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A submersible mixer is a mechanical device that is used to mix sludge tanks and other liquid volumes. Submersible mixers are often used in sewage treatment plants to keep solids in suspension in the various process tanks and/or sludge holding tanks. [1]
The submersible mixer is operated by an electric motor, which is coupled to the mixer's propeller, either direct-coupled or via a planetary gear-reducer. The propeller rotates and creates liquid flow in the tank, which in turn keeps the solids in suspension. The submersible mixer is typically installed on a guide rail system, which enables the mixer to be retrieved for periodic inspection and preventive maintenance. [2]
Examples of applications where submersible mixers are commonly applied: [3]
Sewage sludge is the residual, semi-solid material that is produced as a by-product during sewage treatment of industrial or municipal wastewater. The term "septage" also refers to sludge from simple wastewater treatment but is connected to simple on-site sanitation systems, such as septic tanks.
The Imhoff tank, named for German engineer Karl Imhoff (1876–1965), is a chamber suitable for the reception and processing of sewage. It may be used for the clarification of sewage by simple settling and sedimentation, along with anaerobic digestion of the extracted sludge. It consists of an upper chamber in which sedimentation takes place, from which collected solids slide down inclined bottom slopes to an entrance into a lower chamber in which the sludge is collected and digested. The two chambers are otherwise unconnected, with the more liquid sewage flowing only through the upper sedimentation chamber and only a slow flow of sludge in the lower digestion chamber. The lower chamber requires separate biogas vents and pipes for the removal of digested sludge, typically after 6–9 months of digestion. The Imhoff tank is in effect a two-story septic tank and retains the septic tank's simplicity while eliminating many of its drawbacks, which largely result from the mixing of fresh sewage and septic sludge in the same chamber.
A septic tank is an underground chamber made of concrete, fiberglass, or plastic through which domestic wastewater (sewage) flows for basic sewage treatment. Settling and anaerobic digestion processes reduce solids and organics, but the treatment efficiency is only moderate. Septic tank systems are a type of simple onsite sewage facility. They can be used in areas that are not connected to a sewerage system, such as rural areas. The treated liquid effluent is commonly disposed in a septic drain field, which provides further treatment. Nonetheless, groundwater pollution may occur and can be a problem.
Wastewater treatment is a process used to remove contaminants from wastewater and convert it into an effluent that can be returned to the water cycle. Once returned to the water cycle, the effluent creates an acceptable impact on the environment or is reused for various purposes. The treatment process takes place in a wastewater treatment plant. There are several kinds of wastewater which are treated at the appropriate type of wastewater treatment plant. For domestic wastewater, the treatment plant is called a sewage treatment plant. For industrial wastewater, treatment either takes place in a separate industrial wastewater treatment plant, or in a sewage treatment plant. Further types of wastewater treatment plants include agricultural wastewater treatment plants and leachate treatment plants.
In industrial process engineering, mixing is a unit operation that involves manipulation of a heterogeneous physical system with the intent to make it more homogeneous. Familiar examples include pumping of the water in a swimming pool to homogenize the water temperature, and the stirring of pancake batter to eliminate lumps (deagglomeration).
Biosolids are solid organic matter recovered from a sewage treatment process and used as fertilizer. In the past, it was common for farmers to use animal manure to improve their soil fertility. In the 1920s, the farming community began also to use sewage sludge from local wastewater treatment plants. Scientific research over many years has confirmed that these biosolids contain similar nutrients to those in animal manures. Biosolids that are used as fertilizer in farming are usually treated to help to prevent disease-causing pathogens from spreading to the public. Some sewage sludge can not qualify as biosolids due to persistent, bioaccumulative and toxic chemicals, radionuclides, and heavy metals at levels sufficient to contaminate soil and water when applied to land.
The activated sludgeprocess is a type of biological wastewater treatment process for treating sewage or industrial wastewaters using aeration and a biological floc composed of bacteria and protozoa. It uses air and microorganisms to biologically oxidize organic pollutants, producing a waste sludge containing the oxidized material. The general arrangement of an activated sludge process for removing carbonaceous pollution includes the following items: An aeration tank where air is injected in the mixed liquor. This is followed by a settling tank to allow the biological flocs to settle, thus separating the biological sludge from the clear treated water. Part of the waste sludge is recycled to the aeration tank and the remaining waste sludge is removed for further treatment and ultimate disposal.
Anaerobic digestion is a sequence of processes by which microorganisms break down biodegradable material in the absence of oxygen. The process is used for industrial or domestic purposes to manage waste or to produce fuels. Much of the fermentation used industrially to produce food and drink products, as well as home fermentation, uses anaerobic digestion.
An aerated lagoon is a simple wastewater treatment system consisting of a pond with artificial aeration to promote the biological oxidation of wastewaters.
Onsite sewage facilities (OSSF), also called septic systems, are wastewater systems designed to treat and dispose of effluent on the same property that produces the wastewater, in areas not served by public sewage infrastructure.
Sedimentation is a physical water treatment process using gravity to remove suspended solids from water. Solid particles entrained by the turbulence of moving water may be removed naturally by sedimentation in the still water of lakes and oceans. Settling basins are ponds constructed for the purpose of removing entrained solids by sedimentation. Clarifiers are tanks built with mechanical means for continuous removal of solids being deposited by sedimentation. Clarification does not remove dissolved species. Sedimentation is the act of depositing sediment.
