Methods for removing heavy metals from water using chemical precipitation and field separation methods

A method for removing particulate material from water, comprising the steps of:

• (a) admitting a stream of water to be treated to a vessel such that the water remains therein for a residence time;
• (b) providing magnetic seed particles and a flocculating polymer in said vessel as necessary so that said particulates are adhered to magnetic seed particles by said flocculating polymer, forming a floc;
• (c) allowing a first portion of said floc to settle out of the water;
• (d) removing the remainder of said floc by passing the water containing the remainder of the floc past one or more magnetized surfaces in said vessel at least partially submerged in the water from which the floc is to be removed, such that the remainder of the floc is collected on the magnetized surface(s);
• (e) removing the remainder of the floc from the magnetized surface(s) of the disks by scraping the collected floc therefrom, so that the removed floc is returned to the vessel;
• (f) removing a stream of cleansed water from the vessel;
• and
• (g) separating the particulates from the magnetic seed material, for reuse of the magnetic seed material;
• wherein the settling, flocculation, and magnetic collection steps are performed in the same vessel.

A method for removing dissolved heavy metals from water, comprising the following steps:

• (a) precipitating heavy metals by adding lime, limestone, caustic, magnesium hydroxide, soda ash or any other material that will precipitate the heavy metals as hydroxides or carbonates;
• (b) removing the precipitated heavy metal formed in step (a) by gravity clarification methods or by field separation methods selected form the group consisting of magnetic separation, dissolved air flotation, vortex separation, expanded plastic flotation or any other method that uses field forces rather than filtration to remove particles from the water;
• (c) precipitating the residual heavy metal remaining in solution after steps (a) and (b) by addition of organic sulfides, inorganic sulfides, sodium borohydride, ferrous compounds, or any other chemical that can precipitate more metals from the water than hydroxide and carbonate chemicals;
• and
• (d) removing the heavy metals precipitated in step (c) by field separation methods selected from the group consisting of gravity clarification, magnetic separation, dissolved air flotation, vortex separation, expanded plastic flotation or any other method that uses field forces rather than filtration to remove the particles from the water;
• and
• (e) wherein a bonding agent comprising an organic flocculating agent is employed in at least one of steps (b) or (d) to attach metal precipitates or other fine particles to expanded plastic with a density less than water, so that the attached particles can be removed by flotation forces.

A method for removing particulates from water, comprising the steps of:

• (a) adding particles of positively-charged expanded plastic to the water;
• (b) employing a negatively-charged organic flocculating agent to cause said particulates to be adhered to said particles of expanded plastic forming particles, forming attached particles with a density less than water, so that the attached particles float on the surface of the water;
• (c) withdrawing clean water from beneath the surface of the floating attached particles;
• (d) removing the particulates and expanded plastic;
• and
• (e) cleaning and reusing the expanded plastic.