4.1 Physico-chemical parameters.
The physicochemical parameters and bacteriological analysis for different domestic water sources discussed in WHO and USEPA guidelines for drinking water quality. The hydrogen ion concentration (pH) of water affects biological and chemical activities that only occur within a specific range serves as evidence of the importance of this parameter (Kolawole OM et. al., 2013). Industrial or home garbage on considerably impacts the pH levels of the nearby waterbodies (Campbell IC, 1978). The pH trend in tap water has been found to be fairly acidic, and the pH range was within acceptable range for drinking water, which is 6.5 to 8.59 (WHO 2011). This outcome approves by (Shittu OB, Olaitan JO, 2008). Who discovered that the pH range of the water used for drinking and swimming in Abeokuta, Nigeria, was the same. Average pH readings below 6.5 are considered to acidic for humans to consume and can lead to health issues, such as infections with acidosis. Synergistically, low pH decreases the toxicity of heavy metals in waterbodies (Effendi H, 2015). Numerous human actions, such as washing, bathing, and using bathrooms close to waterbodies, may also impact on pH levels, air temperature and various chemical and biological processes impact the pH of water bodies (Manjare SA, Vhanalakar SA, 2010). The majority of fish can survive in a pH range of 5.0 to 9.0, and a smaller pH change has no noticeable effects on aquatic life. However, pH changes impact the availability and solubility of different chemicals, exacerbating nutritional issues for aquatic life. Here, it might be inferred that the pH levels of the River Ganga have no appreciable influence on its aquatic life, human population, or plant life. The obtained samples contained levels of total dissolved solids (TDS) ranging from 69.7 to 399 µg/L in each of the three seasons. In October 2018, the highest TDS value was recorded (79.1–399). TDS levels that are too high raise the water temperature impede photosynthesis, and lessen water clarity (Rahman MS, 2014). TDS concentrations, however, were found to be much below the 1000 mg/L WHO guideline limit, which is intended to safeguard fisheries, aquatic life, and domestic water supplies. Electrical conductivity, which determines the number of ions in water, singnificantly impacts and, in turn, user approval of the water (Florescu D et. al., 2011). Each subterranean water sample had an average value within the WHO-acceptable level. Electrical conductivity (EC) is a common way to gauge the total concentration of ionized water elements, and a higher conductivity indicates more water contamination (Wilcock RJ, Stevenson CD, 1981). The EC values of the water samples taken for this study across various seasons were very similar (Table 4). From the physicochemical parameter analysis, it could be concluded that the water of the River Ganga is satisfactory in terms of EC, pH, and TDS values.
The BOD level detected in water samples fell within the range depicted in the table (according to WHO). BOD assesses how much oxygen is used by bacteria and other microbes to oxidize the stuff in the water (Aniyikaiye et al., 2019)(Bhateria & Jain, 2016)(Wondie TA, n.d.). The water samples from October 2018, February 2019, and June 2019 were tested for DO values ranging from 8.1 to 9.4, 6.4 to 10.5, and 6.5 to 9.2 mg/L. These results were compared to WHO acceptable criteria for drinking water. Depending on the water's temperature, very little oxygen is dissolved in warm water compared to cold water (Nduka JK, Orisakwe OE, 2008). Therefore, one of the reasons for the low DO values found in this study could be the high temperature of the water sources. All living things depend heavily on dissolved oxygen, which can enter bodies of water directly from the air or be produced by autotrophs through photosynthesis. The surface water sources' DO readings throughout this study period were within WHO guidelines. The dissolved oxygen content has been decreasing in river water samples, which may indicate that too many bacteria are present (Olajire & Imeokparia, 2001). It has been noted that DO oxidiszes both organic and inorganic compounds, reducing their ability to cause consumer annoyance. Although dissolved oxygen may not directly endanger human health, it may impact other water substances (Chapman, D. and Kimstach, 1996).
