Tyrimas su flokuliantais jar test: praktinis vadovas optimalioms koagulantų ir flokuliantų dozėms nustatyti
Water treatment jar testing is a method of mechanically and physically testing chemical treatments on samples of wastewater to determine the optimal chemical treatment and related chemical dosages for a specific water or waste stream. Essentially, jar testing is a scaled down version of a water treatment system. It is great for getting a “snapshot” of what will be needed to treat the water on a larger scale. The jar test is the single most important tool used in determining the best chemical path for achieving individual water treatment goals. Through jar testing, you are able to test how specific chemicals will function within your treatment system in order to determine what chemicals are best for your specific application. The test not only saves time, but it saves money, as well.
Jar testing is also useful because it can help you determine what a specific waste stream consists of, along with whether the sample of wastewater will require a pH adjustment, filtration, or different chemical load than originally expected. Every wastewater sample has a unique composition, requiring a unique treatment. To do extensive jar testing, it is best to use what is called a gang stirrer. (We recently broke down the pros and cons of six stirrers on the market.) A gang stirrer is an instrument that can stir multiple beakers of water at a time, so multiple different chemicals or dosages can be tested on a sample at once. The instrument also ensures that the mixing is uniform throughout the samples. However, you can still complete a jar test without access to a gang stirrer.
Once you have your stirring system setup, you will need to acquire the chemicals that you plan to test on the water. The chemicals should include a coagulant, flocculant, or both. Typically, when completing a jar test, two different chemicals are used. The pH of the wastewater being used in the test may also need to be adjusted. pH Adjust - Sometimes coagulants and flocculants will not work at a certain pH. Sometimes an oily waste stream requires what we call an, “Acid crack.” This is when you adjust the pH of the oily water with acid, and those oils are pulled out of the water. This makes treatment much easier. After acid cracking, you can bring the pH back up to a desired level with a base or caustic soda.
Coagulants have positively-charged molecules and, when added to wastewater, they destabilize the negatively-charged particles in the water. The process of coagulation creates “pin flocs.” Pin flocs are small, neutrally-charged molecules. Flocculants have longer polymer chains than coagulants do; therefore, they link more particles to a polymer chain. Flocculants will create “macrofloc,” which are clumps of solids larger than pin flocs. To begin, make sure you understand the goals of your test. What are the treatment goals for the water? What is currently being used for treatment? Is the water in a DAF tank? Will it be run through a filter? All of these questions can greatly aid in the jar testing process and save you time.
Next, collect a representative sample of the waste water. A representative sample means the sample has been mixed very well, and that you are collecting from the bottom up. Having a representative sample ensures you are getting a full profile of the wastewater. If you collect water from the top of a sample, you won’t be getting material that has settled or that has a greater density.
Now, place your water into 4-6 600 mL beakers. Fill the beakers up to 500 mL. Place your samples on the instrument you are using to mix, such as a gang stirrer with numerous paddles. Set the mixing time on the stirring instrument to reflect how it would be mixed in treatment, or set a timer if you are without a gang stirrer.
Gather your chemicals. This can include pH adjusters, such as sulfuric acid and caustic soda, as well as your coagulants and flocculants. If the water is oily, you may also have an oil emulsifier. While the water samples are being stirred, check the pH of the sample. This will help determine if a pH adjustment is needed. Caustic soda will increase the pH, and an acid such as sulfuric acid will lower the pH. We recommend checking your coagulants and flocculants to see what pH they work best at.
Review any necessary background information, as well. Once the optimal pH is achieved, it is time to screen your coagulants. The coagulants need to be diluted in order to accurately dose them. This is done by adding 10% of the coagulant to 90% water and mixing, creating a 10% coagulant solution. With this solution, every 1 mL added to the 500 mL of water equates to 200 parts per million (PPM) of chemical. Next, line up the coagulant solutions that you wish to test, one in front of each beaker. In each beaker, add 10 ppm of chemical, or one drop from 1 mL syringe. Mix at 100 rpm for 1 minute. Note that rpm and mix times will vary depending on actual operating parameters. After 1 minute, stop mixing and observe. At the coagulation phase, we are looking for small or micro-particles often referred to as a “break”. The amount of particles combined with the level of clarity in between those particles can indicate adequate chemical dosing.
