Patent Application
20220194835
This invention relates to treatment processes and systems, and in particular to processes and systems which reduce total activated carbon consumption utilized to produce low chemical oxygen demand (COD) treated streams.
Wastewater streams are commonly treated by a wide variety of processes in order to remove organics, solids, and any other undesirable contaminants therefrom. For example, wastewater streams may be contacted with activated carbon for a time effective to remove an amount of chemical oxygen demand (COD) therefrom. In some instances, activated carbon is further combined with biological material, the latter of which is suitable for the removal of readily biodegradable organics from the wastewater stream. Globally, wastewater streams are requiring lower maximum allowable levels of COD and like contaminants. To arrive at these lower levels (e.g., <50 mg/L COD), in many instances, two activated carbon stages (activated carbon in two or more separate vessels) may be provided in series to achieve the desired lower COD concentration.
Having two activated carbon stages, however, requires a significant overall or total carbon consumption in the associated system and process, which requires significant cost, storage, and transportation of materials. To reduce the total carbon consumption, spent activated carbon from the stages may be regenerated by wet air oxidation (WAO) at an elevated temperature, elevated pressure, and in the presence of an oxygen-containing gas. This recycling of the carbon will lower the amount of fresh carbon needed. However, the total carbon consumption needed in a two stage system to reduce COD levels below their maximum allowable limit for most commercial applications is typically too great for a single WAO unit. Due to the proliferation of large industrial park wastewater complexes or integrated refinery facilities coupled with decreasing effluent limits, the WAO unit has become excessively large or requires two units. The repeated addition of significant fresh activated carbon and/or the addition of a second WAO unit can significantly increase the costs of the associated system or process.
The present inventors have developed systems and processes for reducing the overall carbon consumption needed for the generation of low COD treated water. In certain aspects, the systems and processes described herein include an oxidation stage (e.g., one that utilizes ozone, hydrogen peroxide, ultraviolet, or any other suitable oxidant/oxidizing agent or a combination thereof for oxidation) between a first activated carbon stage and a second activated carbon stage to reduce a total carbon consumption within the associated system or process. Without wishing to be bound by theory, it is believed that oxidation between the two activated carbon stages may significantly reduce total activated carbon needed to achieve low COD (<50 mg/L) treated wastewater. In certain embodiments, the presence of the oxidation stage reduces a total carbon consumption by 25% by mass or greater.
In accordance with another aspect, the systems and processes described herein utilize two or more carbon stages, each comprising a combination of activated carbon and biomass to reduce chemical oxygen demand (COD) in a wastewater stream. The presence of an oxidation stage which oxidizes a treated stream from a first carbon stage (optionally comprising biomass) results is an increased fraction of biodegradable COD and/or an overall decrease in COD, relative to the first treated stream. This allows the COD concentration to be more easily reduced in the second carbon stage by biomass therein, thereby reducing the carbon required in the second stage and the total carbon consumption of the system.
In accordance with an aspect of the present invention, there is provided a water treatment system comprising: (i) a first carbon stage comprising a first vessel containing at least a first amount of activated carbon effective to reduce a first amount of chemical oxygen demand (COD) from a wastewater stream and generate a first treated stream having a first reduced amount of COD; (ii) an oxidation unit disposed downstream of the first carbon stage, the oxidation unit configured to oxidize a second amount of COD from the first treated stream and generate a second treated stream having a second reduced amount of COD; and (iii) a second carbon stage downstream of the oxidation unit comprising a second vessel containing at least a second amount of activated carbon effective to reduce a third amount of chemical oxygen demand (COD) from the second treated stream and generate a third treated stream having a third reduced amount of COD at or below a predetermined concentration limit.
In accordance with another aspect, there is provided a water treatment process comprising: (i) generating a first treated stream having a first reduced amount of COD via contacting a wastewater stream with a first amount of activated carbon; (ii) generating a second treated stream having a second reduced amount of COD via subjecting the first treated stream to an oxidation process; and (iii) generating a third treated stream having a third reduced amount of COD at or below a predetermined concentration limit via contacting the second treated stream with at least a second amount of activated carbon; wherein, relative to a process without the oxidation step, the oxidation process reduces a total carbon consumption required to bring the COD to or below the predetermined concentration limit.
