Development of a New Testing Approach for Decentralised Technical Sustainable Drainage Systems

Round 1

Reviewer 1 Report

From my point of view, authors have re-arranged and re-structured their work according to the different comments of the reviewers. From my point of view, the manuscript can be accepted for its publication at Water journal after the following amendment:

Figure 1. The legend of the figure has to be updated to reflect the new references order (eg. Milissil granulometry refers to [26] in the figure and to [40] in the figure caption).

The same comment can be applied to Figure 6.

Author Response

Dear Sir or Madam,

thank you very much for the feedback. The error in the legends of Figures 1 and 6 has been corrected.

Kind regards

Johannes Neupert

Reviewer 2 Report

SuDS capacity for pollutant removal is a relevant topic. This paper adresses the issue of test procedures for quantifying the efficiency of this process.

The paper is well structured and provides result-consistent conlcussions. 

However, in my opinion, there are some aspects that should be clarified.

L69-73. Two German regulations are mentioned, DIBt and North Rhine-Westphalia (NRW), but only the DIBt is detailed presented. It woul be interesting to know which are the disadvantages of the NRW regulations regarding these test procedures.

L94-98. A brief description of the compared systems should be included.

L102-105. Authors could consider revising the wording of this paragraph.

Clearer context regarding the characteristics and magnitude of rainfall events considered could be provided. It would also be welcomed some comments about the influence of the rainfall events on the pollutant removal efficiency.

The proposed test procedure and test substance are compared with existing test procedures based on MillisilW4. As I'm not familiarized with these regulations (DIBt), I would like to know if there are other test substance that may fit better than Millisil W4 for testing purposes in the context presented in this study. 

I recommend this paper to be published after minor revision.

Author Response

Dear Sir or Madame,

thank you very much for the feedback. I will respond to your comments below:

L69-73. Two German regulations are mentioned, DIBt and North Rhine-Westphalia (NRW), but only the DIBt is detailed presented. It woul be interesting to know which are the disadvantages of the NRW regulations regarding these test procedures.

Additional information has been given in LN 73/74. The focus is on the DIBt test protocol in this paper, because the determination of the TSS retention of the regulation in North Rhine-Westphalia is based on the DIBt test protocol.

L94-98. A brief description of the compared systems should be included.

The relevant principles of action of the SuDS are mentioned. In the previous version, the systems were named, but this led to confusion. Therefore, it was decided to present the systems without a clear name in the revision.

L102-105. Authors could consider revising the wording of this paragraph.

            Paragraph has been revised (see LN 104-107)

Clearer context regarding the characteristics and magnitude of rainfall events considered could be provided. It would also be welcomed some comments about the influence of the rainfall events on the pollutant removal efficiency.

Additional information has been given in LN 305/306. The pollutant load of the road runoff samples was not analysed as it was not within the scope of the investigations.

The proposed test procedure and test substance are compared with existing test procedures based on MillisilW4. As I'm not familiarized with these regulations (DIBt), I would like to know if there are other test substance that may fit better than Millisil W4 for testing purposes in the context presented in this study. 

In the DIBt test protocol Millisil W4 is the only test substance regarding the TSS retention.

Kind regards

Johannes Neupert

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

The subject of the paper is very interesting and suitable for publication in Water. However, there are several lacks in presenting the results and additional measurements are recommended to verify the proposed results. In addition, the structure of the paper is very poor:

• The introduction does not summarize the current scientific knowledge. Recent international publications are missing (e.g., Rommel et al. Settling of Road-Deposited Sediment: Influence of Particle Density, Shape, Low Temperatures, and Deicing Salt; Lanzerstorfer Heavy metals in the finest size fractions of road-deposited sediments). The different types of decentralized systems should be summarized and presented. DWA-A 102 is only valid for surface waters; DIBt only for groundwater. No objective is presented, maybe in lines of the M-M-section.
• Parts of the M-M-section should be transferred to the introduction, e.g. lines 60-81, 122-128, and 165-173. Description of sample collection and analysis is sometimes poor.
• The results are often not supported by the measurements or only 5-6 measurements were performed not representing the large differences of real samples. This is also in contrast to the objective of the paper and the first results presented that have approx. 40 samples taken. The amount per sample collected is not mentioned. Sample preparation and analysis are not presented sufficiently.
• The second half of the discussion section is not based on the paper and should be deleted. Furthermore, results of Table 1 are not discussed.
• Conclusions are missing.
• References: please translate the German titles into English; names of the authors are written differently.

• There are too many Figures. Figure 5 is accounted twice. Figure 1 can be deleted. Other figures might be summarized.
• Please delete the editorial hints, e.g. lines 339-340 and 352-363

Further hints and recommendations:

• L 27/28: which... - this part of the sentence must be improved
• L 32 AADT instead of DTV; please introduce each abbreviation
• L 42 What is DWA? different writing of DWA-A 102
• L 61 reference is missing, e.g. Lucke et al. Pathways for the Evaluation of Stormwater Quality Improvement Devices - the Experience of Six Countries
• L 65 NRW is not doing it in accordance with the DIBt test protocol (only most of the TSS test)
• Lines 91/92: reference is missing
• L 98 What is AFS63?
• Lines 98-101: consequence of using alternative test materials is missing.
• L 104 show the differences of the measurements in detail
• L 110 maintenance intervals are considered by the DIBt
• L 122 these objectives should be at the end of the introduction
• L 131 number of locations and measurements per location and season are missing. More information is needed.
• L 138 recovery rate and type of performing it is missing
• L 156 the determination of the loss of ignition could be helpful to determine the organic fraction
• Figure 4: two words are red underlined
• L 201 How is the accuracy checked? E.g., by mass balances over time?
• L 214 reference is missing
• Table 1: rain intensity 2.5 or 3? DIBt has different inflow concentrations per rain event; this is in contrast to the presented RDS-method.
• L 235 reference is missing
• Figure 5a: please show the 8 sections as distance to the curb. How wide was the road?
• Figure 5b: present 1000 µm as 100% because the large fraction is not dominated by real RDS (such as litter); than the results are different but more comparable to Millisil.
• L 269: a fraction of RDS is usually not washed off at lower rain intensities. How long and high were the measured rain intensities. Were the same locations used as for the collection the RDS? There is a lack of information and consistency of sample collection.
• L 278: no reliable measurements
• Figure 7: n is very small and not representative
• L 316 The conclusion is in contrast to the presented importance of TSS63 in the introduction. Why should larger particles be added to a test protocol if they are not relevant according to DWA-A 102?

