Design and Development of a Pilot-Scale Industrial Wastewater Treatment System with Plant Biomass and EDTA
Round 1
Reviewer 1 Report (Previous Reviewer 1)
Comments to the manuscript water-2564793
The manuscript presents the use of E.crassipes biomass to treat high Cr6+ containing wastewater and its adsorbent capacity was enhanced by adding EDTA. The comments are listed below;
1. Only Cr6+ were measured in this study. Did Cr3+ occurred due to the treatment process and did you measure it? Which Cr ion is dominant in tannery wastewater and its concentration? This information should be included in the manuscript.
2. There are several typing mistakes, please check it carefully such as
- E. crassipes, E. crassipes changes to E. crassipes
- Regu-lation (line 58), en-hances (line 69)
- Initial Cr6+ concentration of 200 mg/L (line 202) changes to 400 mg/L
- Figure 2 (line 219) changes to Figure 3
- Militros (Milliliter?)
- Afluent, etc.
3. In the chromium determination, the Cr6+ was measured by using UV-vis spectrophotometer, add a reference for this analytical procedure in line 98. The next paragraph of spectrophotometer can be removed, its information was the same as the previous paragraph. In addition, what is UV84, series of UV-vis? The brand and series of analytical instruments should be included.
4. Explain more details of EC1 and EC2 preparation; just simply mixing EDTA powder and E. crassipes powder, or immerse E. crassipes powder in EDTA solution, or other? Clarify. When the EDTA was increased double, the removal efficiency was slightly increased. The scientific reason should be added in the discussion. Are there any limitation of EDTA addition reported in literatures?
5. What was the meaning of break point? It referred to the starting of efficiency reduction, did not it? Add some literatures which used break point to evaluate the adsorption performance, compare and discuss.
6. The adsorption of Cr6+ by E. crassipes and E. crassipes+EDTA in this study was assumed to be second-order kinetic and Langmuir isotherm. Why?
7. In Figure 6, the system was called “bioreactor system”. Was it double mechanisms of biological and adsorption occurred? In addition, no samples 11 and 12 in the figure however they were mentioned in the text.
8. Explain how to use the finding/results from lab-scale to develop the pilot-scale. Explain the reason for improving the efficiency in pilot-scale rather than lab-scale.
English is acceptable
Author Response
1. Only Cr6+were measured in this study. Did Cr3+ occurred due to the treatment process and did you measure it? Which Cr ion is dominant in tannery wastewater and its concentration? This information should be included in the manuscript.
Response: In the first mechanism, Cr(VI) is reduced to Cr(III), due to the interaction of this metal with OH groups, which act as electron donors. The biomass is oxidized because Cr (VI) reacts with its hydrogen ions, generating OH and H2O, going from dichromate (Cr2O7)-2 or Cr (VI) to chromium oxide Cr2O3 or Cr (III) [25].
When Cr (III), which at that time is chromium oxide Cr2O3, is reduced and begins a process of chemical diffusivity with the biomass, the electron-charged biomass reacts with chromium adsorbing it while oxygen reacts with protons from ( H+) in the biomass [25;27].
2. There are several typing mistakes, please check it carefully such as
- E. crassipes, E. crassipes changes to E. crassipes
- Regu-lation (line 58), en-hances (line 69)
- Initial Cr6+ concentration of 200 mg/L (line 202) changes to 400 mg/L
- Figure 2 (line 219) changes to Figure 3
- Militros (Milliliter?)
- Afluent, etc.
Response: This was improved.
3. In the chromium determination, the Cr6+was measured by using UV-vis spectrophotometer, add a reference for this analytical procedure in line 98. The next paragraph of spectrophotometer can be removed, its information was the same as the previous paragraph. In addition, what is UV84, series of UV-vis? The brand and series of analytical instruments should be included.
Response: This was improved, with “Chromium measurement. Chromium (VI) laboratory measurement: 200 and 400 mg/L of Cr (VI). In sampling, aliquots of the reaction mixture were analyzed for residual chromium concentration using a UV84. Samples were taken in the flask at each interval, analyzing the residual chromium concentration. Adsorption experiments were carried out in a 100 mL glass vessel with constant stirring (IKA Ks 4000 shaker) at 20 °C, 250 rpm. All ex-periments were carried out in triplicate, with an average of the final values. 20 µm sam-ples were taken and then placed in the centrifuge (KASAI MIKRO 200) [27].
