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 menstrual cycle. On average, a woman's menstrual cycle lasts 28 days, but cycles can vary from 24 to 35 days. After puberty, most women develop a regular menstrual cycle, with around the same length of time between periods. Menstrual bleeding usually lasts two to seven days, with the average being five days.here is always a different amount of time between periods and always last for a different amount of time. Sometimes i can be on my period for 2 to 3 weeks others 1 week, they are never 5 days or less.