“a process for treatment of highly acidic effluent (wastewater) containing fluoride and recovery of natural resources”

Abstract

Application no. 202531005093 ABSTRACT A VALUE ADDED PROCESS FOR TREATMENT OF HIGHLY ACIDIC EFFLUENT (WASTEWATER) CONTAINING FLUORIDE AND RECOVERY OF NATURAL RESOURCES The present disclosure is related to a process for treatment of a highly acidic effluent (wastewater) containing Fluoride from Glass frosting industry, as well as recovery of natural resources from the effluent. Particularly Ammonia & Fluoride, the present disclosure is related to treatment of wastewater produced during the process of making frosted glass. Fig. 2 & 3

Description

DESC:FORM 2THE PATENTS ACT 1970(39 OF 1970)&THE PATENTS RULES, 2003PROVISIONAL SPECIFICATION(See section 10 and rule 13)TITLE OF THE INVENTION“A VALUE-ADDED PROCESS FOR TREATMENT OF HIGHLY ACIDIC EFFLUENT (WASTEWATER) CONTAINING FLUORIDE AND RECOVERY OF NATURAL RESOURCES”APPLICANTS(1) SAXENA DINKARHIG 284 SECTOR 16 SIKANDRA AVAS YOJNA, SIKANDRA AGRA 282007, UP, INDIA (2) DINKAR Nivedita HIG 284 SECTOR 16 SIKANDRA AVAS YOJNA, SIKANDRA AGRA 282007 UP, INDIA (3) DASGUPTA Jennifer FLAT NO. 1 / 5 / 17 CALCUTTA GREENS HIG-A,1050 / 2 SURVEY PARK,KOLKATA-700075, WEST BENGAL, INDIAThe following specification particularly describes the invention and the manner in which it is to be performedFIELD OF THE INVENTIONThe present disclosure is related to a value-added process for treatment of a highly acidic effluent (wastewater) containing Fluoride from Glass frosting industry, as well as recovery of natural resources from the effluent. Particularly Ammonia & Fluoride, the present disclosure is related to treatment of wastewater produced during the process of making frosted glass. Background technologyGlass having a frosty finish on one or both of its surfaces is increasingly being used in numerous interior design applications in both residential and commercial settings such as doors, shower screens, partitions, interior screens, furniture etc. to obtain visual privacy while allowing light transmission at the same time. Although frosting of glass is extremely decorative, frosting is not done for aesthetics alone. Such frosted glass can also be utilized as a light diffusion layer to reduce glare when used in facades.Conventionally, to obtain a frosty finish on the surface of a glass, a method is used in which the surface is etched with a hydrofluoric acid solution with added salts such as ammonium Fluoride, or a mixed solution of hydrofluoric acid and sulfuric acid with added salts such as ammonium Fluoride. Such a method can provide a frosted surface, but the use of a strong acid, such as hydrofluoric acid as an etching agent, can make the handling of agents difficult and can require washing with an acid and water. The waste acid and wastewater after frosting it is discharged without treatment, which seriously endangers people's health and pollutes water and air.• Nature & Origin of Effluent:The composite sample of effluent was tested for treatability and possible options for treatment of Glass Etching effluent. Chemical Composition Value UnitAmmonia 403.20 PPMAnionic Detergents (as MBAS) BLQ, (LOQ-0.01) Calcium (as Ca) 52.0 PPMChloramines (as Cl2) BLQ, (LOQ-0.05) Chloride (as Cl) 2299.29 PPMCyanide (as CN) BLQ, (LOQ-0.03) Fluoride (as F) 8680 PPMMagnesium (as Mg) 7.29 Mineral oil BLQ, (LOQ-0.1) PPMNitrate (as NO3) 13.0 PPMPolynuclear aromatic hydrocarbons (as PAHs) BLQ, (LOQ-0.00001) Phenolic substances (as C6H5OH) BLQ, (LOQ-0.0005) PPMPolychlorinated biphenyls BLQ, (LOQ-0.00001) Residual Free Chlorine BLQ, (LOQ-0.1) Methods of remediating frosted glass wastewater are known in the art. However, such methods suffer from various drawbacks, including not being efficient in removing or degrading a diverse range of chemicals. Further, in certain industries, such as the wastewater industry, the quest for improvements, is never ending.Existing Treatment of Fluoride-containing wastewater:To treat glass frosting wastewater, the primary focus is on neutralizing the acidic components, typically from hydrofluoric acid used in the frosting process, through the addition of a neutralizing agent like Calcium hydroxide (lime) to precipitate Fluoride ions, followed by settling and filtration to remove solids, and potentially further treatment steps like pH adjustment and ion exchange depending on local regulations and wastewater characteristics. Key steps in glass frosting wastewater treatment:• STEP I: Preliminary screening:Remove large debris through a sieve or screen to prevent clogging in subsequent stages. • STEP II: pH adjustment with lime addition:Add Calcium hydroxide (lime) to the wastewater to raise the pH till 7.5 and precipitate Fluoride ions as Calcium Fluoride, which will settle out as a precipitate / sludge. Alternative neutralizing agents:• Magnesium hydroxide:Can be used instead of Calcium hydroxide to precipitate Fluoride ions as magnesium Fluoride.