DELOACH BLOG

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.

Avoid problems with calcium chlorite and corrosive gasses with your odor control scrubber.

When planning or designing an odor control system, one should pay close attention to several key variables that can cause havoc on a chemical odor control scrubber when trying to treat hydrogen sulfide or ammonia gases. The need for odor control occurs in many different forms. It is essential to understand the process that is creating the odorous or corrosive gas and the need for odor control & air emissions treatment.

First, begin to identify

all the potential obstacles that may creep up later after the chemical odor or corrosive gas control system goes online, like acid or caustic consumption. For example, chemical odor control systems designed for water treatment for the municipal industry are typically needed and attached to a degasification or decarbonation process, often needed to treat hydrogen sulfide (H2S). However, designers often may not pay close enough attention to the type of water process available for “make-up” water for the chemical scrubber. The addition of caustic can create scaling or fouling. This unknown variable of the makeup water quality can lead to a complete tower shutdown if the chemical scrubber distribution and media bed scales or fouls. The most commonly used chemicals for a hydrogen sulfide (H2S) scrubber are either chlorine in the form of sodium hypochlorite or caustic in the form of caustic soda. Both of these chemicals are common to a water treatment facility and are already in place to adjust and control pH.

The makeup water plays a significant role in the operation of a chemical scrubber.

When water containing high hardness levels is used as the source for the makeup water, your chemical scrubber can become fouled, and scaling can occur in a matter of hours, depending on the alkalinity and salts within the water. Solidification can occur from the scaling when combining sodium hypochlorite and raw feed water at specific pH ranges and these ranges are usually the range needed to achieve peak performance. Calcium chloride will form, and your chemical odor control scrubber will become a solid chunk of calcium chlorite making, making the ability for water or air to pass freely through the media packing next to impossible. No matter what type of media packing is utilized in the odor control or gas scrubber, it can foul and scale if the water chemistry is incorrect.  Trust me when I say “been there and done that”!  I have seen operators who have allowed a chemical scrubber to become out of balance with pH control and completely solidify the tower column to the degree that neither air nor water passage is possible. The problem can still occur with ammonia scrubbers but are different with different sets of parameters.

What is the best process for hydrogen sulfide treatment? Biological odor control Scrubber or a Chemical Scrubber?

Most industrial water treatment, municipalities, and private customers are responsible for water and wastewater treatment and often generate "hydrogen sulfide" off-gas odors. Professionals who either provide the design engineering or maintain the water or wastewater collection systems need to address and control "hydrogen sulfide" odors. They often find themselves in a situation where they must select what type of odor control system will perform for their customer or at their location. A chemical odor control scrubber may utilize "chlorine" or "caustic" as a scrubbing agent or just "caustic" alone. Typically, "acids" are not used when treating "hydrogen sulfide" gas, but "acid. " Acid is used when treating other types of off-gases such as ammonia. The application or process, including incorporating "artificial intelligence" into the machinery to provide more rapid responses to operators to predict maintenance and other operational functions—treating process air generated by either a "decarbonation" tower or a "degasification" tower for the removal of "carbon dioxide (CO2) or "hydrogen sulfide (H2S). It is important to understand the basics of either of the processes to allow the design professional to properly select the best type of "odor control" scrubber to utilize and make the decision to either select a chemical scrubber that uses "caustic" or "chlorine" or a biological scrubber for the treatment of the hydrogen sulfide that only requires the use of "caustic" to buffer the recirculation water. In other types of processes involving treatment, such as ion exchange, a design professional or owner must understand that the process may also produce an off-gas that requires treatment. "Ion exchange" can be used as a standalone treatment process to treat hard water utilized as a post-treatment process after reverse osmosis. Regardless of when "ion exchange" is utilized, we recommend removing the carbon dioxide (CO2) before the process to prevent the formation of carbonic "acid" and to extend and save the life of the Ion Exchange resin. It may also be necessary to adjust the pH of the water either pre or post-treatment by injecting either an "acid" solution when lowering the pH or injecting a "caustic" solution when raising the ph. It is important to remember that the efficiency of the process depends on proper pH control.

