Wastewater flotation utilizing streaming potential adjustment

• US 4,219,417 A
• Filed: 10/25/1978
• Issued: 08/26/1980
• Est. Priority Date: 12/21/1976
• Status: Expired due to Term

• Current Assignee: Metal Resources
• Original Assignee: Dravo Corporation
• Inventors: Ramirez, Ernest R.
• Primary Examiner(s): Wyse, Thomas G.
• Application Number:
  US05/954,359
• Time in Patent Office: 671 Days
• Field of Search: 210/44, 210/51-53, 210/221 M, 210/221 P
• US Class Current: 210/707
• CPC Class Codes: C02F 1/24 by flotation C02F1/465 takes precedence
• CPC Class Codes: C02F 1/465 by electroflotation

Abstract

A flow of wastewater is adjusted to near zero streaming potential by injecting a non-coagulant mineral acid or base into the wastewater. The potential is measured in streaming detector units. The thus adjusted flow enters a basin where it is subjected to a decreasing gradient of small bubbles to form and separate off a buoyant floc from which valuable materials are more readily recoverable, a floc of higher solids content, and a floc of lesser relative volume than other systems employing similar manipulative steps.

Claims

1. A method for removing particulates from wastewaters by flotation, comprising:

obtaining a supply of wastewater having charged particulate matter;

adjusting the streaming potential of particulates in the wastewater to approximately zero, in the absence of any added trivalent metal coagulant compounds, by adding to the wastewater a non-coagulant chemical consisting essentially of an inorganic mineral acid or base;

forming a flow path of the thus adjusted wastewater to a confined location;

supplying dense quantities of small bubbles within said confined location;

entering overflow from the confined location into a long flotation zone;

baffling the overflow by flowing through perforated baffles in said flotation zone;

said flotation zone having a downstream, quiescent portion;

forming buoyant floc in the long flotation zone; and

separating the floc from the wastewater.

2. The method of claim 1, wherein the non-coagulant chemical is an inorganic acid and the wastewater is a packinghouse or meat processing wastewater having protein, fat and oil particulate matter.

3. The method of claim 1, wherein the non-coagulant chemical is an inorganic base and the wastewater is a water used in the beneficiation of mineral ores, said water having insolubilizable, dissolved heavy metals.

4. The method of claim 1, wherein the baffling reduces turbulence, channelling and back diffusion by permitting free passage of about 30 to 80 percent of the flow through the long flotation zone.

5. The method of claim 1, said wastewater also including certain adsorbable ion values, said bubbles in said confined location being supplied electrolytically, and at least 50 percent of the ions being removed from the wastewater.

6. The method of claim 1, further comprising adding about one half to 15 ppm of polyelectrolyte flocculant to the confined location.

7. The method of claim 1, wherein the steps of forming and separating buoyant floc includes supplying bubbles formed electrolytically or by release of pressurized dissolved gas bubbles within the portion of the long flotation zone that is upstream of the quiescent portion, the volume of microbubbles present in the wastewater of said upstream portion of the long flotation zone being about 3 to 10 times greater than the volume of microbubbles in the downstream quiescent portion.

8. The method of claim 1, wherein the steps of forming and separating buoyant floc in the long flotation zone includes providing bubbles in a pattern that gradually decreases in density in the downstream direction.

9. The method of claim 1, wherein the steps of forming and separating buoyant floc includes forming bubbles electrolytically and supplying said bubbles in four quartile stages, the stage at the first, most upstream stage of the long flotation zone having a current density between about 7.5 to about 20 amperes, the second quartile stage having a current density between about 3.5 to about 10 amperes, the third quartile stage having a current density between about 1.5 to about 5 amperes, and the fourth, most downstream stage being said quiescent portion within which no current is supplied, said current densities being the average amount of amperage supplied per square foot of each quartile, calculated based on the floor area covered by each quartile stage.

10. The method of claim 1, wherein the steps of forming and separating buoyant floc include supplying bubbles within the long flotation zone to develop a bubble density at the upstream end of the long flotation zone that is 2 to 5 times greater than the bubble density at the mid-line of the zone.

11. The method of claim 1, wherein said steps of supplying dense bubbles, entering the long flotation zone, baffling, forming buoyant floc and separating floc together provide a gradient of bubble densities that gradually diminish in density along said flow path, the greatest density being at the influent end of the flow path;

contacting said flowing wastewater with said gradually diminishing gradient; and

creating high water turbulence within the wastewater only at the influent end, said high water turbulence being created and maintained within the confined location by the dense quantities of small bubbles formed by said influent end greatest bubble density.