• Flocculation and sedimentation:Add a flocculant to further aggregate the precipitated solids and facilitate settling in a sedimentation tank. • STEP III: Filtration:Pass the treated water through a sand filter to remove remaining suspended solids. • STEP IV: Optional further treatment:Depending on the concentration, volume of other pollutants, additional steps like ion exchange or reverse osmosis (RO), Multi effect evaporator (MEE) processes may be needed to further purify the wastewater. The above process is very expensive & frequent choking of RO membrane does not allow the treatment scheme to attain desired Zero Liquid Discharge (ZLD) status. Moreover, there is no address to ammonia present in the wastewater which impart damage to surface of RO membrane, resulting failure of the RO elements and frequent Cleaning in Process (CIP) reduces the life of the RO element.The prior art “CN108545952B” discloses frosting production process of glass bottles. The technical solution adopted by the cited art is to solve the technical problem associated to a glass bottle frosting production process, including the following processes (1) preparing the glass bottle, (2) cleaning pretreatment, (3) the first drying stage, (4) preparation of frosting liquid, (5) frosting, (6) cleaning, (7) second drying stage, (8) inspection and packing, (9) waste gas and waste liquid treatment. Treatment of Fluoride-containing waste liquid according to the cited art:Neutralize with lime water: pass the wastewater containing hydrofluoric acid into the neutralization tank, the neutralization temperature is 30 ?-70 ?, add the lime aqueous solution, and bubbling with compressed air to stir, the reaction produces Calcium Fluoride, other acids such as concentrated Hydrochloric acid, Sulfuric acid and lime water respectively produce Calcium chloride and Calcium sulfate. The emulsion of these products is passed through a roller filter, and the solid Calcium compound attached to the surface of the roller is scraped off with a scraper, and the filtrate is sent to the filter tower for filtration, The filtered water can be discharged after checking that the pH meets the national standard discharge requirements.Thus, there is a great need in the industry for an improved process to recover the costly elements (Ions) from the effluent such as Fluoride and Ammonium. Thereby increasing the life of RO membrane, lowering of treatment cost, besides recovery of Fluoride and Ammonium hydroxide and attaining Zero Liquid Discharge (ZLD) status.OBJECTS OF THE INVENTIONThe primary objective of the invention is to deliver a safe and environmentally sustainable solution for treating the effluent (wastewater) produced during the glass frosting process.Another object of the invention is to provide sustainable processes that facilitate the recovery of natural resources like Fluoride. This recovered natural resources can be recycled and reused by various industries, creating a circular economy and also have cost-saving advantage. These savings translate directly into increased profits for the stakeholders.How the foregoing objects are achieved will be clear from the following description. In this context it is clarified that the description provided is non-limiting and is only by way of explanation. SUMMARY OF THE INVENTIONThe method for value added processing of an effluent generated during glass frosting, the method comprising the steps of:Bar screening to remove large floating particles from the influent;Coagulation and removal of small, suspended particles with the help of Dissolved Air Flotation producing tiny bubbles to lift suspended solids which removed by skimming, or by using tube settler depending on the nature of suspended particles;Neutralizing wastewater by adding alkali in the steps• Adding alkali (to wastewater to attain the pH value 8.5, followed by the addition of Sodium Hydroxide to attain the pH value 11~13 at a temperature of 3180K;• Increased pH releases the ammonium ions as ammonia gas that allows them to pass and washed through the wet scrubber containing neutralizer agent Sulfuric acid that results in the production of Ammonium Sulfate in liquid form and Carbon Dioxide is released to the atmosphere;Reverse osmosis (MOC PVDF) recovers the water for reuse;Concentrated wastewater from RO fed into multi effect evaporator for further recovery of water & concentration of treated effluent; Hot and concentrated wastewater from multi effect evaporator is fed into a crystallizer to separate the sodium salts and rest of the liquid again fed into the multi effect evaporator to reconcentration;BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGSThe nature and scope of the present invention will be better understood from the accompanying drawings, which are by way of illustration of a preferred embodiment and not by way of any sort of limitation. In the accompanying drawings: -Figure 1 shows a flow diagram showing the conventional method of treating wastewater produced in the Glass frosting process.Figure 2 shows a flow diagram showing the method of treating concentrate effluent produced in the Glass frosting process according to the present invention.Figure 3 shows a flow diagram showing another embodiment of method of treating dilute effluent produced in the Glass frosting process according to the present invention.DETAILED DESCRIPTION OF THE INVENTIONHaving described the main features of the invention above, a more detailed and non-limiting description of a preferred