Per-and polyfluorinated substances (PFAS) have been used for decades in many consumer products, and they are man-made and have a high residual time in the environment. These chemicals are used for various purposes, including nonstick surfaces, heat protection of circuits, water resistance, fighting fire as they are utilized in fire depression foam, and many other industrial applications. The difficult thing about PFAS is that the very reason they work so well on so many manufactured products is why they are so challenging to get rid of or treat once they have entered the environment or water supply. PFAS are being more and more regulated, and requirements are being put in place by many states and agencies to require the treatment and removal of PFAS and safeguard and protect drinking water.

PFAS are soluble in water, and they are not a volatile organic chemical (VOC), so traditional treatment methods such as utilizing an air stripping tower or degasification system are not effective methods to remove PFAS. One of the first technologies to remove PFAS from drinking water and the environment is activated carbon absorption. In recent years, utilizing ion exchange resins has proven effective and is gaining popularity for the treatment method. Ion exchange resins attach and bond with the PFAS and remove it effectively from the water. Some chemicals tested and studied with success include perfluorooctanoic acid (PFOS). In addition to these technologies, reverse osmosis utilizing high-pressure membranes has an 80-90% effective rate and has proven to be technically efficient in removing PFAS. An R.O. process produces a concentrated waste stream.

In process control systems, it is often required to handle fluids that have a harsh chemical nature. In these cases, it is necessary to be aware of material chemical compatibility. Chemical compatibility is a general term referring to the way a specific chemical interacts with a specific material. This information is taken into consideration when selecting materials of construction for tanks, valves, pipework, tubing, and other devices that may encounter harsh chemicals. Common chemical types that are used in process systems are acids, bases, corrosives and oxidizers, and hydrocarbons. Typical chemical resistant materials include natural and synthetic rubbers, vinyl polymers, fluoropolymers, and stainless steel. In order to determine which materials are compatible with certain chemicals, a chemical compatibility chart is often used. A chemical compatibility chart contains tabulated data about how a given material interacts with a given chemical.

The basics of water decarbonation, the removal of CO2 from water

the removal of carbon dioxide (CO2). The need to remove (CO2) is essential in most Aquaculture, Municipal, Industrial, and Food & Beverage Processes To understand you must familiarize yourself with Henry’s Law.

Henry's Law defines the method and proportional relationship between the amount of a gas in solution

in relationship to the gases partial pressure in the atmosphere. Often you will see and hear various terms like degasification, decarbonation, aeration, and even air stripping when discussing the removal of dissolved gases and other convertible elements from water. Understanding the impacts that Carbon Dioxide (CO2) can have on both equipment and aquatic life provides the basic reasons why the need to decarbonate water, exists. Carbon Dioxide (CO2) can exist naturally in the raw water supply or be the results of ph control and balance. In either case the the process called Decarbonation or Degasification provide the most cost effective and efficient manner to reduce or tally remove (CO2) from the water. In addition to Carbon Dioxide (CO2), water can contain a variety of other contaminants that may impact the removal efficiency of the Carbon Dioxide. A variety of elements as well as dissolved gases such as oxygen, nitrogen and carbon dioxide (CO2). A full analytical review of the water chemistry is required to properly design and size the “Water Treatment” process.

Breaking the bonds in water to release a dissolved gas

such as carbon dioxide (CO2) you must change the conditions of the vapor pressure surrounding the gas and allow the gas to be removed.  There are many variables to consider when designing or calculating the “means and methods” of the removal of carbon dioxide (CO2). When I refer to the means and methods. I am referring to the design of a decarbonator and its components. The means equals the size and type (Hydraulic load) of the decarbonator and the “method” equals the additional variables such as cubic foot of air flow (CFM) and “Ratio” of the air to water to accomplish the proportional condition needed to remove the carbon dioxide (CO2).

A BIOLOGICAL ODOR CONTROL SCRUBBER IS JUST ONE OF MANY DIFFERENT TYPES OF AVAILABLE TECHNOLOGIES

To treat air emissions that may contain harmful gases. This class of equipment commonly falls into a category referred to as “Odor Control Scrubbers” and they are utilized to remove dangerous or noxious odors from an air stream. The Biological Odor Control System has gain popularity among many end users such as municipal operators due to the reduced operating cost and more simplistic operating requirements. A typical chemical odor control scrubber often requires two or more chemical additives, and more instrumentation is required to maintain system performance. With the additional chemicals required and instrumentation comes the need for more hands-on maintenance, calibration, and safety requirements which increases the operating costs and workload of the operator.

