MBR technical engineering example (1)

The UK PORLOCK MBR sewage treatment plant uses Kubota membrane bioreactors to treat urban sewage.
The total infrastructure investment of the treatment plant including pipelines, buildings, pumps and electrical equipment is about 4 million US dollars
.

The facility covers an area of ​​only 100m×20m, including the control room, pumping station, grid pretreatment (fine grid with a grid spacing of 3mm) and 4 aeration tanks, each with peak storage capacity

Figure 5-10 Process flow diagram of PORLOCK MBR sewage treatment plant

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4.

①In the treatment process, the sludge concentration MLSS is increased several times, which greatly reduces the area occupied
.

②The effluent quality is good, better than Grade A, and can be reused directly
.

The SS in the effluent is lower than the detection limit (below 1mg/L), BOD is less than 2mg/L, COD is less than 30mg/L, and ammonia nitrogen is less than 1mg/L

③The sludge output is small (about 50% or less of the traditional process), which reduces the cost of sludge disposal
.

④It can be used for the treatment of high-concentration organic wastewater (BOD greater than 800mg/L, COD greater than 1500mg/L), and the effluent quality is also up to standard
.

⑤Long service life, the service life of the membrane module reaches more than 10 years
.

⑥The maintenance workload is small, and there is no need for daily maintenance and cleaning
.

⑦ Simple cleaning method, online cleaning, low cost and high efficiency
.

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2 Composition of Kubota Flat Membrane Module

The flat membrane module is shown in Figure 5-11
.

The flat membrane module is composed of a membrane frame, a membrane support (membrane in liquid), a diffuser frame, a diffuser tube, a hose, and a water collection tube

Figure 5-11 Schematic diagram of flat membrane module

Figure 5-12 Schematic diagram of membrane structure in liquid

(1) The structure of the membrane in liquid is shown in Figure 5-12
.

①The monolithic in-liquid membrane is composed of filter plate, membrane pad, membrane layer and water intake
.

②The filter plate is composed of an outer frame and an inner support
.

The filter plate mainly supports the membrane pad and membrane layer attached to the surface

③The membrane pad is the physical support of the membrane filter layer
.

Membrane pads are tightly attached to both sides of the filter plate

④The material of the film layer is polyvinyl chloride, and the film layer is uniformly attached to the surface of the film pad
.

⑤The water intake is the outlet of the final treated water
.

The filtered water flows through the water flow groove on the inner support of the filter plate, and flows out under the action of hydraulic pressure or external suction

(2) Main technical indicators of liquid membrane

①The average pore diameter of the membrane in the liquid
.

0.
4um (belonging to microfiltration membrane, MF)

②The effective filtration area of ​​a single membrane

1000mm×500mm (EK type): 0.
8m ²

1600mm×500mm (EW type): 1.
28m ²

③ Membrane flux
.
When the pollutant load of 0.
4～0.
8m2/(d·m2) is high, the designed membrane flux is small
.
Municipal sewage generally takes 0.
5 to 0.
6
.

(3) Filtration mechanism of membrane in liquid

① Principle of physical filtration
.
The liquid membrane is immersed in sewage
.
Sewage flows between the two liquid membranes.
The clean water flows into the filter plate of the liquid membrane under the action of pressure or external suction, and then flows out to the collecting tank through the water intake of the liquid membrane to reach the solid-liquid The role of separation
.
The sludge accumulated on the surface of the membrane is separated from the surface of the membrane under the action of the air bubble shearing force, so that the solid-liquid separation ability of the membrane is continuously maintained
.

② Principle of biological filtration
.
In addition to the physical filtration principle of ordinary membranes, Kubota's liquid membranes also grow a dense biofilm uniformly outside of the membrane layer of the liquid membrane in actual operation
.
This layer of biofilm makes a great contribution to solid-liquid separation
.
Most of the solid particles are actually retained by this layer of biofilm
.
The filtration of the biofilm greatly slows down the pollution rate of the physical membrane.
The membrane in Kubota Liquid can run for several months without cleaning, mainly because of the biofilm
.

Related links: Application of MBR in industrial wastewater and other wastewater