... beinghighest in the sewer systems and shear being the strongest in river systems. Density relationships for flocs in freshwater are no different than those in engin-eered or marine systems. In ... 2004/11 /19 — 02:47 — page 30 — #630 Flocculation in Natural and Engineered Environmental Systems Flocs formed in the water column via various physical, chemical, and biologicalmeans, as discussed in ... 2004/11 /19 — 02:47 — page 42 — #1842 Flocculation in Natural and Engineered Environmental Systems 20. Liao, B.Q., Allen, D.G., Leppard, G.G., Droppo, I.G., and Liss, S.N., Interparticleinteractions...