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The Government of Nepal implemented a nationwide lockdown from 24 March 2020 to 21 July 2020 to control the person-to-person transmission of COVID-19. This study was conducted in a trafficintensified area of Kathmandu valley, where vehicular movement represents one of the main sources of air pollution. Hence, this study was intended to quantify the concentration of particulate matter (PM2.5) for 11 hours of daytime from 23 April to 20 May 2020. It was also to evaluate the influences of lockdown on air quality. PM2.5 was observed using HAZ-Dust, Environmental Particulate Air Monitor in the 18 different traffic sites of the Kathmandu valley. During the lockdown period, a substantially low mean concentration of PM2.5 ranging from 3.69±1.78 µg/ m3 to 7.58±3.98 µg/m3 was recorded in Kathmandu valley, which reflected improved air quality due to the cessation of vehicular activities. Therefore, the study outcome suggests that controlling the existing vehicular activities and promoting energy-efficient vehicles like electric vehicles in specific locations in the city will improve air quality and benefit public health.

This research was investigated to evaluate the quality assurance of water from different sources. All together 250 water samples (135 well water, 48 boring water, 50 treated water, and 17 tap water) were received from different parts of Nepal from December 2019 to April 2020. The physicochemical parameters of water samples were performed according to the standard methods for the examination of water and wastewater. The membrane filtration technique was applied for the determination of Total Coliform bacteria. The measurements of water quality parameters were compared with the upper and lower limits of the National Drinking Water Quality Standards (NDWQS), 2005. Out of 135 well water samples, pH (1.48%), conductivity (2.22%), turbidity (42.96%), total hardness (4.44%), iron (54.07%), ammonia (48.88%), and nitrate (2.22%) elevated values compared to National Drinking Water Quality Standards, 2005. Likewise, 2.08%, 6.25%, 64.58%, 4.1%, 47.91%, and 58.33% of boring water samples showed higher values than the National Drinking Water Quality Standards for pH, conductivity, turbidity, total hardness, iron, ammonia, respectively. Conductivity, total hardness, chloride, and iron were found below the standards for both treated and tap water samples. Arsenic concentration was found within the standard for all water samples while 0.74% of well water samples showed a higher concentration of chloride compared to the standard. Results revealed that the minimum and maximum concentrations of some parameters were found to vary among the water sources. Among the total water samples, 94.8% well water, 76.4% tap water, 56.0% treated water, and 14.6% boring water samples showed the presence of coliform bacteria. This concludes that most of the water sources were polluted with fecal contamination and without proper purification may lead to the risk of waterborne diseases. Therefore, systematic and regular monitoring of water sources should be implemented to maintain water quality.

Uropathogenic

Due to its harmful impact on biota, microplastic pollution is the top priority research in many countries. However, there is hardly any research on microplastic pollution in Nepal's freshwater. Therefore, the present research was accomplished in Phewa Lake to evaluate the occurrence and distribution of microplastic contamination in shoreline sediments. The average abundance of microplastic varied from 55 to 122.5 items/kg dry weight (dw). The highest value appeared on densely populated eastern side of the lake and the western region reported the lowest concentration of microplastic. With regard to the shape, fibers dominated the sediments of Phewa Lake accounting for 62.03%. The dominant color was transparent (23.53%) followed by blue (21.39%). The size category 0.2-1 mm recorded the highest abundance of microplastic. Similarly, Fourier transform infrared spectroscopy (FTIR) reveal the dominant polymer type as polypropylene (PP) and polyethylene (PE). The outcome of this result adds a step toward filling the existing knowledge gap and providing a database on microplastic pollution in Nepal's freshwater.

