All About Filtration

The history of water filtration can be traced back to around 10,000 BC when various tribes developed ways to filter, purify and transport water. A study published in Science Magazine found that these techniques were an important factor in what made us human by allowing us to travel more and be able to survive longer as a species. Some of the early methods used include hollowed-out gourds used for holding and straining water, placing charcoal or sand at one end of a pipe (typically bamboo), and directing running water through it. Early on there were many variations of pouring water through some kind of material as a filtration method, sand being the most commonly used material in the ancient world.

One of the oldest known examples of a filter-specific tool was found in what’s now Israel and dates to roughly 1,500 B.C. This example wasn’t even technically a filter, it was a sieve that people used to strain out solids from their drinking water. However, it’s still the earliest known physical example of a tool used for filtration to treat water before they drank it or used it for irrigation. Below is the actual picture of this filter.

 

The earliest modern ancestor that utilized a plumbing system came from ancient Rome which was comprised of lead pipes connected together with clay joints. The Romans also pioneered aqueducts for transporting fresh clean drinking water throughout cities. In 537 AD, a Persian engineer named Al Razi invented an elaborate system that uses siphons to bring in fresh spring water from areas outside cities. This allowed many households within Roman towns (and later other civilizations) to enjoy a fresh clean drinking supply. Around this same time, it is believed that the famous Greek scientist, Hippocrates invented the first early water filter… in the form of a cloth bag. This simple device was known as the "Hippocratic sleeve". The cloth acted as a sieve to filter out the impurities from the Greek aqueducts.

These early forms of filtration were the main form of filtration for nearly 1,000 years, throughout this time span there were many variations but basically the same principle. It wasn’t until the mid-1700s, Joseph Amy obtained the first patent for a water filter. His design incorporated wool, sponge, and charcoal layers to help purify drinking water. The first home water filters were made available for sale in 1750.

In the year 1800 in London, England. John Doulton, created a water filter because of the drastic increase in water-borne diseases that were rampant. Doulton, now with the partnership of Martha Jones and John Watt, created water filter cases made of ceramics that were packed with powder carbon known as the gravity filter.

Royal Doulton Gravity Filter

When Queen Victoria came to throne, her highness acknowledged Doulton and his team by establishing their company brand as an innovative manufacturer of industrial products. In the year 1835, Queen Victoria requested Doulton to make water filters for the Royal household. It was then during that time they developed gravity-fed stoneware units crafted in delicately-designed ceramics.

In 1806, a large water treatment plant opened in Paris, using the River Seine as a source. Water was settled for 12 hours prior to filtration then run through sponge prefilters that were renewed every hour. The main filters consisted of coarse river sand, clean sand, and pounded charcoal. The filters were renewed every six hours. A simple form of aeration was also part of the process, and pumps were driven by horses working in three shifts (steam power was too expensive). This plant operated for 50 years. A year later in Glasgow, Scotland, filtered water was piped directly to customers.

The year 1832 saw the first slow sand filtration plant in the United States built in Richmond, Va. In 1833, the plant had 295 water subscribers. The next US plant to open was in Elizabeth, N.J., in 1855. A typhoid epidemic in 1850s London was associated with bad water, but the actual cause of the disease was unknown. British physician Sir John Snow traced the 1854-1855 cholera outbreak in London to sewage contamination of a particular public well. His discovery became known as the “Broad Street Pump Affair.” Up until the late 1860s, only 136 waterworks operated in the US. Many of these delivered what was considered to be pure water that did not require filtration. Following the Civil War, waterworks construction increased significantly. Slow sand filters were introduced in Massachusetts in the mid-1870s. Sand filters and other treatments were primarily designed to improve the aesthetic quality of water. It took major developments in bacteriology during the 1870s and 1880s to demonstrate that microorganisms that exist in water supplies can cause human and animal diseases. This led to the realization that water treatment could help prevent disease. Robert Koch, the German physician and microbiologist who postulated the germ theory of disease, and the Scottish surgeon Joseph Lister were major players in this work.

In 1881, William Stripe, superintendent of waterworks at Keokuk, Iowa, issued an invitation to all persons concerned with waterworks design, construction, operation, maintenance, and management to gather at Washington University in St. Louis, Mo. The 22 respondents to this call to exchange information pertaining to the management of waterworks, mutual advancement of consumers and water companies, and to secure economy and uniformity in the operation of water companies together founded the American Water Works Association.

Most modern water filters fall into one of two categories—ionization and distillation. Ionization is fairly straightforward; it involves exposing contaminants to a source of electricity (usually a charged rod) that’s strong enough to split away electrons, which then attach themselves to sediment and are removed through a series of filtration mechanisms. Distillation methods, on the other hand, use chemicals or heat to separate clean drinking water from contaminants in a liquid stream by way of evaporation. 