High pH and hydrogen sulfide will not convert or be removed by “degasification” and the “carbon dioxide” cannot be removed.

Opting for the appropriate odor control scrubber can lead to significant cost savings!

We have discussed the importance of understanding the source and concentration of an odor issue before selecting the type of treatment or odor control system. In addition to these critical items is the consideration of operating costs.

Many types of odor control systems work and remove odors, but selecting and designing a system that works efficiently and effectively without breaking the bank can be challenging.

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

Have you ever walked on a sidewalk or in a parking lot and passed by a lift station or manhole and noticed a smell so bad you thought you were going to pass out? 

Most people who encounter these types of odors do not live in the world of designing and building odor-control treatment systems.  For those of us who do we fully understand that when we encounter such a noxious smell it most likely needs an odor control system.  It does not matter if the odorous smell is coming from an industrial water treatment process, food and beverage plant, wastewater plant, or from the off-gas of a “degasification process”.  All of these types of industries and many more can generate odors and quite often these noxious odors must be addressed and treated because of either safety or public outcry. Many times odorous gases are generated as the result of processing and purifying drinking water.  When water contains contaminants like hydrogen sulfide (H₂S), carbon dioxide (CO₂), or ammonia (NH₃) there is a need to treat and remove these harmful elements from the water. 

Odors come from many sources

When processing and purifying drinking water which requires pH adjustment by adding acid to lower the pH and allow for the removal of hydrogen sulfide (H₂S) which will not convert at higher pH levels.  After the pH level is properly adjusted the hydrogen sulfide can be removed by degasification.  After the degasification process the pH will rise in the water from the removal of the carbon dioxide (CO₂) and if the pH remains slightly acidic then caustic is normally injected into the water stream to raise the pH back up to a neutral level of 7.  This entire required process to purify the water is what generates the odor and creates the requirement for an odor control scrubber.  Odor control scrubbers may utilize chemicals such as acid and caustic to treat the air gas noxious odor or it may be a biological Scrubber that consumes the contaminants within the noxious gas air stream including ammonia and hydrogen sulfide.  Noxious or corrosive odorous gases are not always from wastewater treatment plants or underground lift stations that are commonly referred to as “wet wells”.  Quite often odors are generated during manufacturing or food processing as well as from the efforts just mention in a municipal water treatment and purifying plan.  During the period of pH adjustment hydrogen sulfide (H2S) and other odorous substances can be released by means of Decarbonation or Degasification.  Some odors have a pungent smell and other odors are harmful corrosive gases that must be contained to protect the surroundings or even human life.  There are many types of odors and off gases that must be contained, captured, treated, or neutralized.  Understanding the; who, what, where, and why, first will normally put you on the road to selecting the right solution for odor control.

Water treatment towers and storage tanks are high places that require special precautions when entering. While the majority of people who enter these locations for work can be trusted, there are some hazards that make it more important than usual to follow safety procedures.

These locations can get very hot and humid, and can also be filled with harmful chemicals and microorganisms that can cause serious health issues if inhaled or absorbed through the skin. Therefore, the general standard for workplace safety is much higher when entering locations like these.

Make sure you have read and understood the following information about safety when entering a water treatment plant. It will help you understand how to stay safe and protect yourself from harm when entering a water treatment plant. normal installation, maintenance, or even emergency repairs, it is often required to enter into a water treatment tower (degasifier, air stripper, decarbonator, or clear well/ storage tank). When this occurs, full safety protocols should be followed at all times, in accordance with OSHA regulations.  A tower or tank B classification is a "Confined Space" location. For more information visit the OSHA combined space regulations page.

In addition, there are other safety risks that an operator or technician can be exposed to while inside these types of closed locations. The risk can come from fumes of hydrogen sulfide (H2S), chlorine from an injection line, or a lack of oxygen O2. A proper confined space permit should be prepared and only technicians with proper training and certifications should enter into these types of confined spaces.