Process for reducing perchlorate in water

A method or process for removing perchlorate ions from water includes mixing water containing perchlorate ions with a reducing agent such that the perchlorate ions and the reducing agent undergo an oxidation-reduction reaction. During the oxidation-reduction reaction, perchlorate ions are reduced to chloride ions and the reducing agent is oxidized. The oxidized reducing agent is separated from the water containing chloride ions and the oxidized reducing agent is regenerated and reused in the reduction of the perchlorate ions.

BACKGROUND OF THE INVENTION

Drinking water or potable water must be of a sufficiently high quality such that consumption of the water does not pose serious risks. One type of contaminant often found in groundwater is perchlorate salts. Perchlorate salts are generated as a by-product from rocket fuels and other explosives. Some perchlorate salts also occur naturally in the environment. Over time, the perchlorate salts each into the groundwater supply. Perchlorate salts dissolve into a cation and a corresponding perchlorate anion, ClO4−, which is particularly toxic to humans. Several reports suggest that ingestion of ClO4−inhibits normal function of the thyroid gland and contributes to hormonal imbalances. Recently, the U.S. Environmental Protection Agency (EPA) determined that ClO4−must be regulated as a water contaminant under the Safe Drinking Water Act (SDWA). Further, several states have independently enacted drinking water standards for ClO4−. Accordingly, there is considerable interest in effectively and efficiently removing ClO4−from drinking and potable water sources.

One method of removing ClO4−from drinking and potable water sources is through selective ion exchange. In this process, the water is directed through a strong base anion exchange resin and the ClO4−in the water binds to the resin. Over time, the resin becomes saturated with ClO4−and the resin needs to be regenerated. Because the ClO4−binds very tightly to the strong base anion resin, a solution having an extremely high salt concentration, typically between 7-12%, is required to remove the ClO4−from the resin. Further, it is difficult to dispose of the brine recovered from regenerating the resin because it is highly concentrated in ClO4−. Current methods for disposing of the brine include deep well injection. Accordingly, there is a need for an improved method of removing ClO4−from water, including brines recovered from resin regeneration, having a high concentration of ClO4−.

SUMMARY OF THE INVENTION

The present invention relates to a method of removing perchlorate ions from water. Water containing perchlorate ions is mixed with a reducing agent such that the perchlorate ions and the reducing agent undergo an oxidation-reduction reaction. During the oxidation-reduction reaction, perchlorate ions are reduced to chloride ions and the reducing agent is oxidized. The oxidized reducing agent is separated from the water containing chloride ions and the oxidized reducing agent is regenerated and reused in the reduction of perchlorate ions.

Other embodiments of the present invention include filtering and downwardly adjusting the pH of the water containing perchlorate ions prior initiating the oxidation-reduction reaction.

DESCRIPTION OF THE INVENTION

The present invention relates to a process for removing perchlorate ions, ClO4−, from water. As used herein the term “water” broadly means any water source that contains dissolved ClO4−, and includes, for example, groundwater and brine recovered as an ion exchange regenerant. However, the process of the present invention may be applied to any aqueous solution containing dissolved ClO4−. The process of the present invention entails reducing the ClO4−in the water into Cl−ions through an oxidation-reduction reaction. A reducing agent used to reduce the ClO4−into Cl−can be regenerated and reused. Although the embodiments herein describe the reduction of ClO4−into Cl−, the process described herein can be adapted to reduce other contaminants, such as nitrate species.

Referring toFIG. 1, the water treatment system of the present invention is shown therein and generally indicated by the numeral10. In this embodiment, the system includes a filtration unit15, a recovery tank20, a pH adjustment zone25, an oxidation/reduction reactor30, a filtration unit35, and a regeneration zone40.

