Investigation and assessment of supplied water quality in Rajshahi City Corporation of Bangladesh

This paper has investigated the extensive implementation of distinct types of pipes in the Water Distribution System (WDS) and evaluated the impacts of particular leachable organic chemicals and bacteriological issues. Besides, 10 the paper inspects significant water quality parameters like the population of Rajshahi City, Bangladesh relies on water provided via pipes for drinking and other domestic purposes. This study aims to assess the quality of physical, chemical, and microbiological parameters of supplied drinking water through lines in Rajshahi City Corporation (RCC) by Rajshahi Water Supply and Sewerage Authority (RWASA). Therefore, the study managed sixteen physical, chemical, and microbiological parameters to analyse them in the laboratory. The experimental results showed that all samples' pH and 15 hardness were within the allowable limit as per Bangladesh Drinking Water Standards (BDWSs) and World Health Organization (WHO). All models contained an extreme level of iron and manganese. They also included a negligible amount of arsenic. The experiment detected lesser Dissolved Oxygen (DO), Residual Chlorine (Residual Cl), and the undesirable odour in about 90 % samples. All samples contained Total Coliform (TC) and Escherichia coli (E. coli) bacteria. A few samples contained a significant amount of turbidity, Chemical Oxygen Demand (COD), Biological 20 Oxygen Demand (BOD), and Electrical Conductivity (EC). The authors developed a statistical analysis by SPSS software to co-relate the parameters. This study recommends the presence of such bacteria, iron, and manganese in the pipeline.

40 % households of the city. Currently, RWASA faces improving the quality of supplied water to the customers, as RWASA could not serve water satisfactorily to its consumers. People found blackish and reddish water due to high-level manganese and iron and complained about water quality during the field survey. The supplied water by RWASA contains physical, 40 chemical, and microbiological parameters apart from the presence of manganese and iron. However, field specialists have not studied these parameters.
Nowadays, the water quality problem is one of the most significant problems in developing countries like Bangladesh (Akoto et al., 2017). Again, drinking water is a potential vehicle of exposure to both physical and chemical contaminants. The contaminants may occur naturally or artificially (Fernández-Navarro et al., 2017). Liu et al. (2017c) inspected many potentially 45 leachable substances from pipes with the widespread application of different categorical pipes in Drinking Water Distribution Systems (DWDSs). Contaminants can enter into the Water Distribution System (WDS) due to human activity (Anthropogenic contaminants), locally available materials (Natural contaminants like Fe, Mn, and As), and pharmaceuticals (Benson et al., 2017;Liu et al., 2017a). Additionally, the intermittent water supply system is another major cause to degrade water quality (Agathokleous and Christodoulou, 2016;Erickson et al., 2017;Vairavamoorthy et al., 2007). The first one is the treatment 50 process from Anthropogenic contaminants, including coagulation-flocculation, disinfection, disinfection by-products, filtration, adsorption, and sedimentation. Such processes produce contaminants. As a result, they incorporate with supplied water. The second type contaminants (Zinc or Cadmium) incorporate with drinking water during distribution and storage.
Poorly designed, constructed, and operated water systems deteriorate the water quality in the distribution system resulting in consumer complaints (Doull et al., 1982). Source water, supply infrastructure, and the supply system's operation influence 55 the formation of biofilm in DWDSs (Douterelo et al., 2016). It is unnecessary to say that biofilms alter and degrade water quality (Liu et al., 2017b). Biofilm influences to increase bacterial counts or regrowth in the distribution system resulting from detachment of bacteria from the biofilm, reduce Dissolved Oxygen (DO) content resulting from microbial activity in the biofilm, taste and odour changes resulting from products of microbial metabolism within the biofilm, red water resulting from the activity of iron bacteria and increased hydraulic roughness. From another literature review, pipe materials (Wang et al.,60 2018), type of surface materials, the interaction between the disinfectants , hydrodynamics, water temperatures, and residual disinfectants are another factors to influence the biofilm formation, taste, and odour (Zhou et al., 2017).
The study collected fifty-six water samples based upon public objections from fourteen wards out of thirty wards to investigate the harmful contaminants. The authors performed the analysis of physical, chemical, and microbiological 65 parameters like pH, turbidity, Electrical Conductivity (EC), hardness, heavy metals (Iron, Arsenic, and Manganese), DO, odour, temperature, Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), Residual Chlorine (Residual Cl), Escherichia coli (E.coli), and Total Coliform (TC) in the laboratory following the standard procedures. Nevertheless, the experimental results were not satisfactory. Investigating public opinion and lab tests, the concentration of manganese and iron was extreme. Arsenic presented in water in a negligible amount. Other targeted parameters deviated from the World Health 70 Organization (WHO) standards and Bangladesh Drinking Water Standards (BDWSs) in some samples. Even the microbiological parameters did not give a satisfactory report. Elevated concentration of manganese, iron and their consumption in extreme amount cause severe health problems (Memon et al., 2011).
The authors also checked the essential physical and chemical parameters to understand the significance of local consumers' water quality issues. This study aims to measure the deterioration of water quality flowing from sources to the consumers. This 75 knowledge will be more useful for the professionals of water quality sectors and use as a reference for the city's drinking water quality. Furthermore, the study attempts to help the RCC and RWASA delivering salient information regarding the present quality of supplied water in the city and make them cautious of supplying good quality water. RCC is one of the twelve city corporations, located in the north-west part of Bangladesh. It lies between 24 0 21 / and 24 0 26 / N latitude and between 88 0 28 / and 88 0 37 / E longitude. The city is bounded on the east, north, and west by Paba Thana, and the south by the Padma River with about 47.78 square km (Rahman, 2004). RCC consists of 30 wards, as shown in Fig. 1.

