Extended Aeration

In extended aeration process the raw sewage goes straight to the aeration tank for traetment. The whole process is aerobic. This simplification implies longer aeration time which has earned for the process the name "extended aeration". The BOD removal efficiency of the extended aeration process is higher than activated sludge process which makes it especially desirable to use where it is to be followed by tertiary treatment for reuse.

UASB (Upflow Anaerobic Sludge Bed) Tank

UASB  is an anaerobic treatment technology in wastewater treatment and is now becoming a popular treatment method for industrial wastewater because of its relatively low operate cost.

Wastewater enters the bottom of the reactor vessel through its inlet distribution system design. This ensures that the influent is well-mixed.  The wastewater passes upwards through the dense anaerobic sludge bed. Biodegradable COD, mostly in the form of volatile organic acid (VFAs) is readily converted to biogas which is rich in methane. The biogas generated will attach to the anaerobic granules. The biogas attached granules will float up, thus creating an upward circulation of water. The settler will separate the biogas from the granules. As the gas attached granule contact the settler, biogas will be detached from the granules. The dense, granular sludge particles now free from the attached gas bubbles will sink back to the bottom. This will result in return downward circulation.

The upward flow of the wastewater, in addition to the downwards flow of the denser anaerobic granules, will ensure effective sludge to wastewater contact. Therefore, there is no need for any energy consuming mechanical or hydraulic agitation within the reactor. This will also greatly reduce the maintenance cost of the system. The exceptional design of the reactor allows a highly active biomass concentration in relation to soluble organic solids passing through the sludge bed. "

SBR (Sequencing Batch Reactor)Tank

SBR systems represent a variation of the activated sludge process. Like any other activated sludge process, SBR works by developing a mixed culture of bacteria which is effective in removing BOD, COD and nutrients commonly found in wastewaters. SBR can treat a wide range of domestic and industrial wastewaters, at flows ranging from a few thousand gallons to millions of gallons per day.

The effluent of UASB flows into 2 sets SBR, and after the process of fill (1 hr), react (2 hrs), settle (1 hr), decant (1 hr) idle (1 hr),  90% COD could be removed .There are 3 (2 duty and 1 standby) sets blower which could supply the compressed air to the SBRs .There are also 2 sludge pumps in the bottom of tank  in order to discharge surplus sludge on schedule.

MBR (Membrane Bioreactor)

MBRs are now widely used for the treatment of domestic and industrial wastewater. They consist of a bioreactor coupled with membranes. MBRs have several advantages (i) they can retain high biomass concentrations and operate at long SRT if required , (ii) they require a small foot print and (iii) they have the ability to treat high strength wastewater . Apart from keeping the biomass in the bioreactor, the membrane may also retain some of the organic carbons from escaping for subsequent biodegradation (depending on their molecular weight). For example, it have reported that approximately 12 % of pollutants removal could be attributed to the membrane compared to 85 % by the bioreactor (although this would depend on both membrane type [UF vs MF] and nature of the organics).

A feature of the MBR is membrane fouling which leads to transmembrane pressure (TMP) increase or permeate flux decrease and shortens the life of the membrane. In order to prolong the life span and reduce the maintenance cost, fouling control is important. Energy input is required to hydrodynamically reduce fouling and chemical cleaning of membrane is employed when the operation of the system is unacceptable. However, the methods used are not always efficient due to the required system shutdown or loss of production. These problems tend to obstruct the MBR from reaching its optimum potential. In this section, pertinent studies are reviewed to obtain insight into alternative designs for MBRs with especial focus on modifying specific cake resistance, irreversible membrane fouling control and hybrid MBRs with supported biomass (i.e. PAC, polymer beads etc) and supernatant rather than mixed liquor filtration concepts.

MBBR (Moving Bed Bioreactor)

The MBBR process is based on the biofilm techologuy and it has maximized the advantages of activated sludge and other biofilm systems without being restrained by their disadvantages. Suitable carriers which have a density slightly lower than water are used. The process is feasible for most of wastewater: industrial and municipal, and is used for organic removal, nitrification and denitrification. The ease of retrofitting an existing bioreactor to a moving bed bioreactor process makes it a good alternative for upgrading of old wastewater treatment plants.

The process can be delivered as a pure biofilm treatment system or combined with activated sludge to meet nitrification requirements.
Some of the advantages of MBBR process are:

1. Compact
2. No clogging of biofilm carriers
3. Strong biofilm
4. Flexible reactor design
5. Low load on particle separation
6. Easy upgrade for existing plants
7. Easy to operate and control
8. No sludge return