Once it is determined that an optimum coagulation dosage has been achieved, the next step is to dilute a flocculant. The flocculant needs to be mixed with water to make a solution. Typically, a 0.25% solution in water is created. The solution can be achieved by taking 1.25 ml of flocculent, adding it to 500 ml of water, mixing thoroughly by shaking or mixing. Adding 1 ml of a 0.25% solution of flocculant to 500 ml of water equates to a dosage of 5 ppm. In each beaker, add 1 ml of the flocculant solution and mix for 1 minute at an rpm of 75. During the addition of a flocculant, look for large floc particles called macro floc that are popcorn-like in appearance, well-formed, and separated from each other. Stop the mixer after you see large floc particles form.
To know if the water meets your treatment goals, there are a few extra steps you can take. You can filter the water and measure the turbidity on a turbidity reader, you can look at the clarity and appearance of the water, or you can put it through different micron levels of filters. If the clarity and floc formation do not meet your treatment goals, this typically means that other coagulants or flocculants need to be evaluated. Interpreting results depends on the unique waste stream and treatment goals. It is important that observations of jar testing take into consideration the design of the actual treatment system, and that the best effort is made to replicate real-life treatment scenarios.
Looking for assistance conducting a jar test? Do you have samples you'd like our lab to test for you? PurposeTo determine the optimum concentration of coagulant to be added to the source water. MaterialsVolumetric flask (1,000 mL)Analytical balanceCoagulants and coagulant aidsMagnetic stirrer (optional)A stirring machine with six paddles capable of variable speeds from 0 to 100 revolutions per minute (RPM)Beakers (1,000 mL)Pipets (10 mL)Watch or clockTurbidometer and sample tubesStirring MachineStirring MachineProcedureDecide on six dosages of the chemical(s).You should use the chemicals in use at the treatment plant you visit. These chemicals may include coagulants, coagulant aids, and lime.The dosages should be in a series with the lowest dosage being lower than the dosage currently used in the plant and the highest dosage being higher than the dosage currently used in the plant. Insert the six dosages into your data sheet.
If pre-lime has to be fed, it is usually best to hold the amount of lime constant and vary the coagulant dosage. Prepare a stock solution of the chemical(s).It is not necessary to know the purity (strength) of the chemicals you use since the strength will be the same for plant operation. All results of the jar tests are in parts per million or milligrams per liter. (1 ppm = 1 mg/L). You will need to prepare a stock solution for each type of chemical used. The strength of the stock solution will depend on the chemical dosages which you decided to use in step 1. The table below shows what strength stock solution you should prepare in each circumstance. Appx dosage, mg/L soltn concentration, mg/L 1 mL added to 1 L sample equals 1-10 mg/L 1,000 mg/L 1 mg/L 10-50 mg/L 10,000 mg/L 10 mg/L 50-500 mg/L 100,000 mg/L 100 mg/L
For example, if all of your dosages are between 1 and 10 mg/L, then you should prepare a stock solution with a concentration of 1,000 mg/L. This means that you could prepare the stock solution by dissolving 1,000 mg of the chemical in 1 L of distilled water. However, this would produce a much larger quantity of stock solution than you need and would waste chemicals. You will probably choose instead to dissolve 250 mg of the chemical in 250 mL of distilled water.
