Comparison of the efficiency of Deebag and jute made bag for faecal sludge management and wastewater treatment.

Faecal Sludge Management (FSM) has become a prominent environmental concern in the today's world. Dewatering of sludge and the treatment of wastewater (WW) are the prime spiny issue because of the deleterious essence of faecal sludge (FS) and WW in the environment. The main focus of this study was on FSM by 'Deebag' and 'Jute Bag' through dewatering and filtering. Deebag is a dewatering as well as filtering media which is made with geotextile and polypropylene. Contrariwise, three types of jute bags were made of jute fiber for using as the same purposes of Deebag. A polyacrylamide polymer was used in this study and both filtering and dewatering were done in two ways-with and without the presence of polymer. Biochemical Oxygen Demand at 5 days (BOD5), Chemical Oxygen Demand (COD), pH, Electrical Conductivity (EC), Chloride (Cl-), Phosphate (PO43-), Nitrate (NO3-), Total Suspended Solid (TSS) and Total Dissolved Solid (TDS) parameters of raw and filtering samples were analyzed to assess the performance of WW treatment by Deebag and jute bags. Only using polymer was observed as one kind of treatment of WW. Deebag has been found to show the maximum dewatering capacity as well as treatment efficiency comparing with the jute bags. However, among three types of jute bags, double jute layered bag has shown the best performance. Maximum dewatering for Deebag and jute bags were found 88% and 83% respectively while using the polymer.

Introduction

Management of faecal sludge (FS) in an appropriate and sustainable approach is now a major concern in the world. Because, Lack of proper management of FS has become a source of the transmission of many infectious diseases, including cholera, typhoid, hepatitis, polio, cryptosporidiosis, ascariasis, and schistosomiasis [1]. With the rapid growth of population in the world, biological sewage sludge is being generated at a higher rate that of course should be disposed properly [2]. Solutions for effective and sustainable faecal sludge management (FSM) present a significant Global need [3]. In many developed countries, FS with WW is treated with sewage treatment plant, whereas this scenario is not very common in the developing countries. Without proper management, FS is often allowed to accumulate in poorly designed pits, and WW is discharged into storm drains and open water, or is dumped into waterways, wasteland, and unsanitary dumping sites [4]. The World Health Organization (WHO) estimates that 2.2 million people die annually from diarrheal diseases and that 10% of the population of the developing world are severely infected with intestinal worms related to improper waste and excreta management [5,6]. It is evident that the management of FS is a critical need that must be addressed, and that it will continue to play an essential role in the management of the global sanitation into the future [3].

FSM is also a vital concern in Bangladesh. In Dhaka city, only 20% of the population are under the coverage of highly expensive sewerage network and the rest of the population are using on-site sanitation system such as septic tanks, pit latrines, unhygienic latrines or none at all [7]. The proper management and appropriate treatment of FS in Bangladesh is only a small percentage and no environmental friendly or environmentally sound system for collection and disposal of FS in Bangladesh is present now [8]. The outlet of most of the septic tank is connected with public sewer. Consequently, untreated WW is directly discharged into the public drain. Moreover, there is no proper emptying mechanism for pits or septic tanks. In most cases, it is done manually by sweepers when the problem becomes visible by overflowing or creating a nuisance. Emptying through using the mechanical suction device, known as vacutug is very limited [8].

The third largest city of Bangladesh is Khulna, which is situated in the southwestern part of the country lying in the delta of the river Ganges [9]. Around 1.6 million population has lived in this city with 66,257 number of households [10]. Unfortunate that, Khulna is in lack of sewerage system with its big population [11]. Recently, a designated site has been developed in Rajbandh near Khulna city for dumping FS safely or the treating FS and WW [10]. Some vacutugs are available to carry FS to the designated site under the operation and maintenance of Khulna City Corporation (KCC). Vacutug is a truck which has a mounted cylinder container laying down on the back site of the truck to carry FS and WW from collection site to the diposal site or treatment plant. Due to lack of available spaces in the city area, city dwellers have to reuse their on-site sanitation system. However, emptying of on-site sanitation system is still in a big problem in Khulna city. Though some vacutugs are available, in most of the cases, WW is discharged into the public drains by the city dwellers due to carrying cost of vacutug. Discharged WW is finally gone to either ponds or river. Many people have been suffering from infectious diseases by using those pond or river water. Discharging this polluted water to the environment has significant negative impacts [3].

Dewatering is one of the most important treatment mechanism and it is necessary prior to resource recovery for applications such as composting, or combustion as a fuel [3]. Because in FS, water is found either in bound forms or in free and the free water is fairly easy to remove from the FS, while removal of the bound water is much more difficult [12]. Moreover, removing of microorganisms from water is difficult while they are physically bound to solids and it needs the addition of chemicals or the use of centrifugation, pressure or evaporation [3]. Besides, FS composes of 75% water in an average and this water is heavy and expensive to transport to the disposal or treatment site [13].

This study was aimed at FSM by dewatering and filtering treatment of WW through Deebag and three types of jute bags. Treatment efficiency of Deebag and jute bags was also focused in the study. Deebag is a new concept manufactured in Malaysia for dewatering the faecal sludge with filtration capacity. But Deebag is costly and not available in Bangladesh. Considering these issues, three jute bags were made from locally available burlap and used for dewatering of FS with filtering and comparing the performance with Deebag. Dewatering capacity and WW treatment efficiency of both Deebag and jute made bags are also evaluated in the study.

