Water quality status of groundwater and municipal water supply (tap water) from Bagmati river basin in Kathmandu valley, Nepal

Poor waste management in the Kathmandu valley has deteriorated the water quality of surface and groundwater sources. The objective of this study was to assess the status of water quality (WQ) in drinking water sources of groundwater and municipal supply (tap water) from the Bagmati river basin in Kathmandu valley. A total of 52 water samples from deep tube-well, tube-well, dug-well, and tap water were collected and analyzed for physical, chemical, and microbiological parameters using standard methods. The results revealed that chloride, total hardness (TH), copper, nitrate, sulfate, and turbidity were within the recommendations of the National Drinking Water Quality Standard (NDWQS). Total coliform (TC) bacteria in 84.6% of the samples exceeded drinking water guidelines. Similarly, the isolates of different enteric bacteria, namely Escherichia coli (21.5%), Citrobacter spp. (20.9%), Klebsiella spp. (19.8%), Proteus spp. (13.9%), Enterobacter spp. (8.72%), Salmonella spp. (5.8%), Shigella spp. (5.2%), and Pseudomonas (4.1%) were identified in the samples collected from the respective sources. Out of the 52 water samples, 7.7% of samples had fecal contamination of somatic coliphage. The groundwater and municipal water supply in the study area are not safe for drinking purposes. Treatment of water is required before its use for household applications. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licence (CC BY 4.0), which permits copying, adaptation and redistribution, provided the original work is properly cited (http://creativecommons.org/licenses/by/4.0/). doi: 10.2166/washdev.2020.190 om http://iwaponline.com/washdev/article-pdf/11/1/102/836956/washdev0110102.pdf 2021 Pabitra Bhandari Megha Raj Banjara Anjana Singh Central Department of Microbiology, Tribhuvan University, Kirtipur, Kathmandu, Nepal Samikshya Kandel Deepa Shree Rawal Bhoj Raj Pant (corresponding author) Nepal Academy of Science and Technology, Khumaltar, Lalitpur, Nepal E-mail: environmentnast@gmail.com


GRAPHICAL ABSTRACT INTRODUCTION
Water quality of the Bagmati river in the Kathmandu valley has swiftly deteriorated due to the discharge of untreated wastewater in the river and disposal of municipal solid waste in the open fields near the river bank (Regmi ).
The state of the river and its tributaries are in degraded condition owing to indigent water quality. Such situations can negatively affect the groundwater quality along the riverside and can contaminate soil and air quality. This can consequently affect the availability of safe drinking water as groundwaters are largely been used for drinking purposes (Gurung et al. ).
The diarrheal disease remains a leading cause of illness and death in the developing world, which alone causes 2.2 million of the 3.4 million water-related deaths per year.
About 90% of these deaths involve children less than 5 years of age. In the fiscal year 2015/2016, a total of 1,248,093 diarrheal cases among 2-59 months children were reported in Nepal, of which 0.2% suffered from severe dehydration (MoHP ). The World Health Organization (WHO) has estimated that about 80% of the waterborne diseases are due to inadequate sanitation and lack of safe drinking water. Unsafe drinking water is responsible for a large number of diseases, such as typhoid, cholera, dysentery, hepatitis, protozoan, and helminthic infections.
Organic matter has a direct relationship with coliform contamination in water (Seo et al. ). Coliform bacteria are considered an important water quality indicator related to human health (Seo et al. ). Fecal indicator organisms have largely been used as a measurement of drinking water quality as it is not feasible to test water for all known waterborne pathogens to assess its safety (Tallon et al. ). The WHO guidelines recommend Escherichia coli and/or thermotolerant fecal coliforms as indicator organisms for the potential presence of fecal contamination and waterborne pathogens (Tallon et al. ). However, bacteriophages that infect E. coli, Enterococcus, and various Bacteroide spp. are also considered as possible indicators of fecal contamination (WHO ). The most common indicator for fecal contamination is male-specific coliphage such as E. coli with an RNA genome or Fþ RNA. These viruses fit with the criteria for an ideal indicator of microorganisms. The etiological study of waterborne diseases reveals that common agents are more likely to be viruses and parasitic protozoa than bacteria ( Jofre et al. ).
The objective of this research was to assess the status of water quality (WQ) in drinking water sources of groundwaters and tap water from the Bagmati river basin in Kathmandu valley.

