Hybrid Constructed Wetland to Improve Organic Matter and Nutrient Removal
, M. A. Jaramillo-Morán 2 and M. Garrido 2Round 1
Reviewer 1 Report
Interesting work that could be useful for the scientific community. The work appears to be distinctive and was performed using a new approach which adds to the overall novelty. However, the manuscript warrants major revisions to enhance the clarity and statistical relevance of the presented data. Substantial revisions in the presented Tables and Figures are recommended.
Specific comments:
Line 14: Abstract - Typo in the word it.
Line 35: Add a reference.
Line 40 and 42: Require a reference from scientific literature.
Line 74: Any reference?
Table 1: I suggest the authors redesign the table and represent the data in the form of 95th percentile of confidence intervals. For example, COD of 1700 ± 560 mg/L (just an example, may not be right). It will be more reader friendly and relevant from statistical perspectives.
Table 2: Typos have to be resolved and if possible represent data with 95th percentile confidence intervals.
Methods: Section 2.1.1 – Any estimation of how much thick solids are received on a periodical basis (in say mg/L per week)?
Methods: Add a section to highlight the statistical procedures adopted in this study. Were experimental and analytical replications performed? It will be critical to highlight.
Figure 3: The authors need to add error bars to the data. Else, how are the authors confident with the data? Also, I will recommend (for all relevant figures) that the X-axis be changed from exact dates to a more professional representation (say day 1, 2, 3etc..).
Figure 3 and 4: What does the secondary axis represent? The figures are not clear. I recommend the authors add axis titles to aid the reader’s understanding.
Results: I am not satisfied with the way the authors have represented the data in the results section. It warrants a thorough revision, particularly on data values that are represented as exact numbers. For example,
Line 257: NH4+ removes efficiency at the VFCW output achieves a mean value of 46% in this stage of…
Although the author’s have performed statistical studies in table 3 and 4, the data represented here is exact whole numbers. I recommend the authors revise it and represent it in the form of X ± y% in the entire text. If possible, the use of statistical tools such as the t-test to highlight differences in data is highly recommended.
Table 6 and related discussions should be moved to the previous sections (not in conclusion).
Author Response
Responses to reviewers.
We thank the reviewers’ comments. We do agree with some of their views. We have carried out the modifications proposed and we think that these changes have improved the quality of the work. Below, we clarify each of the points.
Reply to Anonymous Referee #1
Interesting work that could be useful for the scientific community. The work appears to be distinctive and was performed using a new approach which adds to the overall novelty. However, the manuscript warrants major revisions to enhance the clarity and statistical relevance of the presented data. Substantial revisions in the presented Tables and Figures are recommended.
Specific comments:
Line 14: Abstract - Typo in the word it.
This change has been realized in the manuscript.
Line 35: Add a reference.
Line 40 and 42: Require a reference from scientific literature.
Line 74: Any reference?
According to the referee’s suggestion, we have included the following references:
Gallego A.; Rodriguez, L.;Hospido, A.; Moreira, M.T.;Feijoo, G. Development of regional characterization factors for aquatic eutrophication. Int. J. Life Cycle Ass.2010, 15, pp. 32-43.
Karaouzas, I.; Smeti, E.; Vourka, A.; Vardakas, L.;Kalogianni, E. Assessing the ecological effects of water stress and pollution in a temporary river - Implications for water management.Sci.Total Environ.2018, 618, pp.1591-1604.
Directive 91/271/EEC of 21 May 1991 concerning urban wastewater treatment.
Table 1: I suggest the authors redesign the table and represent the data in the form of 95thpercentile of confidence intervals. For example, COD of 1700 ± 560 mg/L (just an example, may not be right). It will be more reader friendly and relevant from statistical perspectives.
We agree with the referee. Table 1 has been modified in the manuscript according to the reviewer’s suggestion. Currently, this Table has been re-organized in the manuscript and for this reason the number of the Table is 2.
Table 2. Input load of the treatment plant.
|
Parameter |
Average |
95% confidence interval |
Standard Deviation |
Maximum |
Minimum |
|
COD (mg/L) |
1,770.00 |
± 399.00 |
998.00 |
4420.00 |
655.00 |
|
BOD (mg/L) |
566.00 |
± 158.00 |
387.00 |
1672.00 |
120.00 |
|
TSS (mg/L) |
911.00 |
± 215.00 |
538.00 |
2152.00 |
154.00 |
|
PT (mg/L) |
28.90 |
± 3.26 |
7.26 |
47.00 |
20.00 |
|
NT (mg/L) |
194.80 |
± 44.60 |
106.80 |
560.00 |
71.60 |
|
NH4+ (mg/L) |
116.20 |
± 26.90 |
65.90 |
330.00 |
43.50 |
|
pH |
7.26 |
± 0.14 |
0.33 |
7.94 |
6.47 |
|
CDC (µS/cm) |
1,567.00 |
± 231.00 |
565.00 |
3070.00 |
690.00 |
Table 2: Typos have to be resolved and if possible represent data with 95th percentile confidence intervals.