Pseudomonas aeruginosa is an opportunistic human pathogen that has developed antibiotic resistance (AR) and causes a range of illnesses, including respiratory pneumonia, gastrointestinal infections, keratitis, otitis media and bacteremia in patients with compromised immune system. The production of metallo-β-lactamases (MBLs) is one of the major mechanisms of AR in this bacterium with ensuing infections difficult to treat. The main goal of this study was to provide a quantitative estimate of MBLs producing clinical P. aeruginosa isolates among the Nepalese patients and determine if MBL correlates with multi-drug resistance (MDR). Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guideline was followed for meta-analysis of relevant literature using PubMed, Research4Life, and Google Scholar. The prevalence of MBLs in P. aeruginosa from clinical samples was determined using R 4.1.2 for data pooled from studies published until 2021. The meta-analysis of a total of 19 studies selected (of 6038 studies for which titles and abstracts were reviewed) revealed the prevalence of MBLs producing P. aeruginosa (MBL-PA) was 14 % (95 % CI: 0.10-0.19) while MDR isolates among P. aeruginosa was 42 % (95 % CI: 0.30-0.55) in Nepal. Combined Disc Test was predominantly used phenotypic method for confirming MBLs phenotypes among the studies. Sputum was the most common specimen from which MBL-PA was recovered. A significant positive correlation was observed between MDR and MBL production in P. aeruginosa. We conclude that MBL producing strains are widespread among the clinical isolates of P. aeruginosa in Nepal and responsible for emerging MDR strains. It is paramount that antibiotics prescription against the bacterium should be monitored closely and alternative therapeutic modalities against MBL-PA explored.

The limited availability, accessibility and deterioration of the water quality in Kathmandu valley have led to the high demand of ground water. This study aims to evaluate ground water quality of the Kathmandu valley. In this study, the physio-chemical parameters of water samples were performed using standard procedures. Also, total coliforms were enumerated using standard membrane filtration technique to quantify the bacterial contamination. Water samples were collected from July 2017 to July 2018. The results revealed that 56% and 73% of well and boring water samples, respectively exceeded standard value of iron recommended by National Drinking Water Quality Standards, 2005. Likewise, ammonia content was higher in 41% of well water and 35% of boring water samples than standard. However, few numbers of water samples were contaminated with arsenic (0.27% and 2.6% of well and boring water samples, respectively) and nitrate (3% and 8% of well and boring water samples, respectively). Besides, 96% of well water samples and 88% of boring water samples were contaminated with total coliform bacteria. Our data indicated that groundwater quality of Kathmandu valley was poor, which was not suitable for direct drinking purposes. Therefore, regular monitoring and treatment of groundwater is recommended before using accordingly.

Objectives: The aim of this study was to assess quality status of ground water in Kathmandu valley and describe the antibiotic susceptibility of the isolated Klebsiella pneumoniae. Methods: A total of 100 samples were collected from different places of Kathmandu valley with 50 each from two different groundwater sources namely boring and well. This study was conducted from June to September, 2019 at Environment and Climate Study Laboratory, Nepal Academy of Science and Technology (NAST). The physicochemical analysis of the samples was done according to standard methodology. Membrane filtration technique was performed for the enumeration of total coliform and different biochemical tests were performed for isolation and identification of Klebsiella pneumoniae followed by Kirby-Bauer disc diffusion method for antibiotic susceptibility test. Results: This study reveals the poor microbiological aspects of ground water sources as 98% of total water samples crossed the standard value for total coliform count. The pH, turbidity, ammonia, nitrate and iron content were found to be higher than Nepal Drinking Water Quality Standard (NDWQS 2005) in 15%, 26%, 34%, 7% and 26% of total water samples respectively. The chloride and arsenic content in all the water samples were within the NDWQS, 2005. The 12 out of 18 isolates of Klebsiella pneumoniae from ground water source were highly resistant against first generation Cefazolin however, 15 out of 18 isolates were sensitive to Chloramphenicol. Additionally, four isolates showed zone of inhibition in intermediate range provided by Clinical and Laboratory Standard Institute (CLSI) guideline towards Imipenem and Meropenem. Conclusion: This study concludes that ground water sources were heavily contaminated by coliform bacteria and most of the physicochemical aspects were under standard limit. Although Klebsiella pneumoniae isolated from ground water were not multidrug resistant, one isolate was recorded to be resistant to Meropenem. These results alarm for circulation of antibiotic resistance in environmental bacterial isolates. Therefore, the appropriate water purification methods should be applied before consumption and should be examined periodically.

