**3. Results and discussion**

equation data, all masses of the resin corresponding to effluent NOM concentrations were

*<sup>C</sup>*= × (25)

= -× (*C CV* <sup>0</sup> ) (26)

*ADC VADS m* = / (28)


(30)

/ (27)

0 *<sup>C</sup> m M*

Adsorbed amount of NOM (α) in mg O2, at each sampling point was calculated as shown:

Regarding the fact that samples have been taken randomly, calculation of the adsorption

a t

Obtaining *VADS* data was a real contribution to equalize the adsorption process during the contact time of the complete experiment. Adsorption capacity of Amberlite IRA-958 in the time of experiment duration - specific adsorption capacity (*ADC*) in mg/gh - was calculated using

The mutual relation of *ADC* values at measured *C* values was described as exponential

d b

*β* (L g-1 h-1) and *δ* are empiric adsorption coefficients obtained from the experimental data and calculated from the plot ln *ADC* vs. *C* (equation 30) as intercept and slope, respectively.

The total *ADC* (*ADCa*) in mg/gh, during the experiment, was calculated by integration of the

regression plot. General equation form of the curve was represented (equation 29).

*<sup>C</sup> ADC e*

ln ln *ADC C* = -× b d

surface above the curve using the following equation 31:

where *VADS* (mg/h) is adsorption rate and τ (h) is time between two sampling points.

*VADS* =

a

where V is the volume of the effluent between two samplings (L).

process rate as represented in equation 27 was an essential step:

equation 28:

calculated using the mathematical expression (25).

88 Ion Exchange - Studies and Applications

The following results present data obtained during the determination of optimal specific flow rate, sorption characteristics, and kinetics of strongly basic ion-exchange resin.

### **3.1. Results obtained during determination of optimal specific flow rate of strongly basic ion-exchange resin**

During the changes of SFR and EBCT, significant data of measured parameters were obtained. Dependence of measured parameters and flow rate values in experiments with non-chlorinated and chlorinated water are shown in Figures 4-7. Figure 4 presents the dependence of pH value and bicarbonate content in the effluent and SFR values (A) and influence of SFR on electrical conductivity and chloride concentrations (B) in both nonchlorinated and chlorinated water.

In the initial sorption contact of groundwater with the resin, an abrupt decrease in the effluent pH effluent was noted. This observation was especially pronounced in the case of chlorinated water. A high affinity of the resin to bicarbonate ions in the initial phase of ion exchange lead to the increase in the effluent acidity. The minima of the pH and bicarbon‐ ate concentration were observed at the lower SFR values compared to those measured in non-chlorinated water. These results are the consequence of the presence of the nascent

**Figure 4.** Influence of SFR on the bicarbonate and pH (A), and electrical conductivity and chloride (B) content

oxygen in chlorinated water, which accelerates ionic exchange of chloride for bicarbonate on the resin. The initial intensive exchange of these ions is gradually counterbalanced by the adsorption of the anions of humic acids taking place to the SFR of 50 BV/h, since the sites at which the dynamic equilibrium of sorption and desorption of bicarbonate is shifted to the interior of the resin granules, while humic acid binds to the functional groups on their outer surface. At the end of the investigated range of SFR, the HCO3 concentration in the effluent remained almost constant and asymptotically reached the concentration in the groundwater. At higher SFR, effluent pH value approached the pH value of the raw water as a consequence of the change in the bicarbonate concentration. After the value of SFR 50 BV/h, the resin is in the chloride form. Figure 4(A) also shows that in the initial part of the working cycle of resin with chlorinated water, there has been an immediate decrease of bicarbonates in the effluent already at SFR 2-6 BV/h after which the contents of bicarbonates slowly rises to SFR 50 BV/h, where the bicarbonates till the very end of the working cycle reach the concentration similar to that in raw water. The enormous in‐ crease in the chloride concentration at small SFR takes place simultaneously with the marked decrease in the content of bicarbonate in the effluent Figure 4(B). This chloride concentra‐ tion rise, a singly charged small and high diffusion rate, results in the increase in the measured conductivity. A higher increase in the chloride concentration was observed in the case of chlorinated water, which is understandable taking into consideration the release of chloride from hypochloric acid. The differences in the peaks of chloride concentration and electrical conductivity in the effluent for chlorinated and non-chlorinated water are certainly a consequence of the generation of nascent oxygen, which also activates the resin's functional groups and thus contributes to a more effective ion exchange.

