Liquid filtration is a process that we rarely think about, yet we use every day. Filtration is not only essential for creating fresh, contaminant-free water to keep our bodies healthy but is also used in almost any industrial process you can imagine.
I. Brief History
II. Benefits of Filtration in Industrial Applications
III. Types of Filtration Systems
IV. Helpful Additions to Filtration Systems
V. Important Questions to Ask Before Purchasing a Filtration System
I. Brief History
Filtration is the process of separating solids from liquids. It is described as pouring a fluid into a filtration system where the liquid is allowed to pass through a membrane where solids are collected. After the fluid passes through the membrane, impurities are removed leaving only the filtered liquid.
People have always desired clean, clear drinking water and have tried to achieve it by using various filtration methods throughout history.
- Ancient Egypt: Water filters have been depicted in hieroglyphs and descriptions of early filtrations processes were documented in Sanskrit, an ancient Indian language. These primitive systems were comprised of sand and gravel and used boiling water.
- 1st BC: People also used various methods to mask the bad taste of water. Diophanes of Nicaea, a Greek agricultural writer of the 1st century BC, suggested for crushed laurel, a shrub related to the bay tree, to be added to rainwater.
- 370 BC: Hippocrates believed that water was an important element to manage health. He experimented and then created the Hippocratic Sleeve. It was a cloth bag that boiled water was poured into to filter out impurities.
- 1627: In 1627, Sir Frances Bacon began to experiment with removing the salt from seawater, a process known as desalination. He tried to remove salt particles by filtering seawater through sand. Although he was unsuccessful, he inspired other scientists to experiment and continue to advance filtration technologies.
- 1804: The first documented use of sand filters to purify water supplies dates back to 1804. John Gibb, an owner of a bleachery in Paisley, Scotland, installed an experimental filter. He then sold his unwanted surplus of purified water to the public.
- 1829: After two decades of advancements made by engineers, the first treated public water supply was implemented in London in 1829 for the Chelsea Waterworks Company. Chelsea Waterworks was the first water treatment plant. It provided clean water for every resident of the area and was used as a model for other treatment plants.
- 1903: In 1903, water softening was invented and became the preferred method for desalination.
- 1914: Starting in 1914, drinking water standards were created. By 1974, the Safe Water Act (SDWA) was passed, guaranteeing every person the right to safe drinking water.
Filtration has been useful as long as it has existed. It not only keeps our drinking water clean and contaminant free, but it also aides in the manufacturing process.
II. Benefits of Filtration in Industrial Applications
Filtration is used in almost all industrial applications and is integral to many processes.
It is an important step that is used in production processes for automotive, food and beverage, pharmaceutical, chemical and coatings, building services, water treatment, oil and gas, nuclear and contained systems.
Industrial filtration systems can make manufacturing easier and more cost effective, with opportunities to implement cutting-edge, environmentally friendly practices.
1. Reduced Maintenance Costs
Industrial filtration has the potential to cut costs in any application. For most applications, it will protect the life of equipment. Filtration keeps harmful contaminants out of equipment, allowing it to function properly. Equipment that is functioning at its best will produce more, and result in less downtime because less repairs will be required.
2. Lower Energy Costs
Using new industrial filtration systems make it possible to save money on energy costs. By exploring different ways to filter water, it is possible to find an economical solution.
For example, Dow’s Benelux, the largest chemical plant outside of the United States, located in Terneuzen, Netherlands has made major advancements for the use and reuse of wastewater with the help of the local water treatment facility.
Wastewater recycling saves Dow money on electricity and water costs. The site reuses 30,000 cubic meters of municipal wastewater every day. By recycling water, one liter of water is used three times as opposed to only once. Because of this, the plant’s energy use associated with water treatment has been reduced by 95 percent. This process has also cut the plant’s CO2 emissions by 60,000 tons each year.
According to an article printed in “Environmental Leader” magazine, Dow has stated it saves 1.5 million dollars annually by reusing the city’s wastewater instead of desalinating seawater.
3. Increase Process Efficiency
Recycling and reusing water from waste streams diminishes potential water shortage risks and creates greater water security by depending less on raw water. This is particularly advantageous for areas prone to drought and water shortages.