4.2 Heavy metals Analysis
Heavy metal concentrations ranged widely; the levels (in µg/L) in October 2018. As: 2.5–16.1, Pb: 0.008–0.93, Hg: 5.16–7.82, Cd: 0.004–0.19, Cu: 0.319–1.25, Cr: 0.571–7.17, Zn 0.498–9.63, Ni: 0.734–23.2. Same as the concentration in February 2019 were As: 1.24–22.5, Pb: 0.014–2.45, Hg: 0.352–3.78, Cd: 0.142–5.65, Cu: 0.57–3.67, Cr: 0.65–5.95, Zn: 8.59–38.5, Ni 3.46–18.8. Furthermore, in June 2019, the concentrations of heavy metals were As; 1.45–21.1, Pb: 0.38–8.17, Hg: 0.25–9.98, Cd: 0.176–0.99, Cu: 3.15–23.4, Cr: 0.49–18.2, Zn: 10.2–224, Ni: 1.95–32.3 (table-2). The As concentration is high in three seasons compared to WHO values and index calculations. The current investigation found that October’s maximum concentration of As in the Ganga River water was 16.1 µg/L, slightly higher than the WHO-recommended level (10 µg/L). Islam et al., conducted a comparative investigation on the Korotoa River and discovered As levels of 46 µg/L and 37 µg/L throughout the winter and summer seasons, respectively (Islam et al., 2015). Arsenic (As) has a link to hypertension, and Jolly et al. discovered that the As level in water from the Shitalakhya River was within the allowable range (10µg/L) (Jolly YN et. al., 2018). It effects on the cardiovascular system and may harm the liver. In Bangladesh, they investigated the Shitalakhya River's water. They noted a Pb content of 16 µg/L (Jolly YN et. al., 2018) the seasonal change in Pb concentration and found River Korotoa had a Pb level of 35.0 µg/L in the winter and 27.0 µg/L in the summer (Proshad et al., 2018). In a sample of water taken from the River Buriganga, Ahmad et al. discovered a Pb level of 65.45 µg/L (Ahmad MK et. al.,, 2010). Vehicle exhaust, metal plating, wastewater discharge, fertiliser, etc. are all potential sources of lead (Karrari et al., 2012). Haem biosynthesis and erythropoiesis are impacted by lead (Pb). Chronic Pb exposure causes malignancies and anaemia in adults, damage to male reproductive organs, hormonal imbalances, and IQ decline in early children (Siddiqui MK, Srivastava S, 2002)(Tandon et al., 2001). In October 2018 and June 2019, the highest Hg content was higher above the WHO-recommended limits. All of the water samples were found to have very low levels of pollution, according to the analysis of the Nemerow's pollution index (NPI) and the Water quality index (WQI). Every form of mercury is harmful, and its side effects include kidney, nervous system, and gastrointestinal toxicity (Fernandes Azevedo et al., 2012).
4.2.1 Human health risk assessment.
The risks to human health from the heavy metal contamination in the water distribution network can increase through a number of exposure modes. The current study examined the dangers to human health from skin contact and oral consumption that are both non-carcinogenic and carcinogenic. As, Hg, and Cu had the highest and lowest levels of metal content, respectively. When toxic compounds are present in a contaminated environment, humans may be exposed to them, and the human health risk assessment evaluates the type and severity of adverse health impacts. In the current work, exposure and risk analyses were carried out based on the methodology of the USEPA and APHA. Humans acquire heavy metals mostly through drinking water, food, inhaled aerosol particles, and dust (Díaz-Somoano et al., 2009). The frequency of consumption directly affects how harmful heavy metals are to human health. But this research also took cutaneous absorption and consumption from drinking water into account. This led to the health risk estimation of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn revealing the mean HQs suggesting an acceptable level of non-carcinogenic deleterious health risk in all samples taken from the river Ganga water distribution network in three different sessions. The mean values of HI through ingestion, cutaneous adsorption, and total HI demonstrate the negligible non-carcinogenic danger to residents and are summarised in Table no. Pb, Cr (VI), Cd, and Ni are examples of heavy metals that may increase the risk of cancer in people (Tani & Barrington, 2005)(Cao et al., 2014). The above table provides the carcinogenic risk assessment for both male and female adults as well as youngsters. This outcome came after multiple investigations. They stated that youngsters received much larger doses of all heavy metals than adults, which was supported by our findings. For instance, in Australia and Thailand, children's populations had average ADI real values that were approximately 1.7 and 2.5 times greater than those of adults, respectively. (Wongsasuluk et al., 2014)(Saha et al., 2017). The findings of this study indicate that the toxins in the area's drinking water posed a danger of cancer to locals through cumulative consumption and skin contact. A related study also supports these findings. (Cao S et al., 2014)(Wcisło et al., 2002)(Yang G et al., 2014).
