The Sulfur Cycle in Wastewater Systems
- Sulfate Reducing Bacteria - these bacteria under anoxic conditions use sulfate as electron acceptor to degrade organics.
- Sulfur Reducing Bacteria - these chemotrophic bacteria obtain energy by reducing sulfur into sulfide. In most...
- Sulfur Oxidizing Bacteria - chemotrophic bacteria with the metabolic ability to convert reduced...
What are reduced sulfides in wastewater?
Reduced sulfides in wastewater have a high chemical oxygen demand and are toxic to Ammonia Oxidizing Bacteria (AOB) that are required for ammonia removal. Hydrogen Sulfide - a corrosive, highly toxic gas, H2S is released from water into the atmosphere as pH drops in wastewater.
How can sulfur be used in wastewater treatment?
For instance, sulfur sources can easily be incorporated into municipal wastewater systems through seawater toilet flushing or directly introducing highly sulfate-laden waste streams such as desalination brine at the wastewater treatment plant.
What are the chemical methods for reducing sulfate concentration?
Chemical methods for reducing sulfate concentrations include: The simplest technology for reducing high sulfate concentrations is lime precipitation.
What is sulfate reducing bacteria?
Sulfate Reducing Bacteria - these bacteria under anoxic conditions use sulfate as electron acceptor to degrade organics. If you have oxygen or nitrate in the system, sulfate reducing bacteria are outcompeted by harmless bacteria that obtain more energy using oxygen or nitrate as an electron acceptor.
What does sulfate get reduced to?
sulphideSulphate is reduced to sulphide by sulphate-reducing bacteria in bioreactor one using hydrogen as an electron donor. Subsequently, the sulphide is used to precipitate the heavy metals. An excess of sulphide is converted to elemental sulphur by sulphide-oxidizing bacteria in bioreactor two.
How is sulfate removed from wastewater?
Membrane filtration (like reverse osmosis (RO), nanofiltration (NF), and ultrafiltration (UF)), is one of the most effective technologies for removing sulfates from industrial process and wastewaters.
How do you remove sulfide from wastewater?
Hydrogen peroxide (H2O2) is applied to the wastewater system usually where there is a retention time of less than 5 hours and at least 30 minutes prior to the point where the hydrogen sulfide is released. Hydrogen peroxide is a stronger oxidant than either chlorine or potassium permanganate.
How are sulfate-reducing bacteria treated?
If hydrogen sulfide odor is a result of sulfur-reducing bacteria, performing a shock chlorination procedure may reduce, but not eliminate, the bacteria. This process involves placing a strong chlorine bleach solution into the well. Taps then are opened to draw chlorinated water into all parts of the plumbing system.
How are sulfates removed?
Ways to Treat Sulfate Reverse osmosis pushes water through a membrane with tiny pores. The membrane stops many contaminants, including sulfate, while allowing water to pass through. Reverse osmosis usually removes between 93 and 99 percent of the sulfate in drinking water, depending on the type of treatment unit.
How do you separate sodium sulfate and water?
because the solubility of the sodium sulfate decreases at higher temperatures and the sodium sulfate decahydrate does not decompose at lower temperatures. Then the water can be removed from the soluble sodium sulfate by evaporation at an elevated temperature to form the anhydrous sodium sulfate product.
What causes sulfides in wastewater?
Hydrogen sulfide (H2S) results from septic conditions during the collection and treatment of wastewater. This toxic, colorless gas, known for its rotten egg smell, is produced by the biological reduction of sulfates and the decomposition of organic material.
What is the most common source of sulfide in wastewater?
sulfateIt is also present in rainfall, primarily over metropolitans areas, but the most common source of sulfide is in domestic wastewater as sulfate. An industry can also generate sulfate/sulfide wastes that may contribute to sulfide levels in wastewater such as: Sulfate- Seen in sea food processing or fermentation plants.
How can H2S be prevented?
Eye/Face Protection: Wear chemical safety goggles. A face shield (with safety goggles) may also be necessary. Skin Protection: Wear chemical protective clothing e.g. gloves, aprons, boots. In some operations: wear a chemical protective, full-body encapsulating suit and self-contained breathing apparatus (SCBA).
How is hydrogen sulfide removed from water?
Aeration. Since hydrogen sulfide occurs as a gas in water, it can be physically removed by injecting air into the water and allowing the gas to escape. Aeration units may work by cascading, bubbling, or stripping the gas from the water. Aeration may be advantageous because it does not add chemicals to the water.
