Sludge (sludge) is a solid settling material produced by water and wastewater treatment processes. The sludge blanket level is the interface between the settled sludge and the turbid or clear water phase above.
Why is there no distinguishable bottom to a sludge blanket?
What is anaerobic sludge blanket?
How long does it take to shut down a sludge blanket clarifier?
How is sludge blanket controlled?
How does a UASB reactor work?
What is a sludge blanket clarifier?
How long does it take for a sludge blanket reactor to work?
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How is sludge blanket formed?
UASB uses an anaerobic process while forming a blanket of granular sludge which suspends in the tank. Wastewater flows upward through the blanket and is processed (degraded) by the anaerobic microorganisms. The upward flow combined with the settling action of gravity suspends the blanket with the aid of flocculants.
What is sludge blanket clarifier?
A sludge blanket clarifier is a treatment unit combining flocculation and upward flow sedimentation, which is more efficient compared to the conventional sedimentation tank. It has the ability to treat water at a faster rate, resulting in less space requirement.
What is sludge blanket level?
Sludge blanket level measurement works by measuring the distance between the sludge blanket surface and the water level. Once the sludge has reached the required density, the accompanying controller will then switch on the pumps and pump the sludge through into digesters, ready for the next treatment stage.
What is UASB in green technology?
Up-flow anaerobic sludge blanket (UASB) reactor belongs to high-rate systems, able to perform anaerobic reaction at reduced hydraulic retention time, if compared to traditional digesters.
What is sludge blanket?
Up flow anaerobic sludge blanket technology also known as UASB reactor is a form of anaerobic digester which used in wastewater treatment. UASB reactor is a methane-producing digester, which uses an anaerobicprocess and forming a blanket of granular sludge and is processed by the anaerobic microorganisms.
Which chemical is used in clarifier?
Polyelectrolytes and ferric sulfate cause fine and suspended particles in the water to clump together. Water may be treated with these coagulant chemicals prior to entering the clarifier. After coagulation, flocculation by large mechanical paddles allow the coagulate to form denser particles that settle more easily.
What are the two types of sludge?
This residue is commonly classified as primary and secondary sludge. Primary sludge is generated from chemical precipitation, sedimentation, and other primary processes, whereas secondary sludge is the activated waste biomass resulting from biological treatments.
What causes sludge to rise?
Rising sludge occurs in the secondary clarifiers of activated sludge plants when the sludge settles to the bottom of the clarifier, is compacted, and then starts to rise to the surface, usually as a result of denitrification, or anaerobic biological activity that produces carbon dioxide or methane.
What is the sludge layer in a septic tank?
Sludge: The "sinkable" solids (soil, grit, bones, unconsumed food particles) settle to the bottom of the tank and form a sludge layer. The sludge is denser than water and fluid in nature, so it forms a flat layer along the tank bottom.
What is the principle of UASB?
UASB reactor is based on the so-called three-phase separator, which enables the reactor to separate gas, water, and sludge mixtures under high-turbulence conditions. This allows for compact, cheaper designs. The reactor has multiple gas hoods for the separation of biogas.
Why are anaerobic bacteria used in sludge treatment?
Furthermore, anaerobic bacteria are an important element in the wastewater treatment processes. They are responsible for methane fermentation of sewage sludge, facilitating decomposition of macromolecular organic matter into simpler compounds.
What activated sludge removes?
The activated sludge process is a means of treating both municipal and industrial wastewater. The activated sludge process is a multi-chamber reactor unit that uses highly concentrated microorganisms to degrade organics and remove nutrients from wastewater, producing quality effluent.
What type of clarifier is a sludge blanket clarifier?
Sludge Blanket Clarifier Detail - Paramount Limited. Reaction clarifiers (also called High Rate Solid Contact clarifier HRSCC or Solid Contact Clarifier or Solid Contact Clarifier or Sludge Blanket Clarifier) are largely used in pre-treatment of raw water.
What are the three methods of treating sludge?
The most common treatment options include anaerobic digestion, aerobic digestion, and composting. Sludge digestion offers significant cost advantages by reducing sludge quantity by nearly 50% and providing biogas as a valuable energy source.
What is the role of bio clarifier?
CrystalClear Biological Clarifier Plus works to clear brackish water quickly and efficiently resulting in sparkling water year-round. A common misconception is that bacteria will eat living algae when in fact bacteria will not consume anything that is living.
How does the clarifier work?
The clarifier works by permitting the heavier and larger particles to settle to the bottom of the clarifier. The particles then form a bottom layer of sludge requiring regular removal and disposal. Clarified water then proceeds through several more steps before being sent for storage and use.
Sludge Blanket Water Monitoring | ATi
Sludge Blanket monitoring. The continuous measurement of sludge levels in both primary and secondary sedimentation tanks allows sludge extraction pumps to be used efficiently, whilst ensuring poorly settled sludge does not carry over into effluent paths.
The performance of sludge blanket clarifier against conventional ...