Materials

Study area

The study area is Khulna University of Engineering and Technology (KUET) which is situated in the north-west border of Khulna city and graphically lies at 22"50' north latitude and 89"50' east longitudes [14]. The study area is almost the far most point from the Rajbandh FS disposal and treatment site. So, it was hypothesized that more trips by vacutug may be required for disposal of FS from KUET campus to the designated site of KCC. Naturally, it would cost more than any other places of the city for safe disposal of FS and that might have potentially encouraged the people to empty their FS storage pit by other ways.

Collection and preparation of Deebag

Tentate Geosynthatics Asia Sdn. Bhd., a Malaysian company, has manufactured Deebag. It has made with polypropylene, woven mono and split filament Geotextile. Tencate Deebags are available in 1.2 m x 1.2 m x 1.2 or 1.5 m with a maximum safe working load of 3,000 kg. Due to the unavailability of Deebag, the research work was to be performed on a small scale. One square feet surface of the Deebag was collected from SNV Bangladesh, an international development organization situated in Khulna city. From the 0.1 m2 or 1 ft2 Deebag surface, 0.03 m3 or 1 ft3 wooden cistern was prepared, whose bottom portion was fitted with this Deebag surface. The top of the cistern was open and the sides were made of wood so that FS might be poured into the cistern at the top and pass through the Deebag surface at the bottom.

Preparation of jute bags

Jute bags were prepared from burlap. This was chosen for dewatering as well as filtering purposes because it is locally available and jute has the potentiality of absorption capacity of heavy metal ions by jute fibred materials is assessed satisfactorily [15]. According to the design and study of Lee et al., prefabricated vertical drains (PVDs) were made from jute and two layers of jute burlap was used as filter sheath [16-18]. In the study of Bergado et al., One layer of jute geotextile filter sheath was used in making of PVDs [19]. By the literature review, three types of jute or burlap bags were hypothesized to be potentially as filtering media in the research work. These bags are single layer jute bag, double layer jute bag and two layer bag–one layer is jute and another is cotton cloth. Each bag was sized as 0.03 m3 or 1 ft3. Different types of burlaps are available in Khulna city. Among them whose pore size is 0.11 mm to 0.16 mm was selected for preparing the bags. The unit price of this type of jute per yard was BDT TK 72 or $0.85 or €0.72.

Collection of polymer

A Polyacrylamide polymer was used in this study for dewatering. This polymer is commercially known as Aquaestrol 6370 polymer which is generally used for solid and liquid separation in municipal WW treatment. This polymer is marketed by Tianrun Chemical Company in China, of which Charisbrent Pte Ltd has technical, developmental and production collaborations. This polymer was collected with the help of Water & Sanitation for the Urban Poor (WSUP). The dosage of polymer is equal to 2 g per liter of FS solution.

Methods

Procedure of collection of samples

FS was collected from a three compartment septic tank which is situated in KUET campus. A bucket was used at first for collecting FS from the first compartment of the septic tank. Because, first compartment of septic tank contains more sludge in compared with other two compartments. At the first time, no polymer was mixed with the FS. 35 kg equivalent FS was poured into every filtering or dewatering bag and from the FS, raw samples were also collected for laboratory analysis. The raw sample was not actually the supernatant but this is a homogeneous mix of FS liquor. Then for every bag, one sample was collected from the portion of FS passing by the filtration process through each bag for the laboratory assessment. At the same time, the portion of FS was retained inside the bags were weighted and recorded. The individual weight of every bag was also measured before. The dewatering as well as filtering process without using polymer were taken around 42 minutes by Deebag, 53 minutes by single layered jute bag and 61 minutes by double layered jute bag and jute and cotton layered bag.

FS was again collected in the same way described above from the same compartment of the septic tank. At the second time, polymer was used. Polymer was mixed with FS according to the mixing ratio and stirred for homogenous mixing for sometimes and finally, kept 1 hour. It was kept for 1 hour because, polymer takes the time to make flocs of FS. After that, the procedure was followed at the same as before. At that time with polymer, 16 minutes, 18 minutes for single layered jute bag and 22 minutes were required for the dewatering as well as filtering process by Deebag, single layered jute bag and both double layered jute bag and jute and cotton layered bag respectively.

Procedure of laboratory analysis

The quality of the collected samples was analyzed with HACH 125 multimeter and HACHDR 2500 spectrophotometer in the laboratory according to Standard Methods for the examination of water and wastewater by American Public Health Association (APHA), 1998. The analyzed physical properties were biochemical oxygen demand (BOD5), chemical oxygen demand (COD), pH, electrical conductivity (EC), chloride (Cl-), phosphate (PO43-), nitrate (NO3-), total suspended solids (TSS) and total dissolved solid (TDS).

Biochemical oxygen demand (BOD5)

Dissolved oxygen (DO) of each sample were measured by HACH 125 multimeter. 5 mL of each sample was diluted with 295 mL of distilled water, i.e. dilution factor was 60. After measuring DO, all the samples were incubated for five days. The difference between DO at first day and DO at fifth day was multiplied by the dilution factor to find the BOD5.

Chemical oxygen demand (COD) and chloride (Cl-)

Both COD and Cl- were measured by titration method. All samples are diluted with 100 dilution factor that was 1 mL of the sample was diluted with 99 mL of distilled water.

pH and electrical conductivity (EC)

pH and EC were measured with the help of HACH 125 multimeter by inserting the probe of the multimeter into the samples directly. Stabled reading on the screen of the multimeter was taken.

