On the first page of our online submission system, under “I’m submitting:” select the option “any other article type”. Once logged in you can submit your manuscript to a Collection by selecting “Guest Edited Collection”, under the “Choose the appropriate manuscript type” message, and clicking “Continue”. Then when filling out the manuscript information, select the "Nanofiltration in the Global Water Cycle" Collection from the alphabetical list on the “Springer Nature Subject Category” tab. Authors should express their interest in the Collection in their cover letter.