Liquid purification or separation – Processes – Ion exchange or selective sorption
Reexamination Certificate
2000-08-07
2002-04-30
Simmons, David A. (Department: 1724)
Liquid purification or separation
Processes
Ion exchange or selective sorption
C210S665000, C210S666000, C210S724000, C210S726000, C210S727000, C210S734000, C210S735000
Reexamination Certificate
active
06379555
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to wastewater treatment and particularly to treatment of effluent containing dyestuffs and other organics, inorganics, particulates and dissolved materials exiting a garment stonewashing or similar process.
DESCRIPTION OF THE PRIOR ART
Treatment of wastewater effluent from industrial processing has long been the subject of technical inquiry and practical application due not only to the continuing need for clean water but also due to the cost of using water in process water makeup situations and particularly those situations requiring clean water for process makeup. While the present methodology can extend to water reclamation and recycling in a number of industries including food processing, electronics manufacturing, metals plating, pulp and paper, etc., the present methodology is particularly useful for reclaiming and recycling water from the effluent of textile and dye plants and particularly in the processing of stonewashed and/or sandblasted garments wherein detergents, enzymes, fibers, surfactants, silicates, etc., must be removed from processing effluent with the treated water being sufficiently clean to allow recycle. Expensive water dumping fees are thus avoided by the ability to reuse process water according to the invention. In the treatment of garments and similar items by stonewashing and the like, large amounts of water are necessary to form the process medium in which cotton “bluejeans” and garments formed of blends including polyester/cotton blends, rayon/cotton blends, etc. are treated. In typical stonewashing processes, an abrasive such as pumice is used in combination with detergents, bleach and enzymes to alter the color and texture of garments, these garments being processed in industrial washing machines with the treating materials which can further include dyestuffs, treatment periods varying from minutes to hours. A common practice in the prior art has been to simply discharge the effluent from such processing directly into city wastewater systems. The continuing rise in the cost of water for initial process water makeup and the institution of sewer discharge fees causes prior art discharge practices to become prohibitively expensive. The need to recycle water from processing effluent has therefore become quite apparent to the garment processing industry as well as industry in general.
Examples of prior art teachings intended particularly for removal of dye materials from wastewater effluents are provided inter alia by Weber in U.S. Pat. No. 5,360,551, this patent removing color from dye wastewater through acidification and subsequent use of a cationic flocculent. An optional step in the Weber process is the addition of a reducing agent to produce a desired oxidation-reduction potential, the reducing agent being an alkali metal hydrosulfite, an alkaline earth hydrosulfite, mixtures thereof or combinations of an alkali metal bisulfite, an alkaline earth bisulfite, an alkali metal borohydride and mixtures thereof. In U.S. Pat. No. 5,611,934, Shepperd et al remove dye from process water effluent through treatment of the effluent with a reducing agent, adjustment of pH, treatment with a charged neutralization mixture and flocculation after a second pH adjustment. The particular charge neutralization mixture includes an aluminum salt and a cationic polymer consisting of a copolymer of acrylamide with a cationic monomer such as methacryloylethyltrimethylammonium halide and further including organic wherein the mixture exhibits a Zeta potential of 15 millivolts. Flocculation agents according to Shepperd et al include anionic polymers such as acrylic acid/acrylamide copolymers and non-ionic polymers such as polyacrylamides. Further teachings of wastewater treatments for removal of organics include U.S. Pat. Nos. 5,529,696 to Tibbits; 5,529,697 to Braasch; 5,529,698 to Timmons and 5,529,699 to Kuole, the Kuole patent particularly describing flocculating agents used in wastewater treatment processing. Grant et al, in U.S. Pat. No. 5,330,658, utilize precipitation and flocculation techniques to remove contaminents from wastewaters and particularly disclose an acidification step for removal of oxidizing agents.
Wastewater treatment according to the invention is particularly intended to remove color, to lower levels of TBS, TSS, BOD and COD in order to allow recycle of process water with resulting savings in makeup and disposal costs. The processes of the invention are particularly suited to treatment of waste-water effluent issuing from garment stonewashing and similar treatment processes. In such processing, wastewater effluent containing detergents, enzymes, fibers, surfactants, silicates, dyestuffs and particulates are treated to allow reclamation of greater than 95% of water originally used for process water makeup. The present processes remove all cotton lint, synthetic fibers, dissolved silica and solid particulates from effluent and further remove bleach, coloring from dyes either added during garment processing or removed from garments by processing, such coloring typically being black, green, red, blue and the like. The present methodology also allows removal of large quantities of soluble surfactants while lowering BOD, DOD, TSS and TBS levels. Suspended fibers, solids and colored materials are further removed in order to render a treated effluent reusable for process water makeup, reuse being possible many times over before a need exists to discharge major amounts of water originally used for makeup purposes. The present methodology can be practiced inexpensively, the physical system necessary for practice of the methodology also being inexpensive to fabricate and operate.
SUMMARY OF THE INVENTION
The invention provides methodology and system architecture intended for treatment of wastewater emanating from industrial processes particularly including garment washing processes which can involve removal from a garment of at least a portion of a dyestuff originally applied to the garment. The invention particularly intends the treatment of wastewater effluent from a garment stonewashing process such as the stone-washing of “jeans” which can include the removal of dyestuffs from the garment and/or the replacement of dye or color to the garment, the processes of the invention being intended to remove dyestuffs and other organic materials, lint, fibers, silicates and particulate solids inter alia from a stonewashing wastewater effluent in order to render the wastewater or effluent reusable in a stonewashing process or the like. A particular intent of the invention is the removal of materials from the wastewater effluent,which materials were employed for treatment of garments in the process producing the wastewater effluent, such materials including detergents, enzymes, surfactants, silicates and abrasive particulates such as pumice and the like. Processing according to the invention lowers levels of TSS, TDS, BOD and DOD so that water is reclaimed for process water makeup and/or discharge.
In a preferred embodiment of the invention involving the treatment of a wastewater effluent from a “jeans” stonewashing process, the wastewater effluent can optionally be filtered prior to subsequent chemical treatment. Since the present processes envision continuous flow treatment of effluent of only a few gallons and up to millions of gallons daily, initial filtration may be waived as long as any particulate material which might be removed by initial filtration is not converted to a dissolved material by subsequent chemical treatment whereby said nearly dissolved material would be difficult to remove by such subsequent chemical treatment. Initial filtration can be effected by passage of the wastewater effluent through a shaker with a mesh size of from 5 to 120 microns to remove large bits of pumice or similar abrasive and any other contaminants which are large enough to be trapped by filtration.
Preferred processes according to the invention include the step of acidification subsequent to optional initial filtration, i
Prince Fred
Simmons David A.
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