Phosphate (PO43-) and nitrate (NO3-)

For the assessment of phosphate and nitrate concentration in the samples, 50 dilution factor i.e. 1 mL of sample was diluted with 49 mL of distilled water. HACH DR 2500 spectrophotometer was used for the assessment. Phosver 3 and nitover 5 reagents were used for this assessment respectively. All samples were prepared in two ways–one is 10 mL diluted sample and another is 10 mL reagent mixed diluted sample.

Total suspended solid (TSS) and total dissolved solid (TDS)

TSS was measured by filtering with 1 μm pore size GF/C filters (Whatman). 100 mL of sample was taken. The difference between oven dried Whatman filter paper before and after filtration was the measurement of TSS per 100 mL and then it was converted into 1 mL. TDS was measured directly by HACH HQ14D portable meter.

Results and discussions

Treatment or filtration efficiency

Biochemical oxygen demand (BOD5)

In Fig 1, high BOD5 value was found both in raw WW and filtrated water for non-using polymer condition, but these values were found below the permissible limit set by the Department of Environment (DoE), Bangladesh for polymer using condition after filtration and BOD5 of raw WW was also in low range. Since, raw sample was not any supernatant but collected from directly FS liquor, the high BOD5 was observed in the raw sample. High BOD5 in WW indicates that large concentration of organic matter presents in WW. Aerobic bacteria needs huge amount to oxygen to decompose the large concentration of organic matter and that causes a severe decrease of dissolved oxygen in the water. No aquatic life can survive below a certain amount of DO level [20]. From Fig 1, very low BOD5 recovered was observed when no polymer was used. Deebag has found to remove maximum BOD5 that was only 40%, whereas among jute bags, double layered bag removed 36.68%. Due to using polymer, the recovery percentage reached at 75.96% for Deebag and 65.38% for double layered jute bags. The higher recovery percentage was also observed in the case of the other two types of jute bags. BOD5 concentration was dropped down to 62.4 mg/L that is 83.58% reduction of BOD5 concentration from raw WW by only using polymer.

Fig 1

Removal percentages of BOD5.

Chemical oxygen demand (COD)

Fig 2 shows a high COD value in raw WW for the non-using polymer condition because FS liquor was collected as raw sample. High COD is toxic and deleterious for the biological life as well as aquatic environment [21]. On the other hand, due to using polymer, low range COD value was found in the raw sample. Among the dewatering media, Deebag has shown best result in removing COD through filtration. It recovered 52.50% COD after filtration while using polymer and 48.57% without polymer. Doubled layered jute bag recovered maximum percentage of COD comparing other two types of jute bags. 45% COD was recovered by the double layered jute bag in polymer condition and 40% COD was in the non-polymer condition. Polymer by itself decreased 88.57% COD from raw WW. However, no filtering media is sufficiently capable to remove COD below the DoE permissible limit.

Fig 2

Removal percentages of COD.

pH

pH is the indication of acidic or alkaline condition of water. Table 1 shows the acidic condition of raw WW in non-using polymer condition. Filtrated samples were also found acidic. Both raw and filtrated samples without polymer was not within the DoE, Bangladesh Standard limit. Due to using polymer, pH value of raw WW was found as neutral that is within the DoE, Bangladesh permissible limit. All filtrated water also became neutral in polymer using condition. Before and after using polymer, the pH levels of filtrate samples were in the same condition as that of the corresponding WW. So, pH level was not enhanced by the filtration process, but polymer improved the condition.

Table 1

Concentration of different water quality parameter in different samples.

Parameter(a)	Without using polymer					With using polymer					DoE, BD Std.
	Raw water	Jute made bag			Deebag	Raw water	Jute made bag			Deebag
		SL	DL	JCL			SL	DL	JCL
BOD5	380	285	240.6	269.2	228	62.4	35.6	21.6	32.4	15	40
COD	7000	5000	4200	4910	3600	600	420	355	400	300	200
pH	5.27	5.38	5.6	5.49	5.62	7.32	7.26	7.21	7.25	7.1	6.5–8.5
EC	3960	2750	2250	2660	2063	2800	2300	2030	2240	1640	1200
Cl-	8900	4330	4100	4250	3950	5880	3300	3040	3255	2875	600–1000
PO43-	118.3	97.15	91	95	82.25	51.6	44.6	38.4	43.7	23.3	35
NO3-	430	315	301	315	280	240	165	140	156	135	250
TSS	4276	2590.32	1921.06	2464.2	1620	641	340.9	300.32	330	270.56	100
TDS	8851.28	3991.60	3549.98	3949.4	2712.86	1700.86	981.71	673.46	827.2	630	2100

(a)All values except pH and EC are expressed in mg/L and EC is expressed as μS/cm.

S = Single Layered; DL = Doubled Layer; JCL = Jute & Cotton Layered; DoE, BD Std. = Department of Environment, Bangladesh Standard.