In accordance with another aspect, there is provided a water treatment system comprising: (i) a first bioreactor comprising a first amount of activated carbon and a first amount of biomass, the first bioreactor configured to remove a first amount of chemical oxygen demand (COD) from a wastewater stream introduced thereto and to generate a first treated stream comprising a first reduced amount of COD along with a first solids portion comprising the first amount of activated carbon and biomass; (ii) a first separator in fluid communication with the first bioreactor, the first separator configured to separate the first treated stream from the first solids portion; (iii) an oxidation unit in fluid communication with first separator, the oxidation unit configured to oxidize an amount of the COD in the first treated stream and generate a second treated stream comprising a second reduced amount of COD; (iv) a second bioreactor comprising a second amount of activated carbon and a second amount of biomass in fluid communication with the oxidation unit, the second bioreactor configured to remove a third amount of COD from the second treated stream to generate a third treated stream comprising a reduced amount of COD along with a second solids portion comprising the second amount of activated carbon and biomass; and (v) a second separator in fluid communication with the second bioreactor, the second separator configured to separate the third treated stream from the second solids portion.
In accordance with another aspect, there is provided a water treatment process comprising: (i) treating a wastewater stream comprising an amount of chemical oxygen demand (COD) therein in a first bioreactor comprising a first amount of activated carbon and a first amount of biomass therein; (ii) generating a first treated stream comprising a first reduced COD concentration from the first bioreactor; (iii) oxidizing the first treated stream to generate a second treated stream comprising a second reduced COD concentration; (iv) treating the second treated stream in a second bioreactor comprising a second amount of activated carbon and a second amount of biomass therein; and (v) generating a third treated stream comprising a third reduced COD concentration from the second bioreactor.
Now referring to the figures,
The first carbon stage 14 may comprise any suitable components in a configuration which at least utilizes an amount of activated carbon effective to reduce a first amount of chemical oxygen demand (COD) from the wastewater stream 12 and generate a first treated stream 22 having a first reduced amount of COD. In an embodiment and as shown in
In certain embodiments and as shown in
The first amount of biomass 34 may include any suitable population of bacterial micro-organisms effective to digest biodegradable material, including one that does so with reduced solids production. Exemplary wastewater treatment with reduced solids production are described in U.S. Pat. Nos. 6,660,163; 5,824,222; 5,658,458; and 5,636,755, each of which are incorporated by reference herein in their entireties. The bacteria may comprise any bacteria or combination of bacteria suitable to thrive in anoxic and/or aerobic conditions. Representative aerobic genera include the bacteria Acinetobacter, Pseudomonas, Zoogloea, Achromobacter, Flavobacterium, Norcardia, Bdellovibrio, Mycobacterium, Shpaerotilus, Baggiatoa, Thiothrix, Lecicothrix, and Geotrichum, the nitrifying bacteria Nitrosomonas, and Nitrobacter, and the protozoa Ciliata, Vorticella, Opercularia, and Epistylis. Representative anoxic genera include the denitrifying bacteria Achromobacter, Aerobacter, Alcaligenes, Bacillus, Brevibacterium, Flavobacterium, Lactobacillus, Micrococcus, Proteus, Pserudomonas, and Spirillum.
Referring again to
In certain embodiments, the first separator 28 comprises a clarifier as is well known in the art. In other embodiments, the first separator 28 comprises a dissolved gas unit, a hydrocyclone, or a membrane unit which may, for example, comprise one or more porous or semipermeable membranes. In an embodiment, the membrane unit comprises a microfiltration membrane or an ultrafiltration membrane as is known in the art. In addition, the membranes of the membrane unit may have any configuration suitable for its intended application, such as a sheet or hollow fibers or monolithic. Further, the membranes may have any suitable porosity and/or permeability for their intended application. Still further, the membranes may have any suitable shape and cross sectional area such as, for example, a square, rectangular, or cylindrical shape. In one embodiment, the membranes have a rectangular shape. In addition, the one or more membranes may be positioned, e.g., vertically, in a treatment zone of the membrane unit in such a way as to be completely submerged by the wastewater stream 12. In certain embodiments, the first vessel 24 and the first separator 28 comprise discrete individual components. It is understood, however, that the present invention is not so limited.
In other embodiments and as shown in
Referring again to
As set forth above, the presence of the oxidation stage 16 substantially reduces a total carbon consumption needed in the system 10 to generate a final treated stream 20 having a COD concentration below a predetermined amount, e.g., below the stringent COD requirements. In an embodiment, the (final) treated stream 20 from a system or process as described herein comprises a COD concentration of 50 mg/L or less, and in a particular embodiment of 30 mg/L or less. In certain embodiments, the second reduced amount of COD of the second treated stream 40 comprises an increased fraction of biodegradable COD relative to the first treated stream 22 upon the subjecting the first treated stream 22 to an oxidation process. The increased biodegradable fraction renders the COD more easily reduced in the second carbon stage 18.
