Well,

According to BOD INDICATOR, storing mus be not exceeds 20 days.

Sincerely

Dear Alice

Some countries may regulate sample storage but I am not aware of any.

Sample storage is dictated by the laboratories that do the analyses, which in turn is dictated by the methods they deploy to analyse the samples. Laboratories do store samples regularly hence they need to follow the correct procedures to avoid inaccuracies. Sample storage duration, storage temperature and use of appropriate preservative (e.g. acid) vary from parameter to parameter.

You can contact your local lab which should provide the above info.

Kind regards

Selva

You might consult the book Standard Methods for Analysis of Water and Wastewater. I don’t know if there is a book covering sludge specifically. As suggested, certified laboratories may have knowledge, expertise and/or experience with sludge samples, and some may have probably run studies relative to validate storage and sample change through time. For your desired quality control, seek laboratory or research grade analytical chemist with sludge experience who can help advise, train, mentor if you intend to become proficient at this work. As a University research employee, I was tasked with starting a water quality and wastewater lab. The University Agricultural Analytical Chemist (Dr. Pickett) shared his time and equipment to help train me. I helped him with some desired laboratory tasks, starting with properly cleaning or sterilizing glassware, learning to service equipment, mix standards, etc. It takes meticulous attention to details, safety, etc. The normal workday hours did not exist sometimes to have access to equipment and get work done.

Thanks a lot for all help

Kindly use this reference

https://www.eawag.ch/fileadmin/Domain1/Abteilungen/sandec/schwerpunkte/ewm/PURR/pdfs/methods_sampling_characterization_fs.pdf