Arsenic contamination in water is well noted public health issue in Nepal and elsewhere. Adsorbents are important chemical means to purify the arsenic contaminated water. In this study the adsorption of As(III) on iron manganese oxide has been investigated as a function of different parameters. Herein, two iron based adsorbents, iron-manganese oxide-1 (Fe-Mn oxide-1) and iron-manganese oxide-2 (Fe-Mn oxide-2) were prepared by oxidation and co-precipitation methods. Adsorbents were characterized by powder X-ray diffraction (XRD) and scanning electron microscope (SEM). Within 4 hours of reaction time, 90% of the arsenic was removed by both Fe-Mn oxides and removal efficiency of the Fe-Mn oxide-1 was obtained higher than that of Fe-Mn oxide-2. Pseudo-second order model was well fitted to describe adsorption kinetic (R2 =0.99) for both adsorbents. Removal efficiency of the absorbents decreased with increase in the pH value and increased with increase in the concentration of adsorbent in the suspension. Based on the result, the synthesized Fe-Mn oxides have significant potential applications in the inorganic arsenic treatment in the water.

The contamination of groundwater by arsenic is one of the major problems in Nepal. This study was conducted in 20 deep groundwater (>200m) samples of Kathmandu valley to assess the arsenic content of different groundwater zones and to determine the relationship of arsenic with physico-chemical parameters. Samples were collected in the post-monsoon season of 2016. The random sampling method was applied to the collection of water samples.Standard methods as APHA 2005 was followed for the analysis of the water sample.Arsenic concentration showed spatial variation. The maximum concentration of arsenic was found in Central Groundwater Zone at Patan (27040’07.3” and 85019’14”). Karl Pearson’s correlation coefficient revealed that moderate positive correlation of arsenic concentration withelectrical conductivity (μS/cm) (r = 0.58and p =0.01) and turbidity (NTU)(r = 0.67 and p = 0.01). Groundwater consumers of the central zone of the valley are at risk of arsenic-based health issues.

Microplastic particles have been detected in water sources such as in oceans, lakes and rivers worldwide, which have received much attention in recent years. This review includes a summary of the analytical techniques such as sampling, processing and identification used by researchers to evaluate microplastic in lake water from 35 studies. Microplastic abundance and its morphological characteristics were also compared. Bulk sampling and volume-reduced sampling were almost equally implemented during sample collection. During sample processing, digestion were followed by 85.71 % of the researcher’s using hydrogen peroxide (H2O2) to degrade the organic matter present in the sample. Though density separation is the most common approach to extract microplastic from sediment sample, this was not the case in lake water as only 31.43 % used this method. Fibers were the most dominant shape and the maximum abundance of microplastics were found to be in < 0.5 and < 2 mm2 size class. Most studies reported microplastic to be of polyethylene (PE) and polypropylene (PP). HIGHLIGHTS Digestion is an important step during sample processing In lake water density separation is less frequently used method Fibers dominated in the size class < 0.5 and < 2 mm Microplastic in lake water is commonly expressed in volume unit GRAPHICAL ABSTRACT

If we can use toxic aromatic compounds as supplementary carbon source, the simultaneous removal of nitrate (NO

Microplastics are man-made pollutants which have been detected in surface water and groundwater. Research on microplastic concentration in aquatic environment is attracting scientists from developing countries, but in Nepal no information regarding microplastic in freshwater system is available. Therefore, this study investigates the presence and abundance of microplastic in lake surface water of Phewa Lake, the second largest lake in Nepal. The average concentration of microplastic for surface water was 2.96 ± 1.83 particles/L in winter (dry) season and 1.51 ± 0.62 particles/L in rainy (wet) season. Significant difference with t = 4.687 (p