The effect of nascent oxygen on the oxidation of As(III) to As(V) is evident from the fact that in a wide range of SFR, from 2 to 300 BV/h, the total arsenic concentration in the effluent of chlorinated water was constantly below the MTC value [47] (Figure 5(A)). On the other hand, in the case of non-chlorinated water, the arsenic concentrations in the effluent at the SFR<100 BV/h were by 10 times and at 100<SFR<300 BV/h even by 17 times

Effect of Extremely High Specific Flow Rates on the Ion-Exchange Resin Sorption Characteristics http://dx.doi.org/10.5772/60586 91

**Figure 5.** Changes in the sulfate and arsenic concentration (A) as well as NOM concentration (B) of the effluent with SFR

oxygen in chlorinated water, which accelerates ionic exchange of chloride for bicarbonate on the resin. The initial intensive exchange of these ions is gradually counterbalanced by the adsorption of the anions of humic acids taking place to the SFR of 50 BV/h, since the sites at which the dynamic equilibrium of sorption and desorption of bicarbonate is shifted to the interior of the resin granules, while humic acid binds to the functional groups on

**Figure 4.** Influence of SFR on the bicarbonate and pH (A), and electrical conductivity and chloride (B) content

90 Ion Exchange - Studies and Applications

in the effluent remained almost constant and asymptotically reached the concentration in the groundwater. At higher SFR, effluent pH value approached the pH value of the raw water as a consequence of the change in the bicarbonate concentration. After the value of SFR 50 BV/h, the resin is in the chloride form. Figure 4(A) also shows that in the initial part of the working cycle of resin with chlorinated water, there has been an immediate decrease of bicarbonates in the effluent already at SFR 2-6 BV/h after which the contents of bicarbonates slowly rises to SFR 50 BV/h, where the bicarbonates till the very end of the working cycle reach the concentration similar to that in raw water. The enormous in‐ crease in the chloride concentration at small SFR takes place simultaneously with the marked decrease in the content of bicarbonate in the effluent Figure 4(B). This chloride concentra‐ tion rise, a singly charged small and high diffusion rate, results in the increase in the measured conductivity. A higher increase in the chloride concentration was observed in the case of chlorinated water, which is understandable taking into consideration the release of chloride from hypochloric acid. The differences in the peaks of chloride concentration and electrical conductivity in the effluent for chlorinated and non-chlorinated water are certainly a consequence of the generation of nascent oxygen, which also activates the resin's


concentration

their outer surface. At the end of the investigated range of SFR, the HCO3

functional groups and thus contributes to a more effective ion exchange.

The effect of nascent oxygen on the oxidation of As(III) to As(V) is evident from the fact that in a wide range of SFR, from 2 to 300 BV/h, the total arsenic concentration in the effluent of chlorinated water was constantly below the MTC value [47] (Figure 5(A)). On the other hand, in the case of non-chlorinated water, the arsenic concentrations in the effluent at the SFR<100 BV/h were by 10 times and at 100<SFR<300 BV/h even by 17 times

higher. Also, it is evident that the presence of atomic oxygen in chlorinated water hin‐ ders desorption of sulfate from the resin and changes the position of sulfate anions in the Clifford series [35]. This effect was especially pronounced at smaller SFR values of about 25 BV/h, when desorption of sulfate ion was observed. At 170<SFR<300 BV/h, the sulfate removal was more efficient in the case of chlorinated water. At low SFR, the effect of the oxidant on the removal of NOM is more pronounced. In the effluent of the water treated with oxidant, this is evidenced as the lower values of both COD and TOC (Figure 5(B)). At the SFR between 2 and 50 BV/h, there is a competition between humic acids, arsenic, and sulfate with bicarbonate and chloride, which is especially pronounced in the presence of nascent oxygen. With the increase in SFR of chlorinated water, the measured NOM contents in the effluent were higher, which means that NOM removal from non-chlorinated water was higher under these flow conditions. Evidently, the resin's functional groups exhibit a lower affinity toward the newly formed, smaller, organic molecules resulting from the NOM degradation than to the original NOM molecules from the groundwater. Thus, the NOM concentration measured as COD in chlorinated effluent reaches tolerable level of 2 mg O2/ L [47] at 180 BV/h. In the case of non-chlorinated water, this value was not reached until 275 BV/h, suggesting that in such a medium the resin shows a higher affinity to NOM. The effect of contact time of the resin with chlorinated and non-chlorinated water on the NOM removal is presented in Figure 6(A). Changes of arsenic content in the effluent as a function of the contact time of chlorinated and non-chlorinated water are presented in Figure 6(B). As can be seen, more intensive changes in the NOM concentration take place at shorter contact times. To an EBCT value of about 0.05 h, it comes out that the adsorption-desorp‐ tion processes are especially pronounced in chlorinated water. At longer contact times, the COD and TOC values of the effluent become apparently constant. It is evident that in the shortest time of contact of water with the resin, the arsenic removal was most efficient in the presence of nascent oxygen. This is a consequence of the oxidation-reduction process‐ es by which is generated As(V), which exhibits remarkable adsorption affinity to the resin.