As further shown inFIG. 1, the filtration unit15includes an inlet11, a reject line12and a filtrate line13. The filtrate line13extends from the filtration unit15to the recovery tank20. The reject line12extends between the filtration unit15and the pH adjustment zone25. The pH adjustment zone25includes an acid inlet26and a make-up reductant inlet27. A connecting line28extends between the pH adjustment zone25and the oxidation/reduction reactor30. A treated water line31extends from the oxidation/reduction reactor30to the filtration unit35. A filtrate line36and a reject line37extend from the filtration unit35. The filtrate line36extends from the filtration unit35to a collection area or to a point where the water is subjected to additional treatment. The reject line37extends from the filtration lit35to the regeneration zone40. A recycle line41operatively connects the regeneration zone40to the oxidation/reduction reactor30. In the embodiment shown inFIG. 1, the recycle line41extends from the regeneration zone40to a point in the connecting line28disposed upstream of the oxidation-reduction reactor30. However, in another embodiment the recycle line41extends directly from the regeneration zone40to the oxidation-reduction reactor30.

Referring toFIG. 2, the water treatment system shown therein includes the filtration unit15, the recovery tank20, the pH adjustment zone25, the oxidation/reduction reactor30, the filtration unit35, and the regeneration zone40. However, in this embodiment, the recycle line41operatively connects the regeneration zone40to the pH adjustment zone25and the oxidation/reduction reactor30. For example, recycle line41includes secondary lines41aand41b. Line41aconnects recycle line41to the pH adjustment zone25and line41bconnects the recycle line41to the oxidation reduction reactor30. In the embodiment shown inFIG. 2, the line41bextends from the recycle line41to a point in the connecting line28disposed upstream of the oxidation-reduction reactor30. However, in another embodiment the line41bextends directly from the recycle line41to the oxidation-reduction reactor30.

Referring toFIG. 3, the water treatment system shown therein includes the filtration unit15, a brine concentrator50, the recovery tank20, the pH adjustment zone25, the oxidation/reduction reactor30, the regeneration zone40, and a filtration unit45. In this embodiment, the filtrate line13from the filtration unit15extends to the brine concentration50. The brine concentrator50includes an outflow line52which extends from the brine concentrator50to the recovery tank20. Further, in the embodiment illustrated inFIG. 3, the treated water line31extends directly from the oxidation-reduction reactor30to the regeneration zone40. That is, a filtration unit is not disposed between the oxidation-reduction reactor30and the regeneration zone40. The recycle line41extends from the regeneration zone40to a filtration unit45. The filtration unit45includes a reject line43and a filtrate line42. The filtrate line42extends from the filtration unit45to a collection area or to a point where the water is subjected to additional treatment. The reject line43extends from the filtration unit45to a point in the connecting line28disposed upstream of the oxidation-reduction reactor30. However, in other embodiments the reject line43extends from the filtration unit45to pH adjustment zone25or from the filtration unit45to the oxidation-reduction reactor30.

With reference to the process for removing ClO4−from water illustrated inFIG. 1, water containing dissolved ClO4−is directed to the filtration unit15. As shown inFIG. 1, the water in this embodiment, for example, is brine containing ClO4−recovered from regenerating an ion exchange unit. However, in other embodiments, the water can be any water stream containing ClO4−. The filtration unit15, which in one embodiment is a nanofilter, separates most of the ClO4−from the water and produces a reject stream and a filtrate stream. The reject stream is a solution having substantially higher concentration of ClO4−than the filtrate stream. In one embodiment, the reject stream comprises between approximately 90% and approximately 95% by volume of ClO4−and between approximately 5% and approximately 10% by volume of brine and other elements.

The filtrate is directed from the filtration unit15to the recovery tank20through filtrate line13. In some embodiments, the filtrate is recirculated from the recovery tank20back to an ion-exchange unit and treated therein. Typically, the filtrate in the recovery tank20is directed to an ion-exchange unit when the influent water directed into the filtration unit15is brine recovered from regenerating an ion exchange resin. In another embodiment, the filtrate is not directed to the recovery tank20, but rather is directly recirculated to the ion-exchange unit. In yet another embodiment, the filtrate is directed to the recovery tank20and recirculated to a point upstream from the filtration unit15and mixed with the influent water containing ClO4−prior to the water being filtered in the filtration unit15. Alternatively, the filtrate can be directed to the recovery tank20and subsequently discharged therefrom.