4.3 Bacterial quality in river water samples.
The mean total bacterial counts in both the reservoir and the river were greater than what the WHO deemed safe for drinking water. The results of this investigation corroborate those of (Doughari JH, Elmahmood AM, 2007). The extraordinarily high total heterotrophic bacterial load in the water indicated that it may be unsafe for human consumption and has been polluted with possibly harmful microorganisms. Changes in the bacterial population's abundance can be used to identify surface water microbial contamination (Kavka, G.G. et al., 2006). The presence of bacteria in surface water not only suggests that the water is contaminated with excrement but also raises questions about potential risks to human health (Baghel VS et al., 2005). Typhoid, diarrhoea, and cholera are the three main diseases that could develop from bacterial pollution of the groundwater and surface water. As water infiltrates through the soil, the water contains little to no bacteria, which could have been eliminated by thorough filtration. (Uzoigwe CI, 2012). The characterisation of the isolates from the water samples from the study's sampling locations, which were heavily contaminated with one or more bacterial pathogens, served as confirmation of this. From river water samples, the high bacterial loads of the species Klebsiella, Pseudomonas, Proteus, Escherichia, citrobacter, and Acinetobacter were isolated. The significant number of pathogens present in the water sample and the high number of bacteria isolated from it in this investigation point to high faecal contamination and a health risk for human depletion (Schets FM et al., 2005). According to WHO recommendations, there shouldn't be any fecal coliforms in hundred millilitre of drinking water. The reason for the severe pathogen contamination of waters as seen in this study may be related to the river's shallowness and various savage drainage systems, which make it simple for particles from the environment to enter. It could also be a result of the places' unsanitary surroundings (Shittu OB, Olaitan JO, 2008)(Musyoki, A.M. et al., 2013). In Athi River found high number of total coliform count surpassed the WHO allowed limit from water sources in river Ogun (Nairobi River surface water bacterial infections and their effects on downstream people' health). The bacterial species found in the water samples may be caused by farming methods carried out close to the surface water by the habitat of the local population, which may lead to open defecation along the farmland and a tendency for runoff from these farmlands to wash into the River. Human activities including bathing, farming, washing, and human or animal facial seepage run-offs infiltrate the waterbodies and can contaminate the surface water. These activities are capable of spreading a wide range of infectious diseases (Anyanwu CU, 2012). The study's bacterium findings have the potential to infect consumers with urinary tract infections, meningitis and pneumonia. The most common bacteria in water that cause waterborne illnesses like typhoid, dysentery, and diarrhoea, as well as being linked to global mortality, are the coliforms. They are the main bacterial indicator for faecal contamination in water (World Health Organization, 2004). The high abundance of bacteria, including Klebsiella, Pseudomonas, Proteus, Escherichia, Citrobactor, and Acinatobactor spps, found in the river and reservoir water in this study could be attributed to one or to several sewage effluents, including agricultural run-off and direct faecal contamination from natural fauna (Annous B, Gurtler J, 2012).
High levels of bacteria were found in the summertime water samples, which may be the result of environmental runoff that boosted the microbial burden, particularly coliforms. The discovery is made by Esharegoma OS (Esharegoma OS et al., 2018). A concentration of nutrients brought on by midsummer evaporation of water was postulated as the cause of the observed greater microbial counts in the rainy season compared to the dry season (Juma K et al., 2016). This odd pattern in the occurrence definitely demonstrates that specific seasonal factors in the tropics favour their proliferation. A greater pH and an increase in decomposable organics in the waterbody observed during different seasons, which encouraged an increase in the microbial Contamination, may have contributed to the high microbial load.