We agree with the referee, however, Table 2 corresponds to the Legal limits of discharges to water courses for organic matter and solids. This Table appears in Directive 91/271/EEC. For this reason, we have not represented data with 95th percentile confidence intervals.
Reference:
Directive 91/271/EEC of 21 May 1991 concerning urban wastewater treatment.
Methods: Section 2.1.1 – Any estimation of how much thick solids are received on a periodical basis (in say mg/L per week)?
The thick solids were received in two peaks per week. These peaks are related to the cleaning process of the farm and the effect of the larger colloid solids were controlled in the pretreatment and the rest of the thick solid were retain in the HUSB because these digester were designed with a high hydraulic retention time.
Methods: Add a section to highlight the statistical procedures adopted in this study. Were experimental and analytical replications performed? It will be critical to highlight.
According to the referee’s suggestion we have added the description of sampling and analytical processes to highlight the experimental and analytical replication performed.
2.2 Sampling and analytical process.
Four different points were selected to carry out the sampling process: the first point was the influent, before the pretreatment, the second point was before VFCW, the third point was before the HCFW and finally, the fourth one was the effluent. The influent and the effluent were collected with an autosampler to take 200 mL of wastewater each hour during 24-hour with the aim of capturing average characteristics of wastewater over a period of 1 day in a composite sample. Grab samples were collected from the other points early in the morning (9-12 a.m.). The volume of the grab samples were 1,000 mL and the volume of the composite samples were 2,400 mL (100 mL of each hour sample). They all were kept at 4ºC and processed in less than 24 hours after sampling.
The treatment plant was weekly monitored from July 2018 to March 2020. A total of 23 composite influent samples and 23 composite output samples were taken, related to the availability of the autosamplers in the dates pointed out in Figures 3 and 4. A total of 63 grab samples of wastewater before the VFCW and 63 grab samples before the HCFW were gathered, although, for the sake of simplicity, they are not shown in Figures 3 and 4.
Nine variables were measured in each sample: Total Nitrogen (TN), Total Phosphorous (TP), Ammonia (NH4+), Nitrate (NO3-), pH, Electrical Conductivity (EC), Total Suspended Solids (TSS), Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD). These variables were obtained according to standard methods for wastewater treatment analysis [29]. The analytical methods of these nine variables were validated according to the ISO/IEC 17025:2017 [30] by the R+D Laboratory of PROMEDIO (Consorcio para la Gestión de los Servicios Medioambientales de la Provincia de Badajoz ) and the uncertainty associated to the values are presented in Figure 3.
Input load data have been statistically analyzed in order to point out their validity. They are shown in Table 2, where average values of each parameter are presented along with their corresponding 95 % confident intervals and standard deviations. Maximum and minimum values of each one are also provided in order to identify the presence of possible outliers.
2.3 Removal efficiency
The removal efficiency of the treatment process for each variable was obtained by comparing concentrations in influent (Ci) and effluent (Ce) water:
Figure 3: The authors need to add error bars to the data. Else, how are the authors confident with the data? Also, I will recommend (for all relevant figures) that the X-axis be changed from exact dates to a more professional representation (say day 1, 2, 3etc..).
According to the referee’s suggestion we have added error bars in Figures 3 and 4. The error bars represent the uncertainty associated to the analytic method for each parameter analyzed.
The uncertainty for each parameter is as follows:
SST: 22%, COD: 22%, BOD: 30%, NH4+:15%; TN: 19% and TP: 15%.
However, we have not modified the X-axis because in the text in Section 3 Results (lines 270-270) we referred to dates to explain the results in the ammonia and nitrogen total remove. Therefore, we believed that is necessary to show the dates in Figures 3 and 4.
a)
b)
c)
Figure 3. Organic matter concentrations and TSS at the input and output of the plant. Blue bars show the input concentration in the plant and grey bars represent output concentration of the HUSB. a) TSS. b) COD. c) BOD.
a)
b)
c)
Figure 4. Nutrients concentrations at the input and output of the plant. Blue bars show the input concentration in the plant and grey bars represent output concentration of the HUSB. a) NH4+. b) TN. c) TP.”
Figure 3 and 4: What does the secondary axis represent? The figures are not clear. I recommend the authors add axis titles to aid the reader’s understanding.