Field survey
The authors conducted a questionnaire survey from people of the selected wards of RCC to know their concern about the significance of drinking water quality problems. They incorporated the questionnaire survey with questions on the water body, 90 location, population of the village, common diseases in the locality, availability, and quality of drinking water (Alom and Habib, 2016).

Collection and preservation of water samples
The authors selected fourteen wards out of thirty wards of RCC for the investigation based on the public's water quality problems. The investigation mainly covered the central part of the city. They selected three consumers (S1, S2, and S3) points 95 for each water source. They characterised fifty-six samples in total and surveyed the wards to evaluate water quality parameters. The authors collected samples in clean new 200 mL sterile bottles with corks that they pre-treated the bottles through washing with dilute HCl and later rinsed them with distilled water (Oyem et al., 2014). The testers then air-dried them in a dust-free environment.

Immediate analysis
The authors tested the collected water samples immediately after collecting samples for some physical parameters, including EC, pH, turbidity, and temperature (Martínez-Santos et al., 2017). They measured almost all these vital water quality 105 https://doi.org/10.5194/dwes-2020-31 parameters within four hours of collection due to obtaining an accurate value (Fahmida et al., 2013). The testers thoroughly rinsed all probes of multi-parameter and wholly dried them with lint-free wipes or compressed air. The recommended order for calibration of the individual probes on a multi-parameter is EC, pH, and Turbidity (Guidelines for drinking-water quality, 2004).

Results and discussion 110
WHO standards and BDWSs evaluated the present quality of supplied water and the degree of water bodies' pollution. The authors studied the collected data with a statistical model developed by SPSS software (J et al., 2012).

Analysis of physical parameters
pH: It specifies the degree of acidity or alkalinity of water (Guettaf et al., 2017). The laboratory experiment found that 115 pH values ranged from 6.4-7.5 following the BDWSs and WHO standards. Figure 2(a) Turbidity: 50 % of the customers had turbidity higher than the acceptable value. Higher turbidity values were typical of consumers where source water satisfied allowable limit (WHO standards and BDWSs). The maximum value was 25.22 NTU in ward 25 (S2), which means about five times WHO standards. Excessive turbidity or cloudiness in drinking water is aesthetically unappealing and represents a health concern. Turbidity can provide food and shelter for pathogens (Turbidity and 120 water). From the laboratory analysis, the turbidity range for supplied water lied between 0.41-25.22 NTU. Although source water satisfies BDWSs and WHO standards, water contamination occurs during transport, storage with intermittent water supply (Edokpayi et al., 2018;Falconi et al., 2017). Figure 2

(b)
Temperature: Samples collected from RWASA and users had a temperature ranged from 16.5-30 ºC. Comparing BDWSs and WHO standards, the temperature of all samples satisfied BDWSs and WHO standards. However, it is not possible 125 to measure the internal temperature of water within the pipe. Figure 2(c)

Dissolved Oxygen (DO):
Almost all samples, both sources and consumers had a lower amount of DO and ranged from 0.19-3.5 mg L -1 . The experimental results measured a declination of DO when water travelled from source to household premises in maximum wards. Figure 2 The higher value of DO in water than the traditional values means the superior satisfactoriness of that water (Hossain et al., 130 2014). Higher BOD and COD indicate the lower DO. The lower DO indicates a higher amount of TC (Liyanage and Yamada, 2017).