Since 1957, industrial water filtration has been an essential part of manufacturing. Industrial water filtration systems are used to treat and purify industrial wastewater to significantly reduce costs while improving health and safety. They’re an important part of making sure our world runs smoothly after all, there is little that can shut down a factory faster than contaminated water. Today, scientists and engineers continue to look for ways to make these systems more efficient and less expensive. In some cases, that means shifting from older technologies like sand filters or sludge beds (which remove suspended solids) toward newer techniques like membrane technology (which removes dissolved substances).

A step in that direction was taken with a new state-of-the-art reverse osmosis system installed in 2016 at Citgo Petroleum Corporation in Corpus Christi. The system produces nearly 10 million gallons of pure water every day for use in their production processes with 98% recovery rate efficiency – that’s about 500 times as much water as what would come out of your faucet!

Throughout human history, we have been seeking ways to filter water. The industrial revolution made filtration a priority since water is such a vital component of almost all industrial processes. Below is a list of the most common forms of water filtration used.

Mechanical Filtration despite the fact that they cannot remove chemical contaminants, mechanical filters are an excellent option for consumers hoping to rid their water of sediments and cysts (microbial parasites). Mechanical filters contain small holes that remove these contaminants, and they are sometimes used alongside other filtration technologies. If your water supply contains an undesirable amount of dirt and other particles, you may want to consider purchasing a mechanical filter.

Membrane filtration or more commonly known as “reverse osmosis” is a process where water is forced through a semipermeable membrane to remove molecules, ions, and larger particles.  The membrane is encapsulated within a vessel or tube and the applied pressure is used to overcome the osmotic pressure of the water.  The pressure is generated by a high-pressure pump and the pump pressure may vary depending on the type of membrane, condition of the raw water, and the final water quality needed.  The treated water is referred to as “permeate” and the rejected water is referred to as “concentrate”.  The solids comprised of molecules, ions, or even bacteria remain on the outside of the membrane and are rejected through the end of the tube.

Dearation is a process where steam and water are introduced into a dearator “packed column tower” to force a “degasification” process of gases to occur.  Steam is utilized to heat water to near saturation point while maintaining a lower pressure vent.  This is achieved by spraying water into a vertical packed deaerator tower with a distribution system which can be a weir tray, header lateral and multiple layers of trays, or random packed media. Steam is introduced typically at the bottom of the tower and is forced to impact the falling water.  The heated steam from the boiler feedwater system raises the water temperature to saturation level and the dissolved gases are released from the water.  Deaerators are utilized in industrial applications to remove oxygen primarily but can also remove CO2 (carbon dioxide gases).

Decarbonation and Degasification towers are also vertical towers and utilize a distribution system and media bed which can be either PVC tray type or random packed media supported by a false bottom.  A decarbonation tower and degasification tower both utilize a blower to create a cross-current airflow within the tower as it impacts the inlet feed water.  Water is introduced at the top of the tower and by gravity, it travels down and across the media bed as the cross current air flow travels upwards and is exhausted at the top of the tower.  Decarbonators and degasifiers can be either induced draft or forced draft design.

The efficiency of a decarbonator and degasifier to remove dissolved gases such as carbon dioxide (CO2) or hydrogen sulfide (H2S) is far greater than that of a deaerator as it does not require the introduction of steam.  The decarbonator and degasifier efficiencies increase with the rise of water temperature, proper pH adjustment, media type selection, and air flow volume.  The removal of the dissolved gases from the decarbonator and degasifier is based on “Henry’s Law”.  Henry's law states that the amount of dissolved gas is proportional to its partial pressure in the gas phase.  The proportionality factor is referred to as the “Henry’s law constant”.

When water passes through a decarbonator or degasification tower the gases are released.  The release of gases is possible from the reshaping of the water, exposing the gas molecules, and cross-current airflow that creates the disproportional pressure imbalance within the tower.  There are two types of processes that can reshape water within a packed tower. The first process is called “controlled film” and this defines spreading the water thinly over a surface allowing the molecules of dissolved gases to reach the surface of the water and be exposed to the cross-current airflow. 

The second process is called “impingement” and with impingement, waterfalls from one point to another where the water impacts and is “fractured” causing molecules of dissolved gases to be exposed to the surface of the water and be in contact with the cross-current airflow.  In both cases, the “steady state” of the water is altered by the cross-current airflow and the reshaping of the water to expose molecules of gas.  This creates the disproportional relationship of pressure and allows the gases to be stripped and ejected with the exhaust air stream. Different types of media beds for decarbonation and degasification towers have different removal efficiencies and are calculated by defining the NTU (number of turn units) or HTU (height of the turn unit) values.  Media with higher NTU and HTU values typically yield higher removal efficiencies.

