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.
What Is Very Light Period? Despite menstrual cycles vary from person to person, a normal period among women is approximately once in every 28 days. Typically, each period lasts from 4 to 7 days. During menstruation, the amount of lost blood ranges from 50 to 150 ml. Consequently, less than 50 milliliters may be considered a very light period. So, light periods are menstrual flows with unusually light occurance or rather short duration of blood loss. Light periods are not just the same as âamenorrheaâ, or complete absence of menstrual periods.