The second carbon stage 18, for example, as shown in the embodiment of
The second carbon stage 18 may likewise comprise any suitable structures in a configuration which utilizes at least a second amount of activated carbon to contact a stream therein (second treated stream 40) to reduce a third amount of chemical oxygen demand (COD) (relative the wastewater stream 12) and generate a final treated stream 20 having a third reduced amount of COD. In certain embodiments, the third reduced amount of COD is at or below a maximum allowable limit of the COD, e.g., <50 mg/L. Similar to the first carbon stage 14, in certain embodiments (shown in
In addition, the second amount of activated carbon 44 is effective to remove a further amount of chemical oxygen demand (COD) from the wastewater stream 12 (now in the form of the second treated stream 40) and generate a second material 48. As with the first material 30, the second material 48 comprises a mixture of the third (final) treated stream 20 and a second solids portion 50 comprising at least the second amount of activated carbon 44. Likewise, the second carbon stage 18 may comprise a second separator 46 for separating the treated stream 20 from the second solids portion 50. As with the first carbon stage 14, the second vessel 42 may further include a second amount of biomass 52 therein for treating readily biodegradable contaminants within the wastewater stream 12. Still further, in an embodiment, the second carbon stage 18 may comprise a membrane bioreactor comprising activated carbon 44 and optionally biomass 52 therein with a plurality of membranes housed therein as was described above.
In view of the above, in accordance with an aspect and as shown in
In accordance with another aspect, the activated carbon (and biomass if present) may be cycled through the system to limit the need for the addition of fresh carbon, which would add to the overall carbon consumption. Referring to
It is appreciated that at a certain point, the activated carbon in the first or second stage 14, 18 becomes “spent”—meaning that its ability to adsorb or otherwise remove chemical oxygen demand from the wastewater stream 12 becomes compromised. In accordance with another aspect of the present invention, the total carbon consumption of the system 10 may further be minimized via addition of a WAO 54, which may regenerate spent carbon from the first carbon stage 14 and/or second carbon stage 18, and recycle regenerated carbon to the first and/or second carbon stage 14, 18. Referring now to
In accordance with an aspect of the present invention, when the activated carbon in the first carbon stage 14 and/or second carbon stage 18 comprises an amount of spent carbon, the system 10 may further include a WAO unit 54 (also shown in
In an embodiment, the WAO process is carried out at a temperature of 150° C. to 320° C. (275° F. to 608° F.) at a pressure of 10 to 220 bar (150 to 3200 psi). Further, in an embodiment, the material introduced to the WAO unit 54 may be mixed with an oxidant, e.g., a pressurized oxygen-containing gas supplied by a compressor. The oxidant may be added to the material (e.g., prior to and/or after flow of the material (solids portion 32 and/or 50) through a heat exchanger (not shown). Within the WAO unit 54, the material therein is subjected to conditions effective to oxidize contaminants adsorbed on the activated carbon, thereby regenerating the activated carbon material and destroying the biological material (when present). A gaseous portion (offgas) may also be produced having an oxygen content. As shown by double sided arrows 56, 58, the regenerated carbon material 60 may be recycled back to the first carbon stage 14 and/or second carbon stage 18, and well as receive material therefrom. To facilitate movement of the regenerated carbon material 60 through the system 10, the system may further include suitable fluid connections between the components of the system 10.
By way of example,
In accordance with an aspect of the present invention, any of the embodiments of the system 10 as described herein may further comprise suitable components within flow paths of any one of the conduits 60-80 for removing and storing (at least temporarily) any of the materials flowing therethrough. In an embodiment, for example and as shown in
To reiterate, the systems and processes for reducing the overall carbon consumption needed for the generation of low COD treated water. In certain aspects, the systems and processes described herein include an oxidation stage between a first activated carbon stage and a second activated carbon stage to reduce a total carbon consumption within the associated system or process. In certain aspects, the total carbon consumption is reduced due to an increased biodegradable COD portion as a result of an oxidation process (e.g., ozone treatment). As a result, a lesser amount of carbon is needed in the second stage (e.g., more biomass can be utilized). In this way, the total carbon consumption for the system may also be reduced.
While various embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions may be made without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2020/025006 | 3/26/2020 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62829948 | Apr 2019 | US |
