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Dewatering of activated sludge by Fenton's reagent
Advances in Environmental Research 7 (2003) 667–670
Dewatering of activated sludge by Fenton’s reagent Ming-Chun Lu*, Chien-Jung Lin, Chih-Hsiang Liao, Rui-Yuan Huang, Wang-Ping Ting Department of Environmental Engineering and Health, Chia Nan University of Pharmacy and Science, Tainan 717, Taiwan, ROC
Abstract The specific resistance, moisture and element analysis were used to evaluate the increase in filtration and dewatering efficiency when applying the Fenton system, Fe2q yH2 O2 and Fe3q yH2 O2 , to treat excess sludge. Addition of Fe2q, Fe3q and H2O2 were also selected as treatment processes for comparison. The excess sludge used in this study was obtained from the wastewater treatment plant of An-Ping Industrial Park in Tainan, Taiwan. Results show that ferrous and ferric ions can catalyze hydrogen peroxide to promote the filterability of sludge. Four ratios of Fe2q yH2O2 were used to investigate the effect of Fe2q concentration on the reduction of specific resistance. When 6000 mgyl of Fe2q and 3000 mgyl of H2O2 were added into the sludge, the specific resistance of the treated sludge had only 10% of that of the original sludge. Ferric ions also have high catalyzing ability similar to ferrous ions. However, Fenton’s reagent, Fe2q yH2O2, has a higher dewatering efficiency than other processes. The moisture of the cake sludge generated by treatment with Fenton’s reagent was 75.2%, and those conditioned by other processes were approximately 85%. The mechanism by which Fenton’s reagent increased the sludge dewaterability could be the destruction of cells leading to the release of the intercellular material. 䊚 2002 Elsevier Science Ltd. All rights reserved. Keywords: Sludge; Hydrogen peroxide; Ferrous ions; Dewatering; Filtration
1. Introduction All conventional wastewater treatment processes produce large quantities of waste material in the form of a dilute solid mixture known as sludge. Sludge contains a major portion of the pollutants responsible for the offensive and noxious nature of untreated wastewater and therefore, must be treated or processed so that final release to the environment can be made without harmful effects (Benefield and Randall, 1980). Traditionally, excess sludge is usually conditioned to improve its dewatering properties, and then dewatered mechanically. Fenton technology is an advanced oxidation process (AOP) that can oxidize organic compounds efficiently. By applying this technology, organic compounds in activated sludge are destroyed, which may
*Corresponding author. Tel.: q886-6266-0000; fax: q8866266-7323. E-mail address: [email protected] (M.-C. Lu).
lead to increased filterability of the sludge. Mustranta and Viikari (1993) have reported that Fenton’s reagent can be used to improve the dewatering of paper mill sludge efficiently. The Fenton system uses ferrous ions to react with hydrogen peroxide, producing hydroxyl radicals with powerful oxidizing abilities to degrade certain toxic contaminants (Spacek et al., 1995; Lipczynska-Kochany et al., 1995; Lu et al., 1997). The primary oxidant in this catalytic reaction is believed to be hydroxyl radical, which generated by conversion of hydrogen peroxide. Besides, the reaction of hydrogen peroxide with ferric ions is referred to as a Fenton-like process. Pignatello (1992) reported that ferric ionsyhydrogen peroxide could oxidize 2,4-D and 2,4,5-T effectively. This study was to explore the possibility of applying Fenton and Fenton-like processes in increasing the filtration and dewatering efficiencies of excess sludge obtained from An-Ping Industrial Park in Tainan, Taiwan. Specific resistance, moisture and element analyses were selected as the indexes to explore the characteristics of sludge dewatering and filtration.
