My career and working life since 1972 has been in the area of membrane filtration. Mostly in industrial application development, and mostly using plate-and-frame systems and spiral wound elements. A couple of years also SiC-membrane elements.

Spreadsheets and text

The information found on this homepage is informtion I have often been asked about. I will add material to the homepage if I feel like it or if I am requested to do it.


In the early days of membrane filtration (before 1974) computers as we know them today did not exist. Slide-rulers were the only "calculators" available for engineers. In 1972 even a hand held calculator did not exist. To solve a problem it was necessary first to develop differential equations (often quite complex) and then to solve the equations. In this way the number of calculations was limited and precise. Nevertheless, it was still hard work to calculated a complete system. It could take days, and the danger of mistakes was always present. Today, problems are solved by applying the power of modern computers to make numerous iterations. You may ask: "Do we really need to apply the complex formulas resulting from solving differential equations?". My answer is YES. A formula will not only provide an answer, but a result. Although iterations may provide an answer, it is very difficult to gauge the accuracy of this answer. My experience is, that the result of an iterative calculation may be significantly different from the result produced by the appropriate formula.


Some information is considered so simple or common knowledge or proprietary, that it is never written down in an easy-to-understand language. You will find this type of informatetion written down here. The papers have often been started with an seemingly innocent question from Bjarne Nicolaisen: "Can you please write a page about .. ". The papers are not theoretical considerations. They are practial answers to practical questions / problems / challenges.



The book is a follow up to the book published in 1995. It has been re-written to a large extent. It has been updated and new material has been added. Bjarne Nicolaisen has edited and contributed significantly.