<b>Wastewater Systems</b> The sensitivity of the wastewater systems and the particular dangers posed by the contents of a sewage system require particularly competent on-board personnel for the maintenance work. In this respect, these systems only need to be opened and serviced by trained personnel and under supervision and appropriate safety measures. The basic methods of wastewater treatment used in shipping today are: - conventional aerobic activation systems for black water treatment (activation / secondary clarification) with disinfection - conventional aerobic activation systems for black and gray water treatment (activation / secondary clarification) with disinfection - membrane bioreactors (micro and ultrafiltration for black or black and gray water treatment as well as wastewater from the sanitary or hospital sector. - reverse osmosis systems for gray water treatment (cruise ships) In addition to membrane filtration, mainly chlorination, UV light treatment and ozonization are used to disinfect (sterilize) the waste water. In some cases, the wastewater is mechanically pre-treated (sieve, calculator). However, this is essential for the membrane filter technology processes in order to avoid unnecessarily stressing the membrane with coarse matter.