1093-0191/03/$ - see front matter 䊚 2002 Elsevier Science Ltd. All rights reserved. PII: S 1 0 9 3 - 0 1 9 1 Ž 0 2 . 0 0 0 3 9 - 4
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M.-C. Lu et al. / Advances in Environmental Research 7 (2003) 667–670
Table 1 Properties of the original activated sludge Average specific resistance (mykg)
pH
SS (mgyl)
SV30 (mlyg)
Filtrate TOC (mgyl)
Cake moisture (%)
1.17=1013
6.14
8300
63
15.7
85.7
2. Material and methods
ability of the sludge is defined as below,
2.1. Sludge characteristics
SRs
The sludge used in this study was obtained from the wastewater treatment plant of An-Ping Industrial Park in Tainan, Taiwan. Some information concerning the sludge is presented in Table 1. 2.2. Sludge treatment Fenton solution was obtained by preparing a 100-ml solution containing Fe2q or Fe3q, and the initial pH was adjusted to the desired value using HClO4. After the pH adjustment, the solution was poured into a 500ml beaker, and then mixed by a stirrer at approximately 30 8C. Fenton reactions were initiated after adding hydrogen peroxide. Fenton solutions, Fe2q yH2O2 or Fe3qyH2O2, were then poured into the sludge samples to start the treatment processes for 30 min. The oxidation treatments were carried out in 500-ml beakers using 100-ml sludge samples. Additionally, Fe2q , Fe3q and H2O2 were also used to condition the sludge for comparing their filtration and dewatering efficiencies with the Fenton system. 2.3. Analytical procedures Filterability was determined by measuring the specific resistance using the Buchner funnel method. The filter-
2PA2b mw
(1)
where SR: P: A: m: w: b:
specific resistance (mykg); filtration pressure (Nym2); filter area (m2); viscosity of the filtrate (NØsym2); weight of cake solids per unit volume of filtrate (kgym3) and slope of filtrate discharge curve (sym6).
The cake sludges produced from the Buchner funnel process were dried by an oven at 105 8C to determine the water content of the cake sludge for evaluating the dewaterability of sludge treated by the processes in this study. Since the SR is not a constant value when the sludge samples are not taken from the treatment plant at one time, the index for the percentage of SR reduction listed as below is used to compare the filterability efficiencies under different experimental conditions. Reduction of SRŽ%.s
SRoriginalySRtreatment SRoriginal =100%
(2)
where SRoriginal: specific resistance for original sludge without any treatment. SRtreatment: specific resistance for sludge treated by adding chemicals. Organic content in cake sludge was determined by an elemental analyzer (vario EL, Germany). Total organic carbon in filtrate was analyzed by a TOC analyzer (Shimadz 4000, Japan). 3. Results and discussion 3.1. Comparison of different processes on the filterability and dewaterability of sludge
Fig. 1. Comparison of different processes on the reduction of specific resistance. (Experimental conditions: Fe2qs6000 mgyl; Fe3qs6000 mgyl; H2O2s3000 mgyl; initial pHs3).
To confirm the contribution of Fe2q yH2O2 or Fe3qy H2O2 on the filterability of sludge, experiments with adding Fe2q, Fe3q and H2O2 separately were conducted for comparison. The initial pH of the Fenton solutions before being added to the sludge samples was 3. The concentrations of Fe2q, Fe3q and H2O2 were 6000, 6000 and 3000 mgyl, respectively. Fig. 1 shows that
M.-C. Lu et al. / Advances in Environmental Research 7 (2003) 667–670
Fig. 2. Comparison of different processes on the dewaterability of sludge. (Experimental conditions: Fe2qs6000 mgyl; Fe3qs6000 mgyl; H2O2s3000 mgyl; initial pHs3).
669
Fig. 3. Effect on Fenton reaction on the reduction of specific resistance. (Experimental conditions: Fe2qs6000 mgyl; Fe3qs6000 mgyl; H2O2s3000 mgyl; initial pHs3).
