CN1842364A

CN1842364A - Backwash

Info

Publication number: CN1842364A
Application number: CN 200480024762
Authority: CN
Inventors: W·T·约翰逊; T·W·贝克; 查富芳; H·A·拉扎莱德斯; 曹治毅
Original assignee: US Filter Wastewater Group Inc
Current assignee: Siemens Water Technologies Holding Corp; Siemens Industry Inc
Priority date: 2003-08-29
Filing date: 2004-08-27
Publication date: 2006-10-04

Abstract

A method of backwashing a membrane filtration module (4), said module (4) including one or more membranes (5) located in a feed-containing vessel (3), the membranes (5) having a permeable wall which is subjected to a filtration operation wherein feed containing contaminant matter is applied to one side of the membrane wall and filtrate is withdrawn from the other side of the membrane wall, the method including: removing liquid from the feed-containing vessel (3) until the level of liquid in the feed-containing vessel (3) falls to a first level (L2) below an upper level of the membranes; suspending the filtration operation; performing a liquid backwash of the membrane wall until liquid level within the feed-containing vessel (3) rises to a second predetermined level (L1) above said first level; aerating the membrane surface with gas bubbles to dislodge fouling materials therefrom; performing a sweep or drain down of the feed-containing vessel (3) to remove the liquid containing the dislodged contaminant matter; and recommencing the filtration operation.

Description

Backwash

Technical field

The present invention relates to the film filtration system, relate in particular to the backwash of this system.

Background technology

The porous membrane filtration system needs the regular backwash of film, to keep filtration efficiency and flow, reduces transmembrane pressure (TMP) simultaneously, and this transmembrane pressure raises when membrane pores is stopped up by impurity.This system has usually and is arranged in a plurality of films of sub brilliant case for bunchy or array film form.Thereby sub-crystalline substance is applied to film surface and filtrate is regained from membrane well.Typically, in the backwash cycles process, the gas by entering sub brilliant case or unit, liquid or both go out impurity from membrane pores.Comprise from the impurity and the sedimental liquid of film and from case, drain subsequently or flushing.

The waste liquid of discharging from case need solve in the mode of Environmental security usually or handle, and therefore any minimizing of this waste liquid amount all is considered as aspect ambient influnence and cost useful.

The drainage of case or flushing-particularly when using the film of big array-also need the time, this causes resting of filtration cycle.Rest in order to reduce this, need big pumping system to come rapid drainage and be full of case again.In a row arrange in case or unit and use son brilliant (feed) to be full of the place of case again, descend being full of the liquid level that can be created in the process in other unit again.This impacts the operating efficiency of filtration system once more.

The minimizing of backwash volume has also reduced the amount of the chemical that needs in some systems.This has the two-fold advantage that reduces cost aspect chemical need, has also reduced waste disposal problem simultaneously.

Many filtration systems also adopt gas bubble aeration method to help in wash phase from the unwanted deposit of the surface erosion of porous membrane.Effective for this ventilation, film must immerse in the liquid fully.

General cleaning process in this system comprises and stops sub brilliant liquid flow in the container of placing film, continuing the liquid level of infiltration process in case arrives till the film top, with bubble ventilation film so as in a period of time from outer film surface erosion impurity, liquid backwash membrane pores then.Case is drained or flushing then, is included in the waste liquid of telling impurity in ventilation and the backwash process so that remove.

Will be understood that to keep membranes submerged, so that make aeration step effective.Adding liquid backwash when aeration step finishes causes the liquid level in the case to be elevated to more than the film.This is " a refuse amount " keeping the membranes submerged demand side.

Summary of the invention

The present invention seeks to overcome or improve at least this and other shortcoming of prior art.

According to one side, the invention provides a kind of method of backwash film filtration module, described module comprises the one or more films that are placed in the container that comprises the son crystalline substance, this film has the permeable wall that stands filtration operation, the sub-crystalline substance that wherein comprises polluter is applied on the side of membrane wall and filtrate is regained from the opposite side of membrane wall, and this method comprises:

A) remove liquid from comprise the brilliant container of son, liquid level drops to till first horizontal plane below the upper horizontal plane at film in comprising the brilliant container of son;

B) end filtration operation;

C) carry out the liquid backwash of membrane wall, the liquid level in comprising the brilliant container of son is elevated to till described first above water second predetermined level;

D) with the bubble film surface that ventilates, so that isolate the dirt material from it;

E) carry out cleaning or the following row who comprises the brilliant container of son, comprise the liquid of telling polluter so that remove; And

F) begin filtration operation once more.

Preferably, select second predetermined level to make in aeration step liquid level be elevated to the upper horizontal plane of film at least.Preferably, before removing step a), end sub-crystalline substance and flow into the container that comprises the son crystalline substance.For preferably, obtain the removal of liquid wholly or in part by infiltration process.Preferably, in pressurized filtration system, in infiltration process, adopt gas-pressurized, so that in the process of removing step a), pass through the permeable films therefrom wall from the brilliant thruster hydrodynamic of son body.Aeration step can be till beginning before the removal of liquid step and lasting till cleaning or arrange step e) down.

This processing has the advantage that reduces backwash volume.Simultaneously, be not filter down to the needs liquid level, but can drain or pump siphons away liquid in comprising the brilliant container of son, to obtain identical result.This has the advantage that increases the film flow in filter down step, and can finish fast to reduce the filter down time.The sub-crystalline substance of draining can turn back to the import of filtration plant, so that do not waste, perhaps is sent in other case of operation repetitive.

In the method for replacing, can finish diafiltration steps by changing filtrate flows; When liquid level when film descends, this flow adjustment is to keeping constant transmembrane pressure (TMP).

