1 For surface waters, between 20 and 40 mm (upstream the strainer)  For municipal wastewater: for raw water, from 15 to 30 mm (but upstream from a straining and/ or lamellae settling process, fine screening is necessary); for sludge (if necessary), 10 mm or less.
Other studies. According to some studies, 18-year-old males have a refractory period of about 15 minutes, while those in their 70s take about 20 hours, with the average for all men being about a half-hour. Although rarer, some males exhibit no refractory period or a refractory period lasting less than 10 seconds.
A menstrual cycle is the time from the day a menstrual period starts to the time the next period starts. The average menstrual cycle is 28 days long. However, a normal cycle can be shorter or longer than this. It may be anywhere from 21 to 35 days long.Most periods last 3 to 5 days, but anywhere from 2 to 7 days is normal.Menstrual cycles may happen around the same date every month or they may be irregular.owever, a normal cycle can be shorter or longer than this. It may be anywhere from 21 to 35 days long. Most periods last 3 to 5 days, but anywhere from 2 to 7 days is normal. Menstrual cycles may happen around the same date every month or they may be irregular.