Study area
The study area covers the Bagmati river corridor from

Sample collection
A total of 52 water samples in triplicates were randomly collected from the deep tube-well (>30 m depth, 31 samples), tube-well (11-30 m depth, 12 samples), dug-well (3-11 m depth, 7 samples), and tap water (municipal supply, 2 samples) in between July and September 2017, during the rainy season. The sampling sites are located approximately 100 m to the north of the Bagmati river basin in the Kathmandu district. The deep tube-well, tube-well, and dug-well are the prime sources of water supply in Kathmandu valley. Of the groundwater sources, deep tube-well and tube-well are closed, except for an outlet at the top of the ground. But, in the dug-well, the opening is covered by a lid to avoid the entry of dirt. On the other hand, tap water is considered safe for household applications because the water is distributed only after treatment. However, the purity of the water is questioned due to the old pipes used in the water distribution system and the leakage from those pipes.
During the sample, collection samples were stored in a portable icebox and transported to the laboratory within 6 h and stored at ∼4 C in a refrigerator until physical, chemical, and microbiological analyses were carried out.
The sample size was estimated according to the following equation: where N is the sample size, Z α represents confidence interval (95%), p is the prevalence of waterborne diseases, and e indicates an allowable error.
The samples were collected according to the standard method (Greenberg et al. ). Samples to be analyzed for the microbiological parameter (Somatic coliphage and coliform) were collected in polyethylene bottles that were thoroughly cleaned by distilled water and sterilized in an autoclave at 121 C and 15 LB pressure for 15 min. Samples for the analysis of chemical parameters (hardness, chloride, alkalinity, fluoride, iron, manganese, cadmium, chromium, lead, copper, zinc, and arsenic) were collected in polyethylene bottles cleaned by distilled water for several times.
Before collecting the sample, the sample bottles were purged at least three times by the water to be collected from respective sources. A dip sampler was used in sample collection from the shallow wells, while the samples from the tube-well and deep tube-well were collected either by pumping through a hand pump or by using the electric motor. The sampling sites and the number of samples collected from different places are illustrated in Figure 1.

Sample analysis
Physical parameters were analyzed for pH, temperature ( C), turbidity (NTU), and Electrical Conductivity-EC (μs/ cm). The pH was measured by using a digital pH meter (TOA HM-10P). The turbidity and EC were measured using the nephelometer (ELICO, India) and conductivity meter (WTW LF91), respectively.
Chemical parameters were analyzed for chloride, free residual chlorine, total hardness (TH), copper, arsenic, manganese, zinc, iron, ammonia nitrate, fluoride, and sulfate. The TH, chloride, and residual chlorine were determined volumetrically. Fluoride was measured by the SPADNS method using acid zirconyl SPADNS reagent.
The nitrate, ammonia, and sulfate were determined using spectrophotometry. Metal ions, such as iron, manganese, cadmium, chromium, lead, copper, zinc, and arsenic, were