Chromium determination. Using the diphenylcarbazide method (the amount of chro-mium (VI) residue is estimated. For this purpose, the phos-phate buffer solution was prepared by adjusting it to a pH equal to 2 with 90% of the grade of purity (H3PO4). In an ep-pendorf tube 200 µl of 0.5% diphenylcarbazide (with 97% the grade of purity) and (W/V acetone with 97 of grade of puri-ty), 900 µl of phosphate buffer and 100 µl of the residual sample were added. A suitable portion is transferred to an absorption cell and the absorbance is measured at 540 nm.
Spectrophotometer (Evolution 300 spectrophotometer) by monitoring changes in ab-sorb-ance. All procedures for the determination of chromium, for water and substrates, were carried out using the implementation of APHA (Procedure of the American Public Health Association) for standard tests (standard methods for the examination of water and wastewater). Method 3500-Cr. the uncertainty of the measurements estimated in this study showed that the measurements of the heavy elements, specifically Cr(VI) can be made with a level of uncertainty around 3.95 %.
The detection limits of the method obtained for a primary wastewater effluent water of 0.3 µg/L. Initial Performance Demonstration: Prior to sample analysis, the instrument was set up and analyzed enough known samples to determine method detection limit and cali-bration range estimates, after every 10 Cr(VI) samples, and then the final sample, an inde-pendent control sample and a calibration blank were analyzed.
4. Explain more details of EC1 and EC2 preparation; just simply mixing EDTA powder and crassipes powder, orimmerse E. crassipes powder in EDTA solution, or other? Clarify. When the EDTA was increased double, the removal efficiency was slightly increased. The scientific reason should be added in the discussion. Are there any limitation of EDTA addition reported in literatures?
Response: The mixture consisted of going through the biomass in the treatment system under the concentration of 5 g/L and 10g/L of this reagent in 300mL of distilled water. Used in the [27] in process of elutions.
5. What was the meaning of break point? It referred to the starting of efficiency reduction, did not it? Add some literatures which used break point to evaluate the adsorption performance, compare and discuss.
Response: The EC1 composite obtained continuous adsorption capacities of 16 mg/g, a 120% better capacity with the presence of EDTA, and together with a treated volume of 1600 mL, treating 700 mL more water compared to EC alone and with a breakpoint of 120 min, The EC2 biomass presented the highest adsorption capacity in continuous tests, with 18 mg/g. EDTA was increased, but not significantly, because this material has 5 grams more of EDTA in the cellulose xanthate the break time was of 110 min and in the cellulose alkaline was of 90 min [27]. In the experimient with the EC and chloride of iron, the break time was of 125 min [36].
6. The adsorption of Cr6+by crassipes and E. crassipes+EDTA in this study was assumed to be second-order kinetic and Langmuir isotherm. Why?
Response: The Thomas model is used to estimate the maximum adsorption capacity and predict the breakthrough curves, assuming second-order reversible reaction kinetics and Langmuir isotherm [35]. The Langmuir isothermal model assumes that adsorption occurs at specific homogeneous sites in the E. crassipes biomass together with EDTA. The Langmuir model represents the experimental data of heavy metal adsorption in E. crassipes better than the other adsorption models [19;35]. These evidences indicate that the adsorption of heavy metals on E. crassipes adsorbents is a monolayer adsorption. Most of the kinetic adsorption data fit a second order model, therefore, the main control mechanism in adsorption using E. crassipes as adsorbent is chemisorption; the binding between heavy metal molecules and functional surface groups of the E. crassipes biomass plays an important role during the adsorption process [19].
7. In Figure 6, the system was called “bioreactor system”. Was it double mechanisms of biological and adsorption occurred? In addition, no samples 11 and 12 in the figure however they were mentioned in the text.
Response: This was improved.
8. Explain how to use the finding/results from lab-scale to develop the pilot-scale. Explain the reason for improving the efficiency in pilot-scale rather than lab-scale.
