THIOGUARD Magnesium Hydroxide Slurry

Natural Alternative for Caustic Soda and Lime Slurry

Customers have relayed to us that they are being told that lime slurry is similar to THIOGUARD technical grade magnesium hydroxide and can be used as an alternative in the many applications in which THIOGUARD is used.

If by "similar" they mean DIFFERENT, then yes, they are "exactly the same." Confused? That's what our competitors hope.

The simple fact: THIOGUARD, lime slurry and caustic all have different physical and chemical properties that affect how each responds to and reacts with the systems to which they are added. And, because of these differences in properties, the impacts they impart and the utility for their use are starkly different.

Reactor systems treated to an initial pH of 8.5 using THIOGUARD, caustic soda and lime. Equivalent amounts of acid added to each over time.

Reactor systems treated with an equivalent amount of THIOGUARD, caustic soda and lime. At the elevated pHs for caustic and lime, solids and scale begin to form and cause problems.

The Practical Choice: THIOGUARD

Effect THIOGUARD Lime Caustic Soda
Sustainable pH YES NO NO
pH Spikes Above 9.0 NO YES YES
Alkalinity Supplements Above
25 mg/L without pH spike
Produces sludge NO YES NO
Metabolic Stimulant YES NO NO
Enhances Clarification and Dewatering YES YES NO
Improves cake solids YES MAYBE NO
Stabilizes biosolids NO YES NO
Hazardous to handle NO YES YES

Miles of Piles

The use of lime generates significant amounts of sludge in wastewater collections and treatment. On a chemical basis, one ton of lime can generate as much as 11.5 to 15.5 tons of 20% sludge cake to remove or dispose. In contrast, THIOGUARD reactions in wastewater produce only water and water soluble products as TDS with NO added sludge. In fact, customers using THIOGUARD have reported reductions of 15%-25% in total solids/sludge produced, due to a combination of improved biological performance and reduced inorganic solids loading.

Unexpected Consequences

Competing Reactions: Lime Softening Versus Alkalinity Addition


With growing needs for alkalinity in nitrification and BNR processes, operators are often faced with the challenge of supplying higher levels (in excess of 30 mg/L) of alkalinity without upsetting processes or depleting the chemical budget.

On the surface, the cheap cost of lime is an appealing choice. When evaluated in its entirety, it is rare that lime is the most cost effective choice for pH modification and alkalinity supplementation.

WHY? Because lime softening often gets in the way of alkalinity supplementation. Through unintended lime softening, alkalinity levels can be depleted going into secondary treatment. This alkalinity depletion often goes unnoticed because it is masked by pH elevation, which is often assumed to be linked proportionately to alkalinity.

Moreover, unless pH is carefully monitored at BOTH bio-reactor influent AND effluent, pH spikes and instability in the aeration basins and BNRs leads to inefficient biological processes. This inefficiency prompts many operators to increase MLSS, MCRTs/SRTs, and oxygen addition, which in turn leads to increased energy and solids disposal costs.

THIOGUARD’s specific chemical and physical properties ADD alkalinity to the water system, moderately modify pH, stimulate biological activity and improve solids quality.

Imitation is the Sincerest Form of Flattery

With growing needs for alkalinity in nitrification and BNR processes, operators are often faced with the challenge of supplying higher levels (in excess of 30 mg/L) of alkalinity without upsetting processes or depleting the chemical budget.

For years, competitors have claimed that our odor control strategy would either not work at all or would lead to downstream flare off of H2S, but academic and field studies have confirmed the superior performance of THIOGUARD’s unique chemical and physical properties in reducing H2S and other organic odors AND improving performance of wastewater treatment plants. In recent years, some competitors have tried to duplicate our results using caustic soda or lime, ignoring that these hydroxides lack the physico- chemico properties of technical grade magnesium hydroxide...but the efforts only help validate the successes of THIOGUARD.


PROPERTY 50% NaOH 30% Ca(OH)2 60% Mg(OH)2
% Hydroxide 42.5 45.9 60.3
Solubility(H2O, g/100ml) 42 .0185 0.0009
Per Million Gallons 1,750 tons 7.7 tons 75 lbs
Reactive pH 14 12.5 9.0
Freezing Point oF 61 32 32
Weight Equivalency 1.37 1.25 1

To find out more, please contact your regional manager.



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