Why are sulfate-reducing bacteria important?
Sulfate-reducing bacteria (SRB) facilitate the conversion of sulfate to sulfide with the sulfides reacting with heavy metals to precipitate toxic metals as metal sulfide. These metal sulfides are stable and can easily be removed from AMTW (Cohen, 2006).
What causes sulfate-reducing bacteria?
Certain bacteria can take advantage of the oxidation or reduction of sulfur because such chemical changes are a source of energy. Sulfur-reducing bacteria thrive when sulfate-rich water moves into a low oxygen environment.
What is the importance of sulfates in water quality?
New developments in water quality legislation are making it increasingly important for companies to look to new technologies for treating their feed and waste water streams. One area of growing interest is the presence of sulfates. Sulfates are a form of salt that cause scaling in equipment, resulting in reduced performance ...
How does biological sulfate reduction work?
Biological sulfate reduction requires a large input of energy to raise the temperature of feed water, and generates a residual waste that can be toxic. Passive biological systems leave a large environmental footprint, and are suitable for only small flows of water.
How does a water filter work?
They operate by pushing water through a series of micro filters that capture contaminants in the form of a supersaturated liquid. Once the system collects the residual liquid, the liquid is then heated to evaporate the water content, producing a crystalline byproduct that often requires special handling and disposal.
Why is water recovery rate low?
First, water recovery rates can be low because of the complex cocktail of contaminants typically found in industrial wastewater. It is not uncommon to have up to 50 percent of the water end up in the waste product stream. Second, membrane processes can have high energy costs.
What is sulfate in water?
Sulfates are a form of salt that cause scaling in equipment, resulting in reduced performance and premature equipment failure. This is a particular concern in feed water for boiler furnaces and condensers in power generation facilities.
How can energy facilities prevent scaling and corrosion?
In addition, facilities can prevent scaling and corrosion by treating feed water, reducing their equipment maintenance costs. With the current government's renewed focus on the environment, the energy sector has an opportunity to break new ground in waste water treatment and reuse.
Can membrane systems treat contaminated water?
Typically these technologies are either not able to treat contaminated water to a level which complies with new regulations and standards that are being imposed on industry, or they bring either environmental or economic disadvantages. For example, membrane systems have been used for treating wastewater streams in a number of industries, ...
How to keep sulfides in water?
Sulfides can be kept in water phase by increasing pH, adding ferric or sulfide scavengers to the collection system. This is a quick fix, but does not solve generation of sulfides in anoxic/anaerobic zones.
What is the sulfur cycle in wastewater?
The Sulfur Cycle in Wastewater Systems 1 Sulfate Reducing Bacteria - these bacteria under anoxic conditions use sulfate as electron acceptor to degrade organics. If you have oxygen or nitrate in the system, sulfate reducing bacteria are outcompeted by harmless bacteria that obtain more energy using oxygen or nitrate as an electron acceptor. 2 Sulfur Reducing Bacteria - these chemotrophic bacteria obtain energy by reducing sulfur into sulfide. In most wastewater, these are less common than the Sulfate Reducing Bacteria that use sulfur as an alternative electron acceptor. You would find these organisms in mines, subsea volcanic vents, hot springs, and oil formations. 3 Sulfur Oxidizing Bacteria - chemotrophic bacteria with the metabolic ability to convert reduced sulfur species into sulfur and sulfate. While some species can use nitrate as the electron acceptor, most sulfur oxidizers require oxyen as the terminal electron acceptor. If taken to conclusion, you produce sulfuric acid (H2SO4). These are the well documented sewer corrosion bacteria that can form if a vapor phase H2S concentration reaches sufficient levels. In wastewater, Sulfur Oxidizing Bacteria (SOB) are vital to removing reduce sulfides. This does require alkalinity to buffer the system from pH drop. Common genera of wastewater SOB include Thiobacillus, Anwoodia, Paracoccus, and Thiosphaera.
What is sulfur oxidizing bacteria?
Sulfur Oxidizing Bacteria - chemotrophic bacteria with the metabolic ability to convert reduced sulfur species into sulfur and sulfate. While some species can use nitrate as the electron acceptor, most sulfur oxidizers require oxyen as the terminal electron acceptor. If taken to conclusion, you produce sulfuric acid (H2SO4).
How do sulfur reducing bacteria obtain energy?