Objectives: In order to evaluate the quality assurance of drinking water in Kathmandu valley, this study analyzed selected physiochemical and microbial parameters of treated water samples and compared with Nepal Drinking Water Quality Standards (NDWQS). Methods: Treated water samples were collected from all over the Kathmandu valley and analyzed in terms of physicochemical and microbiological parameters over the period of one year from July 2017 to July 2018. The physio-chemical parameters of water samples were performed according to standard methods for the examination of water and wastewater. The total coliforms were enumerated by standard membrane filtration technique. Results: We report that microbiological aspect of treated water was the major problem as 66% of the water samples crossed the guideline value for total coliform count. Above 92% of jar water samples, 77% of tanker water samples and 69% of filtered water samples had the total coliform count exceeding the NDWQS. Moreover, 20% of bottled water was contaminated by coliform bacteria. Iron and ammonia content were found to be higher than the guideline values in 16% and 21% of the total treated water samples respectively. Analyzing the types of treated water samples showed that 35% and 15% of tanker water samples had higher ammonia and iron content respectively, and the same parameters were higher in 23% and 19% in the filtered water samples respectively than the standard criteria recommended by NDWQS. Conclusion: The treated water samples exceed the standard values set by NDWQS and hence had poor quality. The presence of faecal pollution indicating coliform bacteria was the key problem for treated drinking water of Kathmandu valley. Therefore, monitoring and proper treatment of water should be conducted to prevent dissemination of waterborne diseases.

Manganese iron oxide (MnFe2O4), an excellent arsenic(As)/antimony(Sb) removal adsorbent, is greatly restricted for the solid-liquid separation. Through the application of superconducting high gradient magnetic separation (HGMS) technique, we herein constructed a facility for the in situ solid-liquid separation of micro-sized MnFe2O4 adsorbent in As/Sb removal process. To the relative low initial concentration 50.0μgL-1, MnFe2O4 material sorbent can still decrease As or Sb below US EPA's drinking water standard limit. The separation of MnFe2O4 was mainly relied on the flow rate and the amount of steel wools in the HGMS system. At a flow rate 1Lmin-1 and 5% steel wools filling rate, the removal efficacies of As and Sb in natural water with the system were achieved to be 94.6% and 76.8%, respectively. At the meantime, nearly 100% micro-sized MnFe2O4 solid in the continuous field was readily to be separated via HGMS system. In a combination with the experiment results and finite element simulation, the separation was seemed to be independent on the magnetic field intensity, and the maximum separation capacities in various conditions were well predicted using the Thomas model (R2=0.87-0.99).

Aromatic organoarsenic compounds tend to transform into more mobile toxic inorganic arsenic via several processes, and can inadvertently spread toxic inorganic arsenic through the environment to water sources. To gain insight into the transformation mechanisms, we herein investigated how the process of para arsanilic acid (p-ASA) transformation works in detail on the surface of adsorbents by comparing it with phenylarsonic acid (PA) and aniline, which have similar chemical structures. In contrast to the values of 0.23 mmol g−1 and 0.68 mmol g−1 for PA and aniline, the maximum adsorption capacity was determined to be 0.40 mmol g−1 for p-ASA at pH 4.0. The results of FTIR and XPS spectra supported the presence of a protonated amine, resulting in a suitable condition for the oxidation of p-ASA. Based on the combined results of UV-spectra and UPLC-Q-TOF-MS, we confirmed that the adsorbed p-ASA was first oxidized through the transfer of one electron from p-ASA on MnO2 surface to form a radical intermediate, which through further hydrolysis and coupling led to formation of benzoquinone and azophenylarsonic acid, which was identified as a major intermediate. After that, p-ASA radical intermediate was cleaved to form arsenite (III), and then further oxidized into arsenate (V) with the release of manganese (Mn) into solution, indicating a heterogeneous oxidation process.