Response: Thi The aim of this project is the design and development of an industrial wastewater treat-ment system using plant biomass and EDTA on an industrial scale. For this reason, mathematical models were used to design a suitable pilot treatment system to meet the needs of Cr (VI) discharges. To achieve the optimal design, three flow treatment systems were built in series with PET plastic containers and in order to calibrate and validate the models, in which the required treatment was determined, the volume to be treated, thus setting the increase in area of contact and, together with the mathematical model of Thomas, it was determined that the mixture of EC1 is the appropriate one to scale up to a larger pilot system. With these data and established parameters, a fixed-bed column ad-sorption system was designed to treat 80 liters of water from a tannery, with an initial 1000 mg/L of Cr (VI), with the aim of removing more than 99%. of the present chrome this guide. The model provided the parameters and thus a treatment system was developed with the characteristics of 1000 g of E crassipes biomass mixed with EDTA (with a 10:1 proportions ), in a system with parallel and serial flow also with PET containers but this time with a 3-liter capacity, meeting the objective of treating around 81 L of water. The costs of this system of treatment is around 10 dollars, which is quite cheap compared to conventional ones.
Reviewer 2 Report (Previous Reviewer 2)
The research work, entitled "Design and development of an industrial wastewater treatment system with plant biomass and EDTA on an industrial scale." by Uriel Fernando Carreño Sayago, is quite interesting and scientifically updated. The manuscript can be accepted after minor revisions. My comments are:-
1. ml must be written as mL throughout the whole manuscript.
2. At some of the places full stop is placed before the references. Please rectify. The full stop will come only after references for instance in line no 143 "Langmuir isotherm. [35].", at line 192, the biomass. [36-37].
3. Table 4 is in a different font.
4. Most of the paragraphs are not justified.
Author Response
The research work, entitled "Design and development of an industrial wastewater treatment system with plant biomass and EDTA on an industrial scale." by Uriel Fernando Carreño Sayago, is quite interesting and scientifically updated. The manuscript can be accepted after minor revisions. My comments are:-
1. ml must be written as mL throughout the whole manuscript.
Response: This was improved.
2. At some of the places full stop is placed before the references. Please rectify. The full stop will come only after references for instance in line no 143 "Langmuir isotherm. [35].", at line 192, the biomass. [36-37].
Response: This was improved.
3. Table 4 is in a different font.
Response: This was improved.
4. Most of the paragraphs are not justified.
Response: This was improved.
Reviewer 3 Report (Previous Reviewer 3)
Dear Author,
please use the multiplication sign in equations, don't use "*".
Please improve the text in terms of editing ("min" not "Min"; mg/L not mg/l etc.).
Remove "industrial scale" from the title. This is proposal for implementation od laboratory experiments for this.
If experiments have 3 repetitions, on Figures 2-4 must be added mean, max i min for each point (not dots but box-plot).
What does it mean "Militros"?
Author Response
1. please use the multiplication sign in equations, don't use "*".
Response: This was improved.
2. Please improve the text in terms of editing ("min" not "Min"; mg/L not mg/l etc.).
Response: This was improved.
3. Remove "industrial scale" from the title. This is proposal for implementation od laboratory experiments for this.
Response: This was improved.
4. If experiments have 3 repetitions, on Figures 2-4 must be added mean, max i min for each point (not dots but box-plot). What does it mean "Militros"?
Response: This was improved.
Reviewer 4 Report (Previous Reviewer 4)
The paper has been improved, however, some furhter improvements are necessary.
E.g., in materials and methods, the detection limit of the Cr analysis method should be indicated. Please also describe in what form you added EDTA to the biomass. And how you prepare the homogenous biomass with EDTA amendment.
English should be carefully checked because its quality is not good enough. Also, some foreign, not translated words are present, e.g. in Fig 3 and 4 x-axis is not in English. In row 2222 unit is missing. Also, in Fig. 5 English should be corrected. In Table 1, column 2, instead "," it should be ".". In Table 2, Instead Adsortions capacity it should be Adsorption capacity. In row 320: what is ggg?
In row 329 kg, instead Kg. More grammar and language errors are detected in the paper, which is why English should be checked carefully.
The comments were places above.
Author Response
1. The paper has been improved, however, some furhter improvements are necessary.
E.g., in materials and methods, the detection limit of the Cr analysis method should be indicated. Please also describe in what form you added EDTA to the biomass. And how you prepare the homogenous biomass with EDTA amendment.