A Biological Odor Control System relies on active bacteria cultures that recirculate within a water stream and flow across a random packed media bed that is beneficial to the bacteria culture. During the process of metabolizing harmful gases such as Hydrogen Sulfide (H₂S) the biological odor control system requires only the addition of Caustic to control and balance the pH and additional water makeup to replace what has been consumed through evaporation or during the blow down process to eliminate solids. There are several different types of odor control and chemical wet scrubbers on the market today and each provide a solution for the treatment of noxious or corrosive gases and odors in the industry.  And even though Biological scrubbers are commonly utilized in municipal applications for the treatment of hydrogen sulfide (H2S) gases that were produced by a water or wastewater treatment process there are times when a Biological Scrubber does not provide the best solution for treatment. When there are wide or rapidly changing concentration in the ppm (parts per million) level than a Biological Scrubber will have difficulties balancing and acclimating fast enough to prevent break through.  As an example, In water treatment there is a treatment process referred to as “degasification” which strips the hydrogen sulfide gas from the water and then the concentrated H2S gas is exhausted from the tower through an exhaust port.  When the concentration rises above 1 ppm for hydrogen sulfide gas then the levels become both noxious to the surroundings as well as corrosive. Many times, the levels range from 3-7 PPM in concentration with Hydrogen Sulfide and pose a serious health threat, noxious odor, and corrosive environment demanding capture and treatment. When utilizing an Odor Control Scrubber such as a Biological Scrubber the gases are pulled or pushed through an air duct system that is connected to the Biological Scrubber inlet or suction side of the blower. The same process is utilized when treating Hydrogen Sulfide (H₂S) gases that were captured at a wastewater treatment process. These gases may have been generated from a source such as the wastewater treatment plant, lift station or master head-works facility. When captured the gases are also conveyed in a similar manner to the Biological Odor Control Tower for treatment.

A Biological Odor Control Scrubber is in fact a eco system all to itself. The biological scrubber relies upon an initial seeding of tiny microorganisms (bacteria) which attach themselves to the internal media substrate or packing providing both a place to attach and to breed and multiply all the time coming in direct contact with the contaminated air. The bacteria are utilized to breakdown and digest contaminants, and it feeds on the contaminants as a food source which allows it to not only live but continue to grow and multiply.

When utilizing a Biological Odor Scrubber for hydrogen sulfide (H₂S) treatment and removal the by-product that is produced during the reaction is a waste in the form of Sulphuric Acid which is produced as the Sulphur is consumed as a food source. The Sulphuric acid waste lowers the pH of the recirculating water and can create an unhealthy 

The need to remove harmful elements from water such as Hydrogen Sulfide and Carbon Dioxide

from water in the pisciculture and aquaculture market is extremely important. In order to achieve maximum results, the industry utilizes a treatment technology called “Degasification” and controls the pH precisely to maximize results. When utilizing equipment such as the DeLoach Industries degasification systems the hydrogen sulfide and carbon dioxide levels can be removed to 99.999% ug/l.

The need for pH control with water degasification and decarbonation in water treatment includes almost every industry and includes;

aquaculture, food and beverage, industrial, municipal, and even pisciculture.  In some water treatment applications, there are harmful gases such as Hydrogen Sulfide (H₂S) being removed while in other applications Carbon Dioxide (CO₂) or even a combination of both. In addition, there are a host of other organic and inorganic elements found in water both naturally occurring and manmade that require removal during some part of the water treatment process.  

In almost every application of Degasification of Decarbonation you will hear or see the term pH used either by need or by result.  If as an example the water treatment application is requiring the removal of Hydrogen Sulfide (H₂S) be removed either as a “free” gas or requires the conversion of Sulfides into (H₂S) as a gas they you will quite often also see the need to adjust pH of the water chemistry to maximize both the removal and the conversion to increase the efficiency of the equipment being utilized to remove the Hydrogen Sulfide such as a Degasification Tower or commonly called a Degasifier.

Hydrogen Sulfide Chemical Formula and the Molar mass of H2S

What is hydrogen sulfide? H2S is a naturally occurring chemical compound that is created in nature with the decay of organic material. Hydrogen sulfide formula is a chemical compound with a molecular formula comprised of (2) hydrogen atoms and (1) one sulfur atom. The formula is displayed as H2S. The gas is a colorless hydride gas and it is often known as the “Rotten egg gas”. This gas is very dangerous as it is poisonous and toxic to all forms of life. It is also very corrosive and flammable. The H2S molar mass is 34.1 g/mol and it has a melting point of -76 F (-60 C) and a melting point of –115.6F or (-82C).