Electrical Conductivity (EC):
EC is the actual measure of a solution's ionic activity in terms of its capacity to transmit current (Mangi et al., 2017). The test results showed that the samples were high EC insoluble salts to the extent that except eight samples, almost all samples (Consumers and WASA) crossed BDWSs of 1200 µs cm -1 . EC ranged from 450-1900 µs 135 cm -1 . Maximum and minimum values were in the household points of ward 13 and the source of ward 30, respectively. Fortythree samples had the EC range of 1250-1900 µs cm -1 . Figure 2(e) Odour: Out of fifty-six samples collected from the study area, the majority of about 90 % had an objectionable odour. Odour problem creates due to minerals such as iron or copper, may leach into water from the pipes or due to bacteria growing in a pipe or from organic matter or bacteria that are naturally present in lakes, and reservoirs during the particular times of a 140 year (Color, taste and odor problems in drinking water, 2018). Rest of the water samples was free from odour. Figure  Colour: Coloured water is not always harmful to man, but the disinfection of water by Chlorination contains natural organics that produce colour resulting in the formation of Chloroform. So it is crucial to limit the colour of water for domestic and other purposes (Bari and Sarkar, 2017). In this study, twelve water samples had colour values beyond the recommended value of 15 Hazen. About forty-three samples had a colour range of 5-15 Hazen. Colour ranged from 5-20 Hazen. Ward 27, 145 29, and 12 had blackish, reddish, and black-reddish coloured water. They are metallic colours and represent high concentrated iron and manganese.

Analysis of chemical parameters
Heavy metal (Iron, Fe): In the study area, the laboratory tests found a maximum Fe concentration of 3.5 mg L -1 165 (Consumer S2 from ward 12), and a minimum concentration of 0.03 mg L -1 (Sources of ward 11). The experimental analysis found twenty-seven samples (Sources and users) above the permissible limit set by BDWSs. Nine samples had iron ranged from 0.03-0.2 mg L -1 . Four samples were the same as the WHO standards. Twenty samples ranged from >0.3-1 mg L -1 . Rock structures of the area are responsible for the high concentration of iron in the supplied water (Shigut et al., 2017). Figure 3(a) Heavy metal (Manganese, Mn): Mn highly polluted the study area. Almost all samples had Mn greater than the 170 permissible limit of both WHO standards and BDWSs. The minimum and maximum Mn concentrations of 0.6 mg L -1 and 2.1 mg L -1 were recorded in ward 8 (Consumers point S1) and ward 12 (Consumers point S2). Thirty-eight samples from both the consumers and the sources ranged from 0.60-1 mg L -1 . The rest of the samples (S and U) had a range of 1.1-2.1 mg L -1 , which is highly toxic for the consumers. It is mainly due to the depth of water in contact with the area's rock surfaces. A high concentrated Fe and Mn in ward 12 resulted in the black-reddish water, and the consumers complained due to the presence of 175 such type of metallic colour in the water at the survey period. Figure 3

(b)
Heavy metal (Arsenic, As): There was a negligible amount of As present in the selected wards. The amount of As in all wards is below the BDWSs. Thirty-one samples were free from As. Six samples were precisely similar to WHO standards and were 0.01 mg L -1 . Eighteen samples were slightly higher than whom standards ranged from 0.015-0.03 mg L -1 . The experiment found only one sample of 0.04 mg L -1 in ward 28. Figure 3

(c) 180
Chemical Oxygen Demand (COD): COD is always higher than BOD. Out of fifty-six samples collected from the study area, twenty-three and six samples had the COD higher than the desirable level (BDWSs) of 4 mg L -1 , ranging from 4.5-6 mg L -1 , and 6.5-8 mg L -1 respectively. The concentration of two samples was 4 mg L -1, similar to BDWSs. Twenty-five samples ranged from 1-3.5 mg L -1 falling within the allowable range of BDWSs. Figure 3 Total hardness: Water can be soft (<75 mg L -1 ), moderately challenging (75-150 mg L -1 ), hard (150-300 mg L -1 ), and tough (>300 mg L -1 ) according to the concentration of Calcium (Ca) and Magnesium (Mg) (Alam et al., 2017). Out of fourteen sources and forty-two users in the RCC area, two sources and seven consumers exceeded the allowable limit of BDWSs. Four samples collected from both the sources and the consumers fell within the soft category ranged from 45-70 mg L -1 . Fourteen 195 samples ranged from 75-150 mg L -1 fell within the moderate category. Nine samples ranged from 210-290 mg L -1 were in the hard category. Nevertheless, the rests were classified as very hard ranged from 347.2-650 mg L -1 . Figure 3

