阅读说明：本技术 处理采出水的方法 (Method for treating produced water ) 是由 J·科尔皮尔 L·N·S·P·纳哈潘 B·比亚吉尼 于 2018-12-03 设计创作，主要内容包括：本发明公开一种用于处理废水的系统和方法。系统包括用于去除溶解的固体的反渗透单元。所述反渗透单元产生渗透物和浓缩物。为了减小与反渗透单元相关的膜结垢可能性和/或延长膜寿命和/或提高系统回收,使至少一部分浓缩物再循环,并与废水流在反渗透单元上游的点混合。(A system and method for treating wastewater is disclosed. The system includes a reverse osmosis unit for removing dissolved solids. The reverse osmosis unit produces a permeate and a concentrate. At least a portion of the concentrate is recycled and mixed with the wastewater stream at a point upstream of the reverse osmosis unit in order to reduce the potential for membrane fouling associated with the reverse osmosis unit and/or extend membrane life and/or improve system recovery.)

1. A method of treating produced water with a Reverse Osmosis (RO) unit comprising a membrane and reducing fouling of the RO membrane during treatment of the produced water, the method comprising:

pretreating the produced water and removing particulates and scale from the produced water;

after pretreating the produced water, directing the produced water to a first pass RO unit and producing a first permeate and a first concentrate;

directing the first permeate to a second pass RO unit and producing a second permeate and a second concentrate;

directing the first concentrate to a concentrate recovery RO unit in a side stream and producing a third permeate and a third concentrate;

mixing the third permeate with the first permeate or directing the third permeate to a second pass RO unit;

dividing the third concentrate into a waste stream and first and second recycle streams;

recycling the first recycle stream to a point in the side stream upstream of the concentrate recovery RO unit; and is

The second recycle stream is recycled to a point upstream of the first pass RO unit.

2. The method of claim 1:

wherein pretreating the produced water comprises chemically softening the produced water in a chemical softening unit;

wherein the second recycle stream produced by the concentrate recovery RO unit comprises concentrated organic compounds; and is

The organic compounds are removed from the second recycle stream by introducing the second recycle stream into a chemical softening unit and adsorbing the organic compounds onto suspended solids in the chemical softening unit, or co-precipitating the organic compounds with a precipitant formed in the chemical softening unit.

3. The method of claim 1, further comprising reducing accumulation of foulants on at least some of the membranes by intermittently flushing at least some of the membranes with a permeate solution comprising the first and/or second permeate, the permeate solution desorbing the foulants on the membranes from the membranes and dissolving in the permeate solution.

4. The method of claim 3, comprising injecting a surfactant into the osmotic solution, wherein the surfactant forms micelles that sequester foulants that accumulate on the membrane.

5. The method of claim 3, comprising injecting a surfactant into the produced water upstream of the first pass RO unit, wherein the surfactant forms micelles that sequester the foulants such that the foulants remain in solution in the produced water rather than adhering to the membrane.

6. The method of claim 1, comprising removing hardness from the produced water at an ion exchange unit located upstream of the first pass RO unit, and the method comprises regenerating the ion exchange unit and generating a regeneration waste stream, the regeneration waste stream being recycled to the pretreatment unit for pretreating the produced water.

7. The method of claim 1, comprising removing hardness from produced water in an ion exchange unit located upstream of the first pass RO unit; regenerating the ion exchange unit by injecting acid, then injecting caustic soda into the ion exchange unit and producing a caustic injection waste stream, and injecting a caustic rinse into the ion exchange unit and producing a caustic rinse waste stream; and recycling both the caustic injection waste stream and the caustic rinse waste stream to a point upstream of the ion exchange unit for treatment.

8. A method of treating produced water with a Reverse Osmosis (RO) unit comprising a membrane and reducing fouling of the RO membrane during treatment of the produced water, the method comprising:

pretreating the produced water, and wherein pretreating the produced water comprises:

chemically softening the produced water in a chemical softening unit to remove hardness and produce a precipitant;

removing suspended solids and precipitant from the produced water by one or more solid-liquid separation processes;

removing residual hardness from the produced water in an ion exchange unit after removing suspended solids and precipitant from the produced water;

directing the produced water from the ion exchange unit directly or indirectly to an RO unit and removing dissolved solids from the produced water in the RO unit and producing a permeate stream and a concentrate stream;

dividing the concentrate stream into first, second, and third streams;

discarding the third stream;

recycling the first stream to the RO unit or to a point between the ion exchange unit and the RO unit and mixing the first stream with the produced water; and is

The second stream is recycled to the chemical softening unit and treated in the chemical softening unit.

9. The method of claim 8, comprising reducing accumulation of foulants on at least some of the membranes by intermittently flushing at least some of the membranes with a permeate stream that desorbs foulants on the membranes from the membranes and dissolves in the permeate stream.

10. The method of claim 9, comprising injecting a surfactant into the permeate stream, wherein the surfactant forms micelles that sequester foulants that accumulate on the membrane.

