Abstract: System (10) for electrocoagulatively removing contaminants from contaminated water (13), electrocoagulation reactor unit (16), and sedimentation column (302). Electrocoagulation reactor unit (16) includes reactor housing assembly (102) having: lower pair of integrally configured, and complementary upper pair of removably and replaceably configured, electrode positioning, spacing, holding elements, and, two wall electrode or electrode wall electrocoagulatively unreactive zones, each having an interior face of a side wall configured flush against and directly contacting adjacent, nearest neighboring, electrode face, for preventing water flowing and making contact therebetween. Sedimentation column (302) includes first sediments-water separator assembly having a water/sediments distributor assembly, and second sediments water separator assembly having downward flow multi-conduit assembly.