Hydrogen sulfide gas is also created more often from a byproduct of a manufacturing process or from the removal of water or waste water treatment systems. In waste water as organic material decays H2S is released,  captured and treated to protect human lives, reduce corrosion, and reduce odor complaints. During the manufacturing operations at refineries, pulp mills, and mining hydrogen sulfide gas is produced. These higher levels of H2S are released during the manufacturing process and must be captured and neutralized to protect human life and prevent excessive corrosion.  At higher concentration you cannot even smell the gas and it is not distinguishable as the “rotten egg gas” which makes it even more dangerous and drives the need for the equipment known as hydrogen sulfide scrubbers, fume scrubbers, or odor control scrubbers.

According to the “Agency for Toxic Substance & Disease Registry” those who work within certain industries, are exposed daily to higher levels of hydrogen sulfide gas than the normal public. Because the gas is also heavier than air it will settle into lower places like manholes, tanks, basements and it will travel across the ground filling in low level areas. To protect the public OSHA has set guidelines and rules known as “Permissible Exposure Limits” (PEL). A PEL is the legal limit a worker may be exposed to a chemical substance. The PEL limit for hydrogen sulfide is ten parts per million (10 ppm) over an eight-hour period.

Basics of water decarbonation for dissolved organic carbon.

The water treatment industry continues to develop and evolve and over the past two decades there have been many new developments in technology and even more refinement in existing technologies such as "Degasification". The evolution and advancement of water treatment have been driven by the constantly increasing demand from an increase in population that demand cost-effective solutions and recognition to improve safety with the implementation of NSF 61 standards.

All human cultures on our planet share a single commonality and that is the dependency on water to survive.

Many existing technologies such as "Degasification" have evolved with higher efficiency to meet the demand changes and provide safety to consumers and to the systems. Degasification refers to the removal of dissolved gases from liquids and the science to degasify water is based upon a chemistry equation known as "Henry's Law". The "proportionality factor" is called Henry's law constant" and was developed by William Henry in the early 19th century. Henry's Law states that "the amount of dissolved gas is proportional to its partial pressure in the gas". The most "cost" effective method to perform degasification is with the packed vertical tower called a "Degasifier” or “Decarbonator”.

The key words in this previous sentence for owners, operators, and engineers to focus on is "the most cost-effective" as there is no other process more cost-effective at removing dissolved gases at the lowest cost than the use of a Degasifier or decarbonator. The process of degasification is simple enough to understand. Water is pumped to the top of a vertically constructed tower where it first enters the tower through some type of distribution system at the same time there is a cross current air flowing up from the bottom by a blower located at the bottom of the tower and the air encounters the water and is exhausted at the top of the tower through an exhaust port. There are various types of distributions systems and we will explore these in later discussions. Once the water enters the top of the tower and passes through the distribution system it then travels by gravity downward. The next thing the water encounters is some type of media packing. There are various forms of media packing offered in the degasification industry and each type can offer higher performance or have the ability to deter fouling. The selection of the type, size, and volume is where the “experience, engineering and understanding of each application” comes in to play.

On behalf of DeLoach Industries Inc., I would like to thank you for entering our drawing for the first annual "Clean Water Professional Appreciation Award".  As you know we are celebrating our 60th year serving the water and wastewater Industry.

In the production and purification of water for industry

there are many types of different processes available to remove harmful minerals and gases from the water stream but the most effective process and most cost effective from both a capital investment and operational cost is a “Forced Draft Degasification System” (Degasifier).

Degasification is used in a wide range of water processes for industrial and municipal applications which extend from the production of chemicals to the production of semiconductors and in all applications the need to remove contaminants from the water and dissolved gases is key to achieving the end results needed in the industrial water process. Water from the ground often contains elements such as calcium carbonate, manganese, iron, salts, hydrogen sulfide, and sulfur just to name a few of the basic contaminants and these naturally occurring elements can cause serious damage and consequences to process equipment such as boiler systems, piping, membranes, and cation and anion exchange resins used in the demineralization process.

Calcium carbonate can dissolve in water under certain pH ranges forming carbonic acid and releasing carbon dioxide (CO2) gases. These gases are not only very corrosive to equipment like boiler feed systems and boiler tubes but also attack the actual resin beds found in cation and anion softening and demineralization system causing an increase in regeneration and chemical consumption and resin bed replacement.

By incorporating a Force Draft Degasification system you can remove dissolved gasses

like CO2 and hydrogen sulfide (H2S) to as low as 99.999% and improve the cation and anion system performance, extend the resin bed life, and lower the operating cost of the water treatment process.

Quite often Forced Draft Degasification is utilized “post” treatment to also remove newly formed dissolved gases prior to entering the boiler feed system to prevent corrosion damage within the tubes and feed system and pumps. These gases are easily removed with the forced draft degasifier at a much lower cost than chemical additives or liquid cell degasification that requires higher capital cost and much higher operating cost.