Response: Chromium determination. Using the diphenylcarbazide method (the amount of chro-mium (VI) residue is estimated. For this purpose, the phos-phate buffer solution was prepared by adjusting it to a pH equal to 2 with 90% of the grade of purity (H3PO4). In an ep-pendorf tube 200 µl of 0.5% diphenylcarbazide (with 97% the grade of purity) and (W/V acetone with 97 of grade of puri-ty), 900 µl of phosphate buffer and 100 µl of the residual sample were added. A suitable portion is transferred to an absorption cell and the absorbance is measured at 540 nm.
Spectrophotometer (Evolution 300 spectrophotometer) by monitoring changes in ab-sorb-ance. All procedures for the determination of chromium, for water and substrates, were carried out using the implementation of APHA (Procedure of the American Public Health Association) for standard tests (standard methods for the examination of water and wastewater). Method 3500-Cr. the uncertainty of the measurements estimated in this study showed that the measurements of the heavy elements, specifically Cr(VI) can be made with a level of uncertainty around 3.95 %.
The detection limits of the method obtained for a primary wastewater effluent water of 0.3 µg/L. Initial Performance Demonstration: Prior to sample analysis, the instrument was set up and analyzed enough known samples to determine method detection limit and cali-bration range estimates, after every 10 Cr(VI) samples, and then the final sample, an inde-pendent control sample and a calibration blank were analyzed.
2. English should be carefully checked because its quality is not good enough. Also, some foreign, not translated words are present, e.g. in Fig 3 and 4 x-axis is not in English. In row 2222 unit is missing. Also, in Fig. 5 English should be corrected. In Table 1, column 2, instead "," it should be ".". In Table 2, Instead Adsortions capacity it should be Adsorption capacity. In row 320: what is ggg?
Response: All these was improved.
3. In row 329 kg, instead Kg. More grammar and language errors are detected in the paper, which is why English should be checked carefully.
Response: This was improved.
Thank you.
Round 2
Reviewer 1 Report (Previous Reviewer 1)
The revision is acceptable.
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.
Round 1
Reviewer 1 Report
Comments to the manuscript “Design and development of an industrial wastewater treatment system with plant biomass and EDTA on an industrial scale” (water-2516298)
1. The academic writing is required; writing long paragraphs, more discussing in scientific reasons and comparing the current results to literatures.
2. Eichhornia crassipes (E. crassipes) should be written in an italic font style.
3. The methodology is unclear
a. both lab-scale and industrial-scale experiments should be clearly explained with reactor size (i.e., diameter, height, working volume, amount of adsorbent and adsorbent ratio), operating condition (i.e., flow rate, actual or synthetic wastewater used, initial Cr concentration, pH, etc.). In Line 120, the pilot-scale volume was 400 mL which was different from Line 328 (80 L), which value is corrected?
b. If the actual tannery wastewater was used, its characteristic, source and pre-treatment methods should be briefly explained.
c. The equations mentioned in the results and discussion section should be moved to the methodology section.
d. Line 133, the initial Cr were 100 and 200 mg/L which were different from Figures 1-3 (using 200 and 400 mg/L)
4. EC1 (5 g EDTA + 45 g E. crassipes) achieved the best adsorption rather than EC (E. crassipes) and EC2 (10 g EDTA + 40 g E. crassipes). Why? Did you characterize properties of each adsorbent (i.e., surface area, pore volume, surface charge)? How EDTA can enhance the adsorption capacity of E. crassipes, the adsorption diagram with and without EDTA should be included.
5. In this study, the breakpoint was used to determine the best adsorption. How the authors know the breakpoint was reached in the experiments? It seems different values for 200 and 400 mg/L, was not?
6. The effluent concentration of Cr in phase 1 should be mentioned as well as the Cr removal efficiency in phase 2 should be also mentioned and compared to the lab-scale experiment (phase 1).
7. The best adsorption capacity of this study (16 mg/g) should be compared to literatures using E. crassipes as adsorbent or other waste material.
The academic writing is required
Reviewer 2 Report
The title of the article submitted by Sayago seems very interesting and updated, the whole manuscript is written carelessly.
