Water Sources Diagram and Its Applications

Round 1

Reviewer 1 Report

In the manuscript entitled "Water Sources Diagram and its Applications" the authors present a brief summary of WSD applications and future perspectives in the area of process systems engineering suggesting that WSD is a viable choice when a reducing in freshwater consumption is necessary. The paper is well written and requires only a few minor corrections (see below) before it may be released for publication.

Lines 44-45: "WSD not only can deal with that type of problems but also generates the diagram and final network simultaneously". This sentence needs explanation. Please re-write. Line 61: Put "GHGs" in brackets. Line 74: What is "reference contaminant"? Please explain. Equation (2), the ??? symbol is not described in the following text. Please provide its description. The authors should add discussion and provide all the details of Figures 2 and 3.

Author Response

Dear reviewer,

Thank you for your comments. They were implemented as follows:

Lines 44-46: "WSD not only can deal with that type of problems but also generates the diagram and final network simultaneously, which means that it predicts a minimum external water consumption and obtains the corresponding network at the same time". 

We included a brief explanation:

Lines 45-46:

"which means that it predicts a minimum external water consumption and obtains the corresponding network at the same time". 

------------------------------------------------------------------------------------

Line 62: greenhouse gases (GHGs).

We included brackets: (GHGs).

------------------------------------------------------------------------------------

Lines 78-79: "Water Sources Diagram was originally developed to deal with processes with one contaminant or at least one reference contaminant, in which the mass transfer of all other contaminants is based on" [28].

We included a brief explanation:

Line 79:

"in which the mass transfer of all other contaminants is based on"

------------------------------------------------------------------------------------

Line 145-146: "Cf,j is the final (higher) concentration of interval j "

Cf,j is now described.

------------------------------------------------------------------------------------

"The authors should add discussion and provide all the details of Figures 2 and 3". 

In order to better explain WSD methodology we included the following text for the Figure 2 and 3.

Figure 2

Lines 153-169:

"In each interval, starting from i = 1, the water sources that are available to be allocated for each operation must be identified, evaluating, in this case, if  the flowrate to be allocated corresponds to the assimilation of mass load (value within the brackets) for the operation in a given interval.

 Thus, in the first interval, only water at 0 ppm (quality of the external source) can be used in operation 1, requiring a flowrate of 20 t/h. likewise, the external source is used in operations 2 and 3, which are present in the interval 2: 50 t/h and 20 t/h, respectively.

The value of 20 t/h of operation 1 in i = 1 is transferred, as a priority, for the same operation to interval 2, and can completely assimilate the mass load of 1 kg/h.

In interval 3, operations 1 and 2 are already completed with their respective effluents at a concentration of 100 ppm, which means that they now represent internal sources of 100 ppm that can be made available for reuse in the operations of subsequent intervals (i = 3 e i = 4).

In this case, it is possible to verify that, in addition to 20 t/h from operation 3 in the interval i = 2, 20 t/h used from the reuse source at 100 ppm is still necessary, in order to completely assimilate the contaminant mass load in the interval i = 2 of operation 3.

At i = 4, in addition to 40 t/h from the previous interval of operation 3, there is a need to allocate 5.7 t/h from the internal reuse source (at 100 ppm) to assimilate the mass load of 4 kg/h from operation 4".

Lines 172-175:

"The choice of the reuse source is irrelevant in this case, once it can be used for both operation 1 or 2, because both have their effluents at the same concentration of 100 ppm. In practice, however, priority can be given to the source of reuse that comes from the operation that is physically located closest to the operation that will receive the effluent, due to the lower cost".

Figure 3

Lines 183-188:

"Figure 3 represents the water network defined from the WSD generated in Figure 2. It is possible to notice the direct distribution of 90 t/h from the external source at 0 ppm for operations 1 (20 t/h) and 2 (50 t/h), in addition to 20 t/h at 0 ppm combined with 20 t/h of effluent from operation 1 (water reuse) in operation 3. Furthermore, from a total of 50 t/h of effluent from operation 2, only 5.7 t/h are reused in operation 4. The final effluents from the water network are sent later for possible treatment and disposal".

