Water plays a vital role in maintaining human life and welfare. Pure drinking water is now recognized as a fundamental right of human beings. Around 780 million people do not have access to clean and safe water and around 2.5 billion people do not have proper sanitation. As a result, around 6 - 8 million people die each year due to water-related diseases and disasters . Therefore, water treatment is a top-priority policy agenda in many parts of the world . In today’s world, water use in household supplies is commonly defined as domestic water. This water is processed to be safely consumed as drinking water and for other purposes. Water quality and suitability for using are indicated by its taste, odor, color, and concentration of organic and inorganic materials . Contaminants in the water can affect the water quality and consequently human health.
Drinking water is the major need of human life. Freshwater quality is a vital concern for mankind since it is directly linked with public health. Drinking water quality has always been a major issue in many countries, especially in developing countries like Bangladesh . Although safe drinking water is a basic demand for people all over the world, a huge proportion of people in the world are deprived of pure drinking water including Bangladesh . Groundwater is decreasing day by day prominently in Asia, South America, North America and ecosystems are threatened .
Bangladesh is a low-lying country and is a delta of great three big rivers―the Ganges, the Brahmaputra and the Meghna. In Bangladesh, there are many sources of drinking water such as surface water, groundwater and rainwater. Surface and groundwater are considered the main sources of drinking water. There is no safe drinking water supply system in rural areas, except in some large cities (such as “WASA” in Dhaka city). In Bangladesh, most people consider that groundwater or water from tube wells is free from contamination. For this reason, Hand pumped tube-well water is used as the primary source of safe drinking water in Bangladesh. About 90% of the households use this Hand pumped tube-well technology in Bangladesh . In rural area, most people are depended on untreated groundwater and tube wells. It is an estimation that about 11% of all deaths in the rural area of Bangladesh are caused by diarrheal disease . Recent studies suggest that significant levels of diarrheal disease are caused in part by drinking untreated groundwater  . Natural water resources such as groundwater in coastal areas of Bangladesh are contaminated by salinity and other heavy metal ions because of saltwater intrusion, storm surges and withdrawal of freshwater for using various purposes . In the Noakhali region, contaminated groundwater is used by people for their drinking purposes and is affected by hypertension, heart failure, kidney failure, skin diseases, carcinogenic diseases, diarrhea and other water-borne diseases. For this reason, a detailed study of the drinking water quality of the Noakhali region is very much important . Although several reports on the assessment of drinking water quality based on physiochemical and Microbiological parameters in the Noakhali region have been published by several researchers separately   . Very little information is available about the overall status of water quality in this area. That’s why an investigation was initiated, whose primary objective was to examine the present overall status of drinking water quality of groundwater sources in Noakhali region.
2. Materials and Methodology
2.1. Study Areas
In this study, three upazillas of Noakhali district in Bangladesh drinking water were analyzed. Three upazilas were upazila-sadar, Kabirhat upazila, Chatkhil upazila (Figure 1). Coordinates of Noakhali upazila-sadar is from 22˚50'N to 22˚833'N and from 91˚6'E to 91˚100'E. Coordinates of Kabirhat upazila is from 22˚50'N to 22˚833'N and from 91˚12'E to 91˚200'E. And Chatkhil upazila’s coordinate is from 23˚3'N to 23˚5'N and from 90˚57.5'E to 90˚95'E.
Total samples were nine in numbers. In upazila-sadar maximum people take supply water as drinking water. Some take motor water and some others take tube-well water for drinking. Drinking water samples were collected from three different areas of Noakhali upazila-sadar. The first sample was collected from maijdee and it was supply water (1000 feet deep and treated). The second sample was collected from Dattabari and it was motor water (500 feet deep). The third sample was collected from Sonapur and it was tube-well water (450 feet deep).
Most of the people at Kabirhat upazila take tube-well water for drinking. From kabirhat upazila three different areas drinking water samples were collected. The first sample was collected from Kabirhat-hospital road and it was tube-well water (60 feet deep). The second sample was collected from Kabirhat-kalamunshi road and it was tube-well water (70 feet deep). The third sample was collected from Kabirhat-college road and it was tube-well water (150 feet deep).