Once you decide on the strength and volume of stock solution to prepare, the procedure is as follows: Weigh out the proper quantity of the chemical using the analytical balance. Put an empty weigh boat on the balance and tare it. Then add the chemical slowly to the weigh boat until the desired weight has been achieved. The Jar Test is a common laboratory procedure used to simulate the coagulation/flocculation process in a wastewater treatment plant. It is an essential tool for determining the appropriate chemical dosages required for effective treatment, and for optimizing the performance of the treatment process. This method involves the use of a multi-station gang stirrer that holds a series of six or more jars, where each jar represents a different test condition. The process allows for the simultaneous comparison of different treatment options, providing valuable insights into the most effective treatment method.
The Jar Test is a critical part of the wastewater treatment process. It is used to determine the optimal dose of coagulant and flocculant chemicals needed to remove suspended and colloidal particles from the wastewater. These particles, which can include organic and inorganic materials, bacteria, viruses, and other pollutants, are often too small to be removed by physical filtration processes alone. By adding coagulants and flocculants to the water, these small particles are made to aggregate into larger clumps, or flocs, which can then be more easily removed by sedimentation, flotation, or filtration. The Jar Test helps to identify the best type and amount of chemical to use for this process, ensuring the most efficient and effective treatment.
The Jar Test apparatus consists of a series of transparent jars, usually six, arranged in a row on a gang stirrer. Each jar is filled with a sample of the wastewater to be treated. The gang stirrer allows for the simultaneous stirring of all the jars at the same speed, ensuring consistent test conditions. Each jar represents a different test condition, with varying amounts or types of coagulant and flocculant added. This allows for a direct comparison of the effectiveness of different treatment options. The results of the Jar Test are then used to determine the optimal treatment conditions for the full-scale wastewater treatment plant.
The Jar Test procedure involves several steps. First, a sample of the wastewater to be treated is added to each jar. Then, the coagulant is added, and the water is stirred rapidly to distribute the coagulant evenly throughout the water. This rapid mixing stage is followed by a slow mixing stage, which encourages the formation of flocs. After the slow mixing stage, the stirring is stopped, and the flocs are allowed to settle to the bottom of the jar. The clarity of the water above the settled flocs is then observed and compared across the different jars. The jar with the clearest water indicates the most effective treatment condition.
Coagulants and flocculants are chemicals that promote the aggregation of small particles into larger flocs. There are many different types of coagulants and flocculants, each with their own strengths and weaknesses. The choice of coagulant and flocculant depends on the specific characteristics of the wastewater, including the type and concentration of particles, the pH of the water, and other factors. Common coagulants used in wastewater treatment include aluminum sulfate (alum), ferric chloride, and polyaluminum chloride. These chemicals work by neutralizing the charge on the particles in the water, allowing them to come together.
The choice of coagulant depends on the specific characteristics of the wastewater, including the type and concentration of particles, the pH of the water, and other factors. Alum is a widely used coagulant that is effective for a wide range of water conditions. However, it can cause a decrease in the pH of the water, which may require the addition of a pH adjusting chemical. Ferric chloride and polyaluminum chloride are also commonly used, and can be more effective than alum for certain types of wastewater.
Flocculants are chemicals that help to bind the coagulated particles together into larger clumps, or flocs. They are typically polymers, with a long chain structure that allows them to bind multiple particles together. There are many different types of flocculants, including natural polymers, synthetic polymers, and inorganic polymers. Natural polymers, such as chitosan and alginate, are biodegradable and environmentally friendly, but may not be as effective as synthetic polymers for certain types of wastewater. Synthetic polymers, such as polyacrylamide, are highly effective, but can be more expensive and less environmentally friendly. Inorganic polymers, such as polyaluminum chloride, can be used as both a coagulant and a flocculant.
The results of the Jar Test are used to determine the optimal treatment conditions for the full-scale wastewater treatment plant. The jar with the clearest water indicates the most effective treatment condition. However, it is also important to consider other factors, such as the amount of sludge produced, the pH of the treated water, and the cost of the chemicals. It is also important to note that the Jar Test is a laboratory procedure, and the results may not always translate directly to the full-scale treatment plant. Other factors, such as the mixing and settling conditions in the plant, may affect the effectiveness of the treatment. Therefore, the results of the Jar Test should be used as a guide, and the treatment conditions should be adjusted as necessary based on the performance of the full-scale plant.