The reject stream having a relatively high concentration of ClO4−is directed from the filtration unit15, through the reject line12, to the pH adjustment zone25. Upon exiting the filtration unit15, the pH of the reject stream is typically between approximately 7 and approximately 3. However, the pH of the reject stream varies depending on the salt concentration thereof. It is noted that the lower the pH of the reject stream, the faster the reduction reaction of ClO4−ions into Cl−ions occurs in the downstream oxidation-reduction reactor30. Thus, in the pH adjustment zone25, an acidic solution is added to the reject stream in the pH adjustment zone25through inlet26and decreases the pH of the reject stream to a desired value. The acidic solution may comprise any acid, such as, sulfuric acid. However, any other acidic solution can be used to decrease the pH of the reject stream.

In one embodiment, it is desired to decrease the pH of the reject stream in the pH adjustment zone25to approximately 4. At this pH the subsequent reduction reaction of ClO4−in the oxidation-reduction reactor30proceeds slowly with some reduction of ClO4−occurring after approximately 4 hours. In another embodiment, it is desired to decrease the pH of the reject stream in the pH adjustment zone25to approximately 1 or below. When the pH of the reject stream is lowered to approximately 1, the reduction reaction of ClO4−in the oxidation-reduction reactor30proceeds very quickly, with approximately 99.99% reduction of ClO4−occurring within hour 1. However, practical considerations, such as corrosion and costs may impose a limit on the pH reduction. Thus, in other embodiments, it is desired to decrease the pH of the reject stream in the pH adjustment zone25to approximately 2.

The pH adjustment zone25may also include a pH monitor (not shown) that monitors the pH of the reject stream in the pH adjustment zone25either periodically or continuously. The pH monitor may provide a signal to alert the system operator to adjust the pH of the water in the pH adjustment zone25. Alternatively, the pH monitor may be coupled to a controller that is configured to adjust the flow of the acidic solution through inlet26to decrease the pH of the reject stream in the pH adjustment zone25to the desired value.

In the embodiment shown inFIG. 1, the pH adjusted reject stream is directed from the pH adjustment zone25, through connecting line28, to the oxidation-reduction reactor30. In one embodiment the oxidation-reduction reactor30comprises a vertical tube mixer such as the TURBOMIX™ reactor marketed by Veolia Water, a continuous stirred tank reactor (CSTR), a fixed bed reactor (FBR), or a standard kettle reactor. In one embodiment, the oxidation-reduction reactor30is a standard kettle reactor operated as a batch system. In another embodiment, the oxidation-reduction reactor30is a CSTR operated as a continuous system.

Once the pH adjusted reject stream is directed into the oxidation-reduction reactor30, it is mixed with a reducing agent. The reducing agent reduces the ClO4−into Cl−ions and the reducing agent becomes oxidized. In one embodiment, the reducing agent is Ti(III) and is supplied to the pH adjusted reject stream in the form of titanium sulfate, Ti2(SO4)3. When Ti (III) is used as the reducing agent to reduce ClO4−into Cl−, the Ti(III) is oxidized into Ti(III). However, other reducing agents may also be used in the present invention. Examples of other suitable reducing agents include zero-valent iron (Fe0), ferrous iron (Fe2+), manganese on (Mn2+), sodium borohydride (NaBH4), and sodium hydrosulfide (NaHS).

In one embodiment, the pH adjusted reject stream is mixed with the reducing agent in the oxidation-reduction reactor30in the presence of a catalyst. The catalyst accelerates the rate of reduction of ClO4−into Cl−. When the reduction reaction occurs in the presence of a catalyst, the reaction is referred to as a catalytic reduction. In some embodiments, the catalyst also adsorbs ClO4−onto its surface which aids in the reduction reaction. Examples of suitable catalysts used in the present invention include, but are not limited to, titanium oxide (TiO2) and manganese oxide (MnO2).