Secondary treatment is the removal of biodegradable organic matter from sewage or similar kinds of wastewater. The aim is to achieve a certain degree of effluent quality in a sewage treatment plant suitable for the intended disposal or reuse option. A "primary treatment" step often precedes secondary treatment, whereby physical phase separation is used to remove settleable solids. During secondary treatment, biological processes are used to remove dissolved and suspended organic matter measured as biochemical oxygen demand (BOD). These processes are performed by microorganisms in a managed aerobic or anaerobic process depending on the treatment technology. Bacteria and protozoa consume biodegradable soluble organic contaminants while reproducing to form cells of biological solids. Secondary treatment is widely used in sewage treatment and is also applicable to many agricultural and industrial wastewaters.
Sewage sludge treatment describes the processes used to manage and dispose of sewage sludge produced during sewage treatment. Sludge treatment is focused on reducing sludge weight and volume to reduce transportation and disposal costs, and on reducing potential health risks of disposal options. Water removal is the primary means of weight and volume reduction, while pathogen destruction is frequently accomplished through heating during thermophilic digestion, composting, or incineration. The choice of a sludge treatment method depends on the volume of sludge generated, and comparison of treatment costs required for available disposal options. Air-drying and composting may be attractive to rural communities, while limited land availability may make aerobic digestion and mechanical dewatering preferable for cities, and economies of scale may encourage energy recovery alternatives in metropolitan areas.
A trickling filter is a type of wastewater treatment system. It consists of a fixed bed of rocks, coke, gravel, slag, polyurethane foam, sphagnum peat moss, ceramic, or plastic media over which sewage or other wastewater flows downward and causes a layer of microbial slime (biofilm) to grow, covering the bed of media. Aerobic conditions are maintained by splashing, diffusion, and either by forced-air flowing through the bed or natural convection of air if the filter medium is porous. The treatment of sewage or other wastewater with trickling filters is among the oldest and most well characterized treatment technologies.
Sewage treatment is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable for discharge to the surrounding environment or an intended reuse application, thereby preventing water pollution from raw sewage discharges. Sewage contains wastewater from households and businesses and possibly pre-treated industrial wastewater. There are a high number of sewage treatment processes to choose from. These can range from decentralized systems to large centralized systems involving a network of pipes and pump stations which convey the sewage to a treatment plant. For cities that have a combined sewer, the sewers will also carry urban runoff (stormwater) to the sewage treatment plant. Sewage treatment often involves two main stages, called primary and secondary treatment, while advanced treatment also incorporates a tertiary treatment stage with polishing processes and nutrient removal. Secondary treatment can reduce organic matter from sewage, using aerobic or anaerobic biological processes.
A chopper pump is a centrifugal pump which is equipped with a cutting system to facilitate chopping or maceration of solids that are present in the pumped liquid. The main advantage of this type of pump is that it prevents clogging of the pump itself and of the adjacent piping, as all the solids and stringy materials are macerated by the chopping system. Chopper pumps exist in various configurations, including submersible and dry-installed design and they are typically equipped with an electric motor to run the impeller and to provide torque for the chopping system. Due to its high solids handling capabilities, the chopper pump is often used for pumping sewage, sludge, manure slurries, and other liquids that contain large or tough solids.
Jet aerators are applied across a wide range of water, wastewater and biosolids treatment applications. Their primary purpose is to transfer oxygen to the liquid or sludge. A Jet aerator works through aspirating technology by simultaneously introducing large volumes of high kinetic energy liquid and air through one or more jet nozzles. The high velocity liquid exits the inner, primary jet and rapidly mixes with the incoming air in the outer jet. This intense mixing and high degree of turbulence in the gas/liquid cloud travels outward from the jet along the basin floor prior to the vertical rise of the gas bubble column to the liquid surface.
Sludge is a semi-solid slurry that can be produced from a range of industrial processes, from water treatment, wastewater treatment or on-site sanitation systems. For example, it can be produced as a settled suspension obtained from conventional drinking water treatment, as sewage sludge from wastewater treatment processes or as fecal sludge from pit latrines and septic tanks. The term is also sometimes used as a generic term for solids separated from suspension in a liquid; this 'soupy' material usually contains significant quantities of 'interstitial' water. Sludge can consist of a variety of particles, such as animal manure.
Fecal sludge management (FSM) is the storage, collection, transport, treatment and safe end use or disposal of fecal sludge. Together, the collection, transport, treatment and end use of fecal sludge constitute the "value chain" or "service chain" of fecal sludge management. Fecal sludge is defined very broadly as what accumulates in onsite sanitation systems and specifically is not transported through a sewer. It is composed of human excreta, but also anything else that may go into an onsite containment technology, such as flushwater, cleansing materials, menstrual hygiene products, grey water, and solid waste. Fecal sludge that is removed from septic tanks is called septage.
The Crossness Sewage Treatment Works at Crossness (TQ487805) in the London Borough of Greenwich is located at the eastern end of the Southern Outfall Sewer. It was opened in 1865 and is one of the largest sewage works in the United Kingdom. It treats the waste water from the Southern Outfall Sewer serving South and South East London, and is associated with the adjacent Crossness Pumping Station. It is operated by Thames Water.
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