Odor Control

Odors occur when wastewater pH allows (H2S) hydrogen sulfide to evolve from liquid phase hydrosulfide (HS-). THIOGUARD® 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 < 7.0, the equilibrium reaction favors hydrogen sulfide (H2S) and odorous gas evolution. At pH > 7.0, the reaction favors hydrosulfide, (HS-).

Unlike other alkali choices, THIOGUARD® contains slowly dissolving technical grade 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 (Volatile Organic Sulfur Compounds) like mercaptans (Thiols: R-HS) by adsorption and base reaction to form non-volatile 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 30-100 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.




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