DELOACH BLOG

A Biological Scrubber is a wet odor control scrubber that treats and removes contaminants from an air stream.

It utilizes caustic typically to control the pH of the re-circulation solution. There are several types of odor control and chemical fume scrubbers on the market today. Each plays a role in treating noxious or corrosive gases in the industry.

Biological scrubbers are used in municipal applications to treat low and high hydrogen sulfide (H2S) gas levels. This colorless gas is removed from the water or wastewater treatment process. 

Water treatment equipment such as “degasification” or “decarbonation” towers.

Strips the hydrogen sulfide gas from the treated wastewater and exhausts the gas from an exhaust port. These gases are captured and sent to the biological scrubber via an air duct system. The health effects of hydrogen sulfide can cause eye irritation, loss of appetite, and fluid in the lungs. Hydrogen gases are captured at a wastewater treatment process, including treatment facilities, lift stations, or head-works facilities. The PVC or FRP duct system sends the gases to the biological scrubber.

How does a Biological Scrubber work?

A biological scrubber utilizes tiny microorganisms (bacteria) to break down and digest contaminants. The bacteria feed on the contaminants and utilize this as a feed source to live and grow. When utilizing a biological scrubber for hydrogen sulfide (H2S) treatment, the by-product waste is acid from the digested H2S. This lowers the pH and requires the use of caustic to buffer the water and nutrient solution that is recirculated within the scrubber to maintain a neutral pH. The captured gas containing contaminants enters the bottom of a vertical biological scrubber. Similar to how the gas enters any other type of chemical scrubber or single or dual pass odor control scrubber.

The gas stream travels upward. Passes over a media bed that has been cultured to grow live microorganisms. A biological odor control scrubber already has “artificial intelligence” because of the millions of microbes colonies it supports.  

The type of Odor Control Wet Scrubber selected for the treatment and neutralization of Ammonia (NH3) gases depends on several variables, including the type and source of the ammonia gas and whether or not it is “Free” ammonia and or unionized.

Ammonia is a very miscible and stable molecule with solid hydrogen bonds, making it very soluble in water and difficult to treat without using a properly designed and sized ammonia scrubber. The concentrations, air flow rates, temperature of the gas stream, and chemical reagents being utilized, such as caustic to remove and then treat the ammonia, all play a significant role in the removal efficiency of the ammonia gas scrubber system. Unlike other types of “odor control scrubbers,” an ammonia scrubber is much more sensitive to variables such as the gas stream temperature because of the solubility of ammonia.

the process is called the Haber Process by combining nitrogen with air and adding pressure, you can make ammonia.

It takes about 200 atmospheres of pressure, and the process varies from refinery to refinery. Still, on average, you can only make approximately 15% of ammonia during each pass which takes multiple passes to achieve the 15%. The reaction to make ammonia is exothermic when produced in a refining process. 

However, ammonia is also formed in nature in smaller quantities. Most ammonia (90%) is utilized for fertilizer production, but ammonia can be found in food, pharmaceutical products, and cleaning supplies. When ammonia gas is released into the air, it has a very noxious and pungent odor that can be dangerous to inhale, so often, odor control scrubbers are required to capture and treat the ammonia gas.

In the United States manufacturing industry, an astonishing 400 million gallons of water per day (MGD) is consumed to generate steam.

Out of this amount, approximately 60 MGD is sent to blow-down drains, while another 300 MGD is used for direct injection of steam. The common denominator in all of these processes is the need for purified and treated water. Without proper treatment, manufacturers would face frequent shutdowns and increased capital expenditure, significantly impacting their cost of goods. One effective method of water treatment to protect boilers is through degasification and deaeration.

Degasification towers play a crucial role in removing harmful gases such as hydrogen sulfide (H2S), carbon dioxide (CO2), and often dissolved oxygen (DO). The elimination of these corrosive gases is vital for enhancing the lifespan and efficiency of boiler systems. If these gases are allowed to remain in the boiler feed water, particularly carbon dioxide (CO2), it can lead to disastrous consequences, including higher operating costs and reduced system longevity. Carbon dioxide (CO2) can convert into carbonic acid, creating a corrosive environment for the boiler and other critical components. In cases where an ion exchange process is implemented prior to the boiler, the presence of carbon dioxide (CO2) can drastically increase regeneration costs as the resins are consumed. By removing carbon dioxide (CO2), the life of the resin is extended, and the pH of the water is elevated, reducing the need for additional chemicals and further lowering operating costs.

When do you know if your decarbonation system needs service?

When a degasification tower or decarbonator becomes fouled, several indicators identify you may have a problem or that it's time to clean your system. If the efficiency of the degasifier has dropped, you will see an increased consumption rate of chemicals. If you remove less hydrogen sulfide gas from the degasifier, chlorine consumption will increase. When you increase the amount of chemical reaction occurring in the water, you will see an increase in the TSS levels and a drop in water quality. As the H2S reacts with chlorine, more solids will form and be present in the water, and the water quality will diminish.

