How to Prevent the Formation and Release of Hydrogen Sulfide

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How to Prevent the Formation and Release of Hydrogen Sulfide

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Odors occur when wastewater pH allows hydrogen sulfide to evolve from liquid phase hydrosulfide. Thioguard technical-grade magnesium hydroxide prevents the formation and release of H2S gas in several important ways:

First, sulfate-reducing bacteria operate best at pH levels 6.8 to 7.2. Above this ideal pH range, less sulfide is produced, and SRB growth rate is stunted. Thioguard raises wastewater pH above 8.0, so less sulfide is generated.

Second, H2S formation is extremely sensitive to pH. At pH levels of less than 7.0, the equilibrium reaction favors hydrogen sulfide and odorous gas evolution. At pH of greater than 7.0, the reaction favors hydrosulfide.

Unlike other alkali choices, Thioguard contains slowly dissolving magnesium hydroxide particles. These particles have high surface pH and high surface area, applying additional physical adsorption and chemical bonding properties to make Thioguard more effective, even when wastewater pH returns to neutral, 7.0.

Thioguard may also reduce some odorous VOSCs like mercaptans (Thiols: R-HS) by adsorption and base reaction to form nonvolatile ionic Thiolates: R-S-.

Thioguard actually buffers water, gently raising pH without overshooting. Hydroxyl alkalinity is gradually released as needed, when acid or CO2 is produced within the system. This automatically controls pH in the correct range to prevent formation and release of H2S. Overdosing simply adds alkalinity, as OH- and HCO3-.

Since Thioguard reactivity varies with wastewater chemistry, a titration is necessary to determine the optimum rate of addition. In general, it takes only 30 to 100 gallons of Thioguard per million gallons of sewage to raise and hold the pH in a range of 8.0 to 8.5. Once determined, the feed rate is seasonally constant, despite variances in sulfide concentration.

Thioguard is well suited for applications to safely control odors and acid gases such as hydrogen sulfide, and to enhance biological treatment processes. Thioguard is owned, mined and produced in the U.S.

To find out how you can harness the power of technical-grade magnesium hydroxide for your wastewater treatment plant or collection system, please visit and locate your regional representative on the contact page, or call 800/227-4287.  


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