DELOACH BLOG

The water and wastewater industry has a constant need for dependable odor control systems that are reliable and effective. The most popular process types of scrubbers are biological and chemical scrubbers. Each is effective at treating and removing noxious odors that arise from hydrogen sulfide (H2S) and methane.

Chemical injection systems can include biological agents, hydrogen peroxide, or proprietary agents in addition to odor masking agents that do not react but rather cover up odors. Methane odors typically only appear in wastewater applications, but hydrogen sulfide can be present at either water or wastewater treatment facilities.

The common questions for deciding which type to use normally come down to two variables: “What will it cost to install and operate annually?” and “Are the odors caused by corrosive gases which need to be neutralized to prevent equipment damage, instead of just covering up the odorous smell?” In some cases, the remoteness of the location can also dictate the type of process to use. If the location is very remote with infrequent visits then it may make more sense to have a low-maintenance chemical masking or injection system installed. However, if the location does have frequent visits or an operator then the two previous rules normally govern the selection process. Quite often the selection is made improperly because of salesmanship or relationships to suppliers. This should be avoided at all times to prevent safety risks, damage to equipment, or high economical costs. Many times suppliers will offer discounted or even free equipment to secure chemical use contracts for a long-term commitment to chemical sales.

The first step is understanding the chemical analysis of the water you will treat.

Suppose this is an aeration process for iron (Fe) removal. In that case, it is vital to understand the water's concentration, pH, and alkalinity and the amount of calcium carbonate or other minerals present. Once you've determined that the water is suitable for the desired treatment process, you must choose equipment based on the water's volume and flow rate. Remember that water treatment equipment is not one-size-fits-all and is vitally important when selecting equipment to consider your water conditions.

If a tower's internals is damaged due to the weight of random pack media or fouled water and airflow, the pack media will become completely clogged, and water flow will be blocked. This will result in an expensive shutdown and repair. It is advised that routine service cleanings are carried out under a service contract.

For heavy fouling conditions, a slat tray media selection can save you both downtime and costs. Slat trays provide an anti-fouling benefit based upon the design intended to “shed” particulate as it is formed. They still need to be cleaned in heavy conditions, but far less often, and cleaning is more manageable. The tower process application requires high removal efficiency, then loose fill media may be the only choice unless a pretreatment tower with slat trays is installed in front of the process. Each application must be evaluated on its merits and reviewed for potential fouling and anticipated operating cost.

If fouled completely, loose fill, random pack media will block water flow and air and can, in some circumstances, become so heavy that the weight can damage the internals of a tower. This will cause a shutdown and more expenses to remove and repair. Routine service cleanings under a service contract are highly recommended.

Industrial water treatment systems play a crucial role in maintaining the quality and sustainability of water used in various industrial processes. One of the key challenges faced by industries is the presence of dissolved gases, particularly carbon dioxide (CO2), and corrosive gases like hydrogen sulfide (H2S) in the water. These gases can have detrimental effects on equipment, cause pH imbalances, and even compromise the overall efficiency of industrial processes.

When operating a forced or induced draft water treatment tower system it is important to properly maintain your distribution system.

The distribution system is a fundamental component for any type of unit: an Aerator, Degasifier, Scrubber, or Air Stripper. It must be designed and constructed with precision and accuracy. This will ensure its optimal performance throughout its lifetime.

It is essential that the distribution system undergo regular and thorough maintenance. This will ensure it can do its job effectively.

Maintenance should include cleaning and inspecting pipes and connections. Additionally, worn or damaged parts should be replaced or repaired. Lastly, test the entire system to ensure proper functioning.

Regular maintenance is essential. It helps to prevent costly breakdowns or failures. Additionally, it minimizes disruptions to the distribution system.

Regular maintenance helps the distribution system run efficiently. This leads to better, more reliable service for customers.

The key role of the distribution system is to properly distribute the water flow over the media bed. If the distribution system is designed incorrectly then water will not be properly distributed which can cause multiple problems.

