Membrane failures are often caused by poor pre-treatment design and/or poor operation. Systems are frequently designed and built without a clear understanding of the chemistry of the feed water to be treated and the physical characteristics of the particulate matter it contains. The larger the system the more likely is some incident of pre-treatment failure, often at a high financial cost to the operator. Such problems are common with medium and large surface water systems, particularly those using sea, lake, river and recycled effluent waters.
It is standard practice to carry out pre-treatment chemical trials (coagulation and flocculation) on-site. However, new techniques such as on-line particle counting and the examination and analysis of SDI papers allow more comprehensive scientific investigation to be made under laboratory conditions.
Results from laboratory studies mean that it is often possible to improve pre-treatment operation, even on a well run system. This paper considers traditional membrane autopsy techniques and looks at some of the new laboratory tools available to improve pre-treatment system performance. The authors discuss some of the laboratory techniques involved such as the use of ‘particle counting’ and the chemical examination of SDI papers and show how they can help pre-treatment systems operate more effectively without the need for costly re-engineering. Real case experiences are used to illustrate this discussion.