1. In abstract Liner no 14, the name of the plant must be Italics.
2. In line 16, the author said, cellulose and hemicellulose help in the adsorption of heavy metals mainly. This is not correct.
3. In line 20 “vegetal”?
4. In the introduction section, most of the paragraphs are 3-4 lines better merge them and divide it into 2-3 paragraphs only.
5. In Line 58, the sentence is not complete. Continuously? (used)
6. All the units must be in SI like ml must be mL, ul must be uL.
After going through the introduction several mistakes and errors have been found. Manuscripts are not written very casually. There is a discontinuity in the sentences. The whole manuscript needs serious English editing before submission in any other journal.
The manuscript must be rejected in its current form.
It must be edited by a professional especially a technical one.
Reviewer 3 Report
Dear Author,
as per my view, the article contains many errors in the methodology. The author, based on the experience without at least three repetitions, wants to transfer the laboratory scale to the technical scale. The experiment should be repeated as well as the calculations.
My decision is to reject the manuscript. After correction, the manuscript may be resubmitted.
Please see the comments below.
Specific comments:
The title should be about modeling. The title in its current form suggests that experimental research was carried out on a semi-technical scale and will be transferred to a technical-industrial scale.
The abstract contains information specific to the introduction (line 10 - 18). The abstract should briefly describe the purpose, methodology, results and conclusions.
Lines 14 and 26 - please do not use abbreviations or explain them
The Introduction should include information on the concentration of chromium VI in industrial wastewater.
Line 78 – The author studies 3 systems on a pilot scale. They are not properly described in the methodology. There are also no at least 3 repetitions of the experiment, which are used to determine the range of variability of test results (e.g. by standard deviation).
Methodology - The author describes the 1st phase of the research (200 and 400 mg/L of Cr (VI). In line 119-123 the test stand is described. However, its diagram or photo is missing.
Phase 2 - no description in the methodology. The author at line 133 starts exploring 200 and 100 mg/L of Cr(VI). The authors write about duplicate studies and calculating the average. Does this mean that the tests were only repeated 2 times? Where is the basic statistic describing this research?
Line 136 – Is "Model Evaluation" the third part of the experiment?
Line 139 – 140 – in the tables in the description of the Thomas Model, the formula is hardly readable. The formula describing the Carreno model lacks the description of 4 variables.
Results - the part concerning the research results should be divided into 3 parts, which the author writes about. They should be described in detail in the methodology beforehand.
Formula 1 - Kf or kf? Previously there was a variable V, now v. What is an As?
Formula 4 - Ln or ln?
Figure 1 - 3 - contain two curves for 200 and 400 mg/L of Cr (VI). The description in the text only applies to the case of 200 mg/L of Cr (VI). Why?
Line 187 - should be 1600 ml, not 1400 ml.
Formula 10, line 242 – data is substituted into the formula, but there is no final result.
Line 336 - why did the author decide to take 1000 mg/L of Cr (VI) as the initial concentration? There is no information about this in the methodology. In Introduction, the concentration of 1000 mg/L of Cr (VI) is not supported by any literature or research results of other authors. It is not explained.
Conclusions should be improved based on more in-depth laboratory studies based on at least 3 replicates.
Line 399 - what patents does the author have on this subject?
Reviewer 4 Report
The paper is interesting, but it should be improved before publication. The detailed remarks are as follows:
1. Please improve the quality of the scheme (Fig. 4); it is hard to read the scheme in its present form.
2. Please include the experiment scheme (first and second phases) because the description is not informative enough.
3. In equation q is mentioned twice and two meanings are intoduced.
4. No symbols are described in Careno model.
5. Please explain why the authors applied such models as they used, why not other models. What was the reason to chose them?
6. Please describe more carefully Fick's equation.
7. Please explain why you used the concentrations of Cr(VI) solutions 400 and 400 mg/L?
8. Put the unit in Table 3; it is missing.
9. Pleas put the information if any other methods of waste generated during treatment are available. E.g., in Europe, disposal of such waste is abandoned. What alternative management of waste could be used?
10. Please improve the text editing. It is careless.
11. Please give more information on other types of biomass used in Cr(VI) removal from wastewater). Include the table concerning the technological parameters of the methods.
The English must be checked by native speaker, because many grammar errors are present.
