How to Control Hydrogen Sulfide Corrosion

Hydrogen sulfide corrosion is a common, well-documented problem in many waste water treatment systems. Hydrogen sulfide corrodes the metal and concrete pipes and tubing used for sewer systems. Hydrogen sulfide also attacks copper contacts and forms copper sulfide. Another danger of hydrogen sulfide is that when it forms in waste water, it is released as a gas and enters the atmosphere of the sewer.

Instructions

• 1

  Lower the temperature of the system. The EPA reported that the production rate of sulfide is increased seven percent or more for every Celsius degree up to 40 degrees Celsius.

• 2

  Control your discharge. The potential for corrosion is lowered when sulfide-bearing wastes are controlled. High organic strength wastes lower the rate of sulfide generation. The same is true for wastes containing fats and oils and grease.

• 3

  Oxidize the hydrogen sulfide in the waste water. This can be done by involving air or oxygen injection or by adding oxidizing chemicals to the waste water. Air injection--such as direct injection or dissolution--is an inexpensive treatment. Oxygen injection is five times more soluble than air injection. It can be injected like an air injection or in a third manner--in a pressurized side stream. Hydrogen peroxide, chlorine and potassium permanganate are examples of oxidizing chemicals. The cost of oxidizing chemicals is higher than the injection methods.

• 4

  Use a metallic salt, such as iron salt or zinc salt, to precipitate the hydrogen sulfide. The conversion of the dissolved sulfide into an insoluble precipitate prevents the release of hydrogen sulfide. The two soluble salts react in a solution, forming an insoluble product. That product separates from the liquid and is now referred to as a precipitate. Iron salt is economical; however, the dosages vary depending on the level of the hydrogen sulfide. The zinc salts are regulated.

• 5

  Raise the pH level. Elevating the pH level causes the inactivation of the sulfide-reducing bacteria found in the slime layer. A higher concrete alkalinity reduces the corrosion rate, according to the Environmental Protection Agency (EPA). A high concrete alkalinity--for example, over nine on a pH scale--can also compromises the adhesive and bonding systems.