RESULTS AND DISCUSSION
Kathmandu valley is densely populated, and limited municipal water supply cannot fulfill the large demand for water.
Most of the people in the valley depend on groundwater to fulfill their daily requirements; hence, groundwater is considered a crucial source of water for domestic and other applications.
The water temperatures vary widely between the sites and this variation in water temperature can be caused due to the variation in the weather at the time of sample collection (Table 1).
There are no standard guidelines for water temperature and the impact associated with public health. However, the temperature facilitates the growth of microorganisms in water and alters its quality (WHO ). The Canadian drinking water guidelines have recommended a maximum drinking water temperature of 15 C (HC ). The average range of pH was 6.38-6.9 in the respective samples. The minimum pH of groundwater (deep tube-well, tube-well, and dug-well) was acidic and measured in the range of 6.0-6.1 pH. Nevertheless, the pH of tap water was within the recommendations of NDWQS. The variation in drinking water pH from normal pH (pH 6.8-8.5) to acidic (<7.0 pH) or alkaline pH (pH > 7.0) can affect public health. Out of the 52 water samples, 46.15% of samples comply with the NDWQS guideline.
The EC ranged from 43.6 to 1,012.3 μS/cm and the conductivity of the tested water complies with the NDWQS guidelines (Table 1). In general, groundwater tends to have high EC due to the presence of metallic ions and dissolved salts (Prakash & Somashekar ). Our findings also reveal that higher EC levels are higher in groundwaters than in tap water as tap water is treated before distribution.    Free residual chlorine formation in water is pH-dependent (Pal ). The hypochlorous acid, a major component of residual chlorine is formed when chlorine reacts with water at a pH ranged between 5 and 10 pH.
Within this pH, the chlorine exists as hypochlorous acid and hypochlorite. The variation in the pH dissociates these products into separate components, resulting in the reduction of water disinfection efficiency. Similarly, the chemical reaction between chlorine with organic matter, inorganic substances, and microorganisms present in water can also produce the reaction byproducts, which are hazardous to public health. In this study, the average free residual chlorine in the water ranged from 0.89 to 4.44 mg/L, and 84.6% of samples were within the range specified in the NDWQS, but 15.4% of samples exceeded the guideline value for residual chlorine. The amount of residual chlorine in tap water is comparatively less than in groundwaters. The reason for low residual chlorine in tap water may be due to pre-treatment of water before distribution. The fluoride in the water sample was between 0.15 and 9.2 mg/L, and 59.62% of samples were above the drinking water standard value for fluoride, and 40.38% of samples comply with the guidelines for drinking water quality. Fluoride is an essential mineral of public health concern. The use of the water containing the maximum concentration of fluoride is susceptible to dental fluorosis and bone demineralization (Burlakoti et al. ).
The estimated range of maximum iron level was between 3.8 and 4.56 mg/L in deep tube-well, tube-well, dug-well, and tap water ( Table 3).
The average concentration of iron in the water (1.91-2.89 mg/L) exceeded the maximum limit as recommended by the NDWQS. Iron is an essential mineral required in the recommended amount by living organisms (Crichton ). However, excess iron intake causes toxicological problems of acute exposure and chronic iron overload.
Ingestion of iron in exceeding amount (>0.5 g) can cause liver, heart, and lung diseases, as well as diabetes mellitus, hormonal abnormalities, and dysfunctional immune system (Gurzau et al. ). Similarly, the maximum concentration of iron makes the water esthetically unacceptable due to discoloration, metallic taste, metallic odor, turbidity, staining of laundry, and plumbing fixtures (Kontari ).
Our finding shows that iron is rich in the groundwater and tap water sources available in the Bagmati river basin in The coliform was present in all the water samples tested (Table 4), and these values exceed the drinking water guideline recommended by NDWQS (0 CFU/mL).
The thermotolerant coliform was positive in 67.3% of samples (Table 4) Similarly, for microbiological analysis, the highest number of coliphage were present again in the water of deep tubewell, tube-well, and dug-well. Thus, the study demonstrates that considering the analysis of chemical and microbiological parameters, water from all three groundwater sources is hazardous compared with the tap water source.

CONCLUSIONS
The study suggests that the water from the sources cannot be used for drinking purposes due to the presence of ammonia, residual chlorine, fluoride, iron, and manganese that exceeded the recommendations of NDWQS, and also the existence of somatic coliphage bacteria. We recommend incorporating a suitable scientific method for water treatment to make the water potable. In general, groundwaters are contaminated due to the practices like untreated disposal of solid waste and waste waters. Disposal of wastewater and solid wastes in the open field can be seen  in most of the places in the study area, which can leach to groundwater sources by contaminating the water. Therefore, to protect the groundwaters from bacterial contamination, environmental protection practices should be introduced, mainly focusing on the safe disposal of solid waste and wastewaters in the case of the Kathmandu valley.