**Figure 6.** Influence of EBCT on the NOM (A) and arsenic (B) removal

### **3.2. Results obtained during strongly basic ion-exchange resin sorption characteristics determination**

During the investigation of optimal specific flow rate of strongly basic ion-exchange resin, it has come to the conclusion that optimal flow rate of the Amberlite IRA-958 was 40 L/h, i.e. SFR of 30 BV/h ± 5% when used on described groundwater. This research was conducted in order to determine resin sorption characteristics based on the experimental data and data given by the manufacturer [11]. Based on the data given by the manufacturer, one gram of the resin can adsorb from 3.47 to 5.21 mgO2 NOM expressed as COD. Investigated groundwater contains 7.73 mgO2/L NOM, expressed as COD. The calculation shows that one gram of SBIX may adsorb the NOM from 0.45 L to 0.67 L of such water. Taking into account the mass of the resin of 970 g, it can be calculated that the overall volume of the groundwater from 436.5 L to 650 L may be effectively treated with the used the SBIX. If this is expressed via the BV values, the expected adsorption capacity of the resin for NOM is in the range from 312 BV to 464 BV.

**Figure 7.** Changes of NOM (A) and arsenic (B) content in the effluent as a function of the overall volume of raw water passed through the SBIX

In the initial part of the sorption process, at small volumes of raw water of about 2,900 BV, as well as at the large volumes of over 13,500 BV, the NOM removal from chlorinated water is more efficient. In the first part of the operation cycle, the nascent oxygen generated from hypochloric acid causes NOM degradation and more efficient sorption of the degradation products of HAs and FAs compared to the native humins present in non-chlorinated water. These processes take place in the environment of the ion competition, as described by authors [40]. At increased volumes of groundwater passing through the system, surface adsorption is a dominant process, by which organic matter accumulates on the outer surface of the resin pearls. In this process, native HAs from non-chlorinated water are more efficiently bonded to the resin functional groups than the smaller molecules formed by the degradation of humin under the influence of nascent oxygen. Due to the larger number of the newly formed molecules in the effluent of chlorinated water at a smaller overall volume of water passing through the system, the resin's saturation and COD limit of 2 of mgO2/L [47] is attained faster, at about 3,000 BV. At the same time, the adsorption of larger molecules on the resin that was in contact with non-chlorinated water is slower, and the COD limit appears at 4,000 BV. From the analysis of TOC values of the effluent from chlorinated water, it comes out that the changes of this parameter with the volume of treated water are similar to the changes observed for the COD. However, the TOC changes in the effluent of non-chlorinated water show that up to the value of about 8,000 BV, the NOM removal expressed via TOC is more efficient than if expressed via COD, and after that these values become proportionally equivalent. This difference can be explained by the fact that in the absence of the oxidant in water, the COD determination by the permanganate method gives lower results. Namely, permanganate is not a sufficiently strong oxidizing agent to oxidize entirely the humic matter, but only its more easily oxidizable part - fulvic acids. On the other hand, the TOC method encompasses all the dissolved NOM, and this is the reason for the discrepancy between the COD and TOC results presented in Figure 7(A). In the initial phase of resin saturation, the NOM molecules that are more easily oxidized (that is CL) are preferentially adsorbed on the resin. With the increase in the amount of adsorbed NOM, proportionally to the volume of treated water above 8,000 BV, the resin affinity to sorption of organic matter becomes lower and larger amounts of easily oxidized NOM remain in the effluent, so that the changes in COD and TOC are proportional, which is evident from Figure 7(A). Namely, the appearance of COD and TOC curves above 8,000 BV becomes identical, since the COD value of, for example, 3 and 6 mgO2/L is propor‐ tional to the TOC values of 4 and 8 mg/L. As can be seen from Figure 7(B), the arsenic con‐ centrations in the effluent from chlorinated water are below the MTC of 0.01 mg/L only up to about 700 BV. By monitoring the effect of the further groundwater flow, it can be seen that arsenic removal is approximately equally efficient up to about 5,000 BV, from both chlorinated and non-chlorinated water. At the BV values above about 7,000, the effect of nascent oxygen on arsenic removal represents a complex process. In the investigated groundwater of complex composition, a number of redox reactions can take place in parallel. The reactions of HA degradation dominate over the reactions of As(III) oxidation. With the increase in the volume of treated water exceeding 5,000 BV, the amount of arsenic removed was twice larger when the treated water contained hypochlorite. In the presence of the oxidizing agent, the processes of NOM sorption in competition with arsenate binding to SBIX are more pronounced. The

