Direct Addition for Odor Control

Magnesia chemicals are safe. They offer environmentally responsible solutions to problems related with acid neutralization, biological treatment and biosolids disposal and handling. Premier Chemicals produces over 300,000 tons of MgO and Mg(OH)₂ products annually, developing and maintaining more grades of magnesia chemicals than any other producer.

Premier Chemicals is proud to offer the THIOGUARD^® family of products and services to control odor, corrosion, FOG, and enhance treatment for municipal wastewater systems.

THIOGUARD^® is a safe, alkaline slurry, similar to milk of magnesia. Think of it as industrial-strength milk of magnesia for your sanitary system.

Major Advantages

• Non-Hazardous
• Safe to Handle
• Environmentally safe
• Cost-effective
• Treats Odors, Corrosion and FOG (fats, oils, and grease)
• Positive plant benefits for Nitrification, biosolids production, digestor performance and chlorination

Direct Addition for Odor Control

Added directly to wastewater collection systems, THIOGUARD^® stops odors by preventing the formation of H₂S, hydrogen sulfide gas.

Crown Spray for Corrosion Control

Surfaces periodically sprayed with THIOGUARD^® are gently neutralized and protected from corrosion.

Surface pH/Corrosion

H₂S gas generated in the sewer system is converted by Thiobacillus bacteria residing on concrete and metal surfaces above the waterline to corrosive sulfuric acid. This acid attacks exposed concrete and metal surfaces.

A simple method to measure relative strength of the sulfuric acid and rate of decay of the infrastructure is surface pH testing, conducted with contact pH paper on the wetted surfaces inside wetwells, manholes and sewer lines.

The measured surface pH can then be used to correlate corrosion rate and subsequently, remaining years of useful life of a concrete structure.

The use of THIOGUARD^® by direct addition has been demonstrated to elevate surface pH from a highly corrosive pH = 1-2 up to a more desirable range of pH = 5-7.

Under some circumstances, THIOGUARD^® CROWN SPRAY can be applied to surfaces to provide instant neutralization and a protective, sacrificial barrier on infrastructure surfaces.

When THIOGUARD^® is injected into a wastewater stream, it enters in 3 distinct phases as shown below. These phases are a result of magnesium hydroxide’s unique solubility and reactivity properties and the way it reacts to other qualities of the wastewater (i.e. pH, CO₂ concentration, free acid H⁺, biological activity, etc.):

Phase I (Mg(OH)₂):

Magnesium hydroxide as a particle has a solubility of 9 mg/L. While the solubility is considered relatively low, the particle, having a surface area of nearly 1 acre per gallon, is reactive and/or absorptive to acids, H₂S, CO₂, and some organics. The particle has a positive surface potential and is capable of improving flocculation and settling. In the collection system, it slowly dissolves as it reacts with H₂S, CO₂, acids, FOG, etc… At the plant, it usually enters the biosolids stream through Primary settling. That which passes through to Secondary processing is typically fully consumed by biogenic acids and CO₂ produced during secondary treatment.

Phase II (MgOH⁺ + OH^-):

This ionic phase is transitional from the particle phase to soluble phase and is indicative of magnesium hydroxide’s unique abilities to "buffer" both acids and bases. This species also explains why pH’s in a magnesium hydroxide supplemented stream do not accurately reflect the total amount of hydroxide present (neutralizing capability), since only the first ionized OH^- contributes to the pH values. This is why pH, OH^- and total alkalinity are critical measurements collectively rather than individually.

Phase III (Mg⁺² + 2OH^-):

This ionic phase is the result of complete dissolution of the Mg(OH)² molecule. Complete dissolution occurs as a result of free proton (H⁺) acid neutralization or the formation of bicarbonate (HCO₃^-) from the reaction of OH^- with CO₂. Once dissociated, the divalent magnesium cation (Mg⁺²) aids wastewater treatment by 1) being utilized as a bridging particle for improved flocculation, settling and clarification in both Primaries and Secondaries and improved dewatering and densification in bio-solids processing 2) facilitating the transport and stabilization of P during ADP/ATP conversion and ATP hydrolysis, and 3) supplementing biological nutrients.