Sludge blanket clarifier technology is very popular all over the world and is a good solution for algae removal. The main advantages of sludge blanket clarifiers are that they can produce a high quality effluent at minimum cost, as flocculation and clarification can be accomplished within a single reactor (Lin et al. 2004; Head et al. 1997).
Upflow Anaerobic Sludge Blanket Reactor - an overview - ScienceDirect
The UASB reactor (Fig. 23.1) was initially developed for widespread use in the Netherlands, and is currently the most popular high-rate anaerobic system in the world, used, in particular, to treat different types of wastewaters (Lettinga and Hulshoff-Pol, 1991b; Lettinga, 1995).Unlike some systems, such as fluidized bed and biofilter systems, the UASB reactor does not require attachment material.
What is sludge made of?
Regardless of its origins, sludge contains water, dissolved organic and inorganic materials and suspended solids. The suspended solids normally make up 2−5% of the sludge for municipal wastewater sludge.
What are the characteristics of sludge?
Sludge characteristics depend on both the original feedwater quality and the type of the unit operation from which the sludge is discharged. For conventional municipal wastewater treatment, the two main sludge streams are: from the primary sedimentation stage, producing primary sludge, and. the secondary biological treatment stage, producing waste ...
What unit is used to produce sludge?
for sludge production or generation from a wastewater treatment unit operation, the amount of suspended solids is often normalised against the COD concentration in the feedwater to that unit operation, giving units of kgSS/kgCOD
What is the key part of sludge treatment?
A key part of sludge treatment is the reduction of its volume by reducing the water content. The water in sludge exists in various forms: Free or unbound water is the fraction not associated with the solids or flocs – assemblages of particles held together by biological and organic polymeric materials.
What is the %DS of sludge?
Sludges of different qualities are produced from different biological unit operations. A key sludge quality parameter is its % dry solids (%DS) content, which is 100% minus the percentage water content. The %DS reflects the extent to which the sludge is consolidated. In the absence of any biological degradation of the solids, the sludge volume decreases with decreasing water and correspondingly increasing DS content.
What is the second key sludge quality parameter?
The second key sludge quality parameter, with reference to its processing, is the degradable organic matter content, usually expressed as the chemical oxygen demand (COD) rather than as the biochemical oxygen demand (BOD).
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Welcome back to TPO magazine's Exam Study Guide Series, which offers a pair of water/wastewater study questions with in-depth explanations of the answers. Last time, we covered a set of wastewater and drinking water treatment questions on the topics of Solids Retention Time; and Oxidizing Agents.
What is anaerobic sludge blanket?
Upflow anaerobic sludge blanket ( UASB) technology, normally referred to as UASB reactor, is a form of anaerobic digester that is used for wastewater treatment .
How long does sludge stay in a reactor?
Solids requiring a high degree of digestion can remain in the reactors for periods up to 90 days. Sugars dissolved in the liquid waste stream can be converted into gas quickly in the liquid phase which can exit the system in less than a day.
What is UASB in tanks?
With UASB (but also EGSB and ECSB), the process of settlement and digestion occurs in one or more large tank (s). The effluent from the UASB, which has a much reduced biochemical oxygen demand (BOD) concentration, usually needs to be treated further, for example with the activated sludge process, depending on the effluent quality requirements.
How does UASB work?
UASB uses an anaerobic process whilst forming a blanket of granular sludge which suspends in the tank. Wastewater flows upwards through the blanket and is processed (degraded) by the anaerobic microorganisms.
Why is there no distinguishable bottom to a sludge blanket?
While the top of the blanket is usually well defined there is no distinguishable bottom to the blanket because of the varying density of the particles forming the blanket. The concentration of the sludge blanket is controlled by allowing it to bleed off via suitably placed hoppers or lightweight suspended cones.
What is anaerobic sludge blanket?
As a typical anaerobic treatment unit, Upflow anaerobic sludge blanket (UASB) is a form of anaerobic digester reactor, designed by Lettinga in Wageningen Agriculture University of Holland at late 18th century. In the bottom of reactor called “Sludge Bed,” which is occupied by granular sludge as well as flocculent sludge, the total sludge concentration reaches up to 40–80 gVSS/L. About 70–90% of the total removal is acquired in the Sludge Bed, making this area a major place for the treatment of biodegradable organic matter in wastewater. Above sludge bed always floats with flocculent sludge and free sludge named “Sludge Blanket ”with an average sludge concentration of 5–25 gVSS/L. Sludge blanket can prevent the loss of sludge particles from the reactor as a buffer layer though the limited role of biodegradation. The anaerobic sludge contains various kinds of microorganisms with the form of free sludge, flocculent sludge, and granular sludge displayed in different height scope of reaction zone and shows higher biological activity.
How long does it take to shut down a sludge blanket clarifier?
