proteins [84].The content of the mineral deposit could be obtained in using a
SEM-EDX, giving the elemental composition in a certain area of the sample [111].Following the fouling removal (and buildup) with a direct online measurement with time on a
surface inside a process plant is difficult to do on an industrial scale.It is also possible to measure the protein content by measuring the chemical
oxygen demand (COD) [5, 56] or the Kjeldahl method [31, 49-51].Downsizing the
equipment to a smaller pilot plant is many times used for research purposes, but still has not
given the obvious methods to online and on site follow the changes of the fouling.From effluent analysis, the original
composition of the fouling can be determined, but without any spatial information.Since it's
common to foul the surfaces in a closed system, it is difficult to a priori visualize and
determine the microstructure.The
noninvasive effluent analysis are common in pilot scale cleaning studies [107].The equipment can be dismantled and prepared at different stages and for different
type of analyses.An analysis of the effluent
can only tell when there is nothing left leaving the equipment, but cannot validate that the
surface is clean.The above mentioned methods are the same as discussed in chapter 4 under fouling
characterization.