Electrical conductivity (EC)

Electrical conductivity (EC) is usually a representation of salinity and Cl- is a major constitute of saline waters that directly affect the EC values [22,23]. EC value was comparatively higher than the standard because from the Table 1 higher amount of chloride content was found in all samples. Khulna is the south-west region of Bangladesh and these regions are highly affected by salinity intrusion. Since, KUET is situated in Khulna city and these areas are highly saline prone, that's why high electrical conductivity has been found in the raw wastewater samples. It has been found from Table 1 that the filtering media is not capable of removing electrical conductivity below the standard limit of DoE both in using and non-using polymer condition. It has been observed from Fig 3 that a good removing percentage was found both in the Deebag and the double layered jute bag. Removal percentage was near about the same for all filtering media in both conditions. However, the EC concentration in raw WW was decreased to 21.46% by the using of polymer.

Fig 3

Removal percentages of EC.

Chloride (Cl-)

Fig 4 shows a high chloride concentration in raw WW and filtrated samples. Khulna is a high saline prone area and chloride ions are the main constituents in saline water [24]. So, chloride concentration in water is normally high in this area. High level of chloride is toxic for aquatic plant which is not grown up in the saline zone [25].

Fig 4

Removal percentages of Cl-.

Though chloride content in all samples with and without polymer was not below the permissible limit set by DoE, a good removal percentages was found by the filtering media. Deebag had the maximum removal capacity, whereas among jute bags, the maximum capacity was shown by the double layered jute bag. By using polymer, 33.93% chloride content was removed from the raw WW. From Fig 4, all filtering bags removed almost the same percentages in both conditions that indicates those bags were capable of removing a certain chloride content by the filtration process.

Phosphate (PO43-) and nitrate (NO3-)

Municipal WWs are considered as the main sources of nutrient release, including phosphorous and nitrogen compounds in the aquatic environment as well as ecosystems because of using vast amounts of nutrients in human being’s daily life [26,27]. Discharging of nutrients such as phosphate and nitrate in water is a major concern because it promotes eutrophication that decrease the water quality by causing a rapid growth of aquatic plants such as algae [28-30] and results in the depletion of dissolved oxygen in the water BOD5 that significantly influences the drinking water supplies and the fisheries economically [31,32].

The Low phosphate removal percentage was found by all filtering bags. Phosphate is above the DoE permissible limit. However, after filtering through Deebag and double layered jute bag, the phosphate concentration was found very close to the standard. Filtering bags were able to recover a certain amount of phosphate because, in Fig 5, each filter bag was found to recover almost same percentage of phosphate before and after using polymer. Maximum recovery was done by Deebag that was 30.47%, whereas only polymer reduced 56.38% phosphate content from WW. This removal percentage is not sufficient for jute bags. However, the output can be within the standard for low concentration of phosphate in WW.

Fig 5

Removal percentages of PO43-.

Nitrate content is well below the permissible limit set by DoE for using polymer but that was vice-versa without polymer. It has been found in Fig 6 that 44.19% nitrate content was dropped down into the raw WW sample due to using polymer and after that it became below the permissible limit. Like phosphate, low removal percentage was also observed by the filtering bags. Before and after using polymer, the removal percentage was more or less stable for all filtering bags. So, all filtering bags are inefficient after reaching at a certain percent of removal of nitrate. The maximum removal percentage was found in the Deebag, whereas the double layered jute bag was better among other two jute filtering bags.

Fig 6

Removal percentages of NO3-.

Total suspended solid (TSS) and total dissolved solid (TDS)

TSS and TDS play an important role in the treatment of WW [33]. According to the study of Wu and Maskaly, a reduction in COD removal from WW was observed when TDS was more than 3000 mg/L [34]. The presence of TSS in water is the reason of depletion of oxygen level [33].

Table 1 shows a high amount of TSS and TDS not only in raw WW but also in the filtrated water sample without using polymer and were not met the permissible limit. Low concentration of TSS and TDS was found while using polymer. TDS in the filtrated water sample even in raw WW became below the standard limit set by DoE and TSS of all samples were very close to the permissible limit due to applying polymer. Around 80.78% TDS and 85.01% TSS concentration were recovered from the raw WW with using polymer. Though the Deebag showed the best performance, double layered jute bag also did better in comparison with other two type jute bags.

Dewatering

According to Rose et al. and Strande et al., average 75% water is present in FS that means 25% is solid in an average [13,3]. Collivignarelli et. al. also mentioned in their study that biological sewage sludge typically contains 25 to 20% solids by weight [2]. So in this study, it was hypothesized that emptying of the FS pit by vacutug for safe disposal and cost minimization would be possible due to the dewatering by the filtering bags. Table 2 shows the dewatering capacity of Deebag and three jute bags in both conditions of using polymer and not. Maximum retained or solid separation percentage was found 22.4% by the Deebag while using polymer and among three jute bags, the maximum percentage was found 20.53% that were done by the doubled layered jute bag. Without polymer, these percentages were reduced to approximately a half of those while using polymer for all filtering bags. So, considering 25% solid, maximum dewatering was found 88% for Deebag and among three type jute bags, 83% for double layered jute bags in polymer using condition.

Table 2

Dewatering capacity of different bags.