Sulfur Reducing Bacteria - these chemotrophic bacteria obtain energy by reducing sulfur into sulfide. In most wastewater, these are less common than the Sulfate Reducing Bacteria that use sulfur as an alternative electron acceptor. You would find these organisms in mines, subsea volcanic vents, hot springs, and oil formations.
What is the color of sulfide in septic system?
This form of sulfide can bind with iron and give the dark gray to black color seen in septic wastewater. Sulfides are more soluble in water with a higher pH. Reduced sulfides in wastewater have a high chemical oxygen demand and are toxic to Ammonia Oxidizing Bacteria (AOB) that are required for ammonia removal.
What is the most common form of sulfur?
Sulfate - one of the most common forms of sulfur found in the environment. Sulfate is used by plants and is an important micronutrient for life. Sulfur - the yellow powder or rock form of sulfur. Reduced Sulfides - often seen as S= or in analytical tests as Total Reduce Sulfides. This form of sulfide can bind with iron and give ...
How are sulfides formed?
Unless you have an influent source of reduced sulfides, most sulfide is formed in water under anoxic/anaerobic conditions that favor SRB growth. The best solution for sulfides forming in the system is to disfavor the growth of SRB.
What are the two most significant factors that contribute to the growth of sulfuric acid in wastewater?
The two most significant factors for this are 1) sulfuric acid is one of the world's largest industrial chemicals in terms of volume and its extensive utilization in many industrial processes, 2) mining and metallurgy or application of sulfur containing minerals all result in sulfate-laden wastewaters.
What is the sulfur cycle?
The sulfur cycle connects with carbon, nitrogen and phosphorus cycles, thus a new platform of sulfur based biotechnologies incorporating sulfur cycle with other cycles can be developed, for the removal of sulfate and other pollutants (e.g. carbon, nitrogen, phosphorus and metal) from wastewaters.
What is the pH range of SRB?
SRB can grow in a wide range of environments spanning a temperature spectrum of at least 0−100 °C, salinity from freshwater to halite saturated solutions and a pH range of 3–9.8 ( Mackenzie, 2005 ). SRB even could be found in aerobic habitats ( Wieringa et al., 2000 ), despite their obligatory anaerobic metabolism. This provides a wide range of opportunities to develop SRB-based or related treatment technologies, in which anaerobic sulfate reduction has been recognized as the key step in all sulfur related waste treatment processes ( Huisman et al., 2006 ). Sulfide, generated from organic degradation by sulfate reduction, can serve as an electron donor for nitrogen removal via autotrophic denitrification or as an agent for subsequent precipitation of heavy metals ( Kieu et al., 2011 ). In more cases, sulfide is oxidized chemically/biologically to elemental sulfur and recovered, which can be used as raw material for sulfuric acid production or a substrate for the bioleaching of metal-polluted soils and sediments ( Vallero, 2003, Vallero et al., 2003 ). But some issues accompanied with elemental sulfur production such as local corrosion, clogging of pipelines and valves etc. ( Fang et al., 2008) still needed to be addressed.
What compounds can be used as electron acceptors for SRB?
Nitrate, nitrite, ferric and other compounds (e.g. fumarate, DMSO) can also serve as electron acceptor for some SRB species (Table 2). In conventional anaerobic bioreactors, SRB biomass is either suppressed (Visser et al., 1993, Lens et al., 1998, O’Flaherty and Colleran, 2000), or activated to suit specific purposes.
Can methane be oxidized?
Methane can also be oxidized with equimolar amount of sulfate, yielding carbonate and sulfide respectively (Nauhaus et al., 2002). Marine gas hydrate areas or even hypersaline seep sediments (40−225 Cl g∙L−1) are the evident zones for anaerobic oxidation of methane (AOM) with sulfide production (Avrahamov et al., 2013).
When will sulfate be available?
June 2, 2020. There are many sulfate treatments available, with different advantages and disadvantages. Factors for consideration include capital and operational costs, solid vs. liquid brine reject for disposal, if the need is seasonal or year-round, and suitability for adverse operating conditions.
How do sulfates get precipitated?
Sulfates can be precipitated by adding low solubility counter ions such as barium or calcium. Our BrineRefine system performs chemical precipitation in a smart, automated way to prevent overdosing. If inlet water chemistry changes, so does chemical dosing. BrineRefine enables smart selective precipitation and is:
What is saltworks sensor?