3.2. Effect of FeyH2O2 ratio on the filterability of sludge adding hydrogen peroxide did not improve and even decreased the filterability. However, when the ferrous and ferric ions were present, the reductions of specific resistance increased to 55.4 and 85.5%, respectively. Although the Fenton system has higher efficiencies than other processes, the filterability of sludge treated by the Fenton system was not obviously superior to that of Fe3q since FeCl3 is also a kind of coagulant. Consequently, treatment of sludge by Fe2q yH2O2 or Fe3qy H2O2 and Fe3q can reduce the filterability efficiencies over 80%. Based on the observations in Fig. 1, moisture of cake sludge was further selected as an index to evaluate the dewatering ability of sludge. As shown in Fig. 2, the moistures of cake sludges were approximately 85% except for with Fe2q yH2O2. Clearly, Fenton’s reagent has the highest dewatering efficiency. In this study, the Fenton reaction was started for a period of time, and then poured into sludge samples. Based on the discussion above, the length of the time period could affect the oxidation results because the Fenton reaction may shift from the first stage to the second stage. Therefore, this study also investigated the effect of the Fenton reaction time on the filterability of sludge. As shown in Fig. 3, no significant effect occurred by using different Fenton solutions. This means that for sludge filterability the Fenton solution could be added into the sludge sample at 2 min or 120 min, since the reductions of specific resistances were similar. However, it is suggested that adding the Fenton solution at 2 min could have the best efficiencies in dewaterability as shown Fig. 4. In other words, the Fenton solution has to be added into the sludge sample as soon as possible after it is prepared.
Because the amount of ferrous and ferric ions added directly affects the production of hydroxyl radicals, its influence on the filterability and dewaterability of sludge is also great. In this experiment, 3000 mgyl of hydrogen peroxide were used to construct the Fenton reaction and observe the change of specific resistance reduction when different amounts of ferrous and ferric ions were added. As shown in Fig. 5, the larger the added amounts of ferrous ions, the higher the filterability efficiency. When the concentrations of Fe2q and H2O2 were 1500 and 3000 mgyl, respectively, the reduction of specific resistance was 87.6%. The reduction of specific resistance can reach 95% if the added amount of ferrous ions increased to 9000 mgyl. However, the reduction of specific resistance did not increase with increasing the
Fig. 4. Effect on Fenton reaction on the dewaterability of sludge. (Experimental conditions: Fe2qs6000 mgyl; Fe3qs 6000 mgyl; H2O2s3000 mgyl; initial pHs3).
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M.-C. Lu et al. / Advances in Environmental Research 7 (2003) 667–670
cells, they contain significant amounts of water. Oxidative treatment may cause the destruction of cells; the intercellular material, which has a high water content, is released. As shown in Fig. 6, the organic contents in the original cake sludge and its filtrate were 0.303 and 3.7 mg, respectively. When Fe2q and H2O2 were added to the sludge sample, the organic content in cake sludge was reduced to 0.074 mg, and that in the filtrate increased to 4.1 mg. Therefore, it was assumed that the reason for the increased filterability and dewaterability of sludge could be due to the destruction of cells. The destruction of cells leading to the release of the intercellular material resulted in the increase in organic content of the filtrate. Fig. 5. Effect of FeyH2O2 ratio on the reduction of specific resistance. (Experimental conditions: H2O2 s3000 mgyl; initial pHs3).