Sample Name	Without mixing polymer			With mixing polymer
	Weight of Total FS (kg)	Retained Weight (kg)	Percentage of Retained (%)	Weight of Total FS (kg)	Retained Weight (kg)	Percentage of Retained (%)
Single jute bag	35	2.985	8..53	35	6.416	18.33
Double jute bag		3.895	11.13		7.184	20.53
Jute with cotton bag		3.332	9.53		6.79	19.4
Deebag		4.55	13		7.841	22.4

Conclusions

Dewatering and WW treatment are the most important concern in faecal sludge management. Higher the dewatering lower the WW treatment cost and complexities. The result of the study indicates that both dewatering and treatment efficiency by all the filtering bags were found better due to using polymer. Deebag has found in the best treatment performance and dewatering capacity in both conditions of using and non-using polymer, whereas the doubled layered jute bag is better than other two type of jute bags. 88% dewatering capacity has been shown by Deebag whereas it was 83% for double layered jute bags. Though BOD5, pH and NO3- were found below the standard limit set by DoE, Bangladesh after the treatment of WW by the filtration process through Deebag and three jute bags with using polymer, further treatment is required for COD, EC, Cl-, PO43- and TSS parameters. All the filtering media or bags can be considered as effective in primary treatment and this will help to minimize the cost of the final treatment. But these filtering bags in polymer using condition have shown better performance for dewatering. Only using polymer is also considered as primary treatment of WW because only polymer has reduced a good percentage of concentration of the analyzed parameters in raw sample. Using polymer, 83.58% BOD5 concentration has been reduced in raw WW and 88.57% COD was reduced. However, if the analyzed parameters present in low concentration in WW, the Deebag and the double layered jute bag are efficient to reduce the concentration of the parameters within the standard of DoE, Bangladesh.

Concentration and removal percentages of BOD5.

(XLS)

Click here for additional data file.

Concentration and removal percentages of COD.

(XLS)

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Concentration and removal percentages of pH.

(XLS)

Click here for additional data file.

Concentration and removal percentages of electrical conductivity.

(XLS)

Click here for additional data file.

Concentration and removal percentages of chloride.

(XLS)

Click here for additional data file.

Concentration and removal percentages of phosphate.

(XLS)

Click here for additional data file.

Concentration and removal percentages of nitrate.

(XLS)

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Concentration and removal percentages of TSS.

(XLS)

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Concentration and removal percentages of TDS.

(XLS)

Click here for additional data file.

10 Jun 2020

PONE-D-20-12825

COMPARISON OF THE EFFICIENCY OF DEEBAG AND JUTE MADE BAG FOR FAECAL SLUDGE MANAGEMENT AND WASTEWATER TREATMENT

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Reviewer #1: The paper presents an interesting study on the comparison between the performance obtained with deebag and jute bags applied for the fecal sludge treatment.

The experimental work is quite complete, but several improvements are needed in order to clarify/integrate some experimental results. Moreover, I think that additional tests to confirm the results obtained could be very useful.

Thus, in my opinion, the paper needs significant revision before the publication.

My comments:

Abstract

1) Lines 20-21: I suggest to define the acronyms.

Materials and Methods

2) Line 123: I suggest to report the unit price also in Euro or US $.

3) Lines 130-131: I suggest to replace “Two grams of the polymer are required for every liter solution of FS” with “The dosage of polymer is equal to 2 g per liter of FS solution”.

4) Lines 141-142: The retained FS by the bags were weighted and recorded after the dewatering process. How many hours did the dewatering process ?

5) Line 153: I suggest to replace “(BOD)” with “(BOD5)”. Please, amend the acronym in the whole manuscript.

6) Line 154: Please, replace “electric conductivity” with “electrical conductivity”. Please, amend this term the whole manuscript.

7) Lines 157-195: I suggest to reduce these sections with minor details on methodology. Moreover, I think that this part can be include in 2.6, avoiding the numbering of subsections 2.6.1, 2.6.2, etc. Finally, in 2.6.4 Iron (Fe) is written, but any details on its measurement are reported.

Results and discussion

8) Line 201: BOD is a measure of the amount of oxygen required to remove waste organic matter from water in the process of decomposition by aerobic bacteria. Thus, BOD is often used as an index of the degree of organic pollution in wastewater. It is not a microbial condition of wastewater.

9) Table 1: I suggest to highlight (e.g. with bold fonts) the values higher than DoE BD Standard. Moreover, I think that EC is expressed as µS/cm.

10) Line 214: The sentence “BOD concentration was dropped down to 65.33% in raw WW by only using polymer” is wrong. BOD5 concentration was lower than 62.4 mg/L.

11) Figure 1: I suggest to remove the data referred to concentrations. These values are reported in Table 1. I think that a Figure with removal of pollutants is more suitable. The same comment can be apply to other Figures.

12) Section 3.1.4: I suggest to add comments on the pH values compared with the Bangladesh Standard.

13) Section 3.1.5: Could be an influence of polymer dosage on EC values?

Moreover, the sentence “However, the EC concentration in raw WW was decreased to 29.29% by the using of polymer” is wrong. The correct value is 21.46%.

Reviewer #2: I revised the paper titled COMPARISON OF THE EFFICIENCY OF DEEBAG AND JUTE MADE BAG FOR

FAECAL SLUDGE MANAGEMENT AND WASTEWATER TREATMENT for a possible publication in PLOS ONE. Results are interesting in particular for a possible application in a low-income country, but should be better and deepened commented. The language should be carefully improved. Several grammar mistakes are present in the manuscript. I suggest major revision.

My comments are the following:

1) Abstract should be revised and shortened focusing on main aspect of the research. Some sentences regarding the methods used are not necessary in the abstract (e.g. from line 18 to 22).

2) Line 33-35: In what sense “inappropriate management”. Please, describe better.

3) In the intro, also greywater (GW) should also be cited due to the fact that in low income countries they are often release into the environment without treatments and can contain several pollutants.