Aqueous antimony (Sb) pollution from human activity is of great concern in drinking water due to its adverse health effect. Magnetic Fe3O4 particles, with high separation ability from solution, have been considered as a low-cost Sb adsorbent for contaminants. However, the limited adsorption capacity has restricted its practical application. In this study, a solvothermal approach was developed for doping Ce(III) into Fe3O4, thereby increasing the adsorption efficacy for both Sb(III) and Sb(V). In contrast to un-doped Fe3O4, the adsorption capacity towards Sb(III) and Sb(V) in Ce-doped materials increased from 111.4 to 224.2mg/g and from 37.2 to 188.1mg/g at neutral pH, respectively. Based on the combined results of XPS, XRD, and FTIR, it confirmed that Ce atom successfully doped into the Fe3O4 structure, resulting in the decreased particle size, increased the surface area, and isoelectric point. Furthermore, the vibrating sample magnetometer (VSM) results showed that the Ce doping process had some side effects on the primitive magnetic property, but remaining the high separation potential during water treatment. According to the high removal efficiency and magnetic property, the Ce-doped Fe3O4 of great simplicity should be a promising adsorbent for aqueous Sb removal.

The aromatic organoarsenic compounds including p-arsanilic acid (p-ASA) and roxarsone (ROX) used as feed additives in the poultry appear to be excreted with no chemical structural change, tending to environmental release of inorganic arsenic. Thus, effective removal and understanding the mechanism of organoarsenic compounds are of significant urgency. We herein investigated the interactions of organoarsenic compounds with ferric and manganese binary oxide (FMBO) to investigate their adsorption efficiency and mechanism, whereas ferric oxide (FeOOH), and manganese oxide (MnO 2 ) were also studied for the comparison. The maximum adsorption capacities ( Q max ) of FMBO towards p-ASA and ROX were determined to be 0.52 and 0.25 mmol g −1 (pH = 7.5). FeOOH and MnO 2 showed lower adsorption capability, the corresponsive Q max, p-ASA were 0.40 and 0.33 mmol g −1 and Q max, ROX were 0.08 and 0.07 mmol g −1 , respectively. The elevated pH inhibited the adsorption onto the adsorbents owing to the increased repulsive forces; the Q max, p-ASA and Q max, ROX onto FMBO increased to 0.79 and 0.51 mmol g −1 at pH 4.0. Based on results of UV–vis spectra, UPLC-ICP-MS, FTIR, and XPS, the synergistic effect of heterogeneous oxidation and adsorption was the core for efficient aqueous removal of p-ASA by FMBO. Manganese oxide showed significant oxidation of p-ASA, while adsorption process was observed in ferric oxide and this effect also involves in the adsorption of ROX. Results herein extended the knowledgebase on organoarsenic species adsorption to Fe/Mn oxides, are important for potential engineering treatment application and help us to understand reactions at the interfacial level.

The control of black and odorous substances in sediments is of crucial importance to improve the urban ecological landscape and to restore water environments accordingly. In this study, chemical oxidation by the oxidants NaClO, H2O2, and KMnO4 was proposed to achieve rapid control of black and odorous substances in heavily-polluted sediments. Results indicate that NaClO and KMnO4 are effective at removing Fe(II) and acid volatile sulfides. The removal efficiencies of Fe(II) and AVS were determined to be 45.2%, 94.1%, and 93.7%, 89.5% after 24-h exposure to NaClO and KMnO4 at 0.2 mmol/g, respectively. Additionally, rapid oxidation might accelerate the release of pollutants from sediment. The release of organic matters and phosphorus with the maximum ratios of 22.1% and 51.2% was observed upon NaClO oxidation at 0.4 mmol/g. Moreover, the introduction of oxidants contributed to changes in the microbial community composition in sediment. After oxidation by NaClO and KMnO4 at 0.4 mmol/g, the Shannon index decreased from 6.72 to 5.19 and 4.95, whereas the OTU numbers decreased from 2904 to 1677 and 1553, respectively. Comparatively, H2O2 showed a lower effect on the removal of black and odorous substances, pollutant release, and changes in sediment microorganisms. This study illustrates the effects of oxidant addition on the characteristics of heavily polluted sediments and shows that chemical oxidants may be an option to achieve rapid control of black and odorous substances prior to remediation of water environments.