The equation for reduction reaction of ClO4−into Cl−using Ti(III) as a reducing agent in the presence of a catalyst is shown, in relevant part, below.

In some embodiments it is desirable to maintain the above reaction in the oxidation-reduction reactor30under anaerobic conditions using, for example, nitrogen gas. In the presence of oxygen, Ti(III) is oxidized into Ti(IV) and thus, presents a competing reaction to the reduction of ClO4−and thus, lowers the efficiency of the reaction.

The temperature in the oxidation-reduction reactor30also affects the rate of reduction of ClO4−into Cl−. The higher the temperature in the oxidation-reduction reactor30, the faster the reaction proceeds. For example, at ambient temperature, approximately 20° C., the above oxidation-reduction reaction proceeds slowly. However, at temperature of approximately 100° C. and above, the above reaction proceeds much quicker. However, maintaining the oxidation-reduction reactor30at a temperature above 100° C. can be costly. Thus, in one embodiment is it desirable, to maintain the temperature in the oxidation-reduction reactor30between approximately 80° C. and approximately 100° C. In another embodiment it is preferable to maintain the temperature in the oxidation-reduction reactor30between approximately 85° C. and approximately 95° C.

As described above, the reaction in the oxidation-reduction reactor30produces a solution containing the oxidized reducing agent and Cl−and which is substantially free of C|{ }4−Often it is desirable for the substantially free ClO4−solution to be compliant with government regulations. For example, in one embodiment, the substantially free ClO4−solution contains less than approximately 18 ppb of ClO4−. In another embodiment, the substantially free ClO4−solution contains less than approximately 4 ppb of ClO4−.

In some embodiments, excess reducing agent is added to the oxidation-reduction reactor30and is not used in the oxidation-reduction reaction. In such situations, the substantially free ClO4−solution produced in the oxidation-reduction reactor30contains a mixture of the reducing agent, oxidized reducing agent and Cl−. For example, if Ti(III) is used as the reducing agent, the solution produced by the oxidation-reduction reactor30contains Ti(III)/Ti(IV) and Cl−.

In the embodiment illustrated inFIG. 1, the substantially free ClO4−solution produced by the reaction in the oxidation-reduction reactor30is directed to the filtration unit35. The filtration unit35separates a filtrate containing the Cl−ions from a reject stream containing the oxidized reducing agent. Again, if the reducing agent used in the oxidation-reduction reactor30is Ti(III), the reject stream from the filtration unit35will contain Ti(IV). In one embodiment, the filtration unit30is a nanofilter. However, in other embodiments, the filtration unit35is a filter having larger pores than a nanofilter, such as an ultrafilter or a microfilter. For example, if the oxidized reducing agent is a chemical having a larger ionic radius than that of Ti(IV), any filter capable of rejecting the oxidized reducing agent may be selected.

The filtrate containing the Cl−is directed from the filtration unit35through filtrate line36to a collection area or to a point where the solution is subjected to additional treatment. In one embodiment, the filtrate is directed to an ion-exchange system for reuse. The reject stream containing the oxidized reducing agent is directed from the filtration unit35to the regeneration zone40through reject line37.

In the regeneration zone40, the spent reducing agent, i.e. oxidized reducing agent, is regenerated into its original form through a reduction reaction. For example, if Ti(III) is used as the reducing agent in the oxidation-reduction reactor30, Ti(III) is converted into Ti(IV) during the reaction. In the regeneration zone40, the reject stream containing Ti(IV) is converted back into Ti(III). In one embodiment, the regeneration zone40comprises a chemical regeneration unit. In this embodiment, a reducing agent such as sodium borohydride (NaBH4) or sodium hydrosulfide (NaHS) is mixed with the solution containing the oxidized reducing agent in the regeneration zone40. The reducing agent functions to regenerate the oxidized reducing agent through a reduction reaction. In another embodiment, the regeneration zone40comprises an electrolytic regeneration cell having a cathode and an anode. In an electrolytic regeneration cell, voltage is applied between the anode and the cathode so as to positively charge the anode and negatively charge the cathode. Under these conditions, oxidation of water (H2O) into O2occurs at the surface of the anode while reduction of the oxidized reducing agent occurs at the surface of the cathode.