4) Line 62: “66,257”

5) Line 63: “her” should be amended with “its”. Please, revised all manuscript in order to amend this grammar mistakes.

6) Line 65, Please, describe “vacutags”.

7) Line 77-78: please rephrase

8) Line 78-79: “They are” not “It is”. Please, revise carefully all manuscript.

9) In the Introduction more recent literatures should be inserted. I suggest you some recent papers:

(sludge management and reuse)

Collivignarelli, M. C., Canato, M., Abba, A., Carnevale Miino, M. (2019). Biosolids: What are the different types of reuse?. Journal of Cleaner Production, 117844. https://doi.org/10.1016/j.jclepro.2019.117844

(greywater treatment with low impact processes)

Al-Gheethi, A. A. S., Noman, E. A., Mohamed, R. M. S. R., Bala, J. D., & Kassim, A. H. M. (2019). Qualitative Characterization of Household Greywater in Developing Countries: A Comprehensive Review. In Management of Greywater in Developing Countries (pp. 1-31). Springer, Cham. https://doi.org/10.1007/978-3-319-90269-2_1

Collivignarelli, M. C., Carnevale Miino, M., Gomez, F. H., Torretta, V., Rada, E. C., Sorlini, S. (2020). Horizontal Flow Constructed Wetland for Greywater Treatment and Reuse: An Experimental Case. International Journal of Environmental Research and Public Health, 17(7), 2317. https://doi.org/10.3390/ijerph17072317

10) At the end of the Introduction a paragraph with the main points that your research studied should be inserted.

11) In materials and methods, please divide materials and methods in two new subsection 2.1 and 2.2. It will be more clearer.

12) Line 96-98: Is this a result?

13) “a one cubic foot wooden cistern was prepared”. Please, use international units of measure.

14) Line 140-143. Please rephrase.

15) It is not necessary to describe in detailed the titration method to detect COD and Cl- It is well known.

16) Line 201. In what sense “BOD is a microbial condition of WW”. Please, described well.

17) Line 207: A high concentration of nitrate and COD not necessarily indicates presence of high concentration of BOD.

18) Line 207-209: Describe better.

19) Figures 1, 2, 3, 4, 5, and 6. What is BDS? Please, specify in the caption. Please, divide better the concentration and the removal percentages in the figures to make it clearer. Why Figure 1 is in COD section?

20) Similar figures could be merged into a Figure with more subfigures.

21) Please, review the conclusions and insert some percentages results.

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

6 Sep 2020

Response to the Comments of Reviewer#1

Abstract

1) Lines 20-21: I suggest to define the acronyms.

Response: I have defined the acronyms in line 23-26 of the manuscript with track changes.

Materials and Methods

2) Line 123: I suggest to report the unit price also in Euro or US $.

Response: I have included the unit price both in Euro and US $ in line 144-145of the manuscript with track changes.

3) Lines 130-131: I suggest to replace “Two grams of the polymer are required for every liter solution of FS” with “The dosage of polymer is equal to 2 g per liter of FS solution”.

Response: The line has been replaced in line 153-154of the manuscript with track changesas per the suggestion.

4) Lines 141-142: The retained FS by the bags were weighted and recorded after the dewatering process. How many hours did the dewatering process?

Response: New lines (183-186 and 190-193) have been added in the manuscript with track changes regarding the time taken by dewatering process.

5) Line 153: I suggest to replace “(BOD)” with “(BOD5)”. Please, amend the acronym in the whole manuscript.

Response: BOD has been replaced by BOD5 in the whole manuscript.

6) Line 154: Please, replace “electric conductivity” with “electrical conductivity”. Please, amend this term the whole manuscript.

Response: Electric Conductivity has been replaced by Electrical Conductivity in the whole manuscript.

7) Lines 157-195: I suggest to reduce these sections with minor details on methodology. Moreover, I think that this part can be include in 2.6, avoiding the numbering of subsections 2.6.1, 2.6.2, etc. Finally, in 2.6.4 Iron (Fe) is written, but any details on its measurement are reported.

Response: “2.6.4 iron (Fe)” was a typing mistake. I have divided the materials and methods into two sections– one is Materials and other is Methods. I have removed all subsections. This was also recommended from reviewer 2.

Results and discussion

8) Line 201: BOD is a measure of the amount of oxygen required to remove waste organic matter from water in the process of decomposition by aerobic bacteria. Thus, BOD is often used as an index of the degree of organic pollution in wastewater. It is not a microbial condition of wastewater.

Response: Yes, I agree. It’s my fault. I have omitted this sentence.

9) Table 1: I suggest to highlight (e.g. with bold fonts) the values higher than DoE BD Standard. Moreover, I think that EC is expressed as µS/cm.

Response: All the values which was higher than the DoE, BD standard have been highlighted with bold fonts in the manuscript. EC has been also expressed as µS/cm.

10) Line 214: The sentence “BOD concentration was dropped down to 65.33% in raw WW by only using polymer” is wrong. BOD5 concentration was lower than 62.4 mg/L.

Response: This was typing mistake. I have made correction and now, the sentence is in the line 270-271 of the manuscript with track changes.

11) Figure 1: I suggest to remove the data referred to concentrations. These values are reported in Table 1. I think that a Figure with removal of pollutants is more suitable. The same comment can be apply to other Figures.

Response: Since, the concentrations of different parameter were mentioned in table 1, so all existing figures have been replaced by the figures which have showed only removal percentage (applied for figure 1 to 6).

