| Thioguard Detailed Summary For
over 35 years, Premier Chemicals LLC has been a leader in magnesia production and
application, serving a wide range of industrial, municipal and agricultural markets. A
primary manufacturer of magnesium oxide and magnesium hydroxide in the United States, we
have two major production facilities: Gabbs, Nevada and Port St. Joe, Florida; and several
toll manufacturing/distribution centers strategically placed throughout the US. The
Thioguard division has been selectively staffed to handle the wide ranging needs of
utility wastewater systems.
As an innovative company, we have a strong commitment to research and development. A
significant amount of resources is committed to laboratory and field research, as well as
to partnerships within Academic and Trade organizations. The Premier Chemicals R&D
Center is located in Bettsville, Ohio and our Corporate Headquarters is in West
Conshohocken, Pennsylvania, just outside of Philadelphia.
Introduction
|
 |
| 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. |
 |
Direct Addition for Odor Control
Added directly to sewers, 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.Major Advantages
- Non-Hazardous
- Safe to Handle
- Environmentally safe
- Cost-effective
- Treats Odors, Corrosion and FOG
Sulfur compounds are the primary source of odor, whether in the inorganic form, H2S, or
in one of many organic forms (VOSCs), such as mercaptans, DMS or DMDS.
|
 |
H2S Increase
25 years ago, odor and corrosion were considered nuisance issues. Today, they
have become serious problems that adversely impact our quality of life. — What
changed?
Most municipalities (testing for sulfides) observed a steady rise from the early 1980s
to mid 1990s. These changes were subtle, yet very significant to odor and corrosion.
Many municipalities had never tested for sulfides, but increases of 1500% were not
uncommon, where they were measured (see figure 1)1.
A variety of factors have contributed to increased sulfides:
- Longer retention times caused by urban sprawl and centralized treatment strategies
- Low flow plumbing fixtures and other water conservation measures
- Legislative changes impacting wastewater chemistry and biochemistry
To protect public health, the EPA enacted the 1983 Categorical Pretreatment Act.
This legislation severely reduced metals limits from industrial discharges.
Analysis of influent metals clearly shows the change in chemistry caused by pretreatment. |
fig. 1
|
| In the absence of metals, bacterial activity
increases. At dissolved oxygen concentrations above 1 mg/L, aerobes reduce organic
matter via oxidation. Very little sulfide is produced at this stage. Without
metals to control bacterial growth, oxygen is more quickly depleted. At <0.1mg/L
dissolved oxygen, anaerobic bacteria reduce sulfates to sulfides.
Although reducing metals was necessary to protect public health, pretreatment has
contributed significantly to increased odors and accelerated sulfide related corrosion.
Sewage has changed. If your odor and corrosion control program hasn't improved,
expect more unhappy customers.
|
 
|
| 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. |
SRB Growth
|
The Faces of Thioguard
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.
| 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.
|
 
|
Modes of Action
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.):
Phases:
THIOGUARD’s 3 Distinct Phases makes it unique among its alkaline peers, and highly
suited to biological treatment systems.
I
Mg(OH)2
II
MgOH+ + OH-
III
Mg+2 + 2OH-
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
- 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
- facilitating the transport and stabilization of P during ADP/ATP conversion and ATP
hydrolysis, and
- 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. |
Treatment Plants
Direct addition of THIOGUARD to a collection system provides the following benefits at
the Treatment Plant:
- Odor Control
- Corrosion Control
- Nutrient Addition
- 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 in to
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.
Magnesia 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.
Call us today for an evaluation…
1-800-227-4287
>>> Back to
Thioguard Home <<<
|