Another indicator of a fouling condition is the pH adjustment in the Industrial Water Treatment industry. You are required to meet the set standards. As the performance of the tower drops, the removal of CO2 will also drop, leaving a higher pH level than may be desired. A quick inspection to check out the media bed should be performed. Also, do not forget to inspect the distribution system at the top of your tower and remember that all distribution systems are not alike, and inspecting the condition of each of them may require additional effort on your part. With a header lateral system, you need to inspect the distribution nozzles, but with a Weir or Tray type, you will need to check the amount of scale or fouling building up on the Weir edge or in the bottom of the pan. If the Weir edge becomes fouled unevenly, it will create "Channeling" of the water and increase the initial hydraulic load to a concentrated point on the media bed.

Do you think all distribution systems are made equal? 

if you do you may be surprised that there is a lot of variation in manufacturing protocols for aerators, degasifiers, and decarbonators.  Aerators are often found in use at Industrial Water Treatment and municipal water treatment facilities around the globe. 

For water treatment, you may be surprised to learn that one of the key items that separate different types of aerators and decarbonators for water treatment is the type of distribution system it utilizes.  To improve Carbon Dioxide (CO2) or Hydrogen Sulfide (H2S) removal you need to select the best distribution system for the tower and make sure it's maintained. Now, there are many types of aerators in general and the term is used broadly. From floating pond aerators to wastewater aerators, to vertical tower aerators, decarbonators, and degasifiers for industrial water treatment aerators.  We will focus on vertical tower aerators for industrial water treatment.  All types of Aerators and even degasifiers and even decarbonators and Odor Control Scrubbers require some type of distribution system to begin the process of gas transfer and to remove Hydrogen Sulfide (H2S) from water or Carbon Dioxide (CO2).  It is important to evenly distribute the water or chemical solution across the media bed. 

There are several types of distribution systems available and the three most common ones you will see on the marketplace are the “Tray” type, Weir, or the header lateral utilizing gas release “Nozzles”.  

The selection of what type of distribution system is typically driven by the marketing side of who is selling you the tower.  But in terms of real performance a distribution system utilizing a nozzle system will outperform a tray-type distributor.  All packed towers are designed utilizing Henry’s Law Constant” theory of chemistry and what all towers rely upon is some type of method to break the surface tension of the water and expose the molecules of gases so that they either can escape or can be introduced to a reaction agent.

When towers are designed it is important to properly hydraulically load the top of the media bed.  This is considered " Degasification Basics". This is important for many reasons and we will address these points in future updates.  When using a properly designed nozzle distribution system such as a DeLoach Industries header lateral system then you get the benefit of both proper hydraulic load across the bed and you also gain anywhere from 4-10% removal efficiency depending upon the application.  When looking at a chemical scrubber versus a biological scrubber you will notice they too have very different distribution systems. DeLoach Industries, Inc. has learned over its 60 years in business how to maximize gas transfer release.  If designed and built properly the gas release process or interaction process (if designing a scrubber) has already begun “before” it enters the media bed.

Water treatment in the Caribbean poses unique challenges due to the specific characteristics of the region.

Extending the life of your ion exchange resin in boiler feed water applications

Did you know that when producing steam, it is most effectively accomplished by utilizing a decarbonation process? Decarbonation and Degasification is the most economical way to process fluent water pre-Ion exchange treatment through a vertically packed tower called a decarbonator, often called a degasifier.  This is the most economical method to remove carbon dioxide (CO2) and Hydrogen Sulfide (H2S) to prevent the formation of carbonic acid. Other corrosive conditions are Degasification and Decarbonation, which will extend the life of the ion exchange resin. If CO2 levels remain high in the inlet feed water to the ion exchange system, the resin beds, whether cation or anion, will require more frequent regeneration, and your chemical usage and cost will rise.

In industrial applications, it’s easy to overlook.

Often, there is insufficient focus on selecting the right decarbonation or degasification system to ensure that the process water treatment system performs at the highest optimal level. For water filtration, when the primary process is membrane filtration, often referred to as “reverse osmosis, " too little attention is given to properly removing CO2 from the process to lower the pH and adjust the alkalinity. 

Do you need to remove or increase your reverse osmosis system's hydrogen sulfide removal efficiency?

The industrial water treatment market has many forms of water treatment processes. Most of us would agree that maintaining high water standards and quality requires using multiple treatment systems to achieve results.  Let’s face it, we do not win or get a “that a boy” when we design and build the best reverse osmosis system.

When we turn the brand-new water system on, the water has a "rotten egg odor." Yes, that is an embarrassing moment! 

The problem is we typically design around what we can see or read.  When was the last time you reviewed a water sample that provided details of how much-dissolved gas was in the water?  Most likely never.  A typical water treatment system may deploy reverse osmosis as the primary treatment method, and why true RO will remove particles that have size and weight (ions and molecules) typically defined as a certain size (micron), but RO does nothing to remove the dissolved gases that are already entrained within the water naturally or were created by adjusting the pH.  

Are pH and Alkalinity the Same? Balancing Alkalinity Levels for Optimal Water Quality

Choosing the Right Materials: Ensuring Certification and Performance in Water Treatment