amount of ferric ions added in the reaction mixture. When the concentration of ferric ions was 1500 mgyl and higher than 1500 mgyl, the reductions of specific resistance were 82.3% and approximately 85%, respectively. It can be derived from this result that the oxidization rate after the addition of ferric ions is smaller than that resulting from the addition of ferrous ions at different ratios for FeyH2O2. 3.3. Mechanism of Fenton’s reagent improving the dewatering of sludge According to the above discussion, the main mechanism of increasing the sludge filterability and dewaterability is still not clear. This section further discusses the oxidation reaction using element analysis as the tool to explore the organic contents in the cake sludge and filtrate. Since the activated sludges are mainly microbial
4. Conclusions The filtration and dewatering characteristics of excess sludge treated by Fe2q yH2O2 and Fe3q yH2O2 were investigated in this study. Ferrous and ferric ions can catalyze hydrogen peroxide to promote the filterability of sludge. Ferric ions also have a high catalyzing ability similar to ferrous ions. However, Fenton’s reagent, Fe2qyH2O2, has a higher dewatering efficiency than other processes. Promotion of the filterability and dewaterability could be due to the destruction of cells leading to the release of the intercellular material. Futhermore, study is needed to investigate the economics of the process. Acknowledgments This research is supported by the National Science Council, Republic of China (Grant NSC 89-2211-E041-025) References
Fig. 6. Comparison of organic carbon in cake sludge and filtrate after Fenton treatment. (Experimental conditions: Fe2qs 6000 mgyl; H2O2s3000 mgyl; initial pHs3).
Benefield, L.D., Randall, C.W., 1980. Biological process design for wastewater treatment. Prentice-Hall, Inc, NJ. Lipczynska-Kochany, E., Sprah, G., Harms, S., 1995. Influence of some groundwater and surface waters constitutes on the degradation of 4-chlorophenol by the Fenton reaction. Chemosphere 30, 9–20. Lu, M.C., Chen, J.N., Chang, C.P., 1997. Chemical oxidation of dichlorvos insecticide with Fenton’s reagent. Chemosphere 35, 2285–2293. Mustranta, A., Viikari, L., 1993. Dewatering of activated sludge by an oxidative treatment. Water Sci. Technol. 28, 213–221. Pignatello, J.J., 1992. Dark and photoassisted Fe3q-catalyzed degradation of chlorophenoxy herbicides by hydrogen peroxide. Environ. Sci. Technol. 26, 944–951. Spacek, W., Bauer, R., Heisler, G., 1995. Heterogeneous and homogeneous wastewater treatment-comparison between photodegradation with TiO2 and the photo-Fenton reaction. Chemosphere 30, 477–484.
Dewatering of activated sludge by Fenton’s reagent Ming-Chun Lu*, Chien-Jung Lin, Chih-Hsiang Liao, Rui-Yuan Huang, Wang-Ping Ting Department of Environmental Engineering and Health, Chia Nan University of Pharmacy and Science, Tainan 717, Taiwan, ROC
Abstract The specific resistance, moisture and element analysis were used to evaluate the increase in filtration and dewatering efficiency when applying the Fenton system, Fe2q yH2 O2 and Fe3q yH2 O2 , to treat excess sludge. Addition of Fe2q, Fe3q and H2O2 were also selected as treatment processes for comparison. The excess sludge used in this study was obtained from the wastewater treatment plant of An-Ping Industrial Park in Tainan, Taiwan. Results show that ferrous and ferric ions can catalyze hydrogen peroxide to promote the filterability of sludge. Four ratios of Fe2q yH2O2 were used to investigate the effect of Fe2q concentration on the reduction of specific resistance. When 6000 mgyl of Fe2q and 3000 mgyl of H2O2 were added into the sludge, the specific resistance of the treated sludge had only 10% of that of the original sludge. Ferric ions also have high catalyzing ability similar to ferrous ions. However, Fenton’s reagent, Fe2q yH2O2, has a higher dewatering efficiency than other processes. The moisture of the cake sludge generated by treatment with Fenton’s reagent was 75.2%, and those conditioned by other processes were approximately 85%. The mechanism by which Fenton’s reagent increased the sludge dewaterability could be the destruction of cells leading to the release of the intercellular material. 䊚 2002 Elsevier Science Ltd. All rights reserved. Keywords: Sludge; Hydrogen peroxide; Ferrous ions; Dewatering; Filtration
1. Introduction All conventional wastewater treatment processes produce large quantities of waste material in the form of a dilute solid mixture known as sludge. Sludge contains a major portion of the pollutants responsible for the offensive and noxious nature of untreated wastewater and therefore, must be treated or processed so that final release to the environment can be made without harmful effects (Benefield and Randall, 1980). Traditionally, excess sludge is usually conditioned to improve its dewatering properties, and then dewatered mechanically. Fenton technology is an advanced oxidation process (AOP) that can oxidize organic compounds efficiently. By applying this technology, organic compounds in activated sludge are destroyed, which may
*Corresponding author. Tel.: q886-6266-0000; fax: q8866266-7323. E-mail address: [email protected] (M.-C. Lu).