Many plants have implemented a “Zero Liquid Discharge” policy, this means that not a single drop of water is allowed to leave the plant as waste. This ZLD policy is currently being used in dry, arid states like California, Arizona and Nevada, where water is a coveted resource. ZLD is applied internationally in factories located in Australia and India.
Another important reason to consider ZLD is the potential for recovering resources that are present in wastewater. Some manufacturers choose ZLD for their waste because they can sell the solids that are produced or reuse them as a part of their industrial process.
For example, lithium can be found in high amounts in USA oil field brines, while gypsum can be recovered from mine water and can then be sold for use in drywall manufacturing.
4. Opportunities for Sustainable and Innovative Approaches
The rapidly growing population, urbanization, industrialization, and changes to the planet, like pollution and climate change, are putting a strain on fresh water supply. This strain makes fresh water sources for industrial processes more difficult and expensive to obtain.
Manufacturers are adopting more complete and sustainable designs of industrial filtration that focus on the entirety of the plant and not just pretreatment. Companies are assuming higher responsibility for treating wastewater streams and are trying to reuse water as much as possible.
Using ecological and state-of-the-art approaches like ZLD and the process implemented into the Dow Benelux plant are not only saving companies money but are also helping to promote brand and image to the public.
Concern for the environment and using sustainable practices has become prevalent in recent years. Consumers are doing their research on companies and failure to use environmentally safe practices may negatively impact sales of product and damage the company brand.
III. Types of Industrial Filtration Systems
There are many different types of industrial filtration systems to choose from and each specializes in removing specific contaminants from water and other fluids.
In order to know which system will work best for your application, it is important to understand how each system functions and which impurities each system can remove.
Pipeline / Basket Strainers
Strainers are closed vessels that collect solid particles as fluid passes through a removable screen made of perforated plates or mesh, called a basket. The baskets can remove particles down to 200 mesh or 75 microns. Once the basket becomes full, it must be cleaned.
In addition to collecting unwanted particles, they can also collect wanted materials for use later in the production process. These systems are effective at keeping equipment like meters, pumps, compressors, traps, valves and filters safe from damage caused by contaminants.
***FUN FACT*** Human hair is on average about 50 microns and the human eye cannot see anything smaller than 40 microns.
- Baskets are reusable.
- Extends the life of equipment.
- Can withstand a substantial amount of loading without failure.
- Limited filtration size.
Types of Strainers
Simplex Strainer: These strainers have a single basket and are used when the line can be shut down for short periods of time so that the basket can be cleaned or changed.
Duplex Strainer: Also called a double basket system, it is comprised of two baskets. These strainers are used when the flow or process cannot be shut down and must continue to flow. They allow you to shut down one basket for cleaning while the other basket is still in operation, allowing production processes to remain continuous.
Y-Type Strainer: Y-strainers are generally used when there is a small amount of material that must be removed from the supply line. They need to be installed in a horizontal or vertical position. The basket has got to be located at the bottom of the pipe or facing the downflow so it can effectively collect particles. Y-strainers can also come with a blow-off connection to allow gosh for automatic cleaning.
Automatic Self-Cleaning Strainers
A self-cleaning screen filter is a type of water filter that utilizes system pressure to clean itself. A rigid cylinder screen strains particles out of the water source, trapping debris inside. The layer of buildup causes a differential pressure across the inlet and outlet.
A controller monitors the filter and opens a flush valve when it senses enough differential pressure, creating rapid flow through the internal cleaning apparatus. The cleaning apparatus removes up buildup from the screen and then expels it out.
- Uninterrupted cleaning cycle, continuous flow.
- Can remove debris from water in a variety of applications.
- Investment costs.
Types of Automatic Self-Cleaning Filters
Forsta Automatic Self-Cleaning Filter: These systems use a vacuum as its cleaning element and processes are not shut down during its cleaning process. They have a variety of screen options to choose from and can be used in industrial, municipal and irrigation applications.
Filtaworx Automatic Self-Cleaning Filter: These filters are available in a wide range of configurations and screen sizes, making it applicable for many different industrial and commercial applications.
