Table of Contents
How does a UASB reactor 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. The upward flow combined with the settling action of gravity suspends the blanket with the aid of flocculants.
What is UASB technology?
The upflow anaerobic sludge blanket (UASB) process has been shown to be effective for removal of organic substances from sewage, especially under warm climate conditions.
What are the advantages of UASB reactor?
Table 3
| Sr. number | References | |
|---|---|---|
| Advantages of UASB technology | ||
| (1) | Provides high removal efficiency even at high OLR and low temperature and therefore requires smaller reactor volume | [11, 70] |
| (2) | Simple construction and low operation and maintenance cost due to local availability of construction material and other parts | [84] |
Who developed UASB reactor?
Lettinga
The UASB reactor was developed in the 1970s by Lettinga and his coworkers at the University for Agriculture at Wageningen in the Netherlands [11]. In the UASB reactor (Fig. 2.2C), the anaerobic bacteria form dense granules and it settles and remains as a blanket at the bottom of the reactor.
What is the minimum hydraulic retention time for UASB?
2 hours
3. What is the minimum hydraulic retention time for UASB? Explanation: The hydraulic retention time should not be less than 2 hours.
What are the major disadvantages of UASB?
UASB reactor schematic. A distinctive advantage of the UASB reactor is the very high loading rate achieved by the systems (Speece, 1996)….23.7. 1 Upflow anaerobic sludge blanket (UASB) reactor.
| Advantages | Disadvantages |
|---|---|
| Simple reactor construction | Sensitive response to organic shock loads |
What is the minimum pH to be maintained for the UASB process?
between 6.3 and 7.85
Explanation: The pH value needs to be between 6.3 and 7.85 to allow bacteria responsible for anaerobic digestion to grow. The pH value is also important because at high pH- values, ammonia disassociates to NH3 which inhibits the growth of the methane producing bacteria.
What is the disadvantage of UASB?
What is the significance of Glss in UASB reactor?
GLSS enhanced the efficiency of the UASB reactor by increasing the settleability of suspended particles and accelerating the coagulation of colloidal particles due to the velocity gradient.
What is the temperature UASB which should not be exceeded for the reaction?
What is the temperature which should not be exceeded for the reaction? Explanation: For an optimal growth of these bacteria and thus for an optimal digestion, the temperature should lie between 35-38˚C. Below this range, the digestion rate decreases by about 11% for each 1˚C temperature decrease.
What is the product gases released at the end of the UASB process?
What is the product gases released at the end of the UASB process? Explanation: The micro-organisms in the sludge layer degrade organic compounds. As a result, gases are released. The rising bubbles mix the sludge without the assistance of any mechanical parts.
What is the use of aeration tank?
The biological treatment of the wastewater takes place in the aeration tank. Before the wastewater gets to this tank, it is mixed with activated sludge. This contains countless microorganisms, such as bacteria, that are able to break down the colloidal, organic contaminants dissolved in the wastewater.
What is the minimum hydraulic retention time for Uasb?
How does the wastewater enter in the UASB reactor?
How does the wastewater enter the reactor? Explanation: Wastewater enters the reactor from the bottom and flows forward. A suspended sludge blanket filters and treats the wastewater as the wastewater flows through it. Explanation: Wastewater enters the reactor from the bottom and flows forward.
In which phase of UASB reactor high concentration of biomass contain?
Generally, during the treatment of UASB reactor, the substrate passes through an expanded sludge bed which containing a high concentration of biomass first. After that, the remaining part of substrate passes through a less dense biomass which named the sludge blanket.
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.
Why does aeration tank increase pH?
Excess levels of DO also encourage the growth of unwanted filamentous bacteria; these bacteria compete with and thereby inhibit the beneficial bacteria, reducing treatment efficiency. The pH of the aeration tank should be between 6.5-8.5 to avoid stress on the microbial community and for optimal biological activity.
What are the types of aerators?
The three types of aeration devices in home usage are packed tower aerators, multi-stage diffused bubble aerators, and spray aerators.
- Packed tower aerator.
- Diffused-bubble aerator.
- Spray aerator.
Which bacteria is present in aeration tank?
Aerobic bacteria are used in most new treatment plants in an aerated environment. This means that there is dissolved oxygen available for the respiration of the bacteria.
What causes foaming in aeration tank?
Foaming is the distribution of gas bubbles in the liquid. The gas bubbles are necessary to establish the foam. Air in the aeration unit, nitrogen gas that is produced during denitrification in anaerobic conditions, methane and carbon dioxide that is produced in anaerobic digesters may cause foaming in units (Hug 2006).
Baffles at the top of the reactor allow gases to escape and prevent an outflow of the sludge blanket. As all aerobic treatments, UASB require a post-treatment to remove pathogens, but due to a low removal of nutrients, the effluent water as well as the stabilised sludge can be used in agriculture.
What are the post-treatment options for aerobic reactor effluents?
OPTIONS FOR POST-TREATMENT OF ANAEROBIC REACTOR EFFLUENTS Beginning with a typical municipal raw wastewater, this level of treatment will generally result in an “enhanced primary” effluent quality, intermediate between primary and secondary (between 30-70 mg/l for BOD5).
Who is the author of UASB reactor treatment of sewage?
R.A.Barbosa and G.L.Sant’Anna Jr (1989).Treatment Of Domestic Sewage In An UASB Reactor.Wat . Res. Vol.23 , No. 12 pp 1483-1490,1989.
Why is upflow velocity important in UASB?
Upflow Velocity The upflow velocity in UASB is an important design parameter as the process plays with the balance of sedimentation and upflow (SASSE 1998). On one hand, sludge should not be washed out the reactor, and on the other hand, a minimum speed needs to be maintained to keep the blanket in suspension, and also for mixing (TBW 2001b).