(formerly ELECTRO-PURE SYSTEMS, INC.)
(Alternating Current Electrocoagulation Technology)
The alternating current electrocoagulation (ACE) technology offers an alternative to the use of metal salts or polymers and polyelectrolyte addition for breaking stable emulsions and suspensions. The technology removes metals, colloidal solids and particles, and soluble inorganic pollutants from aqueous media by introducing highly charged polymeric aluminum hydroxide species. These species neutralize the electrostatic charges on suspended solids and oil droplets to facilitate agglomeration or coagulation and resultant separation from the aqueous phase. The treatment prompts the precipitation of certain metals and salts.
The figure below depicts the basic ACE process. Electrocoagulation occurs in either batch mode, allowing recirculation, or continuous (one-pass) mode in an ACE fluidized bed separator. Electrocoagulation is conducted by passing the aqueous medium through the treatment cells in upflow mode. The electrocoagulation cell(s) consist of nonconductive piping equipped with rectilinearly shaped, nonconsumable metal electrodes between which is maintained a turbulent, fluidized bed of aluminum alloy pellets.
Application of the alternating current electrical charge to the electrodes prompts the dissolution of the fluidized bed and the formation of the polymeric hydroxide species. Charge neutralization is initiated within the electrocoagulation cell(s) and continues following effluent discharge. Application of the electrical field prompts electrolysis of the water medium and generates minute quantities of hydrogen gas. The coagulated solids will often become entrained in the gas, causing their flotation.
Attrition scrubbing of the fluidized bed pellets within the cell inhibits the buildup of scale or coating on the aluminum pellets and the face of the electrodes. Coagulation and flocculation occur simultaneously within the ACE cells as the effluent is exposed to the electric field and the aluminum dissolves from the fluidized bed.
The working volume of the fluidized bed cell, excluding external plumbing, is 5 liters. The ACE systems have few moving parts and can easily be integrated into a process treatment train for effluent, pretreatment, or polishing treatment. The ACE technology has been designed into water treatment systems which include membrane separation, reverse osmosis, electrofiltration, sludge dewatering, and thermo-oxidation technologies.
System operating conditions depend on the chemistry of the aqueous medium, particularly the conductivity and chloride concentration. Treatment generally requires application of low voltage (<135 VAC) and operating currents of less than 20 amperes. The flow rate of the aqueous medium through the treatment cell(s) depends on the solution chemistry, the nature of the entrained suspension or emulsion, and the treatment objectives.
Product separation occurs in conventional gravity separation devices or filtering systems. Each phase is removed for reuse, recycling, additional treatment, or disposal.
Current systems are designed to treat waste streams of between 10 and 100 gallons per minute (gpm). RECRA Environmental, Inc., maintains a bench-scale unit (1 to 3 gpm) at its Amherst Laboratory for use in conducting treatability testing.
The ACE technology treats aqueous-based suspensions and emulsions such as contaminated groundwater, surface water runoff, landfill and industrial leachate, wash and rinse waters, and various solutions and effluents. The suspensions can include solids such as inorganic and organic pigments, clays, metallic powders, metal ores, and colloidal materials. Treatable emulsions include a variety of solid and liquid contaminants, including petroleum-based by-products.
The ACE technology has demonstrated reductions of clay, latex, and various hydroxide loadings by over 90 percent. Chemical oxygen demand and total organic carbon content of spiked slurries have been reduced by over 80 percent. The technology has removed heavy metals at between 55 and 99 percent efficiency. Fluoride and phosphate have been removed at greater than 95 percent efficiency. The system has been used to recover fine-grained products which would otherwise have been discharged.
The ACE technology was accepted into the SITE Emerging Technology Program in July 1988. The laboratory-scale testing was completed in June 1992. The Emerging Technology Bulletin (EPA/540/F-92/011) and Emerging Technology Summary (EPA/540/S-93/504) are available from EPA. The research results are described in the Journal of Air and Waste Management, Volume 43, May 1993, pp. 784-789, "Alternating Current Electrocoagulation for Superfund Site Remediation."
Experiments on metals and complex synthetic slurries have defined major operating parameters for broad classes of waste streams. The technology has been modified to minimize electrical power consumption and maximize effluent throughput rates.
EPA PROJECT MANAGER:
Randy Parker
U.S. EPA
National Risk Management Research Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
513-569-7271
Fax: 513-569-7571
TECHNOLOGY DEVELOPER CONTACTS:
Kenneth Kinecki
RECRA Environmental, Inc.
10 Hazelwood Drive, Suite 110
Amherst, NY 14228-2298
800-527-3272
Fax: 716-691-2617