Fil-trek Automatic Self-Cleaning Strainer: This system utilizes a self-adjusting scraper action with multiple brush/blade configurations. It has easily customizable connection arrangements to suit any in-line or offset piping.
Ultraviolet purification sounds like something out of a Sci-Fi novel, but it’s not nearly as complicated as it seems. UV light disinfects by penetrating microorganisms and destroying their DNA. DNA plays an important role in an organism’s functions and reproduction.
By destroying the microorganism’s DNA, it will lose the information it needs to become active and multiply. Without the ability to reproduce microorganisms die off. This process keeps water free from contamination.
- The system is natural, environmentally friendly, effective, economical, safe and chemical free.
- Fast, easy to manage, low energy, only annual servicing (requires an annual change of lamp and periodic change of the filter cartridge).
- No bacteria, viruses, molds or their spores can survive when exposed to the correct dose of UV light.
- UV light can only eliminate microorganisms in water.
- Doesn’t remove contaminants such as heavy metals, salts, chlorine or man-made substances like petroleum products or pharmaceuticals.
- UV Purification is only effective in clear water. UV light cannot reach microorganisms if the rays are blocked by particles.
Bag filters work just like your coffee filter as it makes your morning coffee. The filter is made of a porous material that allows liquid to flow through it, but the holes are still small enough to capture solids and particles. Bag filters are recommended for medium to fast water flow rates because they have to have pressure to function correctly.
- Less waste than cartridge filters, bags can be reused if they are undamaged during the cleaning process.
- Lowest investment costs compared to other methods, and bag filters are generally tolerant of many process conditions and are a good choice for a wide range of applications.
- Bag filters have a smaller surface area than most cartridge filters.
- They require pressure to work correctly.
Types of Bag Filters
Portable Carts: Portable carts are compact, self-contained and easy to operate and move. They provide versatile, reliable filtration for a wide range of industrial applications.
They come equipped with a differential pressure gauge. The gauge can monitor the amount of debris buildup on the inside of the bag, which will alert when a bag change or cleaning is necessary.
Portable carts can be used inline or as a standalone filter station to improve performance, reduce waste and lower disposal costs. They use a single filter bag and have a “no tools required” access for simple bag replacement.
In the normal osmosis process, solvents move from an area of low concentration through a permeable membrane to an area of high concentration. Water tries to naturally balance itself and will equalize the solution concentrations on each side of the membrane, this creates what is known as osmotic pressure.
If pressure is applied to reverse the natural flow of the solvent during regular osmosis, it will result in a process called reverse osmosis, which will leave you with clean, filtered solvent.
For example, in reverse osmosis systems, a water purification tank has salt water on one side of a semi-permeable membrane and pure water on the other. By adding pressure to the salty side, water molecules are forced through the very fine membrane, leaving the unpurified remains behind. One side of the solvent will be clean and pure and the other side will remain at a higher concentration or in this example, salty.
This method removes many types of large molecules and ions from solutions and is the best process for desalination.
- RO systems are long lasting and easy to maintain. The filters only need to be replaced every six to nine months.
- It removes all types of contaminants including bacteria, viruses, dirt, silt, ions, heavy metals, colloids and other organic molecules.
- They are slower than a water filter.
- RO systems wastewater. Four gallons of concentrated wastewater is flushed down the drain per every one gallon of filtered water produced.
Media filters work by layering materials for fluid to pass through. As fluids pass through the various mediums, different sized unwanted particles are extracted and trapped within the gaps present in the media.
- It is a simple form of filtration and most media types are naturally occurring and inexpensive.
- Filters have a long life and require only periodic backwashing.
- They are widely used in home filtration and industrial applications.
- They have limited filtration capabilities.
Types of Media Filters
Sand Media Filters: Water is routed through a sand-filled tank where the sand traps particles large and small. Dirt and debris accumulate in the space between the sand particles, making it difficult for water to pass through, causing pressure in the tank to rise. High pressure is a signal that the tank needs to be backwashed or cleaned. Backwashing can be achieved by reversing the water flow.