11. The method of claim 9, comprising injecting a surfactant into the produced water upstream of the RO unit, wherein the surfactant forms micelles that sequester the foulants such that the foulants remain in solution in the produced water rather than adhering to the membrane.

12. The method of claim 9, comprising regenerating the ion exchange unit and generating a regeneration waste stream, and recycling the regeneration waste stream to the chemical softening unit.

13. The method of claim 9, comprising regenerating an ion exchange unit by injecting acid followed by caustic soda into the ion exchange unit and producing a caustic injection waste stream, and directing a caustic rinse through the ion exchange unit and producing a caustic rinse waste stream; and recycling both the caustic injection waste stream and the caustic rinse waste stream to a point upstream of the ion exchange unit for treatment.

Technical Field

The present invention relates to wastewater treatment, and more particularly, to a wastewater treatment system and method utilizing a reverse osmosis membrane.

Background

Dissolved solids are removed in a wastewater treatment system using a Reverse Osmosis (RO) unit. A challenge in treating wastewater streams (e.g., produced water) with RO units is that even at low concentrations, organics, particularly aromatics, tend to precipitate onto the membrane surfaces used in the RO units. Over time, the precipitates accumulate on the RO membrane, leading to membrane fouling and degradation. At least in some cases, the higher the RO recovery, the higher the concentration of aromatic compounds in the membrane feed/brine channel and, therefore, the higher the rate of membrane fouling and degradation. In many applications, it is desirable to maximize recovery to minimize liquid waste directed to a waste disposal facility. This also contributes to fouling and degradation of the RO membrane. This fouling and degradation shortens the life of the RO membrane. It is known to address the problem of RO membrane fouling by raising the pH of the feed to the RO unit. This is often helpful, but often does not completely remove the organic foulant.

Accordingly, there has been and continues to be a need for wastewater treatment processes employing RO units that extend RO membrane life and/or increase recovery while minimizing the liquid waste that needs to be disposed of.

Summary of The Invention

A wastewater treatment process is disclosed that utilizes one or more RO units that reduce fouling or degradation of the RO membrane and/or achieve higher system recovery.

One embodiment, referred to as mode 1, includes an RO feed tank and a downstream RO unit. The feed, which may have been pretreated, is directed directly or indirectly to an RO unit, producing a permeate and a concentrate. A portion of the RO unit concentrate is recycled to a point upstream of the RO unit. In one design, the RO concentrate is routed to the RO feed tank where it is mixed with the feed. As explained below, this process reduces RO membrane fouling and degradation and thus extends membrane life, and can improve system recovery.

As mentioned above, a portion of the concentrate recycle may be routed to a different point upstream of the RO unit. In another embodiment, sometimes referred to as mode 2, a portion of the concentrate is recycled routed to a pretreatment process, such as a chemical softening process. This allows the concentrate recycle (particularly the organics therein) to be pre-treated with the waste stream being treated. For example, the organics in the concentrate recycle may be co-precipitated with the chemical precipitates formed during the chemical softening process, or may be allowed to adsorb onto the surface of the formed chemical precipitates. As explained below, this process reduces organic membrane fouling and extends RO membrane life while generally increasing the recovery of the system.

Mode 1 and mode 2 may be combined to produce a mode referred to herein as mode 3. Here, the RO concentrate is recycled into at least two streams. In one example, one RO concentrate recycle stream is introduced to the RO feed tank as explained above with respect to mode 1. Another RO concentrate recycle stream may be directed to an upstream pretreatment process, such as a chemical softening process. This process also reduces the possibility of RO membrane fouling while increasing the overall RO recovery rate of the system.

In addition to addressing the problem of RO membrane fouling, the present invention also discloses a method of treating wastewater, particularly produced water, using a first pass RO unit, a second pass RO unit, and a side stream waste (reject) recovery RO unit. The system and method are directed to improving RO system recovery while reducing RO concentrate waste. The first pass RO unit produces a permeate and a concentrate. The concentrate from the first pass RO unit is directed to a reject recovery RO unit, which in turn produces a permeate and a concentrate. The permeate from the reject recovery RO unit is mixed with the permeate from the first pass RO unit and directed to the second pass RO unit. The mode 1 and 2 processes can optionally be combined into this process to reduce RO membrane fouling while further improving RO membrane system recovery. For example, a portion of the concentrate produced by the reject recovery RO unit may be split into two streams. The first concentrate stream may be combined with the concentrate from the first pass RO unit. For example, the second concentrate stream may be directed upstream and mixed with the wastewater treatment stream treated in the pretreatment process. Thus, in this process, recovery is improved by the side stream reject recovery RO unit and membrane fouling is reduced by recycling a portion of the concentrate from the reject recovery RO unit to various points upstream of the first pass RO unit.

Other objects and advantages of the present invention will become apparent upon a study of the following description and the accompanying drawings, which are merely illustrative of the invention.