**Figure 6.** Influence of EBCT on the NOM (A) and arsenic (B) removal

**determination**

92 Ion Exchange - Studies and Applications

passed through the SBIX

**3.2. Results obtained during strongly basic ion-exchange resin sorption characteristics**

During the investigation of optimal specific flow rate of strongly basic ion-exchange resin, it has come to the conclusion that optimal flow rate of the Amberlite IRA-958 was 40 L/h, i.e. SFR of 30 BV/h ± 5% when used on described groundwater. This research was conducted in order to determine resin sorption characteristics based on the experimental data and data given by the manufacturer [11]. Based on the data given by the manufacturer, one gram of the resin can adsorb from 3.47 to 5.21 mgO2 NOM expressed as COD. Investigated groundwater contains 7.73 mgO2/L NOM, expressed as COD. The calculation shows that one gram of SBIX may adsorb the NOM from 0.45 L to 0.67 L of such water. Taking into account the mass of the resin of 970 g, it can be calculated that the overall volume of the groundwater from 436.5 L to 650 L may be effectively treated with the used the SBIX. If this is expressed via the BV values, the expected adsorption capacity of the resin for NOM is in the range from 312 BV to 464 BV.

**Figure 7.** Changes of NOM (A) and arsenic (B) content in the effluent as a function of the overall volume of raw water

increased concentrations of arsenic in the effluent from chlorinated water appear as a conse‐ quence of arsenic desorption. Desorption process was especially pronounced at the volumes exceeding 14,000 BV, taking place simultaneously with the tendency of lowering arsenic concentrations in the effluent from non-chlorinated water.

The expressions (6)-(21) were used to calculate concentrations of NOM and arsenic in the overall volume of groundwater in the experiments with chlorinated and non-chlorinated water, amounts of NOM and arsenic in the effluent during the experiment, as well as the amounts of NOM and arsenic adsorbed on the SBIX. Total amounts of NOM and As that passed through the resin as well as amounts that charged the resin are presented in Table 3.


**Table 3.** Experimentally obtained resins sorption characteristics

**Figure 8.** Dependency of NOM in non-chlorinated (A), (C) and chlorinated water (B), (D) adsorbed on the SBIX and one remained in the effluent during the course of the experiment

NOM fractions, which are more difficult to oxidize, remained in the effluent, and the more easily oxidized NOM compounds were adsorbed onto the resin. The assumption of NOM desorption is supported by the fact that at the longest experimental time, the CODads was 35% smaller than the adsorbed NOM at the intersection of the CODout and CODads curves, as shown in Figure 8(A). Simultaneously, the COD in the effluent (CODout) increased 2.2 times as large. The ratio between the maximum value for the CODads (before beginning NOM desorption) of 61,674 mg O2 and the resin mass of 970 g describes the capacity of the resin for NOM sorption from the non-chlorinated water, with a value of 63.58 mg O2/g. The NOM sorption process in chlorinated water (Figure 8(B)), without desorption, occurred throughout the experiment. The amount of the more easily oxidized fractions was very high; therefore, the CODads values were similar to the CODin values. The total dissolved NOM sorption process in the non-chlorinated water, which was monitored by determining the TOC, was similar to the monitored COD (Figure 8(C)). After 10,900 BV, NOM in the effluent exceeded the NOM adsorbed onto the SBIX. The appearance of NOM desorption can be concluded from the fact that at the longest experimental time, the TOCads was 35% smaller than the TOCads at the intersection of the TOCout and TOCads curves. At the same time, the TOC in the effluent (TOCout) increased 2.2 times as large. As shown in Figure 8(D), the TOCout increased 3.2 times as large, and the amount of NOM adsorbed on the resin remained nearly constant. The NOM desorption began at 7712 BV when oxidant was used. This means that the resin adsorption capacity for NOM in the nonchlorinated water was higher than in the chlorinated water.