embodiment will be given in the following paragraphs with reference to the accompanying drawings.In all the figures, reference numerals represent like features. Further, the shape, size and number of the devices shown are by way of example only and it is within the scope of the present invention to change their shape, size and number without departing from the basic principle of the invention. Further, when in the following it is referred to “top”, “bottom”, “upward”, “downward”, “above” or “below”, “right hand side”, “left hand side”, ”steps” and similar terms, this is strictly referring to an orientation with reference to the apparatus, where the base of the apparatus is horizontal and is at the bottom portion of the figures. The number of components shown is exemplary and not restrictive and it is within the scope of the invention to vary the shape and size of the apparatus as well as the number of its components, without departing from the principle of the present invention. All through the specification, the technical terms and abbreviations are to be interpreted in the broadest sense of the respective terms and include all similar items in the field known by other terms such as “wastewater” of the present invention is same as the “waste liquid” of the cited art, as may be clear to persons skilled in art. Restriction or limitation if any referred to in the specification, is solely by way of example and understanding the present invention.Conventionally, surface frosting of a glass product is performed by immersing the glass product in a frosting solution containing hydro fluoric acid (HF) and Ammonium Hydrogen Fluoride also known as Ammonium Bifluoride, for 10-20 seconds, allowing the surface of the glass product to be corroded in a very short period of time to form frosted texture. This operation is based on the addition of ammonium hydrogen Fluoride in fluoric acid (HF) which causes alkaline metal ions contained in the glass composition to dissolve and precipitate. The insoluble matter that is not removed during corrosion adheres to the surface of the glass. As the reaction time continues, the reactants accumulate into granular shapes. The crystal is firmly attached to the surface, hindering the further reaction of acid etching, that is, it becomes non-uniform erosion, and the result is a semi-transparent rough surface, which scatters the incident light and presents a semi-transparent state with a hazy feeling. Spray the glass product with tap water 2-3 times, then wash the glass product with clean water 2 times. Since the active ingredient in the frosting liquid is hydrofluoric acid, which is corrosive & volatile, it will cause pollution to the water environment. The waste liquid after cleaning also contains a certain amount of Fluoride, and direct discharge will cause pollution to the water. Therefore, waste liquid needs to be treated and discharged. The core essence of the subject invention lies here. It plays two vital roles in wastewater treatment i.e. the claimed process used the wastewater for recovery of natural resources like Fluoride in the form of Sodium Fluoride, a colourless crystalline solid or white powder, or the solid dissolved in a liquid. It is soluble in water. It is non-combustible. It is corrosive to aluminum. It is used as an insecticide. It is also used to fluorinate water supplies, as a wood preservative, in cleaning compounds, manufacture of glass, and for many other uses. These savings translate directly into increased profits for the stakeholders. At the same time eliminates the risk of environmental pollution which is caused by untreated discharge of wastewater into the environment.The present treatment scheme is having been developed to recover the costly natural resources such as Fluoride and Ammonium. Thereby increasing the life of RO membrane, lowering of treatment cost, besides recovery of sodium Fluoride and Ammonium hydroxide to attain Zero Liquid Discharge status.The highlights of the new process are listed below: ? STEP I: Bar Screen (removal of Floating material): This step is used to remove large floating particles from the influent. For better removal efficiency two bar screen (1) are needed i.e. C / C spacing of 25 mm followed by C / C spacing of 12.5 mm.? STEP II: Dissolved air flotation / grit settler as per the influent characteristics, for Removal of suspended particles from influent wastewater This step is needed to coagulate & remove small, suspended particles with the help of Dissolved Air flotation (2) technique. The influent is pressurized and combined with pressurized air, after which the pressure is released, producing tiny bubbles that lift suspended solids to the surface of the dissolved air flotation reactor, where they are removed by skimming, or by using tube-settler as per the nature / properties of suspended particles.Thereby this step produces clear liquid for the further processing.? STEP III: Equalization cum neutralization tank with dosing arrangement followed by Continuous stirred Tank reactor (3) (CSTR) to raise the pH & temperature:This step has three functions a. Neutralizing wastewater by adding required dose of Alkali in following stepsb. first by solution of Sodium bi carbonate, Na2CO3 till