All most the people at Chatkhil upazila take tube-well water for drinking. From Chatkhil upazila three different areas drinking water samples were collected. The first sample was collected from Chatkhil thana road and it was tube-well water (35 feet deep). The second sample was collected from Abu tara nagar road and it was tube-well water (256 feet deep). The third sample was
Figure 1. Noakhali district map.
collected from Bodolkot road and it was tube-well water (800 feet deep).
2.3. Study Duration
This study duration was from July to September 2018.
2.4. Analysis of Physical Parameters
The pH values, temperature, total dissolved solid, electrical conductivity (EC), salinity of the samples was measured by using pre-calibrated Multipara-meter, Model PL-700ALS.
2.5. Determination of Chemical Parameters
Chloride ion determined in a drinking water sample by “Muhr’s Method”. Iron content estimated by the packet of reagent in drinking water Sample.
2.6. Microbiological Test
Total viable bacterial count by serial dilution process. Total coliform count and E. coli detection by MPN (Most Probable Number) method.
Physical Test Results: Tables 1-4;
Microbiological Test Results: Tables 7-9.
Drinking water quality at Noakhali district in Bangladesh is not satisfactory. Contamination, high amount of dissolved solids, higher amount of iron content were the regular scenarios. Though supply water was quite satisfactory in upazillas-sadar,
Table 1. Findings of pH from different drinking water samples of three upazilas.
Table 2. Findings of electrical conductivity from different drinking water samples of three upazilas.
Table 3. Findings of salts from different drinking water samples of three upazilas.
Table 4. Findings of TDS (Total Dissolved Solids) from different drinking water samples of three upazilas.
Table 5. Chloride ion test results from different samples of three upazilas.
Table 6. Iron test results from different samples of three upazilas.
Table 7. TVBC (Total Viable Bacteria Count) results from different samples of three upazilas.
Table 8. Bacterial Growth presence in E.M.B. (Eosin Methylene Blue) Media from different samples of three upazilas.
Table 9. Results of Most Probable Number (MPN) of Coliforms per 100 mL of different samples of three upazilas.
but in other upazillas drinking water were not satisfactory well.
In this study, upazillas-sadar pH was comparatively higher (7.81) than other upazillas. On the other hand, Chatkhil upazila’s drinking water was lower pH (6.18). Ideal pH level of drinking water is 6.5 - 8.5 (by WHO). Chatkhil upazila’s drinking water pH was under the acceptable range. In that region drinking water was comparatively acidic. The corrosive nature of acidic water causes metal ion such as iron, manganese, copper, lead and zinc to leach into the water causing elevated levels of toxic metals in the water. It may also cause aesthetic problems such as a metallic or sour taste. In previous studies  pH of groundwater was 7.1 to 8.4. Sadar & Kabirhat upazilas drinking water pH was similar to the previous studies but Chatkhil upazila’s drinking water pH was comparatively low. The temperature during testing was 26˚C - 28˚C those were similar to the previous studies.
4.2. Electrical Conductivity
The Electrical Conductivity of drinking water sample at upazillas-sadar was 1106 µS/cm which was greater than the acceptable range (Acceptable range 1000 µS/cm by WHO). Kabirhat upazila’s drinking water conductivity was also higher (1104.33 µS/cm) than the acceptable range. Comparatively Chatkhil upazila’s drinking water was lower (252.1 µS/cm) than others and was in an acceptable range. Conductivity measures the water’s ability to conduct electricity. Common ions in water that conduct electrical current include sodium, chloride, calcium and magnesium. Because dissolved salts and other inorganic chemicals conduct electrical current. Conductivity increases as salinity increases. So, upazila-sadar and Kabirhat drinking water samples had higher salinity. In previous studies  Electrical Conductivity of groundwater was 1500 µS to 9711 µS. Sadar & Kabirhat upazilas drinking water conductivity was a little-bit lower than the previous studies but Chatkhil upazila’s drinking water conductivity was comparatively very much low.
