Since Filtration MTDs contain filters that restrict flow rates, they are normally designed for much lower hydraulic loading rates than [[Oil and Grit Separator|Oil-Grit Separator MTDs]] and have longer detention times. Flow restriction occurs due to the small pore size openings of filters and the [[clogging]] of pores and/or the formation of films either on the surface of the filter or within the filter matrix filter. For this reason, inspection and maintenance intervals for Filtration MTDs are normally shorter than for [[Oil and Grit Separator|OGS MTDs]]. The method of maintenance typically involves sediment removal with a hydro vacuum truck as well as filter cleaning or replacement. | Since Filtration MTDs contain filters that restrict flow rates, they are normally designed for much lower hydraulic loading rates than [[Oil and Grit Separator|Oil-Grit Separator MTDs]] and have longer detention times. Flow restriction occurs due to the small pore size openings of filters and the [[clogging]] of pores and/or the formation of films either on the surface of the filter or within the filter matrix filter. For this reason, inspection and maintenance intervals for Filtration MTDs are normally shorter than for [[Oil and Grit Separator|OGS MTDs]]. The method of maintenance typically involves sediment removal with a hydro vacuum truck as well as filter cleaning or replacement. |