Saltworks can provide automated, real-time sensors for sulfate ions. This live data can then be used to optimize a sulfate treatment process through: Bypassing a portion of the flow around the treatment plant, and blending to meet a treatment goal.
Can sulfates be removed?
Sulfates can be targeted for removal, without needing to treat all dissolved mass in an entire flow. Targeted treatment saves money. For seasonal sulfate challenges, chemical precipitation treatment may keep capital investment low, with chemical addition operating costs for only part of the year.
Is sulfate dangerous to humans?
Sulfate Challenges. Sulfates are of concern in many processes e.g. mining, oil & gas, fertilizers, and more. Although not generally very dangerous to humans, high sulfate levels can be regulated to protect the environment. Sulfates can be targeted for removal, without needing to treat all dissolved mass in an entire flow.
Can saltworks be regulated?
Sulfates can be regulated in some discharges and require cost-effective management. Saltworks can help you to monitor and moderate sulfate levels in wastewater flows.
How to remove sulfates from water?
Removing sulfates with distillation. With distillation, the sulfate-saturated liquids are heated to boiling, then the resulting water vapor is cooled in a condenser, and the purified water is captured in a sterile container. Where some separation processes remove the contaminant from the liquid stream, distillation removes the liquid from ...
How much reduction in sulfate with hydrated lime?
Many facilities will see an 80% reduction in sulfate with hydrated lime before they even need to start worrying about the metals, which will minimize the toxicity of initial secondary wastes and sludge created in the precipitation process.
What is the best ion exchange system for removing sulfates?
When it comes to the ideal ion exchange system for removing sulfates, you’ll typically want to see a resin system filled with a combination of cationic (to remove calcium and magnesium) and anionic resins (to then remove sulfates). IX process works best for polishing and with a background stream that is low in other competing salts.
How effective is adsorption?
Adsorption is effective for removing sulfates at relatively low concentration levels and can be achieved with technologies like granular activated carbon filtration. Although the technology is generally cost-effective, the media will likely need to be changed out often, which can add up in both cost and time.
What is the process of adsorption?
The process consists of passing a liquid stream through some type of porous, adsorbent media, and when the soluble contaminants are more attracted to the adsorbent media than they are to the water in the stream, the contaminants bind to the surface of the media while the liquid effluent flows through. Adsorption is effective for removing sulfates ...
Where are sulfates found?
These minerals typically include sulfates, which are present in almost every type of water found in nature, including groundwater, oceanwater, and rainwater, and even crude oil and brines. They are also present in many industrial wastes as a result of the facility’s process—mainly in mining and mineral processing applications where sulfates are ...
Is sulfate harmful to the environment?
In high concentrations, sulfates can be harmful to human health and the environment and corrosive to pipes and equipment, so they are something many industrial facilities look to remove whether the intent is for release into the local POTW or environment or reuse in the facility’s process. You might be wondering, what are ...
What is the standard for sulfate in water?
However, the secondary standard for drinking water in the U.S. is 250 mg/L and concentrations above 600 mg/L may create laxative effects. In Minnesota, future sulfate discharges may be limited to as low as 10 mg/L (an unenforced standard that is currently under review) to protect wild rice habitat. Guidelines for sulfate levels around the world are shown in Table 1.
What is the solubility limit of calcium sulfate?
Adding calcium as pebble lime, hydrated lime, or limestone can precipitate calcium sulfate (gypsum) and reduce sulfate concentrations to the solubility limit of 1,500-2,000 mg/L. Concentrations already below this level will generally be unaffected by lime addition.
What is biological treatment?
Biological Treatment Technologies. If metals are present in the water to be treated, biological treatment has the advantage of being able to remove them along with sulfate via metal sulfide precipitation. Biological processes for removing sulfate include: The THIOPAQ™ process.
How is sulfide produced?
In the THIOPAQ process developed by the PAQUES company (Netherlands), sulfide is produced by contacting the sulfate-containing stream with sulfate-reducing bacteria (SRB) in the presence of a carbon source (electron donor) such as hydrogen gas or acetic acid. The reaction for hydrogen is:
What are the disadvantages of barium addition?
Typical salts used are barium chloride and barium carbonate. The disadvantage of barium addition is the relatively high chemical cost; a recent price for barium chloride was about $2/lb. The Cost-Effective Sulfate Removal (CESR) process was originally developed as the Walhalla process in Europe in the 1990s.
