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.
The average cycle of menstruation commonly lasts up to 28 days, although some women have different menstrual cycles; some as short as 21 days, while others take as long as 35 days. Normally, the menstrual period lasts from two days to several days.Brown Period Blood: Blood Clots and Thick Menstrual Blood. There are some women who have clots in the blood they discharge during their menstrual period.These blood clots vary in color from bright red to dark.ormally, the menstrual period lasts from two days to several days. Brown Period Blood: Blood Clots and Thick Menstrual Blood. There are some women who have clots in the blood they discharge during their menstrual period. These blood clots vary in color from bright red to dark.