Application Of Modified Vermiculite Flocculation In Swine Wastewater Treatment

The traditional inorganic flocculant polymeric ferric sulfate(PFS)has the advantages of fast hydrolysis speed,stable chemical properties,strong flocculation strength,large alum flow,quick settling speed and low corrosiveness.But its shortcomings is iron salts in the iron ions and some of the organic matter in water react to form a water-soluble substances,resulting in tap water with color.But its shortcomings is iron salts in the iron ions and some of the organic matter in water react to form a water-soluble substances,resulting in tap water with color.Even worse,the trivalent iron ions(Fe3+)are reduced to positively charged ferrous ions(Fe2+),resulting in secondary contamination.So the application of PFS flocculant in water treatment is limited to a certain extent.Therefore,the development of non-toxic,inexpensive high flocculant is the current water treatment technology development.Research shows that inorganic mineral materials contain a lot of metal ions,it has flocculation.In water treatment,when a large amount of colloidal water flows through a sandstone or soil runoff containing mineral material,the metal ions of the mineral material neutralize the negatively charged colloids to stabilize,flocculate,precipitate and adsorb.Therefore,for this feature of mineral materials,natural inorganic mineral flocculants can be prepared by chemical treatment.The shortcomings of traditional flocculant Polymeric Ferric Sulfate(PFS)include residual iron ions,difficulty of separating floc and large floc volume.Since natural inorganic mineral materials contain large amounts of iron and aluminum,they are modified to replace PFS as a novel flocculant.In this study,a type of natural expanded vermiculite modified by sulfuric acid(A-EV)was prepared as an inorganic mineral flocculant for swine wastewater treatment.The XRD,SEM,XRF and specific surface area of flocculants for inorganic mineral materials were analyzed.Its flocculation performance of swine wastewater treatment was studied by comparing with traditional PFS.For A-EV,the removal efficiencies of phosphorus,chemical oxygen demand(COD),suspended solids(SS),total nitrogen(TN)and turbidity reached 95.8%,95.7%,70.0%,38.8%and 21.9%,respectively,which were comparable with those of PFS.However,the A-EV floc volume accounted for only 24%of the total volume(less than 64%of PFS floc volumes),and the settling rate of A-EV flocs was 5.8 times that of PFS.Regarding with toxicity of supernatant and A-EV floc by inductively coupled plasma mass spectrometry(ICP-MS),their heavy metal contents both met the national emission standards.Moreover,phosphorus could be slow desorbed from the A-EV floc sediment under weak acidic conditions.Overall,A-EV was superior to PFS flocculants and non-toxic floc sediment could be used as potential phosphate fertilizers.