wastewater attain pH value of 8.5, then pH is raised by Sodium Hydroxide i.e. NaOH, till wastewater pH attain value of 11 ~13.c. Raising the temperature to 3180K d. Release of ammonium ion as Ammonia as gas, which is pass through the wet scrubber (containing Sulfuric Acid as neutralizer) and gets converted as Ammonium Hydroxide and Ammonium Sulphate recovered as liquid and CO2 produced in neutralisation process escape to atmosphere (details as per step IV). This step results into production of Gases besides free anion such as Fluoride, Chloride etc. are converted into corresponding Sodium salt. This step produces recoverable Sodium salts and Ammonium Sulphate.? STEP IV: Scrubber for ammonia striping & Ammonium hydroxide recovery.The gases released from the Continuous Stirred Tank Reactor contain carbon dioxide (CO2) and ammonia (NH3). Since releasing ammonia into the atmosphere is not advisable, the process utilizes its properties to address this issue. The released gases are washed with water in a wet scrubber, allowing carbon dioxide (CO2) to be released into the atmosphere while recovering ammonia (NH3) in the form of ammonium Sulphate. Wet scrubbers (4) work on the principle of absorption, using a liquid solution to capture and neutralize pollutants such as ammonia gas. The process involves passing the contaminated gas through a scrubber tower or chamber, where water or a chemical solution is sprayed or trickled down. This creates a scrubbing action, allowing the solution to come into direct contact with the gas and remove the pollutants.The reaction is follows:The chemistry of ammonia mirrors that of water. It is a polar, protic solvent capable of hydrogen bonding that undergoes an acid-base equilibrium equivalent to that of water. Like water, liquid ammonia undergoes molecular autoionization to form its acid and base conjugates as:2 NH3 ? NH4+ + NH2-Ammonia often functions as a weak base, so it has some buffering ability. Shifts in pH will cause more or fewer ammonium cations NH4+ and amide anions NH2-, to be present in solution. Ammonia Hydration: When ammonia gas comes into contact with water, the water molecules disrupt the hydrogen bonds in ammonia. This reaction produces ammonium ions (NH4?) and hydroxide ions (OH?), resulting in the formation of ammonium hydroxide.Ammonium hydroxide is an effective neutralizing agent because it can react with acidic compounds, such as sulfuric acid or hydrogen chloride, to form stable & usable substances. This reaction, known as neutralization, involves the transfer of protons from the acid to the base, resulting in the formation of water and salt. The salt formed depends on the specific acid used. The formed ammonium salt can be reused as desired. ? STEP V: Reverse Osmosis (RO)for recovery of waterAs thus treated wastewater having salts of Fluoride and other acids but free from NH3 & scale forming Ions such as Ca, Mg, etc, same can be treated by reverse Osmosis to recover the water for reuse in the Etching / frosting / any other suitable application. The concentrated water is further concentrated by Reverse Osmosis (5) till it reached required density for feeding the next stage.? STEP VI: Multi effect evaporator (6) (MEE) for Salt concentration and recovery of waterConcentrated wastewater is further processed to achieve the desired density using a falling film multi-effect evaporator, while the recovered water is redirected for reuse.Typical requirement for concentration of liquid is 55 gm / Lt at 328oK or higher, it may vary with composition of incoming dissolved salts. The concentrated water is fed to next stage i.e. crystallisation of Sodium salts.? STEP VII: Crystallizer (7) for recovery of NaF & NaCl:The hot and concentrated wastewater is fed into a crystallizer so that the Sodium Salts can be separated out and be reused / sale to user / etc. The mother liquid thus produced will again feed into the multi effect evaporator for further concentration.Example: Sample 1 from unit at Aurangabad, Maharashtra, IndiaQuantitative analysis of suggested processTDS of raw effluent : 11580 PPMpH : 3.8Addition of Alkali : Ammonia till pH 11.8 to 13TDS after the neutralization of Free HF by NaOH: : 13100 PPM or 13.1 Gm / LtAlkali required for achieving pH 10 : 10.98 Kg / Cu MFor discharge of 150 KLD : 1647 Kg / dayAs per the test conducted at external lab effluent has Cl to F ratio : 1: 3.77Total available solids in crystalliser 13.1 X 1000 x 150 =1965000 Gm / day or 1967 Kg / day as per the ratio of F: ClEstimated cost of material @65 x 1445.25 = Rs. 93925 (Cost reduction &recovery of resources). 521.75 kg NaCl.Sample 2 from Bahadurgarh, HaryanaTDS of raw effluent : 62500 PPMpH : 3.7Addition of Alkali : Ammonia till pH 11.8 to 13TDS after the neutralization of Free HF by NaOH: : 72500 PPM Alkali required for achieving pH 10 : 33.5 gm / ltNaF produce after evaporating the remaining liquid : 26.54 gm / LtsAs per the test conducted at external lab for NaF purity : 96.1%The present invention has been described with reference to certain drawings and a preferred embodiment solely for clarity and understanding, without imposing any limitations. It encompasses all legitimate advancements within the scope of the preceding description.