The distributor can be damaged or fouled. When this happens, the water pattern is changed. This affects the flow rate across the media bed. This can lead to low or high hydraulic flood conditions in the media bed.It is important to inspect the distribution system within 30 days of the initial startup of a system. Then decide, based upon application, if the future inspections can be extended to 90 or 180 days.

Iron oxidation and H2S require more frequent cleaning of the distribution system than a degasifier used for CO2 removal. This is because they are more corrosive.

 

"Oxidation" refers to electron loss from a reducing agent. It is common to say that "the process has been oxidized."

]Electrons carry negative charges, and the oxidation process leads to an increase in positive valence.

During oxidation, the number of electrons orbiting an element decreases, causing the element to form bonds with oxygen when oxygen is present. Oxygen is naturally attracted to electrons.

Iron can exist in various forms in water, with the most prevalent being ferrous bicarbonate (C2H4FeO6), which is soluble.

Ferrous iron possesses a positive two valence. As ferrous iron undergoes oxidation, the number of electrons decreases, resulting in the development of a positive three valence known as ferric hydroxide: Fe(OH)3.

The most cost-effective method of oxidizing iron in water is thorough aeration using an "aeration tower." The aerator is very similar to a degasification tower or air stripper as it utilizes either forced draft or induced draft air movement to create the enriched oxygen environment needed.

Select the best type of odor control, fume, or air emission scrubber.

Industrial and municipal operations often face the challenges of capturing and treating air emissions from their process operations.  Off-gases, fumes, and odor emissions can be generated from the downstream process or material handling, such as those in the municipal wastewater industry.  However, industrial operations often generate fumes and off-gas air emissions from either the production of chemicals or the use and application of chemicals like acids and a wide range of other chemicals. These types of air emissions share a common need to be safely captured, contained, and treated to make the air steam safe before its release.  Some types of air streams create an odor that becomes a nuisance, as is typical with municipal waste that often releases Hydrogen Sulfide (H2S) and or Mercaptans (R-SH) gas during decomposition.  

Many variables should be considered

when beginning to choose the best type of air emission treatment process.  Within the industry, there are wet chemical scrubbers, dry absorbent scrubbers, biological scrubbers, and destructive type scrubbers such as catalytic and thermal oxidizers and flare technology that utilize heat to destroy and consume and oxidize certain types of off-gases. 

Each type of air emission process has its own parameters where it will perform optimally, and each type of scrubber has different levels of operating challenges and associated operating costs.  So how does one select the best process for each application?

At DeLoach Industries, we like to help customers with this evaluation process by completing a checklist guide, which helps guide the customer to the most economical and safe solution. Going through this process can help eliminate costly mistakes that may otherwise be overlooked.  Solutions are often selected by looking at the contamination only or by familiarity with the process.

All induced draft, forced draft aerators, degasifiers, and odor control scrubbers rely on some type of air blower to enhance removal efficiency or move airflow. When a change in performance is noticed in water effluent quality, the first thing to inspect and troubleshoot is your blower.

An induced draft inspection, at times, can be a bit more tricky because it is located on top of the unit and typically requires some type of access ladder to allow for an inspection. You must always follow proper OSHA safety guidelines when attempting to inspect. Larger units often come equipped with an attached access ladder and handrail system, whereas small units with limited space do not.

The forced draft units have the blower typically mounted on the ground or top of the Clearwell/catch tank so that access to inspect a forced draft blower is less complicated. Once reaching the blower, if the noise of other operating equipment prevents easy listening, place your hand on top of the blower housing to detect if the motor is running. You will feel a vibration from the housing. If the water flows to the unit, but the blower is off and not running, you can determine that the motor is not operating.

Hydrogen sulfide (H2S) contamination in water is a very common issue. A distinctive smell, combined with a dark precipitate that leaves behind damaging deposits, is an indication that there is H2S in your water. From the irritating smell, corroded plumbing & staining, to far more dangerous health concerns, contaminated water can cause serious issues in industrial and municipal environments.

When looking for the best method to remove the gas from your  water treatment system, you want equipment that is highly efficient and cost-effective. You also want the method to be safe and require minimum capital to initiate. Of all the available methods, few are as efficient, cost-effective, and easy to implement as degasification.