After the reducing agent has been regenerated in the regeneration zone40, the solution containing the regenerated reducing agent is directed from the regeneration zone40to the oxidation-reduction reactor30through recycle line41. In the embodiment shown inFIG. 1, the recycle line41extends from the regeneration zone40to a point in the connecting line28disposed upstream of the oxidation-reduction reactor30. However, in another embodiment the recycle line41extends directly from the regeneration zone40to the oxidation-reduction reactor30. In either case, the regenerated reducing agent is mixed with the solution containing ClO4−in the oxidation-reduction reactor30and used to reduce the ClO4−in the solution into Cl−.

With reference to the process for removing ClO4−from water illustrated inFIG. 2, the pH of the reject stream produced by the filtration unit15and disposed in the pH adjustment zone can be controlled in a number of ways. Similar to the embodiment illustrated inFIG. 1, the pH of the reject stream can be controlled by mixing the reject stream with an acidic solution through inlet26in the pH adjustment zone25. As described above, the acidic solution may include sulfuric acid. However, the pH of the reject stream can also be controlled by mixing the reject stream from the filtration unit15with an acidic reducing agent. As shown inFIG. 2, an acidic reducing agent can be directly added to the reject stream in the pH adjustment zone through make-up reductant inlet27. Further, the regenerated reducing agent can be directed from the regeneration zone40to the pH adjustment zone25through lines41and41a. For, example, in one embodiment, the reducing agent used in the oxidation-reduction reactor30is Ti(III), and is supplied in the form of acidic Ti2(SO4)3. Once the reducing agent is regenerated in the regeneration zone40, the solution containing the regenerated Ti(III) is recirculated from the regeneration zone40to the pH adjustment zone25and is mixed with the reject stream therein. In this embodiment, the recirculated solution containing regenerated reducing agent is acidic and can lower the pH of the reject stream in the pH adjustment zone25. When using the recirculated solution from the regeneration zone40to lower the pH of the reject stream, another acid source may be required to lower the pH of the solution to a desired value. Accordingly, an additional acidic solution can be added to the reject stream through inlet26.

The embodiment shown inFIG. 2also permits the solution containing the regenerated reducing agent to be directed from the regeneration zone40to the oxidation-reduction reactor30through lines41and41b. In this particular embodiment, the solution containing the regenerated reducing agent is directed from the regeneration zone40to a point in the connecting line28disposed upstream from the oxidation-reduction reactor30. In another embodiment, the solution containing the regenerated reducing agent is directed from the regeneration zone40directly to the oxidation-reduction reactor30. In either case, the regenerated reducing agent is mixed with the solution containing ClO4−in the oxidation-reduction reactor30and used to reduce the ClO4−in the solution into Cl−.

With reference to the process for removing ClO4−from water illustrated inFIG. 3, the filtrate produced in the filtration unit15is directed to a brine concentrator50through filtrate line13. In one embodiment, the brine concentrator50is an evaporator and concentrates the filtrate. The concentrated filtrate is directed to the recovery tank20through outflow line52. In one embodiment, the concentrated filtrate in the recovery tank20is directed to an ion-exchange unit and treated therein. Typically, the concentrated filtrate in the recovery tank20is directed to an ion-exchange unit when the influent water directed into the filtration unit15is brine recovered from regenerating an ion exchange resin. In another embodiment, the concentrated filtrate is not directed to the recovery tank20, but rather is directly recirculated to the ion-exchange unit. In yet another embodiment, the concentrated filtrate is directed to the recovery tank20and recirculated to a point upstream from the filtration unit15and mixed with the influent water containing ClO4−prior to the water being filtered in the filtration unit15. Alternatively, the concentrated filtrate can be directed to the recovery tank20and subsequently discharged therefrom.