In present work, an efficient purification of selenite-contaminated water using electrolysis-assisted nano zerovalent iron (E-nZVI), which achieved a removal capacity of 15.83 mg Se(IV)/g nZVI and exceeded the none-assisted nZVI system by 135% was tested. Although Se(IV) removal dramatically increased with applied voltages over 2.0 V in E-nZVI system, the kinetics indicate that higher applied voltage (~4.0 V or more) and lower resistance could not result in apparent promotion on the reaction rate constant. Furthermore, the results from separate anode-cathode tests and surface-sensitive quantitative characterization reveal the synergistic effects of nZVI and cathodic reduction on elemental selenium precipitation, and nZVI corrosion aggravated by electrochemical oxidization improved removal performance in the anode chamber. In conclusion, the electrolysis-assisted nZVI showed good removal efficiency of Se(IV) and is a potential water treatment method for removing reducible contaminants.

This study compared the removal capability and mechanisms involved in the removal of aqueous Sb by non-doped and Cu-doped Fe3O4 (magnetite). After doping Cu into Fe3O4, it exhibited a smaller particle size with slightly declined saturation magnetization, and enhanced antimony adsorptive capability. Non-doped Fe3O4 showed a maximum adsorption capacity (Qmax) of 34.46 mg Sb(III) g−1 and 7.07 mg Sb(V) g−1 at pH 7.0. The doping of Cu improved the Sb adsorption with a Qmax of 43.55 mg Sb(III) g−1 and 30.92 mg Sb(V) g−1 accordingly. The co-existing sulfate and carbonate had a negligible effect on Sb removal; however, phosphate at 10 mM decreased the Sb(III) and Sb(V) removal by 50.1% and 18.2% for Fe3O4 and by 14.1% and 58.6% for Cu-doped Fe3O4. As for Cu-doped Fe3O4, the results indicated that the Sb(III) oxidation on CuII–O sites was much more significant than that on FeIII–O sites and the dissolution oxygen amount did not affect this process. Upon the electron transfer from Sb(III) to Cu(II), the formed Cu(I) and Sb(V) tends to release into the solution and the Cu(I) disproportionates to give Cu(II) ions and a precipitate of Cu(0) thereafter. The magnetic Cu-doped Fe3O4 shows good removal efficiency towards both Sb(III) and Sb(V) and is a potential adsorbent for Sb removal in practice.

Air pollution is becoming a serious matter of concern from different aspects of our lives. It adversely affects the well being of the individuals or cause damages to properties. Pollutants identification requires measurements by standard methods of sampling and analysis. In this study, monitoring of TSP, PM10, SO2 and NO2 were performed during the months of April – August, 2008 by using high volume sampler, i. e. Envirotech APM 451 Model. Four hours (11:00 am to 3:00 pm) of monitoring for SO2 and NO2 , 24 hours of monitoring for TSP and PM10 were carried out. SO2 concentration ranged from 4.8 ?g/m3 to 20.5 ?g/m3 and NO2 concentration ranged from 1.2 ?g/m3 to 8.8 ?g/m3 for four hour monitoring period. TSP concentration ranged from 24.7 ?g/m3 to 82.0 ?g/m3 whereas PM10 concentration ranged from 25.4 ?g/m3 to 152.4 ?g/m3 for 24 hours of monitoring. Present study concluded that the air quality of Khumaltar area in Lalitpur, Nepal met WHO as well as NAAQS standards during the study period. Nepalese cities/towns have always been thought to be serious in terms of particulate matter pollution but consideration of the trend of gasesous pollutants emitted from vehicle exhaust is recommended for future research. HYDRO Nepal JournalJournal of Water, Energy and EnvironmentIssue: 17, July 2015

Para arsanilic acid (p-ASA) is extensively used as feed additives in poultry industry, resulting contaminates soil and natural water sources through the use of poultry litter as a fertilizer in croplands. Thus, removal of p-ASA prior to its entering environments is significant to control their environmental risk. Herein, we studied Fe-Mn framework and cubic Fe(OH)3 as promising novel adsorbents for the removal of p-ASA from aqueous solution. The chemical and micro-structural properties of Fe-Mn framework and cubic Fe(OH)3 materials were characterized by X-ray diffraction patterns (XRD), nitrogen adsorption (SBET), zeta (ζ-) potential, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectra (XPS). The maximum adsorption capacity for p-ASA on Fe-Mn framework and cubic Fe(OH)3 was determined to be 1.3mmolg-1 and 0.72mmolg-1 at pH4.0, respectively. Adsorption of p-ASA decreased gradually with increasing pH indicated that adsorption was strongly pH dependent. Azophenylarsonic acid was identified as an oxidation intermediate product of p-ASA after adsorption on Fe-Mn framework. Plausible removal mechanism for p-ASA by Fe-Mn framework was proposed. The obtained results gain insight into the potential applicability of Fe-Mn framework, which can be potentially important for the removal of p-ASA from water.

