Treatment of wastewater

A method of removing contaminants from frac flowback water or oilfield produced water, wherein the contaminants comprise dissolved iron, suspended solids, and oil, and further wherein the dissolved iron comprises ferrous iron, said method comprising the steps of:

• contacting the water with an oxidizing agent wherein the oxidizing agent oxidizes the ferrous iron to form precipitated ferric iron, and removing the precipitated ferric iron from the water,
• contacting the water with a suspended solids module comprising a targeted sorbent having a specific affinity for the suspended solids in the water, wherein the targeted sorbent having a specific affinity for the suspended solids comprises a suspended solids supportive substrate modified with a cationic polymer thereby removing the suspended solids from the water, wherein the cationic polymer is selected from the group consisting of linear or branched polyethyleneimine, poly-DADMAC, epichlorohydrin/DMA condensation polymers, chitosan, cationic starches, and styrene maleic anhydride imide;
• and
• contacting the water with an oil removal module comprising a targeted sorbent having a specific affinity for the oil in the water, wherein the targeted sorbent having a specific affinity for the oil comprises an oil removal supportive substrate modified with a hydrophobic cationic material selected from the group consisting of 3-trihydroxysilylpropyldimethylalkyl (C6-C22) ammonium halide, 3-trimethoxysilylpropyldimethylalkyl (C6-C22) ammonium halide and 3-triethoxysilylpropyldimethylalkyl (C6-C22) ammonium halide, thereby removing the oil from the water.