Usually, the standard limit of salinity for drinking water is zero (recommended by WHO, 1996). Upazila-sadar water sample had comparatively higher salt (554.33 ppm) than the other two upazillas water samples. Kabirhat upazila’s water sample was also higher salt (549 ppm) than Chatkhil upazila’s water sample. Chatkhil upazila’s drinking water samples were a comparatively lower amount of salt (125.47 ppm).
Total dissolved solid below 500 ppm is good for drinking water and the acceptable range is below 1000 ppm by WHO. In this study, upazila-sadar TDS in drinking water were 733 ppm, Kabirhat 725.33 ppm, Chatkhil 165.57 ppm. All three upazillas TDS of drinking water were in acceptable range but not quite good for drinking water. In previous studies  TDS of ground water was 128 µS to 1660 µS. Sadar & Kabirhat & Chakhil upazilas drinking water TDS were almost similar to the previous studies.
Chloride ion in upazillas-sadar and Kabirhat upazilas were very high in amount (Sadar 7326.33 mg/L, Kabirhat 1299.83 mg/L) which were higher than the acceptable range of 250 mg/L by WHO. But in Chatkhil chloride ion in drinking water were in the acceptable range (236.33 mg/L). The high amount of chloride ion in drinking water may wash out beneficiary bacteria from our bodies.
Concentrations of iron in drinking water are normally less than 0.3 mg/L by WHO but in this study upazilas-sadar, Kabirhat upazilas, Chatkhil upazila iron content were very much higher than the acceptable range. A high amount of iron may harm our body such as damage healthy skin which can lead to wrinkles. Vegetables and other foods cooked in such water will blacken and absorb a bad taste.
4.7. Total Viable Bacterial Count (TVBC)
Total Viable Bacterial Count in Chatkhil upazila drinking water samples bacterial load were comparatively lower (3.26 × 106 CFU/mL) than others and was almost similar with previous study . In Kabirhat upazila drinking water sample bacterial load was comparatively higher (7.13 × 106 CFU/mL) than the other two upazilas. According to WHO guideline value, the values of TVBC should remain within 1.0 × 103 but the results of three upazilas showed the values were excessively above the WHO guideline. There is a common belief in Bangladesh that groundwater is relatively free of microorganisms and, therefore, most of the people in rural areas consume tube-well water without any treatment. However, the results of this study show clearly that all water samples that were examined were contained highly. The previous study  TVBC of groundwater was 6.73 × 103 CFU/mL in upazila-sadar. All the results of this study were comparatively higher than previous studies.
4.8. E. coli Detection
Without supply drinking water in upazila-sadar more or less almost all upazillas had E. coli, Pseudomonas, Klebsiella, Enterobacter aerogenes. These water samples were completely polluted by animal or human waste that may cause serious health hazards like bloody diarrhea, severe anemia and so on. According to WHO guideline value, E. coli should be absent in drinking water but the result showed the presence of E. coli in every water sample without supply water in upazila-sadar. So, water samples were not suitable for drinking purposes without pretreatment. The previous study  E. coli was present in upazila-sadar water sample.
4.9. MPN (Most Probable Number) Count
It is a very concern able fact that in upazila-sadar most probable number of coliforms was 24.67/100mL which was very much higher than the other two upazilas (Kabirhat 14/100mL, Chatkhil 16.67/100mL). Total coliforms include bacteria that are found in water have been influenced by human or animal waste. Fecal coliforms are the group of the total coliforms that are considered to be present specifically in the gut and feces of warm-blooded animals. By these coliforms people may fall into diseases like gastrointestinal illness such as severe diarrhea, nausea and possibly jaundice as well as associated headaches and fatigue.
Noakhali district is in the coastal area near the Bay of Bengal. As result, the groundwater quality of Noakhali is not good. Higher iron levels in these areas of water are very common. As far as from sea the groundwater iron level, as well as microbial load, come low than near areas from sea. The supply water of this district cannot provide to all the people. So, maximum people have to take ground unpurified water for living. For escaping from these problems people should take a suitable water purification method as they can. Otherwise, their health will fall into great difficulties by taking such quality water. Awareness about pure drinking water can make them free from many water-borne diseases.
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