Degasification

Generally speaking, degasification is the elimination of dissolved gases from water using various means. In this case, we are looking at the use of a membrane to filter off Hydrogen Sulfide from drinking water to render it clean and safe for use. In membrane degasification, a proprietary membrane cartridge is used to remove the gas from the water. With vacuum conditions on one side of the membrane and the contaminated water on the other side, the dissolved gas (H2S) is moved by the vacuum to the other side of the membrane, leaving the water molecules unable to move across. This happens very quickly and the method is highly effective. The resulting water is void of any contamination, and safe for drinking and commercial use. 

What is the difference between Aeration, Decarbonation, or Degasification, and which one is right for your water process application?

To answer this question, we first need to have a clear understanding of what benefits each of these (3) three different types of treatment processes for your water application.

• 1. The term Aeration means, to induce or maintain the oxygen saturation level in water in a natural state or an artificial one.  When utilizing an Aerator you can expect to induce additional oxygen into the water stream that is passing through the system to the maximum saturation level possible at the current water temperature.  As saturation levels will vary with water temperature it is important to always take the inlet water temperature into consideration. If your goal and objective are to remove iron as an example from the water process an Aerator unit should be considered and utilized as one of the most cost-effective methods of inducing oxygen and initiating the oxidation of iron. Converting Ferrous to Ferric iron then can be settled, collated, and filtered.  Aerators manufactured by DeLoach Industries are NSF-61 certified and fiberglass compliant to RTP-1 standards and are available in a wide variety of sizes and materials. For heavy iron, magnesium, or calcium application the systems are available in a square design allowing for self-cleaning PVC slat trays to be utilized in place of loose fill media which will foul more frequently.  Aerators are also available in a round tower design for non-iron applications to accommodate loose-fill media packing and are either a Forced or Induced draft configuration to accommodate applications where Hydrogen Sulfide may be present within the feed water to prevent corrosion from attacking the blower. The equipment can be manufactured from Fiberglass, Aluminum (depending on other contaminants), Stainless Steel, or rubber-lined steel and are available to accommodate flows from 5 to 4,500 GPM (gallons per minute).
  
  
• 2. The process of Decarbonation refers to the removal of Carbon Dioxide (CO₂) from water. CO₂ can be naturally found in a water process or can be created from other elements such as Carbonic Acid which in the presence of water converts to free CO₂. There are several reasons for removing CO₂ from a water process which includes pH control, corrosion prevention, and reduction of operating costs when utilizing ion exchange for water softening. A Decarbonator is a piece of equipment that is manufactured specifically to remove CO₂ from the water, and it is then exhausted through the vent located at the top of the unit.  DeLoach Industries manufactures’ Fiberglass RTP-1 and NSF-61-compliant Decarbonators for water applications within the Municipal, Industrial, Food and Beverage, and Aquaculture markets. It is very common to utilize a Decarbonator post-membrane filtration, or prior to Anion and Cation treatment.

CO2 & pH In municipal and industrial water processes

Carbon Dioxide (CO2) in municipal and Industrial water can create problems in the water treatment process, increase operational costs of the treatment plant, and cause excessive corrosion to equipment and ancillary equipment.

In nature, one of the most natural common causes that create low pH or acidity in water is an element known as “Carbon Dioxide” (CO₂).  The process of how carbon dioxide enters the water in the first place is a topic worth exploring.  Nature creates one of the most common causes of CO₂ found in the water naturally. When the water reaches an equilibrium with our atmosphere followed by the biological degradation that is aided by the photosynthesis of organic carbon (CH₂O) then carbon dioxide begins to form. Organic carbon is dissolved in water and it forms “Carbonic Acid”

(H₂CO₃).  CO_{2 (g)} + H₂O _(l) = H₂CO_3 (aq). 

The process to form the carbonic acid is slow and only a small portion remains as an acid because proton losses occur during the process.

H₂CO₃ (aq) « H⁺ (aq) + HCO₃^- (aq)

CO₃^- (aq) « H⁺ (aq) + CO₃^2- (aq)