Claims

,CLAIMS:We Claim:

1. The method for value added processing of an effluent generated during glass frosting, the method comprising the steps of:Bar screening to remove large floating particles from the influent;Coagulation and removal of small, suspended particles with the help of Dissolved Air Flotation producing tiny bubbles to lift suspended solids which removed by skimming, or by using tube settler depending on the nature of suspended particles;Neutralizing wastewater by adding alkali in the steps• Adding alkali (to wastewater to attain the pH value 8.5, followed by the addition of Sodium Hydroxide to attain the pH value 11~13 at a temperature of 3180K;• Increased pH releases the ammonium ions as ammonia gas that allows them to pass and washed through the wet scrubber containing neutralizer agent Sulfuric acid that results in the production of Ammonium Sulfate in liquid form and Carbon Dioxide is released to the atmosphere;Reverse osmosis (MOC PVDF) recovers the water for reuse;Concentrated wastewater from RO fed into multi effect evaporator for further recovery of water & concentration of treated effluent;Hot and concentrated wastewater from multi effect evaporator is fed into a crystallizer to separate the sodium salts and rest of the liquid again fed into the multi effect evaporator to reconcentration;2. The method as claimed in claim 1, wherein two bar screens are selected having C / C spacing of 25 mm followed by C / C spacing of 12.5 mm.

3. The method as claimed in claim 1, wherein the alkali is selected from group of Soda alkali: Sodium Carbonate, Sodium bi Carbonate and Sodium Hydroxide.

4. The method as claimed in claim 1, wherein the pH of the wastewater attains the value of 11~13 at a temperature of 3180K.

5. The method as claimed in claim 1, wherein carbon dioxide (CO2) and ammonia (NH3) are released from the Continuous Stirred Tank Reactor.

6. The method as claimed in claim 1, wherein concentration of liquid is 55 gm / Lt at 328oK or higher.Dated this 11th Day of April 2025. To (MONAJ SAHA)The Controller of Patents IN / PA-1884The Patent Office for S.S. Datta & AssociatesKolkata Applicants' Agent