Settle tank

Types of settle tanks

A settle tank or sedimentation tank is a vital part of the wastewater treatment process. It removes solid waste to make treating liquid effluent easier. Settle tanks are usually rectangular or circular and come in various sizes to suit different types of industries. Here are some commonly used settle tanks:

• Clarifier: A clarifier settle tank is used to remove suspended solid particles in water. It is the first part of the water treatment process in many industries. Chemically altered or incoming wastewater floats within the clarifier settle tank. Solids slowly settle to the bottom over time, while clear water rises to the top for further treatment downstream.
• Thickener: Unlike the clarifier that mostly lets solids settle down, a thickener settle tank is designed to let solids rise back up. The thickener works like a clarifier by letting solids settle through gravity. However, some solids are recirculated before they exit the system. The thickener tank is usually sloped at the bottom to help more solids rise. The upward slurry is also called "thickened" material. Repeated recirculation of water in the thickener helps to reduce water wastage in the overall treatment process.
• Dewatering cell: A settle tank can also be used for dewatering purposes. It includes a cloth filter press to separate solids from water. The large pressing filter dewaters solid material by applying pressure to it. The dewatering settle tank helps to reduce water content in the solid waste. It improves solid waste disposal options by making solid material dry enough for landfills.

Specifications and maintenance of a settle tank

Specifications

• Flow Rate: The functioning capacity of a settling tank, frequently calculated in gallons per minute (GPM) or liters per second (LPS). This number indicates the number of wastewater was previously processed.
• Retention time: It is the time spent by the water in the tank, which can determine how long each particle takes to be separated. Common retention times can go from a few minutes to several hours, depending on the specific purpose of the tank.
• Depth: The depth of the tank can affect the velocity of wastewater, since, in a deeper tank, sedimentation may take place due to gravity alone. The average depth can range between 3 and 6 meters for each tank.
• Diameter: The width of the tank is directly linked with the flow rate that can be processed. For circular tanks, the diameter can range from 2 meters to 10 meters or more.

Maintenance

• Frequent inspections: Divide the procedures into weekly/biweekly, monthly, and quarterly/yearly as per supplier requirements. For instance, a weekly inspection may include observing the condition of the settling tank, piping system, and wastewater distribution system; a biweekly inspection may include checking the wastewater level and flow rate; while a quarterly inspection may include a detailed inspection of the tank walls, flooring, and sediments by a professional technician.
• Cleaning: The tank needs to be cleaned to remove the sediments and sludge accumulated on the bottom. The cleaning frequency will depend on the amount of sludge generated and the capacity of the settling tank.
• Preventive maintenance: Carry out the preventive maintenance of the elements related to the settling tank, such as pumps, valves, and piping systems. It will be important to ensure the proper functioning of the distribution and collection system of wastewater and sediments, respectively.
• Control of odors and emissions: In case the settling tank generates unpleasant odors or greenhouse emissions, it will be important to implement proper treatment and/or abatement systems. For example, it may include installing air treatment systems with filters or fumigating the place.

Scenarios of settle tanks

The function of the settler in various industries in Asia can be understood by looking at the different ways they are used.

• Oil and Gas Industry

  In the oil and gas industry sector, the decanter settler plays an important role in crude oil treatment. After extraction, the crude oil usually comes with water and sediment. Therefore, the clarifier is used to separate the water and sediments before refining. Some oil refineries make use of the decanter settler to separate crude oil from unwanted solid materials. This helps in enhancing the quality of the final products and also boosts the efficiency of the downstream processing units.

• Environmental Management

  Environmental management companies make use of settling tanks in sewage and wastewater treatment. In this case, the settler is called a clarifier. The clarifier separator is used to remove suspended solids, grease, and other impurities from the water, making it suitable for discharge or for reuse after treatment. This not only protects the environment but also conserves valuable natural resources like water.

• Food and Beverage Industry

  Food and beverage industry manufacturers use settling tanks for juice clarification. Fruit juices usually come with pulp and solid particles. Therefore, the settler is used to separate the solid particles from the juice. It is also common for manufacturers to use settling tanks to separate unwanted solid materials from beer and wine. This helps in improving the clarity and stability of the final alcoholic beverages products. Additionally, manufacturers in the industry can use settling tanks for edible oil purification. Here, the settler is used to separate unwanted sediment and impurities from crude edible oils derived from plants and seeds. The result is high-quality and clear cooking oils.

• Mining and Mineral Processing

  In the mining and mineral processing industry, settler tanks are used for ore beneficiation. Here, they are used to separate valuable minerals from gangue and impurities, thus increasing concentration of the desired minerals for further processing or extraction.

How to Choose Settle Tanks

When buying the settle tank, the following factors should influence the purchasing decision.

• Purveyor's Quality

  Before purchasing a settle tank, buyers should research the quality of the suppliers. Select suppliers who are known for making settle tanks that comply with industry standards regulations. Also, read testimonials from previous buyers and reviews to gauge the supplier's reliability. Also, consider the settle tank's construction material and design

• Risk Management

  It is important to consider the risks fall in when using the settle tanks in the industry. Consider the potential risks and treat them adequately as this can improve tank performance, extend its lifespan and save a lot of costs. Also, purchase settle tanks that come with warranties and after-sale services. A warranty offers protection against defects, which provides peace of mind.

• Compliance with Regulations

  Find out if the settle tank complies with industry regulations. Regulations vary from one industry to another. However, non-compliance can lead to legal issues and operational setbacks.

• Long-term Investment

  The settle tank buyer should consider the settle tank as a long-term investment. Make sure the settle tank is built to last and withstand the test of time. Factors like maintenance requirements, energy efficiency and operational costs also impact the settle tank's long-term economics.

• Capacity

  The capacity of the settle tank must be in line with production requirements. An adequately sized settle tank will be able to support operations while preventing bottlenecks or unnecessary overspending.

Q&A

Q: What factors should be considered when designing a settler tank?

A: There are many factors to consider when designing a settler tank for any application. Flow rate is an important factor to influence the design. The tank must be able to handle the expected volume of incoming fluid annually. The composition of the fluid must also be considered. The density and particle size of the suspension must be factored into the design. If the fluid contains any specific chemical component, the material of the tank must be able to withstand the component to avoid corrosion.

Q: Are there any alternatives to using a settler tank?

A: Some settler tank alternatives exist. A filter press is one of the alternatives. It uses pressure to separate solids from liquids. Another alternative is a centrifuge. It employs rotational force to separate solids from liquids based on density differences. Dissolved air flotation (DAF) systems can be used to separate suspended solids from liquids using air bubbles. Cartridge filters can also be used to separate suspended solids using different micron ratings.

Q: Can the maintenance of a settler tank affect its performance?

A: The maintenance of the settler tank can affect its performance. Regular maintenance prevents the buildup of sludge inside the tank. If there is an excessive buildup of sludge, it can reduce the settling efficiency and the quality of the separated components. Proper maintenance also prolongs the lifespan of the settler tank and preserves its structural integrity.