There are many factors that can affect the results of the Jar Test. These include the characteristics of the wastewater, the type and amount of coagulant and flocculant used, the mixing and settling conditions, and the temperature of the water. The characteristics of the wastewater, such as the type and concentration of particles, the pH of the water, and the presence of other chemicals, can greatly affect the effectiveness of the coagulant and flocculant. The type and amount of coagulant and flocculant used can also have a significant impact on the results. Too much or too little of these chemicals can lead to poor treatment performance.
The results of the Jar Test are used to adjust the treatment conditions in the full-scale wastewater treatment plant. If the Jar Test indicates that a certain type or amount of coagulant or flocculant is more effective, then this change can be implemented in the plant. However, it is important to monitor the performance of the plant closely after any changes are made, to ensure that the treatment is still effective. It is also important to conduct the Jar Test regularly, as the characteristics of the wastewater can change over time. Regular testing allows for the treatment conditions to be adjusted as necessary, ensuring the most efficient and effective treatment at all times.
While the Jar Test is a valuable tool for optimizing the wastewater treatment process, it is important to be aware of its limitations. The Jar Test is a laboratory procedure, and the conditions in the lab may not perfectly replicate the conditions in the full-scale treatment plant. Therefore, the results of the Jar Test should be used as a guide, and the treatment conditions should be adjusted as necessary based on the performance of the full-scale plant. It is also important to consider the cost and environmental impact of the coagulant and flocculant chemicals. While these chemicals are necessary for effective treatment, they can be expensive and may have negative environmental impacts. Therefore, it is important to use these chemicals judiciously, and to explore other treatment options, such as biological treatment methods, where possible.
Scaling up from the results of the Jar Test to the full-scale treatment plant can be a complex process. The conditions in the lab, such as the mixing and settling conditions, may not perfectly replicate the conditions in the plant. Therefore, it is important to adjust the treatment conditions as necessary based on the performance of the plant. It is also important to consider the cost and availability of the coagulant and flocculant chemicals. While the Jar Test may indicate that a certain chemical is the most effective, it may not be the most cost-effective or readily available option. Therefore, it is important to consider all factors when deciding on the best treatment option.
Coagulants and flocculants are necessary for effective wastewater treatment, but they can have negative environmental impacts. These chemicals can be toxic to aquatic life, and can also contribute to the formation of harmful byproducts. Therefore, it is important to use these chemicals judiciously, and to explore other treatment options where possible. There are also environmentally friendly alternatives to traditional coagulants and flocculants, such as natural polymers and inorganic polymers. These alternatives can be more expensive and may not be as effective for certain types of wastewater, but they can be a good option for reducing the environmental impact of the treatment process. The Jar Test is a valuable tool for optimizing the wastewater treatment process. It allows for the simultaneous comparison of different treatment options, providing valuable insights into the most effective treatment method. It is also important to consider the cost and environmental impact of the coagulant and flocculant chemicals. While these chemicals are necessary for effective treatment, they can be expensive and may have negative environmental impacts.
PurposeTo determine the optimum concentration of coagulant to be added to the source water. MaterialsVolumetric flask (1,000 mL)Analytical balanceCoagulants and coagulant aidsMagnetic stirrer (optional)A stirring machine with six paddles capable of variable speeds from 0 to 100 revolutions per minute (RPM)Beakers (1,000 mL)Pipets (10 mL)Watch or clockTurbidometer and sample tubesStirring MachineStirring MachineProcedureDecide on six dosages of the chemical(s).You should use the chemicals in use at the treatment plant you visit. These chemicals may include coagulants, coagulant aids, and lime.The dosages should be in a series with the lowest dosage being lower than the dosage currently used in the plant and the highest dosage being higher than the dosage currently used in the plant. Insert the six dosages into your data sheet.