Multi-Media Filters: These filters typically contain three layers of media usually consisting of coal, sand and garnet with a non-filtering layer of gravel at the bottom. This mix of materials is chosen because of its varying sizes and densities. The arrangement allows the largest dirt particles to be removed near the top of the media bed with the smaller dirt particles being retained deeper and deeper in the media. This allows the entire media bed to act as a filter, larger filter means longer run times between backwash and more efficient particulate removal.
Specialty Filters: Silica sand, also called IMA-65, is specifically designed for the removal of iron and manganese (along with arsenic) without using potassium permanganate, which is a toxic solution. IMA-65 can remove dissolved iron to as low as .005 parts per million and manganese to 0.001 PPM. After initial activation, IMA-65 speeds up exposure to oxygen which results in immediate oxidation and filtration of contaminants that cannot dissolve in water. This technology has been a trusted method, used in Japan for 30 years and is gaining popularity in the United States. IMA-65 has been tested and certified by the Water Quality Association.
Granular Activated Carbon Filtration: Uses a bed of activated carbon, a porous material that removes contaminants and impurities through a process called adsorption. Pollutant molecules in the fluid become trapped inside the pores of the carbon as it passes through. The removed contaminants move to the surface of the adsorbent, becoming trapped. The particles are positively attracted to the carbon. This filtration method will remove funky tastes and odors from water. It isn’t intended for the removal of minerals, salts or dissolved inorganic compounds.
Separator systems have no screens, slotted baffles, moving parts or filter media so there is no pressure loss and no maintenance is required, except for periodically opening the purge valves to flush out solids.
- They require low maintenance.
- No filter media so there is no pressure loss.
- Cannot be used for every application.
- Primarily used for separating large particles.
Types of Separators
Centrifugal Separators: Separates by centrifugation, where a cylindrical container rotates inside a larger, stationary container. In centrifugal separators, the denser liquid, usually water, gathers at the edges of the rotating container and is collected from the side of the device, while the less dense liquid, usually oil, accumulates at the rotation axis is collected from the center.
Sand: Separates by using gravity, water pushes through the device and the centrifugal forces sling the large particles, sand, debris and sludge outward to the separator will and downward in a spiral motion. It is bounced around until gravitational force pulls the separated solid particles downward past the spin trap plate into the solids holding chamber. Cleaned water then rises through the vortex locator and returns back to the plumbing system. They are specifically used for sand and large particle removal.
Coolant Filtration Systems
These systems are vital for keeping coolant free of solids and tramp oil by removing debris and swarf produced during processing. They can also help control PH, flow rate and the boiling point of the coolant.
Clean coolant provides longer tool life, better part finishes, increased production rates, lower coolant costs, and increased worker productivity. Keeping coolant clean makes it easy to meet part cleanliness specifications.
Buildup of metallic fines and debris reduces the quality of machined parts and also leads to accelerated wear throughout the machinery which causes damage to pumps, nozzles and possibly the machine tool.
- Results in lower maintenance of parts
- Fewer tool replacements
- Faster operation and cycle times
- Slows bacteria growth
- Investment costs
IV. Helpful Additions to Industrial Filtration Systems
Filters are only one element in an entire production process.
There are options for additional equipment that can aide your industrial filtration system to increase its efficiency. They can be used to store, control and redirect the flow or pressure of the fluid that is being manipulated.
Tramp oil skimmers are a cost-effective and simple method for removing tramp oil from coolant. Skimmers mount on a coolant reservoir and they continually draw off tramp oils.
An effective coolant system must recycle every drop of coolant by separating the tramp oil and fines before it is pumped back into production process. High-quality coolant can stay in good condition for years with the right implementation of a tramp oil skimmer and coolant filtration system.
Liquid Storage Tanks
Storage tanks are used to store fertilizer solutions, agricultural chemicals, water, liquid feeds, plant foods and other solvents and liquids. The tanks are corrosion resistant and lightweight with no seams, welds or joints that could leak or rust. They are manufactured using resins that meet FDA specifications that ensure safe storage of potable water and other fluids.
Polyethylene: Is also known as vertical plastic tanks. They have high impact strength, abrasion resistance and a low coefficient of friction. They are moisture, stain and odor resistant. There are a variety of plastic resins that can be used depending on the application.