lead to increased filterability of the sludge. Mustranta and Viikari (1993) have reported that Fenton’s reagent can be used to improve the dewatering of paper mill sludge efficiently. The Fenton system uses ferrous ions to react with hydrogen peroxide, producing hydroxyl radicals with powerful oxidizing abilities to degrade certain toxic contaminants (Spacek et al., 1995; Lipczynska-Kochany et al., 1995; Lu et al., 1997). The primary oxidant in this catalytic reaction is believed to be hydroxyl radical, which generated by conversion of hydrogen peroxide. Besides, the reaction of hydrogen peroxide with ferric ions is referred to as a Fenton-like process. Pignatello (1992) reported that ferric ionsyhydrogen peroxide could oxidize 2,4-D and 2,4,5-T effectively. This study was to explore the possibility of applying Fenton and Fenton-like processes in increasing the filtration and dewatering efficiencies of excess sludge obtained from An-Ping Industrial Park in Tainan, Taiwan. Specific resistance, moisture and element analyses were selected as the indexes to explore the characteristics of sludge dewatering and filtration.
1093-0191/03/$ - see front matter 䊚 2002 Elsevier Science Ltd. All rights reserved. PII: S 1 0 9 3 - 0 1 9 1 Ž 0 2 . 0 0 0 3 9 - 4
668
M.-C. Lu et al. / Advances in Environmental Research 7 (2003) 667–670
Table 1 Properties of the original activated sludge Average specific resistance (mykg)
pH
SS (mgyl)
SV30 (mlyg)
Filtrate TOC (mgyl)
Cake moisture (%)
1.17=1013
6.14
8300
63
15.7
85.7
2. Material and methods
ability of the sludge is defined as below,
2.1. Sludge characteristics
SRs
The sludge used in this study was obtained from the wastewater treatment plant of An-Ping Industrial Park in Tainan, Taiwan. Some information concerning the sludge is presented in Table 1. 2.2. Sludge treatment Fenton solution was obtained by preparing a 100-ml solution containing Fe2q or Fe3q, and the initial pH was adjusted to the desired value using HClO4. After the pH adjustment, the solution was poured into a 500ml beaker, and then mixed by a stirrer at approximately 30 8C. Fenton reactions were initiated after adding hydrogen peroxide. Fenton solutions, Fe2q yH2O2 or Fe3qyH2O2, were then poured into the sludge samples to start the treatment processes for 30 min. The oxidation treatments were carried out in 500-ml beakers using 100-ml sludge samples. Additionally, Fe2q , Fe3q and H2O2 were also used to condition the sludge for comparing their filtration and dewatering efficiencies with the Fenton system. 2.3. Analytical procedures Filterability was determined by measuring the specific resistance using the Buchner funnel method. The filter-
2PA2b mw
(1)
where SR: P: A: m: w: b:
specific resistance (mykg); filtration pressure (Nym2); filter area (m2); viscosity of the filtrate (NØsym2); weight of cake solids per unit volume of filtrate (kgym3) and slope of filtrate discharge curve (sym6).
