Sludge Management at the Kraków-Płaszów WWTP—Case Study
Round 1
Reviewer 1 Report
The manuscript is original, interesting and in my view, it is a great contribution in the field of study. Since it presents a co-digestion system the sewage sludge together with water sludge.
In my opinion, the manuscript is highly attractive to other readers and the proposed methodology is clear. The manuscript is well written. The methodology has been well conducted and the conclusions are clearly supported by the results.
I suggest this paper should be accepted but after minor revisions that can be seen below.
- In my opinion, the manuscript would be more complete if the authors could add additional information on the physicochemical characteristics of the digested sludge from the WWTP.
- In my opinion, additional information is needed to explain the behaviour of the analyzed system when evaluating different mixtures in co-digestion.
Author Response
Thanks for your review. In the article, we corrected the markings that were wrong.
Yours faithfully,
Authors
Reviewer 2 Report
Municipal wastewater treatment plants generate a great amount of sludge that should be disposal properly. The work studied the feasibility of utilization of a water sludge from a water treatment plant in anaerobic co-digestion with a sewage sludge. There are some problems in the manuscript that should be revised. Specific comments are shown below.
The description of references should be revised in the sentence “Cement supplemented with ash, obtained after burning water sludge rich in aluminum compounds and silicates, is more durable and resistant to sul-phate corrosion, as proved by Zdeb et al. [3,4], while [5]”.
Full name of abbreviation should be given when first mentioned in the manuscript, such as “COD”, “PAC”.
In Introduction, studies on biochar derived from sludge should be added. Many researches reported fabrication biochar materials using sludge due to abundant biomass component, and the biochar materials can be used as adsorbents and catalysts for wastewater treatment. References: Production, properties, and catalytic applications of sludge derived biochar for environmental remediation. Water Research, (2020). 187, 116390; Highly dispersed iron-doped biochar derived from sawdust for Fenton-like degradation of toxic dyes. Journal of Cleaner Production, (2021). 297, 126681; A review on persulfates activation by functional biochar for organic contaminants removal: Synthesis, characterizations, radical determination, and mechanism. Journal of Environmental Chemical Engineering, (2021). 9(5), 106267.
The structure of the manuscript should be revised. Some contents in “2. Materials and Methods” are results that should be described in “3. Results and discussion”. For example, XRF and XRD results.
A schematic figure showing the device details of picture 1 should be added.
Line 286 the title “3. Results and discussion” should be revised.
In “3. Conclusions”, “1. The literature review classifies processing of sludge from water treatment plants as a complex process and states that its current understanding is not as broad as in case of wastewater sludge. Selection of an appropriate method of a water sludge disposal involves both economic and technical decisions so there is a need for technologies that would provide an explicit solution to this problem” should be deleted. The key finding based on this study should be described in Conclusion section.
Author Response
Thank You for review. Please see the attachment.
Yours faithfully,
Authors
Author Response File: 
Author Response.docx
Reviewer 3 Report
The article discusses the co-digestion of sludge after water treatment and after wastewater treatment and its influence on the quantity and quality of biogas. Complementing the article with the chemical and physical parameters of the sludge being digested would allow their values to be compared with the data in Table 1.
Author Response
Thank You for review. We corrected the markings in the article.
Yours faithfully,
Authors
