Reuse of Sludge as Organic Soil Amendment: Insights into the Current Situation and Potential Challenges

Round 1

Reviewer 1 Report

Authors need to correct mistakes such as on page 3 line 104 and 105 (359.4×109 m3). Such type of mistakes need to be corrected throughout the manuscript.

Authors need to provide Graphical Abstarct.

Some images can be provided showing various types of sludges as discussed in the manuscript. Icluding picture of those sludes will give good impression to reader.

Author Response

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Reviewer 2 Report

The review is focused on the agronomic effect of different sludges as well as the current and emerging environmental issues that restrict land application. A special focus is also on best practices and regulatory framework that promote sludge reuse as sustainable and eco-friendly biofertilizers.

The available data mostly derive from experimental studies that use sewage sludge as the main wastewater treatment by-product to be applied to croplands. Industrial sludge reuse in agriculture is the least addressed because it is less abundant in terms of volumes and due to greater concerns about contamination risks. Sludge application enhances the physico-chemical and biological properties of depleted soils by providing organic matter and nutrients, consequently improving crop yield. Globally, the presence of contaminants in sludge is variable and depends on population habits and awareness, environmental regulations, and technological advances of wastewater treatment in a given country. Accordingly, it is required to prepare or update country-specific guidelines taking into account the local sludge quality, target agricultural crops, and pedo-climatic conditions. In addition, new classes of emerging pollutants such as pharmaceuticals and related resistant pathogens/genes have been increasingly detected in sewage sludge, which might cause more virulence to humans in case of crop contamination.

Overall, the authors have done a very high level review paper with summarizing all aspects. It is recommend to accept.

Only one comment is the format of references should follow the rules of MDPI publishing.

Author Response

We would like to thank Reviewer#2 for his positive feedback on our review paper. 

The format of references was revised to follow the rules of MDPI publishing when applicable.

Reviewer 3 Report

Dear Authors,i=

I appreciate your time in drafting this manuscript. I have a few questions :

1. Tables 3, 4, 5, 6 - the data presented as countries are for a wide area. For clarity, please specify the regions or areas. Are the datas represented across the tables are are from the same region/sample area (within the country )?

2. What's the expected influence on COD and BOD?

3.  Any statistical evidence for the represented data?

 

Thank you 

Author Response

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Author Response File: Author Response.docx

Reviewer 4 Report

Comments for author File: Comments.pdf

Author Response

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Round 2

Reviewer 4 Report

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