12) Section 3.1.4: I suggest to add comments on the pH values compared with the Bangladesh Standard.

Response: A comment on the pH values compared with Bangladesh Standard has been added in the line 296-298 of the manuscript with track changes.

13) Section 3.1.5: Could be an influence of polymer dosage on EC values?

Moreover, the sentence “However, the EC concentration in raw WW was decreased to 29.29% by the using of polymer” is wrong. The correct value is 21.46%.

Response: Yes, I made typing mistake and I have already corrected the value in the line 320 of the manuscript with track changes. Since, due to applying polymer, EC values were decreased in all samples, so it could be an influence of polymer dosage. It needs another study for this issue.

Response to the Comments of Reviewer #2

1) Abstract should be revised and shortened focusing on main aspect of the research. Some sentences regarding the methods used are not necessary in the abstract (e.g. from line 18 to 22).

Response: Abstract has been revised and shortened as per your suggestions.

2) Line 33-35: In what sense “inappropriate management”. Please, describe better.

Response: Inappropriate management was sensed to mean “lack of proper management”. FSM is a combination of the process of collection, transportation, deposition, treatment and end-use. Proper management indicates the right way to collect, transport, deposit, treat and end-use. “Inappropriate management” has been replaced by “lack of proper management”.

3) In the intro, also greywater (GW) should also be cited due to the fact that in low income countries they are often release into the environment without treatments and can contain several pollutants.

Response: Yes, it is right. Here, I have actually focused on only faecal sludge. Because, the raw samples were collected from the septic of Khulna University of Engineering and Technology (KUET). And there, greywater is directly discharged into public storm drain. Not only in the university but also it is a common scenario in the city areas of Bangladesh. So, only faecal matters are come to the septic tank and that’s why greywater is not considered in this study. Introduction has been also revised (e.g. line 59-65 of the manuscript with the track changes)

4) Line 62: “66,257”

Response: I have corrected as “66,257 number of households” in the line 73of the manuscript with track changes.

5) Line 63: “her” should be amended with “its”. Please, revised all manuscript in order to amend this grammar mistakes.

Response: It has been amended as “its” in the line 74 of the manuscript with track changes.

6) Line 65, Please, describe “vacutags”.

Response: Vacutags are described in the line 78-80 of the manuscript with track changes.

7) Line 77-78: please rephrase

Response: Those lines have been rephrased in the manuscript which are found as line 89-93 with track changes.

8) Line 78-79: “They are” not “It is”. Please, revise carefully all manuscript.

Response: “It is” has been replaced by “They are” in the line 92of the manuscript with track changes.

9) In the Introduction more recent literatures should be inserted. I suggest you some recent papers:

(sludge management and reuse) Collivignarelli, M. C., Canato, M., Abba, A., CarnevaleMiino, M. (2019). Biosolids: What are the different types of reuse?. Journal of Cleaner Production, 117844. https://doi.org/10.1016/j.jclepro.2019.117844

(greywater treatment with low impact processes) Al-Gheethi, A. A. S., Noman, E. A., Mohamed, R. M. S. R., Bala, J. D., &Kassim, A. H. M. (2019). Qualitative Characterization of Household Greywater in Developing Countries: A Comprehensive Review. In Management of Greywater in Developing Countries (pp. 1-31). Springer, Cham. https://doi.org/10.1007/978-3-319-90269-2_1

*-Collivignarelli, M. C., CarnevaleMiino, M., Gomez, F. H., Torretta, V., Rada, E. C., Sorlini, S. (2020). Horizontal Flow Constructed Wetland for Greywater Treatment and Reuse: An Experimental Case. International Journal of Environmental Research and Public Health, 17(7), 2317. https://doi.org/10.3390/ijerph17072317

Response: Since, greywater has not been considered in this study due to the reason mentioned in the Response of comment#3, so nothing is required to cite from the 2nd and 3rd reference mentioned in the comment above. However, from the first reference, it has been cited in line 41-43 and 384-385 of the manuscript with track changes.

10) At the end of the Introduction a paragraph with the main points that your research studied should be inserted.

Response: At the last paragraph of Introduction, the main points of the research has been inserted in the line 96-98 of the manuscript with track changes.

11) In materials and methods, please divide materials and methods in two new subsection 2.1 and 2.2. It will be more clearer.

Response: Materials and methods has been divided in two subsection – one is materials and another is method.

12) Line 96-98: Is this a result?

Response: It can be considered as result. From the practical experience and talking to the local people, it has found that transportation cost of FS from the on-site sanitation system to the KCC designated disposal site was higher from other parts of the Khulna City than the study area. Because, the study area is located at the most away from the designated disposal site. This findings is not the scope of the study. Moreover, the study area was selected based on this key point.

13) “a one cubic foot wooden cistern was prepared”. Please, use international units of measure.

Response: one cubic foot has been converted into SI unit and this has been incorporated in the line 124-125 of the manuscript with track changes.

14) Line 140-143. Please rephrase.

Response: Those lines have been rephrased in the manuscript which are found as line 181-184 of the manuscript with track changes.

15) It is not necessary to describe in detailed the titration method to detect COD and Cl- It is well known.

Response: Ok. I have omitted the details of titration method in the manuscript.

16) Line 201. In what sense “BOD is a microbial condition of WW”. Please, described well.