The embodiment illustrated inFIG. 3also includes a filtration unit45disposed downstream from the regeneration zone40. As shown inFIG. 3, the solution containing the regenerated reducing agent is directed from the regeneration zone40to the filtration unit45through outflow line41. The filtration unit45separates the regenerated reducing agent from other salts in the solution. Filtrate produced by the filtration unit45, which generally contains monovalent ions, is directed to a collection area or to a point where the water is subjected to additional treatment. The reject stream produced by the filtration unit45has a relatively high concentration of the regenerated reducing agent. In one embodiment the filtration unit45comprises a nanofilter. However, in other embodiments, the filtration unit45is a filter having larger pores than a nanofilter, such as an ultrafilter or a microfilter. For example, if the regenerated reducing agent is a chemical having a larger ionic radius than that of Ti(III), any filter capable of rejecting the regenerated reducing agent may be selected.

In the embodiment shown inFIG. 3, the reject stream is directed from the filtration unit45, through reject line43, to a point in the connecting line28disposed upstream of the oxidation-reduction reactor30. However, in another embodiment the reject line43extends directly from the filtration unit45to the oxidation-reduction reactor30. In either case, the reject stream containing the regenerated reducing agent is mixed with the solution containing ClO4−in the oxidation-reduction reactor30and used to reduce the ClO4−in the solution into Cl−.

Notably, the embodiment illustrated inFIG. 3includes three filtration units,15,35, and45. However, in another embodiment, the system may only include two filtration units.

Appearing in Table 1 below is a summary of exemplary data obtained for one example reduction reaction of ClO4−into Cl−. In this example, 15 mg/l of ClO4−was mixed with an aqueous solution in a reaction chamber. A solution having a Ti(III) concentration of 5580 mg/l was added to the reaction chamber and used as the reducing agent. The Ti(III) solution was formed from the addition of titanium sulfate (Ti2(SO4)3) to an aqueous solution. A solution having a TiO2concentration of 300 mg/l was also added to the reaction chamber and used as the catalyst. The initial pH of the aqueous solution was 0.64. The reaction took place under a 380 ml/rain nitrogen gas flow. The reaction was conducted under reduction conditions by maintaining a negative oxidation reduction potential (ORP) value. Maintaining a negative ORP increases the likelihood for the reduction of ClO4−to occur. Using an ORP probe, the values were monitored and recorded. During the reaction, the dissolved oxygen (DO) concentration in the sample ranged between 0.7 and 0.8 mg/l which revealed that the reaction was carried out under reasonably reduced conditions.

Under the above conditions, ClO4−eras reduced from 15 mg/l to less than 0.1 mg/l after approximately 5 hours. Further, for this example, the minimum detection limit (MDL) for the ClO4−analytical instrument was less than 0.1 mg/l. A mass balance calculation revealed that more than 99.9% of ClO4−was reduced into Cl−. Table 1 also illustrates that the Ti(III) present in the solution decreased over time as the Ti(III) was oxidized into Ti(IV). Further, Table 1 illustrates that the amount of Cl−increased as the amount of ClO4−decreased.FIG. 4is a line graph illustrating the data provided in Table 1. The line graph clearly illustrates the increase in Cl−and the decrease in ClO4−over

Table 2 provides data obtained for another example reduction reaction of ClO4−into Cl−. In this example, 15 mg/l of ClO4−was mixed with an aqueous solution in a reaction chamber. A solution having a Ti(IIII) concentration of 3480 mg/l was added to the reaction chamber and used as the reducing agent. The Ti(III) solution was formed from the addition of titanium sulfate (Ti2(SO4)3) to an aqueous solution. A solution having a TiO2concentration of 300 mg/l was also added to the reaction chamber and used as the catalyst. The initial pH of the aqueous solution was 0.82. The reaction took place under a 380 ml/min N2gas flow. As shown below, ClO4−was reduced from 15 mg/l to less than 0.1 mg/l after approximately 7 hours.