Horizontal: These are trailer mounted or stationary tanks, equipped with molded-in legs to support the tank and optional steel hoops for tie down. They are versatile and come in various sizes, configurations and can hold a wide variety of liquids.
Stainless Steel: They are available in heavy gauge steel or stainless steel. It is welded inside and out to prevent any leaking. They are fully customizable.
Flow Control Valves
Doing as their name suggests, they control the amount of liquid or gas that flows through pipes during the production process.
Ball Valves: This type of valve provides both flow-amount and flow-direction control. They are made of durable and reliable materials and can support great pressure and extremely high temperatures.
Butterfly valves: They use a rotating disk mechanism to completely isolate the flow of liquid passing through a pipe by blocking its passageway, or to control its flow. It operates with quarter turns of a disc that is mounted on a rod, as the disk spins different pressures and flows are managed. Designs depend on the kind of industrial application and are based on pressure and usage.
Check Valves: They work with a self-automated mechanism that controls flow in one direction. Keeping flow in one direction prevents any backflow from happening. They are two-sided with one side that allows the flow to enter while the other side allows it to leave. Used in a variety of industrial, commercial and residential applications that include fluid and gas.
Automatic Control Valves: Regulates flow or a pressure of a fluid without an external power source. There is no actuator necessary. This results in a reliable solution that is able to handle extreme pressure and can sense the slightest danger or call for backup in emergencies.
V. Important Questions to Ask Before Purchasing an Industrial Filtration System
It’s critical to know what impurities you need your industrial filtration system to remove, and how it will fit into your application.
Different industrial filtration systems have different strengths and limitations and in order to get the best system for your application, it is important to know the specific needs of your production process.
When selecting a filter for a particular application, the following criteria should be considered:
Is it a continuous or batch process?
Batch: It is the processing of bulk material in batches through each step of the production process. The process should be performed in a defined order. New batches must wait for the batch before it to be finished before it can move on. This results in limited quantities.
Continuous: Continuous process is moving one work unit at a time between each step of the process with no breaks. It saves time, energy and costs when implemented correctly by increasing productivity, decreasing time and will produce more units in a faster time frame. It is more adaptable to customer needs than batch process.
What is the quality of filtration required?
A water treatability study is a test that tells us how the wastewater could be treated. Conducting the study will clearly identify the problems in the wastewater stream, like types of bacteria, sediments and hazardous byproducts.
The study will ensure the proper treatment solution. It is important to also factor in local discharge regulations. Be sure the conductor understands what discharge requirements the plant must meet.
What are the conditions?
Flow rate: This measures the amount of liquid or gas that moves through a pipe. Flow rate is determined by using velocity, change in kinetic energy, temperature, the distance of flow, friction, viscosity and density of the liquid or gas.
Can be calculated ¼ x π x (pipe diameter)² x velocity
Pressure: Pressure is an important element for filtration. It is required for correct filtration processes, especially bag filters and cartridge filters. High or low pressures can dictate which type of filtration system can be used, some systems have minimum operating pressure requirements.
Temperature: Some filtration systems have temperature limits; some cannot perform under high heat, while others are designed to withstand them.
What are the material characteristics of the solids being removed?
How large are the particles? Is the material hazardous? Can the material being remove be recycled back into the process stream at another point?
These are important questions to know the answers to when deciding on which industrial filtration system will best fit your application and production process. Different filtration systems will have different limitations based on the answers to this question.
If employees are at risk of coming into contact with hazardous materials, special equipment and installation methods are required. Some systems are better at removing larger particles like sand and gravel, while some will rid water of things as small as bacteria.
What are the waste disposal costs?
How often do bags or cartridges need to be replaced? Can the waste volume be reduced or eliminated by switching to a different filtration method?
With the correct industrial filtration method, bags and cartridges will usually need filter changes about every two to three months. If you are changing your filters every week or very frequently, it’s possible that the system is using the incorrect micron.
What are the labor and downtime costs for filter or cartridge replacement?
Can downtime be minimized by switching to a different filtration method?
Downtime means loss of profits. It is crucial for smooth production processes that downtime is minimized as much as possible or eliminated altogether. Many industrial filtration methods have options that will allow processes to remain continuous, filtering out impurities without any pauses.