Analysis of microbiological parameters
Potential causes regarding the growth of TC and E. coli in DWDSs are biofilm formation, cell detachment, sample tap 230 contamination, damaged water treatment, and supply infrastructure. They allow the ingress of water from the surroundings (Ellis et al., 2018).

E. coli:
Twenty-eight and twenty-two samples had E. coli ranged from 3-15 CFU (100 mL) -1 , and 16-34 CFU (100 mL) -1 respectively. However, six samples contained a higher concentration E. coli of 40-60 CFU (100 mL) -1 . The maximum and minimum values of E. coli from the samples were 3 CFU (100 mL) -1 (Sources of ward 27), and 60 CFU (100 mL) -1 (User points of ward 29) respectively. Sources of ward 8, 30, and 14 were free from E. coli microorganisms. According to BDWSs 240 and WHO standards, drinking and domestic water should be free from any bacteria. Figure 4(b) So, the RCC area's water does not safe considering the microbiological aspects of water quality standards. Most microbes get shelter in the biofilm on the pipeline's inner surface in WDS (Gulati and Ghosh, 2017). This test result shows that user points contain a higher amount of bacteria than the sources. The paper explained the reasons for regrowth above. Additionally, there is a proportional relationship between high Temperature and the regrowth of microorganisms. Because organism 245 respiration and cell growth become easier at an increased temperature. An increase in microorganisms occurring within WDS results in the decline of DO (Power and Nagy, 1999).

Statistical analysis
The authors collected the samples from RWASA points and household samples of the RCC wards. They analysed a total of fourteen parameters. Out of them, seven samples were chemical (50 %), five were physical (35.71 %), and two were 255 microbiological (14.29 %) parameters.
Mean is the average of numbers, a calculated central value of a set of numbers. Standard Deviation (SD) is the degree used to quantify the difference in the dispersion of a set of data values. Standard Error of Mean (SEM) is a method of statistical data check. The SEM is the method that estimates the SD of a distribution (RICHARDI. LEVIN, 1978). Table 2 shows the results of both physical and chemical parameters found in descriptive statistics [Mean ± SD]. The table  260 also describes the SEM. The obtained results show the characteristics of the overall water quality.   Table 3 shows the minimum and maximum values of RWASA points and household samples. The minimum and maximum values of water samples for pH ranged from 6.5-7.12 and 6.4-7.5, turbidity from 0.5-7.63 NTU and 0. 270 temperature from 20-29 ºC and 16.5-30 ºC, EC from 450-1600 µs cm -1 and 425-1900 µs cm -1 , DO from 0.25-5 mg L -1 and 0.37-5.5 mg L -1 at the RWASA points and household samples respectively. The amount of Fe ranged from 0.03-2.5 mg L -1 and 0.04-3.5 mg L -1 , Mn from 0.6-1.7 mg L -1 and 0.64-2.1 mg L -1 , COD from 1-7 mg L -1 and 1.2-8 mg L -1 , BOD from 0.1-3.2 mg L -1 and 0.2-4 mg L -1 , Residual Cl from 0-1.13 mg L -1 and 0-1.1 mg L -1 , hardness from 45-597 mg L -1 and 60-650 mg L -1 , TC from 10-170 mg L -1 and 18-255 mg L -1 , E. coli from 0-32 mg L -1 and 5-60 mg L -1 , As from 0-0.03 mg L -1 and 275 0-0.04 mg L -1 respectively at the RWASA points and household samples following the WHO (2006) standards and BDWSs.

