11 Retention basin with or without groundwater recharge; water purification, sedimentation and filtration apparatus for clarification, thickening and filtration of environmental and storm runoff water; water purification, sedimentation and filtration apparatus for clarification, thickening and filtration of waste water and industrial water in the field of irrigation; water purification, sedimentation and filtration apparatus for clarification, thickening and filtration of waste water and industrial water in the field of oil and gas; waste water treatment system; hydrodynamic separator