Characterisation of Organic Matter and Its Transformation Processes in On-Site Wastewater Effluent Percolating through Soil Using Fluorescence Spectroscopic Methods and Parallel Factor Analysis (PARAFAC)
Round 1
Reviewer 1 Report
This is an interesting study that characterizes dissolved organic matter in domestic wastewater before and after passage through soil treatment trenches using fluorescence spectroscopy paired with parallel factor analysis. It provides a novel way of examining the types of molecules that make up WW DOM, which are removed preferentially by passage through soil, their role as sources of C and energy for heterotrophic microorganisms, and the interactions between soil and pathogenic organisms.
I have the following comments that I think will improve the manuscript:
- The terms humic and fulvic acid may not be appropriate in this case. It wasn’t clear to me what the authors think are the sources for these – soil particles? Formed in the septic tank? Ingested and excreted? Perhaps all of that could be obviated by avoiding these terms altogether. There has been a significant change in the soil science community from the centuries-old definition of soil humic substances as consisting of molecules formed from plant components intrinsically resistant to microbial attack to microbial products protected from decomposition by interactions with mineral surfaces (see publications of Johannes Lehman et al.). I think the paper would be stronger if the authors focused on the physicochemical properties of these fluorescent components (outside the context of humic substances) and their relevance to wastewater treatment in soil.
- By moving away from humic and fulvic acid, the authors could also reduce the length of the results and discussion. There is a considerable amount of comparison to other types of humic substances, potential process for formation of these substances, etc. that could be edited out. The audience for this paper is more interested in how the information could be used, and less so in the details of particular fractions of fluorescent DOM, their spectra, etc.
- There are a number of spelling, grammar and style errors (e.g., missing table heading, fluvic instead of fulvic) that no doubt the authors and editors will catch.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript entitled Characterisation of Organic Matter and its Transformation Processes in on-Site Wastewater Effluent Percolating Through Soil Using Fluorescence Spectroscopic Methods and Parallel Factor Analysis (PARAFAC) presents the results of study conducted in order to investigate the possibility of the fluorometric methods combined with PARAFAC analysis usage for characterisation of the fluorescent dissolved organic matter in the percolation area of on-site domestic wastewater treatment systems.
Although the results of this study can contribute to understanding of the processes which are occurring after wastewater disposal in the environment, I think that this manuscript can be improved at least in two ways:
1. the writing style is very poor and does not meet the average writing style of scientific papers (some parts of manuscript that should be rewritten are marked)
2. the presentation of the analysis procedure can be presented as sheme.
Comments for author File: 
Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 3 Report
Understanding the NOMs in wastewter recieving sites is important to conserve the whole environment. The paper introduced one-year observation of EEMs of DWWTs, which could give a useful case-study in local area. For the purpose of publication, some more efforts should be contribute to re-organize the focus and highlights, re-analyze the full dataset, and re-consider the innovance of this work. 1. Foundamental design. Performance of percolation process is highly denpandant on soil property and bacterial community. Two cases of local investigation is not strong enough to conclude the mechanisms of such process. Some lab experiments, such as column leaching, should be supplied to convince the proposed major founding in field survey. 2. Sampling. The description of investigated treatment processes are quite confused to understand. The on-site facilities seem to recieve two septic tanks and one integrated RBC reactor. 3. Data selection. There're four times of sampling activities, but not all the data were analyzed and shown in the paper (eg. figure 2 used only two times of sampling, figure 3 showed EEMs for only one sampling at one site). It should to considered that show and analyse full data in all investigation, which PARAFAC is capable of analyzing. 4. Control and dynamics. Suwanne River NOM were used as control for EEMs, however, there are no control sampling of the soil and surface/ground water around the sites, which may affect the NOMs in target samples. By considering there're four sampling activities in one year, the time variation of NOMs should be given and discussed. 5. Determine the FWCs. One assumption in the paper is that C2 presents the FWCs, but it lacks of strong evidences. Cause the wastewater source is directly from household useage, it is possible to investigate the inventory of the discharing materials, including the possible FWCs. Additionally, the FWCs in water/soil could be analyzed by typical instruments such as LC-MS and etc. 6. Clear the discussion. The difference of the paper from literature was given in this section without very clear summary. A table is recommended to specify the actual novel findings in this paper. Moreover, the recommendation to chemical usage in houses, the design and operation of DWWTs, and the risks of FWCs should be highlighted in the discussion.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
The paper can be accepred in revised form.
However, I still suggest to the authors to present the analysis procedure as a schematic.
Author Response
We have already presented the analysis procedure as a schematic, as requested, in our previous response to the reviewer's minor correction?
The original minor comment was down against Reviewer number 3 in error we think (as it was originally Reviewer no. 2's comment), so maybe Reviewer no. 2 has not seen our response as it was down against the wrong reviewer? The schematic is now in the Supplemental Information?
Reviewer 3 Report
Its current state is qualified for publication.
Author Response
We have now added the schematic diagram of the analytical procedure as requested.