Appearing in Table 3 below is a summary of exemplary data obtained for another example reduction reaction of ClO4−into Cl−. In this example, 15.2 mg/l of ClO4−was mixed with a 3% aqueous solution of NaCl in a reaction chamber. A solution having a TOW) concentration of 5580 mg/l was added to the reaction chamber and used as the reducing agent. The Ti(III) solution was formed from the addition of titanium sulfate (Ti2(SO4)3) to an aqueous solution. A solution having a TiO2concentration of 300 mg/l was also added to the reaction chamber and used as the catalyst. The initial pH of the aqueous solution was 0.87. The reaction took place under a 380 ml/min nitrogen gas flow. Under these conditions, ClO4−was reduced from 15.2 mg/l to less than 0.1 mg/l after approximately 3 hours. Additional data points for the reduction of ClO4−in this example are shown in Table 3 below.

Appearing in Table 4 below is a summary of exemplary data obtained for another example reduction reaction of ClO4−into Cl−. In this example, 14.6 mg/l of ClO4−was mixed with a 3% aqueous solution of brine in a reaction chamber. A solution having a Ti(IIII) concentration of 3400 mg/l was added to the reaction chamber and used as the reducing agent. The Ti(III) solution was formed from the addition of (Ti2(SO4)3) to an aqueous solution. A solution having a MnO2concentration of 300 mg/l was also added to the reaction chamber and used as the catalyst. The initial pH of the ClO4−solution was 072. The reaction took place under a 380 ml/min nitrogen gas flow. Under these conditions, ClO4−was reduced from 14.6 mg/l to less than 0.1 mg/l after approximately 7 hours. Additional data points for the reduction of ClO4−in this example are shown in Table 4 below. Note that the results using TiO2as the catalyst shown in Table 2 are quite similar to the results using MnO2as the catalyst in Table 4.

Appearing in Table 5 below is a summary of exemplary data obtained for another example reduction reaction of ClO4−into Cl−. In this example, ClO4−was reduced into Cl−in the presence of a catalyst in a fixed bed reactor system under reduced atmosphere. A 1 inch diameter column was used as the fixed bed reactor and was filled to approximately 8″ from the bottom with MnO2coated granular activated carbon which served as the catalyst. A solution having a ClO4−concentration of 18.4 mg/l (18,400 ppb) and containing 3% brine and a solution having a Ti2(SO4)3concentration of 5500 mg/l were separately pumped through the column. The initial pH of the ClO4−/brine solution was 1.0. The reaction in the column took place under a 380 ml/ruin nitrogen gas flow. The column was operated in a down flow mode at a temperature of between approximately 85° C. and 90° C. After 90 minutes, samples were collected from the column and the ClO4−concentration was measured in each sample. As shown in the Table 5 below, substantially all ClO4−was reduced during the 90 minute contact time. In this example, the MDL for the ClO4analytical instrument was less than 4 ppb. Further, t is noted that at sample number4, the ClO4−concentration in the effluent increased. This increase in ClO4−concentration is attributed to the increased oxidation of the reducing agent. Once the reducing agent is oxidized it is no longer effective in reducing ClO4−. The volume of each sample processed and the ClO4−in the treated effluent are shown in Table 5 below. Note that 1 Bed Volume=100 ml.

TABLE 5SampleNumberBed Volume ProcessedClO4−(ppb) in treated effluent13<425<437<4410451210

In the discussion of the various systems and processes discussed above, a number of filtration units such as filtration units15,35and45have been referred to. The filtration units can include various types of filtering devices such as membrane separators and other known filtration devices capable of performing the described filtration processes.