Acidic and hydrogen peroxide treatment of polyaluminum chloride (PACL) sludge from water treatment

The water treatment sludge including coagulants cannot be easily removed by conventional dewatering methods. The possibility of hydrogen peroxide (H₂O₂) oxidation as a pretreatment to enhance the dewaterability of polyaluminum chloride (PACl) sludge from water works was investigated. H₂O₂ treatment alone was not effective but H₂O₂ treatment under acidic condition significantly reduced both the cake water content and specific resistance to filtration (SRF), indicating the enhancement of dewaterability and filterability. The filterability after acid/H₂O₂ treatment was comparable to polymer conditioning and even more dewatered cake than polymer conditioning was produced. By H₂O₂ combined with sulfuric acid (H₂SO₄), leached iron caused Fenton's reaction, which showed a potential to significantly reduce the amount of solids mass and to produce more compact cake with higher filterability.