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.
So, what is pH? As it relates to water pH it is a term used to describe whether or not the water is “acidic” or “basic”. pH ranges in water can be from 0-14. 0 is the most acidic and 14 is at the far end and is the most basic so that leaves “7” as the neutral state. A pH of 7 is neither acidic nor basic. So, what causes pH to be acidic? In nature the most common cause of a low acidic pH in water is Carbon Dioxide (CO2) which occurs naturally when photosynthesis, decomposition, or respiration occurs in nature. The increase in CO2 causes an increase in ions which in turn produces a lower pH in a simplified explanation.
How does pH play such a significant role in Degasification and Decarbonation? As mentioned above in the example of the removal of certain harmful elements such as sulfides, sulfates, and free H2S Hydrogen Sulfide gases to maximize the removal from water utilizing a degasification tower it is important to maintain as close to a pH of 5 as possible. When the pH begins to rise above a 5 the ability to both convert and to strip the free H2S gas from the water diminishes. When a degasification tower is operating within this specific range and if it has been designed with the higher efficient distribution systems such as the ones utilized by DeLoach Industries than removal efficiencies of 99.999%- 100% can be achieved. If the pH rises to a 7 or above the removal process becomes much more difficult and typically you will much lower results. The adjustment of the pH during the water treatment process is normally accomplished by adding some type of commercially available acid such as “Sulphuric Acid” as one of the most common within the municipal and food and beverage industry.
What happens to the pH in water when you remove Carbon Dioxide (CO2)? If you are treating water that either already has a clot of free CO2 naturally or if the water pH has been previously adjusted lower either to remove H2S or prevent scaling within a membrane treatment of filtration treatment than most likely you already have carbonic acid and free CO2 present within the water. So, when utilizing either a Degasification or Decarbonation tower system by DeLoach Industries as the gases are removed you will see the pH of the water rise. Typically, if the pH is 5 than after Decarbonation the pH will have risen to 6 or as much as 6.5. By removing the free CO2 it allows the alkalinity to rise and become more basic (neutral). Now there are some cases when there are different types of acids used or the pH is taken down too low or all of the organics have been removed when the pH rise may be minimalized during the process. This is why understanding water chemistry and the specific application and need are very important.