 

 

 

 

Reviewer 2 Report

This paper is practically a review; it intends to prove the applicability of the water sources diagram (WSD) for reduction of the technological freshwater demand. It was shown a simple example for the usage of WSD model and then different literature examples were listed for the application of the WSD model. The scientific level of this manuscript may be medium; formulation of the text is acceptable.

Remarks to be taken into account:

More explanation is needed to Figure 1, and also Figure 3. Identification of numbers, lines in the WSD representations is necessary to their better understanding by the readers. Introduction: please formulate exactly the main task of this paper at the end in this subsection; Give more explanations to section 4; Conclusion: it is too general, should be more concrete.

I recommend to revise this manuscript to give more novelty for the readers.

Author Response

Dear reviewer, thank you for your important comments.

Your sugestions were implemented and are detailed below:

-----------------------------------------------------------------------------------------

To the comment:

 "Introduction: please formulate exactly the main task of this paper at the end in this subsection"

We include a brief ideia of the paper in the last paragraph:

Lines 73-76:

This paper addresses the major results obtained applying WSD methodology in different kinds of processes over the years and shows the importance of the technique for the industry. Furthermore, the idea of sources’ diagrams is presented for several types of applications and it demonstrates the flexibility of the core methodology.

-------------------------------------------------------------------------------------

To the comment:

"Conclusion: it is too general, should be more concrete. I recommend to revise this manuscript to give more novelty for the readers."

We included the following text:

Lines 244-245: 

This paper presented a brief summary of WSD applications for different kinds of industries and the future perspectives of Sources’ Diagram idea in the area of process systems engineering.

Lines 249-252:

Two Sources Diagram based methods are already established: (1) Hydrogen Sources Diagram [27], which has been applied in refineries, providing good results and (2) Carbon Sources Diagram [26] which presented interesting results when applied to the Brazilian electricity planning and management of GHGs emissions.

-------------------------------------------------------------------------------------

To the comment:

"More explanation is needed to Figure 1, and also Figure 3. Identification of numbers, lines in the WSD representations is necessary to their better understanding by the readers".

We included:

Figure 1

Lines 121-128:

"Figure 1 indicates the initial stage of the WSD structure, with the problem divided into four concentration intervals (i = 1,..., 4) (Step 1). In this diagram, four operations are represented, which contain their respective limits of initial (inlet) and final (outlet) concentrations. They also constitute the internal water sources, in addition to the external water source available at 0 ppm. In the column positioned to the left of the diagram, the flowrate values for each operation are aligned (Step 2). The values in brackets, positioned above each arrow in the intervals, correspond to the mass load that must be assimilated (Step 3). This value is then used as a basis to determine the water flowrate to be allocated for each operation present in the concentration intervals under analysis (Step 4)".

Figure 3

Lines 183-188:

"Figure 3 represents the water network defined from the WSD generated in Figure 2. It is possible to notice the direct distribution of 90 t/h from the external source at 0 ppm for operations 1 (20 t/h) and 2 (50 t/h), in addition to 20 t/h at 0 ppm combined with 20 t/h of effluent from operation 1 (water reuse) in operation 3. Furthermore, from a total of 50 t/h of effluent from operation 2, only 5.7 t/h are reused in operation 4. The final effluents from the water network are sent later for possible treatment and disposal".

Round 2

Reviewer 2 Report

I think that authors have completed their manuscript according to the rewiever comments, thus I recommend to its publication as it is. (Only to simple typing mistakes are recommended to be corrected: Line 165:  "i=3 e i=4"?; line 258: Contributes 

 

Author Response

Dear Reviewer,

Thank you for your revision. 

We changed the minor error "e" in line 163 to (i = 3 and i = 4).