Response: Actually, BOD is not fully microbial condition. It’s my fault to write. I have omitted this sentence. Rather, BOD is a measure of the amount of oxygen required to remove waste organic matter from water in the process of decomposition by aerobic bacteria

17) Line 207: A high concentration of nitrate and COD not necessarily indicates presence of high concentration of BOD.

Response: Yes, it is right. I have deleted this line from the manuscript to avoid controversy.

18) Line 207-209: Describe better.

Response: Those lines have been described better in the manuscript which are found as line 260-263 with track changes.

19) Figures 1, 2, 3, 4, 5, and 6. What is BDS? Please, specify in the caption. Please, divide better the concentration and the removal percentages in the figures to make it clearer. Why Figure 1 is in COD section?

Response: Concentration portion has been removed from all the figures and only removal percentages have been shown in those figures. This has been made to avoid repetition because table 1 has already showed the concentration of different parameters. Since, concentration portion of the graph has been removed, so BDS has been also removed. Only removal of percentages have been shown in all the graphs.

I am sorry that it was formatting mistake and figure 1 has been placed in the BOD5 section.

20) Similar figures could be merged into a Figure with more subfigures.

Response: It may not be required because Concentration portion has been removed from all the figures and only removal percentages have been shown in those figures.

21) Please, review the conclusions and insert some percentages results.

Response: Conclusions have been reviewed and some percentage results have been included in the line 410-412 and 420-424 of the conclusion section of the manuscript with track changes.

Submitted filename: Response to Reviewers.doc

Click here for additional data file.

22 Sep 2020

PONE-D-20-12825R1

COMPARISON OF THE EFFICIENCY OF DEEBAG AND JUTE MADE BAG FOR FAECAL SLUDGE MANAGEMENT AND WASTEWATER TREATMENT

PLOS ONE

Dear Dr. Mishuk,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Nov 06 2020 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

We look forward to receiving your revised manuscript.

Kind regards,

Mentore Vaccari

Academic Editor

PLOS ONE

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: (No Response)

Reviewer #2: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: (No Response)

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: N/A

Reviewer #2: (No Response)

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: (No Response)

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: (No Response)

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The authors have amended the manuscript according to my comments. In my opinion, the paper could be published after a minor revision.

My comments:

1) Please, use the same word for vacutug. In the lines 77, 89 and 91 (related to clean version) “vacutug” is used; in the lines 83 and 85 “vacutag” is adopted.

2) Replace PO43+ with PO43- (e.g. in the line 192 of clean version). Please, check the whole manuscript. Moreover, I suggest to write BOD5 with “5” in subscript mode.

3) In the manuscript with track of change mode, the Figure 3 does not show the removal percentage of EC. In the clean version the Figure 3 is corrected.

4) Line 358 (of clean version): I suggest to replace “According to Rose and Strande et al.,” with “According to Rose et al. and Strande et al.”.

5) Line 385 (of clean version): “... for other analyzed parameters”. I suggest to specify the other parameters.

Reviewer #2: I revised the paper and I found that my suggestions, where possible, have been implemented. Therefore, in my opinion this paper can be published on this journal.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

26 Sep 2020

Response to the Comments of Reviewer#1

1) Please, use the same word for vacutug. In the lines 77, 89 and 91 (related to clean version) “vacutug” is used; in the lines 83 and 85 “vacutag” is adopted.

Response: “Vacutug” is the right word. I have replaced vacutag with vacutug in the lines 83 and 85 of the clean version. It has been also corrected in the manuscript with track changes.

2) Replace PO43+ with PO43- (e.g. in the line 192 of clean version). Please, check the whole manuscript. Moreover, I suggest to write BOD5 with “5” in subscript mode.

Response: I have replaced PO43+ with PO43- in the clean version of manuscript. I have also write BOD5 with BOD5 that is “5” in subscript mode in the clean version of the manuscript. Both changes have also been done in the manuscript with track changes.

3) In the manuscript with track of change mode, the Figure 3 does not show the removal percentage of EC. In the clean version the Figure 3 is corrected.

Response: This was my mistake and I am extremely sorry for that. I have made change the Figure 3 with the removal percentage of EC in the manuscript with track changes.

4) Line 358 (of clean version): I suggest to replace “According to Rose and Strande et al.,” with “According to Rose et al. and Strande et al.”.

Response: In the line 358 of clean version of the manuscript, “According to Rose and Strande et al.,” has been replaced with “According to Rose et al. and Strande et al.”. This change has also been done in the manuscript with track changes.

5) Line 385 (of clean version): “... for other analyzed parameters”. I suggest to specify the other parameters.

Response: The other analyzed parameters have been specified as COD, EC, Cl-, PO43- and TSS in the line 385 of clean version of the manuscript. Same changes have been also done in the manuscript with track changes.

Submitted filename: Response to Reviewers.doc

Click here for additional data file.

8 Oct 2020

COMPARISON OF THE EFFICIENCY OF DEEBAG AND JUTE MADE BAG FOR FAECAL SLUDGE MANAGEMENT AND WASTEWATER TREATMENT

PONE-D-20-12825R2

Dear Dr. Mishuk,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Mentore Vaccari

Academic Editor

PLOS ONE

12 Oct 2020

PONE-D-20-12825R2

Comparison of the efficiency of Deebag and Jute made bag for faecal sludge management and wastewater treatment

Dear Dr. Mishuk:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

If we can help with anything else, please email us at plosone@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Professor Mentore Vaccari

Academic Editor

PLOS ONE