Request for suggestions for my new publication

Dear Fellow Professionals,

My new book is under preparation under title "Biotechnology of Wastewater Treatment". The emphasis has been given on the role of Microorganisms in Activated Sludge process and how these can be used as indicator for the stability of treatment process. This book will be helpful for STP operators, student and researchers. 

I would like to welcome the suggestion on topics which you think are essential to be included in this publication.