The cake sludges produced from the Buchner funnel process were dried by an oven at 105 8C to determine the water content of the cake sludge for evaluating the dewaterability of sludge treated by the processes in this study. Since the SR is not a constant value when the sludge samples are not taken from the treatment plant at one time, the index for the percentage of SR reduction listed as below is used to compare the filterability efficiencies under different experimental conditions. Reduction of SRŽ%.s
SRoriginalySRtreatment SRoriginal =100%
(2)
where SRoriginal: specific resistance for original sludge without any treatment. SRtreatment: specific resistance for sludge treated by adding chemicals. Organic content in cake sludge was determined by an elemental analyzer (vario EL, Germany). Total organic carbon in filtrate was analyzed by a TOC analyzer (Shimadz 4000, Japan). 3. Results and discussion 3.1. Comparison of different processes on the filterability and dewaterability of sludge
Fig. 1. Comparison of different processes on the reduction of specific resistance. (Experimental conditions: Fe2qs6000 mgyl; Fe3qs6000 mgyl; H2O2s3000 mgyl; initial pHs3).
To confirm the contribution of Fe2q yH2O2 or Fe3qy H2O2 on the filterability of sludge, experiments with adding Fe2q, Fe3q and H2O2 separately were conducted for comparison. The initial pH of the Fenton solutions before being added to the sludge samples was 3. The concentrations of Fe2q, Fe3q and H2O2 were 6000, 6000 and 3000 mgyl, respectively. Fig. 1 shows that
M.-C. Lu et al. / Advances in Environmental Research 7 (2003) 667–670
Fig. 2. Comparison of different processes on the dewaterability of sludge. (Experimental conditions: Fe2qs6000 mgyl; Fe3qs6000 mgyl; H2O2s3000 mgyl; initial pHs3).
669
Fig. 3. Effect on Fenton reaction on the reduction of specific resistance. (Experimental conditions: Fe2qs6000 mgyl; Fe3qs6000 mgyl; H2O2s3000 mgyl; initial pHs3).
3.2. Effect of FeyH2O2 ratio on the filterability of sludge adding hydrogen peroxide did not improve and even decreased the filterability. However, when the ferrous and ferric ions were present, the reductions of specific resistance increased to 55.4 and 85.5%, respectively. Although the Fenton system has higher efficiencies than other processes, the filterability of sludge treated by the Fenton system was not obviously superior to that of Fe3q since FeCl3 is also a kind of coagulant. Consequently, treatment of sludge by Fe2q yH2O2 or Fe3qy H2O2 and Fe3q can reduce the filterability efficiencies over 80%. Based on the observations in Fig. 1, moisture of cake sludge was further selected as an index to evaluate the dewatering ability of sludge. As shown in Fig. 2, the moistures of cake sludges were approximately 85% except for with Fe2q yH2O2. Clearly, Fenton’s reagent has the highest dewatering efficiency. In this study, the Fenton reaction was started for a period of time, and then poured into sludge samples. Based on the discussion above, the length of the time period could affect the oxidation results because the Fenton reaction may shift from the first stage to the second stage. Therefore, this study also investigated the effect of the Fenton reaction time on the filterability of sludge. As shown in Fig. 3, no significant effect occurred by using different Fenton solutions. This means that for sludge filterability the Fenton solution could be added into the sludge sample at 2 min or 120 min, since the reductions of specific resistances were similar. However, it is suggested that adding the Fenton solution at 2 min could have the best efficiencies in dewaterability as shown Fig. 4. In other words, the Fenton solution has to be added into the sludge sample as soon as possible after it is prepared.
Because the amount of ferrous and ferric ions added directly affects the production of hydroxyl radicals, its influence on the filterability and dewaterability of sludge is also great. In this experiment, 3000 mgyl of hydrogen peroxide were used to construct the Fenton reaction and observe the change of specific resistance reduction when different amounts of ferrous and ferric ions were added. As shown in Fig. 5, the larger the added amounts of ferrous ions, the higher the filterability efficiency. When the concentrations of Fe2q and H2O2 were 1500 and 3000 mgyl, respectively, the reduction of specific resistance was 87.6%. The reduction of specific resistance can reach 95% if the added amount of ferrous ions increased to 9000 mgyl. However, the reduction of specific resistance did not increase with increasing the
Fig. 4. Effect on Fenton reaction on the dewaterability of sludge. (Experimental conditions: Fe2qs6000 mgyl; Fe3qs 6000 mgyl; H2O2s3000 mgyl; initial pHs3).