We do agree with his comment.The secondary axis represents the concentrations at the output of the plant in mg/L. We show a secondary axis to better visualize the output concentration because it presents low values concentrations at the output of plant.
The axes have been modified in the manuscript:
“Figure 3. Organic matter concentrations and TSS at the input and output of the plant. Blue bars show the input concentration in the plant and grey bars represent output concentration of the HUSB. a) TSS. b) COD. c) BOD.”
“Figure 4. Nutrients concentrations at the input and output of the plant. Blue bars show the input concentration in the plant and grey bars represent output concentration of the HUSB. a) NH4+. b) TN. c) TP.”
Results: I am not satisfied with the way the authors have represented the data in the results section. It warrants a thorough revision, particularly on data values that are represented as exact numbers. For example,
Line 257: NH4+ removes efficiency at the VFCW output achieves a mean value of 46% in this stage of…
Although the author’s have performed statistical studies in table 3 and 4, the data represented here is exact whole numbers. I recommend the authors revise it and represent it in the form of X ± y% in the entire text. If possible, the use of statistical tools such as the t-test to highlight differences in data is highly recommended.
According to the referee’s suggestion we have presented the data in the form of 95th percentile of confidence intervals. These changes have been realized in the tables and text.
Table 3. Statistics of accumulated removal efficiencies for the HUSB.
|
|
Average |
95% confidence interval |
Standard Deviation |
Maximum |
Minimum |
|
COD (%) |
60.66 |
± 9.10 |
23 |
88 |
4 |
|
BOD (%) |
56.67 |
± 12.96 |
27 |
89 |
4 |
|
TSS (%) |
71.02 |
± 9.71 |
24 |
95 |
16 |
|
TN (%) |
43.50 |
± 11.74 |
22 |
80 |
3 |
|
TP (%) |
15.30 |
± 5.63 |
11 |
36 |
3 |
Table 4. Statistics of accumulated removal efficiencies for the VFCW.
|
|
Average |
95% confidence interval |
Standard Deviation |
Maximum |
Minimum |
|
COD (%) |
86.55 |
4.73 |
11 |
95 |
46 |
|
BOD (%) |
84.00 |
5.00 |
12 |
97 |
44 |
|
TSS (%) |
95.27 |
1.84 |
4 |
99 |
84 |
|
TN (%) |
52.79 |
10.45 |
21 |
85 |
5 |
|
NH4+(%) |
45.06 |
6.99 |
16 |
76 |
15 |
|
TP (%) |
21.77 |
7.34 |
15 |
46 |
2 |
Table 5.Statistics of accumulated removal efficiencies for the HFCW.
|
|
Average |
95% confidence interval |
Standard Deviation |
Maximum |
Minimum |
|
COD (%) |
91.22 |
± 2.80 |
7 |
97 |
65 |
|
BOD (%) |
95.62 |
± 2.67 |
6 |
99 |
72 |
|
TSS (%) |
98.47 |
± 0.53 |
1 |
99 |
95 |
|
TN (%) |
60.31 |
± 9.00 |
19 |
87 |
23 |
|
NH4+ (%) |
61.00 |
± 9.26 |
22 |
91 |
10 |
|
NO3- (%) |
42.93 |
± 14.00 |
21 |
77 |
7 |
|
TP (%) |
20.45 |
± 4.79 |
10 |
39 |
1 |
Table 6 and related discussions should be moved to the previous sections (not in conclusion).
We do agree with his comment. Table 6 and related discussions have been move to Section 3: Results.
Author Response File: 
Author Response.docx
Reviewer 2 Report
In general, the manuscript is not organised and presented appropriately. For instance, starting from the title, which is not well constructed, i.e., Long-term …… dose not fit with conducted investigation from July 2018 to March 2020.
Introduction section
Row 38, which water policies?
Lines 71-74 support that statement with references
Mat & Methods section is the most critical
The authors state that during the study period, sampling was conducted on a weekly basis. However, nothing is stated about the sampling process and the number of replicates, what is critical for the results presentation/discussion later (see down).
Row 132 Conductivity replace by Electrical conductivity (EC)
Table 1 mote data need to be included, like total amount for parameters, volume of water and number of observations/analyses (n)
Data from Table 2 can be incorporated with a new column into the table 1. Also, correct the error DBO5!
The graphically displayed results are not consistent and appropriate with metodology. Mean standard errors should be included. Also, it is not clear what the data on the graphs refer to, are they are mean values (if any period) or individual analyses. If they are individual, there should be many more because, as noted, they are done on a weekly basis.
Table 3, 4 and 5 combine to one, and add more data as explained above for Table 1
Table 6 cannot be placed in conclusion section, move it above to discussion. Also it has some arror int the caption, correct it.