increased concentrations of arsenic in the effluent from chlorinated water appear as a conse‐ quence of arsenic desorption. Desorption process was especially pronounced at the volumes exceeding 14,000 BV, taking place simultaneously with the tendency of lowering arsenic

The expressions (6)-(21) were used to calculate concentrations of NOM and arsenic in the overall volume of groundwater in the experiments with chlorinated and non-chlorinated water, amounts of NOM and arsenic in the effluent during the experiment, as well as the amounts of NOM and arsenic adsorbed on the SBIX. Total amounts of NOM and As that passed

No chlorine 175.65 0.181 241.86 0.249 6.039 0.006 16,231 Chlorine present 179.90 0.185 247.71 0.255 6.186 0.006 16,623

**Figure 8.** Dependency of NOM in non-chlorinated (A), (C) and chlorinated water (B), (D) adsorbed on the SBIX and

NOM fractions, which are more difficult to oxidize, remained in the effluent, and the more easily oxidized NOM compounds were adsorbed onto the resin. The assumption of NOM desorption is supported by the fact that at the longest experimental time, the CODads was 35% smaller than the adsorbed NOM at the intersection of the CODout and CODads curves, as shown in Figure 8(A). Simultaneously, the COD in the effluent (CODout) increased 2.2 times as large. The ratio between the maximum value for the CODads (before beginning NOM desorption) of

**TOCtotal (g) TOCload (g/g) Astotal (g) Asload (g/g) BV**

through the resin as well as amounts that charged the resin are presented in Table 3.

concentrations in the effluent from non-chlorinated water.

**CODload (gO2/g)**

**Sorption characteristics**

94 Ion Exchange - Studies and Applications

**CODtotal (gO2)**

**Table 3.** Experimentally obtained resins sorption characteristics

one remained in the effluent during the course of the experiment

**Figure 9.** Dependence of the amounts of As contained in non-chlorinated (A) and chlorinated water (B) (Asin), adsor‐ bed on the SBIX (Asads) and remaining in the effluent (Asout) on the duration time of the experiment

Arsenic sorption process in the non-chlorinated water occurred throughout the entire experi‐ ment without the occurrence of desorption was shown in Figure 9(A). The only exception was at 166 h, when a short-lasting, dynamic equilibrium between the adsorbed and desorbed arsenic occurred. The amount of arsenic adsorbed during the experiment was very large, and the Asads value was constantly approaching the value for Asin. The pH of the investigated groundwater was 8.06, at which the HAsO4 2- ions of As(V) and H3AsO3 molecules of As(III) dominate compared with the total arsenic content [20, 48]; therefore, Asout mostly represents the amount of As(III), and Asads mostly represents the amount of As(V). The investigated resin was very effective at removing arsenates that were naturally present in the groundwater without the addition of the oxidant. The arsenates formed by the oxidation of arsenites with nascent oxygen simultaneously with competitive reactions of humin oxidation were adsorbed on the resin to a lesser extent, and after contact times exceeding 500 h, they desorbed and went into solution (Figure (9B)). Presence of arsenic desorption is supported by the fact that the Asads was 2.13 times smaller than the Asads at the intersection of the Asout and Asads curves. It is at this point that desorption process for arsenic actually begins. Contemporaneously, the As in the effluent (Asout) increased 1.96 times as larger. The exchange capacities of arsenic sorbed were calculated for the highest values of Asads for both parts of the investigation. Total exchange capacity of adsorbed arsenic Asads for non-chlorinated and chlorinated water was 0.045 eq/L and 0.028 eq/L, respectively. Lower level of adsorption in the chlorinated water is consequence of competition of arsenic anions and smaller molecules originated from NOM oxidation for resin binding cites. Threshold limit value of arsenic [47] was met at 40.48 BV in experiment with chlorinated water. As can be concluded on the basis of Figure 9, the investigated resin is very effective in removing arsenates that are naturally present in groundwater, without addition of the oxidant. The arsenates formed by the oxidation of arsenite by nascent oxygen under the conditions of the simultaneous occurrence of the competitive reactions of humin oxidation are adsorbed on the resin to a lower extent, and at the contact times exceeding 500 h, they are desorbed and passed to the solution.