Microbial pathogens in drinking water are primary cause in gastrointestinal and waterborne diarrheal diseases. Public health authorities still have not achieved success in controlling the most common waterborne diseases in Nepal. The objective of this study was to assess the quality of drinking water supplied from distribution system of Kathmandu. A total of 114 water samples were collected from 4 distribution stations. The physicochemical and microbiological analyses of water were conducted. Heterotrophic plate count (HPC), detection of enteric pathogenic bacteria and antibiotics susceptibility test were done. Distinct variations in physicochemical parameters were observed. The mean free residual chlorine was found 0.24mg/l. Total Coliforms were found in 61.4% (70/114) of water samples among which 15.7% (11/70) had thermotolerant Coliforms. In distance, coliforms were found higher in far points (p=0.002). All thermotolerant Coliforms were identified as Escherichia coli . Mean HPC of water was found log 10 3.15. The mean HPC of water (p=0.003) was found higher in far point. In collected samples, 10 different enteric bacteria were isolated in which E. coli was found most predominant followed by Pseudomonas spp., Citrobacter spp., Klebsiella spp., Shigella spp., Proteus spp., Enterobacter spp. Non-Typhii Salmonella spp., Providencia spp., Edwardsiella spp. In antibiotics susceptibility test, Gentamicin and Ofloxacin were found most efficient (100%) and whereas Ampicillin (11.5%) was least effective. Multiple antibiotics resistance was found among 5.3% of isolates. Nepal Journal of Science and Technology Vol. 13, No. 2 (2012) 179-184 DOI: http://dx.doi.org/10.3126/njst.v13i2.7733

Sixty (56.1%) water samples crossed the permissible limit of WHO guideline value in heterotrophic plate count and total coliform count each. Ten different genera of gram negative bacteria were recovered in which E. coli was predominant followed by Citrobacter spp., Shigella spp., Enterobacter spp., Providencia spp., Klebsiella spp., Salmonella spp., Pseudomonas spp., Proteus spp. and Edwardsiella spp. Higher the temperature of water sample, higher the bacterial growth was obtained (p= 0.002), and similarly higher level of free residual chlorine in water reduced the bacterial growth (p= 0.037) whereas increase or decrease of pH (p= 0.454), turbidity (p= 0.164) and conductivity (p= 0.969) did not affect the microbial growth. A negative correlation (r= -0.162) between heterotrophic plate count and free residual chlorine was observed, however, without statistical significance (p= 0.096). Similarly, a negative correlation (r= -0.383) between total Coliform count and free residual chlorine was observed with statistical significance (p= 0.001). In chlorine assay, all tested eight genera of gram negative bacteria were found to be chlorine resistant at 0.2 mg/l for a contact time of 30 minutes. Average time required for T 99.9 (3-log) and T 99.99 (4-log) reduction of viable isolates from initial population of 2×106 cells/ml were found to be less than 30 minutes and greater than 60 minutes respectively. Log inactivation of various bacterial isolates with chlorine concentration of 0.2 mg/l for a contact time of 30 minutes were found to be ranged from 3 to 3.5-log. Emergence of chlorine resistant organisms in drinking water probably demands alternate disinfection or mitigation strategy. Nepal Journal of Science and Technology Vol. 13, No. 1 (2012) 173-178 DOI: http://dx.doi.org/10.3126/njst.v13i1.7456

Aqueous antimony (Sb) pollution from human activity is of great concern in drinking water due to its adverse health effect. Magnetic Fe