Reviewer 2 Report

The manuscript water 1040069 presents and interesting work about the development and improvement of testing facilities and methodologies for decentralized stormwater filter systems. Although the authors have carried out a good literature review and present an interesting methodology and research work, the article is not properly organized. In its current form, the text does not reach enough quality to be considered for publication in Water journal. So, from my point of view I recommend to authors to perform an in-depth review of the text and re-submit again the paper.

I will present below some detailed comments and suggestions to improve the manuscript. First of all, the article presents several German references (about 18/37, almost 50%), so for an international audience this is clearly a drawback.

At the abstract, I think that authors need to introduce a little bit better the objectives of filter system for stormwater treatment and management.

1.Introduction

Authors focused their introduction to the German context, showing several figures about sediment loads and other related pollutants. In order to make the paper useful for a broader audience, authors would include data from other countries (if available). I also suggest here to define better the meaning of “decentralized and centralized treatment plants” (LN 52), maybe by comparing these systems with more conventional “SuDS” techniques naming, or even with traditional drainage structures such as “gully pot”

2.Materials and methods

2.1. Test procedure

Regarding the test procedure for decentralized systems, I suggest to authors to define clearly which are the main objectives of the test procedures developed by the DiBT (hydraulic efficiency, clogging, sediment trapping, etc).

Authors present a really interesting revision here of the different PSD and properties of Road deposited sediments, tire and wear particles, heavy metals, etc. At LN 95, authors discussed about the use of Millisil as a surrogate of road deposited sediments. Here, several acronyms not previously described are introduced in the text (ASF63, PE, PS). Please, review and introduce these acronyms properly.

Later, authors introduce two proprietary systems (ACO SSA and Budanvinci TPE-N and Innolet GS1)  but the references are again in German, so is really difficult to track this systems. So, maybe authors can rephrase this paragraph to make it more general. Otherwise, they should describe better these systems (including a picture) if they are really in the scope on the manuscript.

This section seems more a review than a M&M section. Authors include here some reference to national level research projects and initiatives I think that authors should introduce this projects / programs at introduction in some kind of  “German research” paragraphs. Ln 124-128 clearly introduce some novelties of the manuscript, so they will be introduced earlier at the introduction.

2.2. Test  material / road sweep study

At this section authors should introduce the characteristics of their field study (catchment description, number of samples, seasonality, antecedent dry period. etc) before describing the road sediment collection procedure.

Regarding the differences between broom and vacumming approaches, authors need to justify why both methods yield similar results (maybe with some reference or with some supplementary information Table / Figure).

2.3. Road runoff study

At this section (and subsequent) I suggest to authors to include the equivalence of runoff in L/s/ha with mm/h, as this unit is used conventionally to determine rainfall volume.

At Ln 174 authors describe a sampling basket developed on two research programs. With the description shown in the text and Figure 3, is really difficult to understand how the basket is used to sampling the runoff (inside a gully pot?).

2.5. Sampling and analytics

This section is quite confused and is not really clear the timing of the discrete sampling (scoop) analysis or the total volume of sampling used for the complete analysis of the runoff. Furthermore, authors include here some reference to RDS loads, which should be stated before.

3. Results

3.1 In situ (Please re-phrase)

This section has to be properly introduced, with some reference to the data which will be presented (first, spatial distribution, then PSD). In Figure 5 please add some reference to the sampling area (1-8 is not representative), and maybe using a conventional PSD distribution plot (instead 3d bar plot).

Fig 5 and Fig 6 can be merged into one. Furthermore, authors need to describe better (at M&M) the differences between the 38 samples (location, seasonality, traffic, etc). Did the authors found any pattern in the PSD with some of these variables ? (e.g. antecedent dry period, which is not discussed in the text).

3.2. Test stand

Here authors present some global results of the tests, but they do not discuss about the different test procedures shown in table 1. Then they present some results related with the RDS PSD determination, but no reference to Milissil test or RDS efficiency is presented.

4. Discussion.

The discussion sections seem more a conclusion section, than a discussion section.

Minor comments

- Ln 42. It would be great if authors can briefly describe how the 1.4 million tonnes of sediment load were estimated.

- Ln 60. Please include some references for Australia, UK, USA testing procedures.

- Ln 90. Heavy metals instead of Heavey metals.

- Please, check the references format because it present several typos and formatting inconsistencies.

Reviewer 3 Report

The manuscript appears to combine two separate projects that are thematically related but otherwise would require coverage in separate papers.  This is because distinctively different methodologies and underlying theories are being used...neither of them fully explained in the current manuscript.  Of the two methods, the 'in situ' section needs the most work.

The authors may want to take another look at organizing their paper.  Information that should be in the Method section is appearing late in the manuscript etc.

Also, there are issues with editing...there are two Figure 6!

Overall, I cannot recommend the current manuscript for consideration in the journal.

I have attached an annotated copy of the manuscript (PDF) that I hope aides the authors in improving their manuscript.

Comments for author File: Comments.pdf