Residual OH^- is reflected in pH readings. Since the reactive pH is 9, it "buffers" strongly in the pH range between pH 8 and 9, and most preferably near 8.4. As pH rises, magnesium shifts back towards Phases I and II. This is how magnesium hydroxide is extracted from brines and seawater for commercial production.

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 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.

Treatment Plants

Direct addition of THIOGUARD^® to a collection system provides the following benefits at the Treatment Plant:

• Odor Control
• Corrosion Control
• Nutrient Addition — Essential Element for Cell Metabolism
• Alkalinity Supplementation
• pH Control

THIOGUARD^® improves secondary wastewater treatment for BOD (Biological Oxygen Demand), TSS, Turbidity, ammonia and phosphorus, while enhancing sludge growth and settling characteristics, and improving biosolids treatment, dewatering and disposal.

Nitrogen compounds are the primary cause of pH/alkalinity degradation in treatment plants, with pH depletion being the major cause of activated sludge bulking, high SVI (Sludge Volume Index), and disinfection problems.

Digestion, Nitrification, Alkalinity and pH Control

Aerobic digestion and nitrification in the activated sludge process depletes natural alkalinity and can cause pH depression. A drop in pH can arrest second-stage nitrification and cause major upset conditions in the secondary clarifiers, resulting in effluent violations for BOD, TSS (Total Suspended Solids), ammonia, etc...Likewise, adequate alkalinity insures biological process stability and improves methane gas production of anaerobic digesters. THIOGUARD^® provides both alkalinity and pH stability for biological processes.

Secondary Clarifiers and SVI

Periodic pH problems interfere with the growth of floc-forming activated sludge. When this happens, sludge bulking and unwanted denitrification may cause SVI levels to increase. THIOGUARD^® provides both pH stability and divalent cations, which improve the Monovalent/Divalent (M/D) Cation Ratio.

Biosolids

These divalent cations and pH stability provided by THIOGUARD^® also improves dewatering/drying performance, polymer use and odor reduction, whether using drying beds, filters, or centrifuges.

Chorine Disinfection

Incomplete nitrification allows nitrite (NO₂^-N) to pass through the clarifiers and into the chlorine contact tank, consuming chlorine at accelerated rates. Moreover, low pH and inadequate alkalinity can hinder rapid hydrolysis of Cl₂ gas, reducing disinfection efficiency. THIOGUARD^® facilitates complete nitrification and provides pH stability for efficient chlorination.

pH Control

Magnesium hydroxide slurry has long been used to maintain pH during nitrification. Because alkalinity is released slowly, there are no hot spots to kill Nitrosomonas or Nitrobacter bacteria.

And since the by-products of magnesium hydroxide reactions are soluble salts, THIOGUARD^® does not increase the amount of sludge produce in the plant. In fact, studies have shown THIOGUARD^® may actually reduce sludge production by 10-20%.

Summary

As sulfide levels have increased, many chemical options become ineffective or too costly. THIOGUARD^® offers municipalities a new weapon in the fight against odor, corrosion, FOG and wastewater treatment.

The comparisons presented between THIOGUARD^® and some of the most common, competitive chemical products in the market are misunderstood in that THIOGUARD^® provides a Total System Treatment approach that many of our competitors cannot. These competitor chemicals fall into the general categories of oxygen providers, metal salts, and pH adjusters. Other common methods for odor control include bacteria addition and air scrubbers, biological, physical, or chemical.

Selection of an appropriate odor control strategy is a complex process that must consider many factors. We believe THIOGUARD^® is well suited for applications to safely control odors and acid gases such as hydrogen sulfide, and to enhance biological treatment processes.