670
M.-C. Lu et al. / Advances in Environmental Research 7 (2003) 667–670
cells, they contain significant amounts of water. Oxidative treatment may cause the destruction of cells; the intercellular material, which has a high water content, is released. As shown in Fig. 6, the organic contents in the original cake sludge and its filtrate were 0.303 and 3.7 mg, respectively. When Fe2q and H2O2 were added to the sludge sample, the organic content in cake sludge was reduced to 0.074 mg, and that in the filtrate increased to 4.1 mg. Therefore, it was assumed that the reason for the increased filterability and dewaterability of sludge could be due to the destruction of cells. The destruction of cells leading to the release of the intercellular material resulted in the increase in organic content of the filtrate. Fig. 5. Effect of FeyH2O2 ratio on the reduction of specific resistance. (Experimental conditions: H2O2 s3000 mgyl; initial pHs3).
amount of ferric ions added in the reaction mixture. When the concentration of ferric ions was 1500 mgyl and higher than 1500 mgyl, the reductions of specific resistance were 82.3% and approximately 85%, respectively. It can be derived from this result that the oxidization rate after the addition of ferric ions is smaller than that resulting from the addition of ferrous ions at different ratios for FeyH2O2. 3.3. Mechanism of Fenton’s reagent improving the dewatering of sludge According to the above discussion, the main mechanism of increasing the sludge filterability and dewaterability is still not clear. This section further discusses the oxidation reaction using element analysis as the tool to explore the organic contents in the cake sludge and filtrate. Since the activated sludges are mainly microbial
4. Conclusions The filtration and dewatering characteristics of excess sludge treated by Fe2q yH2O2 and Fe3q yH2O2 were investigated in this study. Ferrous and ferric ions can catalyze hydrogen peroxide to promote the filterability of sludge. Ferric ions also have a high catalyzing ability similar to ferrous ions. However, Fenton’s reagent, Fe2qyH2O2, has a higher dewatering efficiency than other processes. Promotion of the filterability and dewaterability could be due to the destruction of cells leading to the release of the intercellular material. Futhermore, study is needed to investigate the economics of the process. Acknowledgments This research is supported by the National Science Council, Republic of China (Grant NSC 89-2211-E041-025) References
Fig. 6. Comparison of organic carbon in cake sludge and filtrate after Fenton treatment. (Experimental conditions: Fe2qs 6000 mgyl; H2O2s3000 mgyl; initial pHs3).
Benefield, L.D., Randall, C.W., 1980. Biological process design for wastewater treatment. Prentice-Hall, Inc, NJ. Lipczynska-Kochany, E., Sprah, G., Harms, S., 1995. Influence of some groundwater and surface waters constitutes on the degradation of 4-chlorophenol by the Fenton reaction. Chemosphere 30, 9–20. Lu, M.C., Chen, J.N., Chang, C.P., 1997. Chemical oxidation of dichlorvos insecticide with Fenton’s reagent. Chemosphere 35, 2285–2293. Mustranta, A., Viikari, L., 1993. Dewatering of activated sludge by an oxidative treatment. Water Sci. Technol. 28, 213–221. Pignatello, J.J., 1992. Dark and photoassisted Fe3q-catalyzed degradation of chlorophenoxy herbicides by hydrogen peroxide. Environ. Sci. Technol. 26, 944–951. Spacek, W., Bauer, R., Heisler, G., 1995. Heterogeneous and homogeneous wastewater treatment-comparison between photodegradation with TiO2 and the photo-Fenton reaction. Chemosphere 30, 477–484.