If pre-lime has to be fed, it is usually best to hold the amount of lime constant and vary the coagulant dosage. Prepare a stock solution of the chemical(s).It is not necessary to know the purity (strength) of the chemicals you use since the strength will be the same for plant operation. All results of the jar tests are in parts per million or milligrams per liter. (1 ppm = 1 mg/L). You will need to prepare a stock solution for each type of chemical used. The strength of the stock solution will depend on the chemical dosages which you decided to use in step 1. The table below shows what strength stock solution you should prepare in each circumstance. Appx dosage, mg/L soltn concentration, mg/L 1 mL added to 1 L sample equals1-10 mg/L 1,000 mg/L 1 mg/L10-50 mg/L 10,000 mg/L 10 mg/L50-500 mg/L 100,000 mg/L 100 mg/L
For example, if all of your dosages are between 1 and 10 mg/L, then you should prepare a stock solution with a concentration of 1,000 mg/L. This means that you could prepare the stock solution by dissolving 1,000 mg of the chemical in 1 L of distilled water. However, this would produce a much larger quantity of stock solution than you need and would waste chemicals. You will probably choose instead to dissolve 250 mg of the chemical in 250 mL of distilled water.
Once you decide on the strength and volume of stock solution to prepare, the procedure is as follows: Weigh out the proper quantity of the chemical using the analytical balance. Put an empty weigh boat on the balance and tare it. Then add the chemical slowly to the weigh boat until the desired weight has been achieved. Precipitation is the chemical conversion of soluble substances (including metals) into insoluble particles. The amount or dosage of a precipitant, coagulant and/or flocculant required to precipitate and remove metals in wastewater solutions is not only dependent on the concentration of such metals in solution, but also on several other factors.
Pour a sample of untreated wastewater into a beaker (ex 300 ml). While mixing, adjust the pH using caustic soda or sulfuric acid to the optimum pH for hydroxide precipitation of mixed metals, i.e. While stirring the sample, use an eyedropper to add the precipitant until the ORP value drops rapidly by 150mV (typically to -250 mV). Add 1 or 2 drops of coagulant solution. Mix at high speed for 1 to 3 minutes. Turn off mixer and observe the coagulation (agglomeration) of the precipitated particles. If the particles appear to be coagulating but need assistance to accelerate their settling, a flocculant may be added to the solution followed by a slow mixing to allow for floc building. Note: When the supernate has a yellow or orange tint (similar to the color of the precipitant), that is an indication of overdosing the precipitant. If necessary, dilute the precipitant before adding it to the wastewater. Make note of the dilution ratio for determining the optimum full-scale dosage.
Water Specialists Technologies can recommend control systems for dosing precipitants. Such systems utilizes an electrode for accurate measurement (in millivolts) of the reduction reaction of precipitants in wastewater. The electrode signal is monitored by the controller that controls the metering pump for dosing the required amount of precipitant. Systems are also available for pH adjustment under electrode control. The solubility of metallic particles is pH dependent. That is, dissolved heavy metal ions can be precipitated chemically by adjusting the pH of a wastewater stream. The pH is important because all metals have a pH at which their solubility is minimal. Although this pH differs for all metals, it generally lies between 7.5 and 11.
Water Specialists precipitants will simultaneously precipitate a variety of metals at any given pH within the above range. When used as a “polishing” precipitant, the dosage of a precipitant can be lowered depending on the quantity of metals that are precipitated as hydroxides by pH adjustment. While a pH of 8.5 is normally recommended for the polishing effect - the pH value will vary depending on the presence of chelating and/or complexing agents in the wastewater. For adjusting pH, sodium hydroxide is recommended. However, other common chemicals can be used - such as soda ash and lime.
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