They are not suitable for stop/start operation. Restart following a lengthy shut down may take more than 24 hours. However this could be reduced if sludge from a similar clarifier is available for seeding the blanket. Stoppages of 3–6 hours, can however be accommodated. There is also a constraint on flow turndown, which is normally limited to about two thirds of the maximum flow. The Pulsator clarifier, because of its high intermittent flow, can be operated down to about one third of the maximum flow.
How is sludge blanket controlled?
The concentration of the sludge blanket is controlled by allowing it to bleed off via suitably placed hoppers or lightweight suspended cones. Sludge is also removed from the bottom of the hopper. The hopper-bottomed tank is not cheap to construct as the total water depth, governed by geometry, is usually about the same as a dimension of the plan. During construction care must be taken to ensure that the inverted pyramid is reasonably accurate and the inlet pipe discharges at the geometric centre; if it does not, streaming of the water to one side can occur and upset the stability of the sludge blanket. The inlet velocity (m/s) should be maintained at around a quarter of the rise rate in the vertical section of the clarifier (m/h), to avoid ‘boiling’ at the blanket surface. The surface loading of hopper-bottomed tanks is within the range 2–3.5 m 3 /h.m 2, the lower velocity may sometimes be needed for floc formed in the removal of colour from a soft reservoir water.
How does a UASB reactor work?
The up-flow anaerobic sludge blanket, commonly known as a UASB reactor, works on the principle that an anaerobic sludge blanket at the bottom of the reactor acts like a filter and medium for anaerobic microorganisms to grow and utilize the organic matter in the wastewater supplied into it. Wastewater is introduced into the reactor via an inlet at the bottom of the reactor in an up-flow manner. When the wastewater passes through the sludge blanket it is filtered and treated by the microorganisms in the sludge blanket. This is the most widely used type of reactor around the globe due to its convenience as it allows for the separation of liquid, solid, and gas phases in the upper part of the reactor. Singh and Mittal [37] investigated the applicability of UASB to process leachate from a municipal landfill with an OLR of 3.00 kgCOD/m 3 /day and an HRT of 12 h. The removal efficiency of soluble COD for fresh leachate was a 91%–67% reduction and for old leachate a reduction from 90% to 35%. They concluded that UASB leachate treatment leads to more toxicity of the leachate.
What is a sludge blanket clarifier?
Sludge blanket clarifiers are suitable for many types of waters, including turbid ones, provided the particulate matter is of low density. A safe upper limit for turbidity is about 500 NTU but, depending on the nature of the particulate matter, much higher (up to 1000 NTU) peaks can be accommodated. Heavy particulate matter tends to settle on the bottom of the clarifier. When used in such applications these clarifiers should be provided with scrapers or other methods for intermittent removal of bottom sludge. Alternatively they should be drained down and cleaned after the rainy season, or about once or twice a year. In this respect, hopper-bottomed tanks which have bottom drains are more appropriate for highly turbid waters. For heavily silt laden waters sludge blanket clarifiers should be preceded by simple rectangular or circular sedimentation basins as described in Section 8.14. The surface loading rates of flat-bottomed sludge blanket clarifiers typically vary from 2 to 5 m 3 /h.m 2. They have a side water depth of about 4.5–5 m, which is typically made up of a bottom distribution zone of 0.6–1.0 m, sludge blanket of 2.15–2.25 m and clarified water depth of 1.75 m. In some designs the clarified water depth could be as low as 1.0 m. In sludge blanket tanks, the blanket concentration is typically 20–25% v/v (after 10 minutes settlement in a 250 ml cylinder) and 0.1–0.2% w/v, although with some waters containing high settleable solids due to high colour and turbidity it could be as much as 30–35% v/v and 0.25–0.5% w/v.
How long does it take for a sludge blanket reactor to work?
Upward flow anaerobic sludge blanket reactor (UASB) technology is effective mainly for organic-loaded wastewater such as sugar industry wastewater where the whole process is completed in three phases involving a total time of 10–30 days depending on the waste strength . In the first phase of bacterial action, which takes around 10–15 days, the complex organics are completely hydrolyzed or solubilized to be fit for absorption by the bacteria in the subsequent phase. In the second stage, another group of bacteria converts solubilized substrates into organic acids through an action called acidogenesis. Then the methane-producing (methanogenic) anaerobic bacteria use the acid products, which causes complete decomposition of the substrates producing methane gas. The process thus produces a three-phase material comprising solid-sludge particles, treated water, and generated methane gas. At the top of the reactor, the water outlet via a V-notch weir, the conical gas cap, and the horizontal baffles effect three-phase separation as shown in Fig. 3.13. The bottom sludge bed is about 2 m deep and contains thick material while the top sludge blanket is about 2% Dry Matter (DM). The technology is similar to submerged aerated filter technology as the sludge in this case serves the purpose of a filter. As incoming wastewater enters the reactor at the bottom and moves up through sludge blanket, which is located slightly above the feedwater entry point, the suspended particles get largely filtered out by the sludge. Settling of the sludge particles is also aided by the actions of the baffles that change the direction of the uprising particles.