In removal of liquid step, can monitor this TMP, and how much following be used to determine when that liquid level has dropped to film top horizontal plane following or that liquid level has dropped on the film.Following is possible: because many more films expose, filtration area is few more, and TMP will increase.TMP also will be owing to the following fact increases: most filtrate flows are advanced far away along the chamber, have therefore increased chamber drops (supposition flow keep constant and filtrate is regained from the upper end of membrane well).Therefore, before beginning liquid backwash step, the change of TMP can be used for monitoring the liquid level of sub brilliant case.This also can be used to regulate filtrate flows and keep constant TMP, thereby avoids the remarkable change of flow on the residual filtrate zone.Replacedly, this method can be used in control TMP to the predeterminated level of any expectation, and the liquid level in comprising the brilliant case of son of for example can expecting to descend keeps TMP to be in the maximum TMP that allows, and supposes 85kPa.

Description of drawings

Only describe the preferred embodiments of the present invention with reference to the accompanying drawings now in the mode of example, wherein:

Fig. 1 a illustrates the schematic diagram that is in according to the thin-film module of the different phase of the backwash process of the embodiment of the invention to 1e.

The specific embodiment

To 1e, illustrated embodiment of the present invention has been described with reference to Fig. 1 a.Filtration module 4 is installed in and comprises in the brilliant outer casing container 3 of son to be filtered.Filtration module 8 is included in the hollow fiber membrane 5 of a branch of or bunchy of corresponding extension between upper and lower end plate 6 and 7.Bottom plate 7 provides a plurality of openings 9 inner with fibre bundle and that inlet ports 10 communicates.Son is brilliant to be supplied by port one 1 under the control of valve AV1.

Permeate/filtrate is regained by chamber 12 and line 13.Liquid backwash also can apply by line 13.

Fig. 1 a illustrates the module that is in the normal filtration operation, and wherein the liquid level in the container 3 is in the L1 place that covers upper head plate 6.When the backwash stage will begin, in this embodiment, stop brilliant the flowing of son by shut off valve AV1.Filtrate is retracted continuously by fiber core and chamber 12 and line 13.Shown in Fig. 1 b, the liquid level in container 3 drops to liquid level L2.

In case arrive liquid level L2, liquid flowed back to by fiber core and wall via line 13 and begin liquid backwash.This causes liquid level once more at the L1 that is elevated in the container shown in Fig. 1 c.As shown in Fig. 1 d, send gas to and begin aeration step subsequently by port one 0 and opening 9.In another embodiment, the liquid level that is caused by liquid backwash can just in time be lower than horizontal plane L1, arrives horizontal plane L1 by this in the aeration step process, and as the result who has bubble in liquid, liquid level further rises simultaneously.In the liquid backwash process, can obtain similar result by the beginning aeration step.

In case aeration step is finished, container cleaning or drainage shown in Fig. 1 e are so that remove the waste material of telling that is accumulated in the vessel liquid.Immediately following this step, introduce in the container once more and diafiltration begins once more by opening valve AV1 crystalline substance.

Although this embodiment relates to the perpendicular positioning film, will be understood that to the invention is not restricted to this location and film can position with any desired position or structure.

Will be understood that the present invention can be applied to compression system simultaneously and comprise the not compression system that the brilliant container of son opens wide to atmosphere.

Will be understood that within the spirit and scope of the present invention various embodiment and example will be possible.

Claims

1. the method for a backwash film filtration module, described module comprises the one or more films that are placed in the container that comprises the son crystalline substance, this film has the permeable wall that stands filtration operation, the sub-crystalline substance that wherein comprises polluter is applied on the side of membrane wall and filtrate is regained from the opposite side of membrane wall, and this method comprises:

B) end filtration operation;

F) begin filtration operation once more.

2. the method for claim 1 comprises and selects second predetermined level to make in aeration step liquid level be elevated to the upper horizontal plane of film at least.

3. method as claimed in claim 1 or 2 wherein, was ended sub-crystalline substance and is flowed into the container that comprises the son crystalline substance before removing step a).

4. as the described method of each claim of front, wherein, aeration step is till beginning before the removal of liquid step and lasting till cleaning or arrange step e) down.

5. as the described method of each claim of front, wherein, obtain the removal of liquid wholly or in part by infiltration process.

6. method as claimed in claim 5 comprises applying gas-pressurized to the liquid on a described side of membrane wall, passes through membrane wall so that promote liquid in infiltration process.

7. method according to any one of claims 1 to 4 wherein, obtains the removal of liquid by coming the liquid that comprises in the brilliant case of son down.

8. method according to any one of claims 1 to 4 wherein, siphons away the removal that liquid obtains liquid by pump from comprise the brilliant case of son.

9. as the described method of each claim of front, comprise when diafiltration begins again and the liquid of removing to be returned the step that comprises in the brilliant container of son.

10. as the described method of each claim of front, comprise that the liquid that will remove returns the step in the brilliant container of son of comprising of further filtration system.

11., when comprising the steps: that liquid level reduces in comprising the brilliant container of son, change filtrate flows from film to keep the substantially invariable transmembrane pressure (TMP) that crosses described film as the described method of each claim of front.

12. method as claimed in claim 11, wherein, transmembrane pressure maintains or is lower than predetermined value.

13. as the described method of each claim of front, comprise the steps: to monitor the transmembrane pressure that crosses described film, so that determine the liquid level that comprises in the brilliant container of son described.

14. method as claimed in claim 13 wherein, is carried out described monitoring step in the process of removing step a).