How to remove Fluoride from Industrial Wastewaters?
Fluoride-containing wastewater is discharged into the environment by several businesses, including iron and steel metallurgy, copper and zinc smelting, battery manufacture, and cement making. As a result, the discharge of excessive fluoride effluent poses a hazard to both human life and the ability of the environment to maintain life.
Fluoride Concentration in Wastewater
Fluoride concentrations in these wastewaters can range from 100 milligrams per litre to more than 10,000 milligrams per litre. Fluoride discharge limits are generally fewer than 20 mg/L if wastewater is disposed of in a public sewer system, and less than 5 mg/L if wastewater is disposed of in an aquatic environment. The fluoride discharge limit in some jurisdictions might be as low as 2 mg/L. It should also be noted that some municipalities add fluoride to their drinking water (0.5–1.5 mg/L) to help prevent tooth cavities. Excess fluoride, on the other hand causes skeletal fluorosis (bone disease).
Treatment methods for the removal of fluoride from Industrial Wastewater
Precipitation of CaF2 or calcium fluorideand coagulation, adsorption, ion-exchange, membrane-based technologies such as reverse osmosis and electrodialysis are all treatment methods for fluoride wastewater removal. The advantages and disadvantages of fluoride remediation technologies are all discussed in this article.
1: Precipitation of CaF2 and Coagulation
Advantages of Precipitation of CaF2 and Coagulation
• It is a popular approach that involves precipitating calcium fluoride (CaF2) down to its solubility limit using lime {Ca.(OH)2} or calcium chloride (CaCl2). Following that, aluminium-based coagulation is used to further lower fluoride levels in order to fulfil low discharge limitations.
• It gets rid of other pollutants including acid, silica, and heavy metals (cadmium, copper, chromium, lead, mercury, and zinc).
Disadvantages of Precipitation of CaF2 and Coagulation
• It has long hydraulic retention durations due to two independent reaction mechanisms.
• The precipitates of CaF2 and Al.(OH)3 produce fine particles that take a long time to settle, necessitating the use of large sedimentation and clarifying tanks.
• It produces excess wet sludge due to overdosing of lime and coagulation agents, resulting in excessive chemical expenses.
2: Ion-exchange and adsorption
Advantages of Ion-exchange and adsorption
• Adsorbents such as activated alumina, modified activated carbon, hydroxyapatite, zeolites, char, and fluoride specific ion exchange resin are readily available.
• Fluoride levels are reduced to 1 mg/L.
• It's best for removing fluoride in low concentrations.
Disadvantages of Ion-exchange and adsorption
• Due to high adsorbent consumption and/or high ion exchange resin regeneration costs, it is not cost-effective for industrial effluent with high fluoride concentrations.
• pH has to be kept between 5 and 8.
•Fluoride removal efficiency is reduced when other anions (e.g., chloride, nitrate, and sulphate) are present in the effluent.
• The management of an ion exchange wastewater brine is required.
3: Electrodialysis & Reverse Osmosis
Advantages of Electrodialysis & Reverse Osmosis
• Fluoride levels are reduced to 1 mg/L.
• It gets rid of any other pollutants, such as total dissolved solids.
• The chemical usage is kept to a minimum.
• Compared to alternative solutions, it has a smaller footprint and more automation.
• If required, it acts as a good polishing process.
Disadvantages of Electrodialysis & Reverse Osmosis
• Membranes are incompatible with wastewater containing hydrofluoric acid or fluorosilicic acid.
• Other inorganics and organics in the wastewater could foul the membrane.
• Pretreatment is frequently necessary.
• A concentrated brine reject is created, which must be managed.
Membrane-Based Defluorination
How can we help?
For the fluoride removal from Industrial Wastewaters, contact Netsol Water. Our process experts at Netsol assist our clients by giving various options for analysis. We help you choose the best treatment for your fluoride-laden wastewater. Because providing you with the best solution is our top priority.
We can add our testing, automation, and piloting skills to the project once a treatment technology has been selected. Please contact us on+919650608473 or contact via email at enquiry@netsolwater.com for further consultation or product purchase related query and to learn more about how we can assist you in overcoming your fluoride difficulties.