Equations 22-24 were used to calculate the sorption efficiency on the resin of the NOM (expressed via COD and TOC) and arsenic. Figure 10 shows the sorption efficiency of NOM expressed as ECOD and ETOC.

**Figure 10.** Changes of the efficiency of NOM sorption on SBIX expressed via COD and TOC (A) and arsenic (B) with the time of treatment of chlorinated and non-chlorinated water

As can be seen from Figure 10, the efficiency of NOM sorption expressed as ECOD decreases with time in the experiment with non-chlorinated water, and the changes are almost linear. On the other hand, the analogous dependence for chlorinated water is of a different pattern. In the initial part of the experiment, to 100 h, as well as after 400 h, the efficiency of NOM sorption from chlorinated water is more pronounced. This means that the conditions of the presence of the oxidant in the groundwater in the beginning of resin saturation and at the end of this process favor the sorption of NOM, expressed either as ECOD or ETOC, compared to the desorption processes. The course of the changes of ETOC, reflecting definitely the overall content of humic substances, shows that the preferential sorption of NOM is pronounced in one-third of the overall treatment cycle, that is between the 48th and 395th h of the experiment. The large humin molecules are more readily adsorbed than the smaller molecules formed by their degradation. Since the efficiency of NOM removal by the resin decreases with time, the outer sorption layers become more attractive to smaller molecules, so that they are more competitive, and at the longest time, the NOM sorption from chlorinated water is more efficient. As can be seen, the efficiency of arsenic removal from chlorinated water is high only in the beginning of the working cycle. Evidently, the presence of the oxidant, which converts As(III) to As(V), does not contribute to the efficiency of arsenic removal. If one considers the entire working cycle of the resin, the average efficiency of arsenic removal from chlorinated water is about 60%, and from non-chlorinated water it is about 80 %.

into solution (Figure (9B)). Presence of arsenic desorption is supported by the fact that the Asads was 2.13 times smaller than the Asads at the intersection of the Asout and Asads curves. It is at this point that desorption process for arsenic actually begins. Contemporaneously, the As in the effluent (Asout) increased 1.96 times as larger. The exchange capacities of arsenic sorbed were calculated for the highest values of Asads for both parts of the investigation. Total exchange capacity of adsorbed arsenic Asads for non-chlorinated and chlorinated water was 0.045 eq/L and 0.028 eq/L, respectively. Lower level of adsorption in the chlorinated water is consequence of competition of arsenic anions and smaller molecules originated from NOM oxidation for resin binding cites. Threshold limit value of arsenic [47] was met at 40.48 BV in experiment with chlorinated water. As can be concluded on the basis of Figure 9, the investigated resin is very effective in removing arsenates that are naturally present in groundwater, without addition of the oxidant. The arsenates formed by the oxidation of arsenite by nascent oxygen under the conditions of the simultaneous occurrence of the competitive reactions of humin oxidation are adsorbed on the resin to a lower extent, and at the contact times exceeding 500

Equations 22-24 were used to calculate the sorption efficiency on the resin of the NOM (expressed via COD and TOC) and arsenic. Figure 10 shows the sorption efficiency of NOM

**Figure 10.** Changes of the efficiency of NOM sorption on SBIX expressed via COD and TOC (A) and arsenic (B) with

As can be seen from Figure 10, the efficiency of NOM sorption expressed as ECOD decreases with time in the experiment with non-chlorinated water, and the changes are almost linear. On the other hand, the analogous dependence for chlorinated water is of a different pattern. In the initial part of the experiment, to 100 h, as well as after 400 h, the efficiency of NOM sorption from chlorinated water is more pronounced. This means that the conditions of the presence of the oxidant in the groundwater in the beginning of resin saturation and at the end of this process favor the sorption of NOM, expressed either as ECOD or ETOC, compared to the desorption processes. The course of the changes of ETOC, reflecting definitely the overall content

h, they are desorbed and passed to the solution.

the time of treatment of chlorinated and non-chlorinated water

expressed as ECOD and ETOC.

96 Ion Exchange - Studies and Applications
