The usual discussion of sulfide removal emphasizes iron chemistry and fails to mention other reaction products resulting from the chloride and sulfate being released when the iron combines with the sulfur to form iron sulfide, a black precipitate. Additionally, iron strips alkalinity when used inside the plant. If there is also a chronic phosphorus deficiency, the result is needless organism death and higher plant biosolids disposal costs. The focus in this write-up is on odor control complications with iron sulfate.
WHAT HAPPENS WHEN IRON SULFATE IS USED FOR ODOR
CONTROL IN WASTEWATER?
1. The first step in the reaction produces iron sulfide as a precipitate and sulfuric acid. If this were all that happens in wastewater, iron would be fed at a stoichiometric rate of 4.5 lbs. of ferrous sulfate to remove 1 pound of H2S. This turns out not be the case and 2 to 3 times that amount is necessary for sulfide reduction. Why? There are competing reactions in wastewater that will consume iron. Phosphorus, chlorides, sulfates, hydroxide, carbonate, oxygen and other common compounds compete for the available iron.
2. Now let us examine what may happen to the H2SO4 that is produced as a reaction product. First, it is corrosive and works to lower the pH in the wastewater. Second, sulfuric acid rapidly dissociates and will allow SO4-2 to be used as an oxygen source by the sulfate reducing bacteria producing more H2S.
3. Theoretically, iron sulfate could produce as much sulfide as it removes stoichiometrically, which then must be removed with additional iron. Lowered wastewater pH will also allow more H2S to be released as gas.
COMPARISON TO THIOGUARD CHEMISTRY
In contrast, Thioguard does nothing to lower the pH of the wastewater, produces no reaction products that can lead to additional sulfide production, and produces no sludge to settle out in the system or to be dewatered at the WWTP. The reaction is as follows:
The Magnesium binds the sulfide in a similar manner to iron and it will not be released unless the pH drops to 5.5 which is not normal in wastewater. More importantly, Thioguard is preventative and controls the formation of sulfide by increasing the pH and retarding the Sulfate Reducing Bacteria activity.
CHOOSING THIOGUARD WILL:
For a nearly one million gallon a day plant in Lambertville, NJ the good news just kept on coming. First, they started using Thioguard to condition their primary sludge to reduce odors from the plant. This worked so well, they began to ask, “Where else can Thioguard be applied?”
As the winds whipped in early Spring, it was discovered that a significant amount of odor was coming from the nearly quarter million gallon sludge holding tank at their site. Since Thioguard worked to reduce the primary sludge odors, they wondered if it would work for stored sludge waiting to be pressed.
After establishing a stable pH range of 7.5-8.0 s.u., with just a couple of gallons a day, odors were reduced to satisfactory levels… and then something very interesting happened. Not only were odors in the press building reduced, but the press cake was drier. On average nearly 20-40% drier.
Why? Thioguard is technical grade magnesium hydroxide: a buffered source of alkalinity that is used to increase pH. Elevated pH promotes better polymer performance. Not only that, but due to divalent cation bridging, the press supernatant quality can be clearer as well. Any remaining alkalinity is then returned in the supernatant to the headworks of the plant.
The Lambertville results were recently verified on a much larger scale through bench testing at a treatment plant in Newark, Ohio. The chart below illustrates expected typical annual cost savings in hauling and tipping after the addition of Thioguard at a 100 MGD plant. The bottom line? For every 1% improvement in cake solids, the plant would save approximately $214K in hauling and tipping costs. In multiple tests, the use of Thioguard consistently resulted in 5% to 13% improvement in cake solids with greatly reduced water weight. Drier cake solids means less to haul, and fewer loads translates directly into operational savings.
The influence that magnesium has on the way our bodies process vitamin D has big implications for bone health. The studies suggest that taking a magnesium supplement can help people reach their desired level of vitamin D faster. Not only can they reach that level faster, but magnesium may also more effectively facilitate the actions of vitamin D on bone health. An additional 200 mg of magnesium is all it should take to get the average person up to an adequate intake.13% improvement in cake solids with greatly reduced water weight. Drier cake solids means less to haul, and fewer loads translates directly into operational savings.
Magnesium is important in regulating levels of vitamin D.
Many Americans fail to get enough magnesium as well
as vitamin D in their diet.
Improving levels of both minerals could improve bone strength
and lower risk of cancer and heart disease.
For more information about the health benefits of Magnesium click here
With the THIOGUARD® Advantage Package, it’s your process Mg+nified!(TM)
Benefits outlined in this table require Thioguard’s superior technical grade magnesium hydroxide combined with the Thioguard Advantage Package of consulting, performance testing, inventory control and delivery services.
THIOGUARD BENEFITS IN YOUR COLLECTION SYSTEM
Odors | Corrosion | FOG (Fats, Oil, Grease) | Air Relief
Comments: Customers can “dial in” the desired level of treatment. Best acid neutralization prevents premature infrastructure corrosion & replacement, adds numerous benefits downstream. Thioguard can reduce FOG related SSOs. Thioguard can reduce pumping costs on long force mains.
THIOGUARD BENEFITS IN WASTEWATER TREATMENT
BOD (Biological Oxygen Demand) | TSS (Total Suspended Solids)
NH3 (Ammonia) | Phosphorus | FOG
Comments: Thioguard is the only liquid phase treatment used in the collection system that can enhance the treatment process at the Wastewater Treatment Plant.
THIOGUARD BENEFITS IN BIOSOLIDS TREATMENT
Digestion | CH4 Methane Production | Enhanced DewateringComments: Thioguard added to the collection system or sludge digestion process can also help the digestion and dewatering processes at the Wastewater Treatment Plant.
THIOGUARD BENEFITS IN NUTRIENT REMOVAL/MODIFICATION
Comments: Thioguard added to the collection system or sludge digestion process can also help the digestion and dewatering processes at the Wastewater Treatment Plant.