In the laundry wastewater treatment field of solids/liquid separation, suspended and emulsified solids are removed from water by a variety of processes, including sedimentation, straining, flotation, filtration, coagulation, flocculation, and emulsion breaking among others. Additionally, after solids are removed from the wastewater they must often be dewatered. Liquids treated for solids removal often have as little as several parts per million (ppm) of suspended solids or dispensed oils, or may contain several thousand ppm of suspended solids or oils. Solids being generated as sludge may contain anywhere from 0.1 to 6 weight percent solids prior to dewatering, and from 20 to 50 weight percent solids material after dewatering by a plate and frame press. Solids/liquid separation processes are designed to remove solids from liquids and the more solids generated in the process, the more costly its disposal.
While strictly mechanical means have been used to effect solids/liquid separation, the modern methods often rely on mechanical separation techniques that are augmented by synthetic and natural polymeric materials to accelerate the rate at which solids can be removed from water. These processes include the treatment of wastewater with cationic organic and inorganic coagulants that coagulate suspended particulates to form larger particles that then may be brought together by an anionic flocculent to create particles large enough to be removed from the waste stream by mechanical means, i.e., flotation or clarification, and make the effluent suitable for industrial reuse or disposal in compliance with local permit discharge requirements.
In the industrial laundry industry, the chemical treatment of wastewater to a typical municipal standard of 100 ppm of oil and grease (EPA method 1664) prior to the introduction of this invention has been: the hydraulic equalization of untreated wastewater followed by the metered flow of the wastewater through a pipe or tanks to provide for retention time for the injection of a variety of chemicals including combinations and individually, both organic and inorganic coagulants and aids, followed by an organic component flocculent to produce coagulation and flocculation. These inorganic components used for coagulation or coagulation aids, typically have simple hydration factors of approximately 6-12 water molecules and may also be used in conjunction with a separate component, i.e. perlite or diatomaceous earth or bentonite clay, to act as a “body builder” to produce sludge so that in down stream processes it may be dewatered. A variety of organic and inorganic coagulants and aids exist throughout the marketplace. Historical data has shown that used in correct combination these chemistries can produce suitable effluent with sludge generation of approximately 1.1 to 2.5% of influent flow, whereas by use of this invention sludge production is reduced to approximately 0.25 to 1.0% of influent flow.
Chemical treatment generally refers to the removal of nonsettleable material by coagulation and flocculation. Chemical treatment for wastewater clarification is typically employed when colloidal and microemulsified solids need to be removed so that the total petroleum hydrocarbons (TPH), fat, oil and grease (FOG), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), and other contaminants being discharged to a receiving stream need to be minimized. Typically, such treatment comprises using a cationic coagulant with one or more inorganic components, injected in combination or individually, followed by an anionic flocculent. Coagulation is the process of destabilization of the colloid waste particle by causing the coagulant (at 50-1000 ppm) to absorb by means of charge neutralization to form microfloc and impart residual cationic surface charge of the coagulated particles. The second step is to introduce a coagulant aid, i.e., ferric chloride, aluminum sulfate, ferrous sulfate, calcium chloride, polyaluminum chloride, typically at a rate of 75-700 ppm depending on the species, to increase the ability to form a more highly cationic surface that will cause the further adsorption of the coagulated particles onto the surface of an additional chemical, usually bentonite clay, at 200-900 ppm through a “sponge” effect. Flocculation occurs when the highly charged anionic flocculent bridges the previously formed cationic particles. Once neutralized, particles no longer repel each other and can come together to form larger agglomerated solids or sludge, which may then be removed from the water. The third step that is occasionally taken is the addition of sludge thickeners that assist in allowing the sludge to dewater, i.e. perlite, bentonite clay, diatomaceous earth and others. This invention is specifically directed to eliminating the second and/or third steps, i.e., the addition of coagulant aids and/or sludge thickeners and a resultant reduction of the formation of sludge by up to 80% compared to previous historically used methods.
Clarification chemicals are typically utilized in conjunction with mechanical clarifiers including dissolved air flotation systems (DAFs), induced air flotation systems (IAFs), and settlers for the removal of solids from the treated water. The clarification chemicals coagulate and/or flocculate the suspended solids into larger particles, which can then be removed from the water by gravitational settling, flotation, or other mechanical means.
Processes for the preparation of high molecular weight cationic dispersion polymer flocculents are described in U.S. Pat. Nos. 5,006,590 and 4,929,655. High molecular weight, high active polymer cationic solution polymers for water clarification, dewatering and retention and drainage are disclosed in U.S. Pat. No. 6,171,505.