Author Response
Responses to reviewers.
We thank the reviewers’ comments. We do agree with some of their views. We have carried out the modifications proposed and we think that these changes have improved the quality of the work. Below, we clarify each of the points.
Reply to Anonymous Referee #2
In general, the manuscript is not organized and presented appropriately. For instance, starting from the title, which is not well constructed, i.e., Long-term …… does not fit with conducted investigation July 2018 to March 2020.
We do agree with the referee and we have reorganized the manuscript and have improved the description of the experimental and analytical processes. Also we have eliminated the expression “Long term” from the title.
Introduction section
Row 38, which water policies?
Lines 71-74 support that statement with references
The water policies is Directive 91/271/EEC concerning urban waste water treatment-
This Directive is included in the manuscript.
Mat & Methods section is the most critical
The authors state that during the study period, sampling was conducted on a weekly basis. However, nothing is stated about the sampling process and the number of replicates, what is critical for the results presentation/discussion later (see down).
We have introduced a new Subsection related to the sampling and analytical processes to highlight the number of samples, the date of samples, the different sample points and the statistical process to show the results.
2.2 Sampling and analytical process.
Four different points were selected to carry out the sampling process: the first point was the influent, before the pretreatment, the second point was before VFCW, the third point was before the HCFW and finally, the fourth one was the effluent. The influent and the effluent were collected with an autosampler to take 200 mL of wastewater each hour during 24-hour with the aim of capturing average characteristics of wastewater over a period of 1 day in a composite sample. Grab samples were collected from the other points early in the morning (9-12 a.m.). The volume of the grab samples were 1,000 mL and the volume of the composite samples were 2,400 mL (100 mL of each hour sample). They all were kept at 4ºC and processed in less than 24 hours after sampling.
The treatment plant was weekly monitored from July 2018 to March 2020. A total of 23 composite influent samples and 23 composite output samples were taken, related to the availability of the autosamplers in the dates pointed out in Figures 3 and 4. A total of 63 grab samples of wastewater before the VFCW and 63 grab samples before the HCFW were gathered, although, for the sake of simplicity, they are not shown in Figures 3 and 4.
Nine variables were measured in each sample: Total Nitrogen (TN), Total Phosphorous (TP), Ammonia (NH4+), Nitrate (NO3-), pH, Electrical Conductivity (EC), Total Suspended Solids (TSS), Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD). These variables were obtained according to standard methods for wastewater treatment analysis [29]. The analytical methods of these nine variables were validated according to the ISO/IEC 17025:2017 [30] by the R+D Laboratory of PROMEDIO (Consorcio para la Gestión de los Servicios Medioambientales de la Provincia de Badajoz ) and the uncertainty associated to the values are presented in Figure 3.
Input load data have been statistically analyzed in order to point out their validity. They are shown in Table 2, where average values of each parameter are presented along with their corresponding 95 % confident intervals and standard deviations. Maximum and minimum values of each one are also provided in order to identify the presence of possible outliers.
2.3 Removal efficiency
The removal efficiency of the treatment process for each variable was obtained by comparing concentrations in influent (Ci) and effluent (Ce) water:
Row 132 Conductivity replace by Electrical conductivity (EC)
This change has been realized in the manuscript.
Table 1 more data need to be included, like total amount for parameters, volume of water and number of observations/analyses (n)
According to the referee’s suggestion these data are included in the new 2.2 Subsection.
Data from Table 2 can be incorporated with a new column into the table 1. Also, correct the error DBO5!
This error has been corrected in the text.
The graphically displayed results are not consistent and appropriate with metodology. Mean standard errors should be included. Also, it is not clear what the data on the graphs refer to, are they are mean values (if any period) or individual analyses. If they are individual, there should be many more because, as noted, they are done on a weekly basis.
According to the referee’s suggestion we have added error bars in Figures 3 and 4. The error bars represent the uncertainty associated to the analytic method for each parameter analyzed.
On the other hand, we have presented the data of organic matter and nutrients removal efficiencies in Tables 3, 4 and 5 in the form of 95th percentile of confidence intervals.
Table 3, 4 and 5 combine to one, and add more data as explained above for Table 1
We thank the reviewers’ comment. However, we considered that displaying three tables (one for each processing stage) indicating the organic matter and nutrients removal efficiencies, facilitate the interpretation and visualization of the results in the text.
Table 6 cannot be placed in conclusion section, move it above to discussion. Also it has some error int the caption, correct it.
According to the referee’s suggestion we have included Table 6 and related discussions in the Section 3: Results.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
Author Response
We have checked the spelling/grammar of the manuscript and we have improved it. Thank you so much.
Author Response File: Author Response.docx
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