Correlation matrix of the physicochemical parameters
Pearson correlation (r) verifies the co-relationship between the physical, chemical, and microbiological parameters of different water sources. The Pearson correlation finds a correlation between at least two continuous variables. The correlation value ranges from -1.00 to +1.00. There are two kinds of correlation: (1) Positive correlation and (2) Negative correlation. The 280 Pearson correlation values can range between 0.00 (No correlation), and ±1.00 (Strong correlation). More precisely, the parameters having r = 0.7 are strongly correlated. The parameters of r-value between 0.5 and 0.7 have a moderate correlation (Springer paper). The test revealed several significant interactions among the study area water samples' physical, chemical, and microbiological variables. Many parameters showed different correlations at the water from the RWASA points and household samples (Table 4 and Table 5). 285     The presence of specific pollution indicators influences the presence of or increase in some other parameters. The increase 335 in one physical or chemical parameter indicates the increase or decrease of another parameter. For example, a higher TC means more cations than anions in water. The EC of water increases with more ions in water. We can ultimately determine the EC concentration through measuring the EC of water.
340 Figure 5: Supplied water condition in the wards of RCC Area.
In Fig. 5, the authors ranked the supplied water conditions based on water parameters and standards' quality. They termed the conditions following the weighted-index method. According to Fig. 5, they found water to condition the best in ward 9 (i.e. very good), and ward 29 (i.e. good). On the other hand, the worst-conditioned water existed in ward 25.

Health effects
The concentration of Mn in a water body is associated with lower memory, attention, motor functions, mathematics achievement scores, perceptual reasoning, working memory, and behaviour problems. Moreover, epidemiological evidence and previous reports anticipate that elevated Mn concentration in drinking water is responsible for lower IQ in a group of 350 school-aged children of 6-13 years (Dion et al., 2018). A high concentration of the metals (Coupling of Fe and Mn) creates the major esthetic problems that lead to taste and odour problems. Elevated concentration causes harmful health effects (Ander et al., 2016). The taste (Organoleptic problem) is affected when Fe's concentration is above 0.3 mg L -1 . High Fe in the DWDSs and its ingestion can cause hemochromatosis with symptoms like chronic fatigue, arthritis, heart disease, cirrhosis, diabetes, thyroid disease, impotence, and sterility (Khan et al., 2013). The water of hardness below 300 mg L -1 , is portable. Nevertheless, 355 it causes gastrointestinal irritation beyond this limit.
Biofilms create taste and odour problems in the distributed water. Top categories of E.coli are not harmful, but some can cause diarrhoea, abdominal pain, fever, sometimes vomiting, and urine infections. Furthermore, certain types of E.coli infection may lead to kidney failure (What to know about E. coli infection, 2017). Bacterial gastrointestinal diseases like cholera, salmonellosis, and shigellosis transmit through water. Undesirable pathogens in DWDSs are responsible for the 360 outbreak of water-borne diseases (Sharif et al., 2017). Salmonella typhi and Salmonella paratyphi cause typhoid fever (Jayaswal et al., 2018). There is an intimate relationship between public health and water. People suffer from various waterborne diseases consuming poor-quality supplied water by RWASA. The questionnaire survey reported the percentage of RCC people suffered from various types of diseases like diarrhoea, cholera, typhoid, mental disorder, and other problems as 45 %, 25 %, 15 %, 55 %, and 15 % respectively (Fig. 6). 365

Conclusions
Water quality deterioration of RWASA sources occurred during the household storage. The concerned authority poorly 370 practised the regular monitoring of supplied water quality. Deteriorated water quality resulted in the outbreak of various waterborne diseases. User points contained a higher amount of bacteria than the sources. Wards with lesser DO and Residual Cl (i.e. ward 8, 9, and 3) indicate a higher amount of microorganisms, BOD, and COD. So, the parameters DO, Residual Cl, TC, and EC have an apparent interrelationship. All samples contained a higher concentration of Mn. Majority of the samples had a higher amount of Fe. pH, temperature, and colour were within the allowable range. The study also found elevated concentration 375 of BOD and COD as per the BDWSs and WHO standards.
Limitations of the study. The authors cannot investigate Pseudomonas Aeromonas, Artrobacter, Caulobacter, Klebsiella Bacillus, Enterobacter, Citrobacter, and Acinetobacter Prosthescomicrobium, Alcaligenes, Serratior, and Actinolegionella due to insufficient lab facilities. The knowledge of water storage lengths at the households, length of pipes from tap to 380 consumer storage, no fittings, and cross-connections are unknown.
Code availability. Application of SPSS software.
Data availability. The authors collected the necessary data from a field survey.

385
Author contributions. SAP was the investigator and contributed to the statistical analysis. AH and HIT contributed to the investigation, and involved in the statistical analysis. HMR involved in the supervision and contributed to the methodology. HIT prepared the manuscript with contributions from all co-authors. 390 Competing interests. The authors declare that they have no conflict of interest.