Ion exchange is commonly known as a water softener. When an ionic substance is dissolved in water the molecules dissociate into cations and anions.   Cations are positively charged particles.  Negatively charged particles are referred to as anions.  Ion exchange resins work by attracting other molecules or atoms based upon their electrical charge and replacing them within the water process leaving the removed molecule attached to the resin within the ion exchange system.  Over time the ion exchange system becomes saturated and it must be back washed, regenerated and recharged.  This is typically done with a backwash system and regenerate solution located near the ionic exchange process equipment. Since water softeners use sodium for the exchange this is a serious problem because of the impact on your health and environment. There is an alternative to a water softener; HydroFLOW allows you to keep the healthy calcium and magnesium in the water while rendering it harmless to your equipment. Learn more about how HydroFLOW is an alternative to using a water softener.

Cationic exchangers are normally classified as either strong (SAC) or weak (WAC) acid systems depending on the type of resin the unit is charged with.  Both strong and weak acid resins are utilized in the demineralization process at an industrial water treatment location.  Strong acid cations are utilized for water softening and weak acid cation systems are used for dealkalization applications.  Contaminants typically removed by cation resins include:

Calcium (Ca2+), Chromium (Cr3+ and Cr6+), Iron (Fe3+), Magnesium (Mg2+), Manganese (Mn2+), Radium (Ra2+), Sodium (Na+), and Strontium (Sr2+).

Anionic exchangers are normally classified as either strong (SBA) or weak (WBA) base anion systems depending on the type of resin the unit is charged with.  Strong base anion resins are utilized in the demineralization process at an industrial water treatment location, while weak base anion systems are used for acid absorption.  Contaminants typically removed by anion resins include:

Arsenic, Carbonates (CO3), Chlorides (Cl-), Cyanide (CN-), Fluoride, Nitrates (NO3), Perchlorate (ClO4-), Perfluoro octane sulfonate anion (PFOS), Perfluorooctanoic acid (PFOA), Silica (SiO2), Sulfates (SO4), and Uranium (U).

How to choose the right water filtration system?

Now we know the different kinds of filtration that are available to consumers. It became very confusing when selecting the right filtration cartridge to buy for the problems you’re experiencing. This is why it’s very important to identify the issues that are specific to your situation. To give you an idea, the list below is contaminates that are problematic for most homeowners in the United States in order of how common the issue is.

Top 20 contaminates that affect most homes? 

1. Silt
2. Iron
3. Lead
4. Copper
5. Arsenic
6. Trihalomethanes (THMs)
7. Mercury
8. Nitrogen
9. Phosphorus
10. Fluoride
11. Glardia
12. Ecoli
13. Cryptosporidium
14. Radium
15. Radon
16. Uranium
17. Aluminum
18. Hydrogen Sulfide
19. Chromium
20. Nitrate/Nitrite

We recommend this product to get a good idea of the issues you are facing in your water. Otherwise, have your water tested by a lab so you can be 100% sure of the contaminates in your water.

Another consideration when choosing a filtration cartridge is what material it’s made from:

• Ceramic: Ceramic filter cartridges take advantage of the millions of tiny .5-micron size holes to trap bacteria and other contaminates.
• String Wound: String wound cartridges are designed for the removal of dirt, rust and sediment from water. These cartridges are rated for temperatures up to 125 °F. Polypropylene construction for excellent chemical resistance. No binders, additives, or lubricants to leach into the water.
• Melt Blown: Melt blown polypropylene cartridges are designed for the removal of dirt, rust and sediment from water. These filters have graded density layers, meaning the outer layers are more porous, catching larger particles while the inner layers are a finer micron, catching smaller particles.
• Pleated: Pleated filters are designed to have an increased surface area and longer life. These cartridges are washable & reusable and come in a range of sizes and micron (µ) ratings.

Once you’ve established the different contaminates in your water use this table to select the correct filtration cartridge for your situation. The replacement frequency will depend on the level of contaminants you’re removing.

Chlorine is added to almost all municipal water systems and needs to be filtered out!

Another thing to consider when choosing a filtration product. If you get your water from a municipal water source, then it will have chlorine in it. The problem isn’t necessarily with chlorine, it’s when chlorine combines with naturally occurring organic matter in the water to form compounds called disinfection byproducts (DBPs). DBPs can cause negative health effects after regular exposure.

Not only drinking DBP’s is dangerous, but even inhaling them while showering is also unhealthy. DPB’s are also absorbed by the skin so showering in municipal water that isn’t filtered isn’t recommended. The most common type of DBP’s are trihalomethanes (THM’s). THM’s are known to be carcinogenic and cause cancer. Your water quality report issued by your drinking source is required to tell you the levels in your water.

To learn more about the harmful effects of DBP’s please visit the Center for Disease Control and Prevention.