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Microbiology and Drinking Water Filtration

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• Gary S. Logsdon 3  

Part of the book series: Brock/Springer Series in Contemporary Bioscience ((BROCK/SPRINGER))

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Water filtration research has been undertaken for a variety of reasons. Studies have been performed to develop information for filtration theories and for design of filtration plants to remove suspended matter such as clays, algae, suspended matter in general, and asbestos fibers from water. Filtration studies related to removal of microorganisms have generally been motivated by the need to learn about the removal of pathogens or indicator organisms, or both. Reducing the risk of waterborne disease has been a goal of microbiologically related filtration research for nearly 100 years. This chapter briefly reviews that research and then discusses the results of recent investigations.

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Logsdon, G.S. (1990). Microbiology and Drinking Water Filtration. In: McFeters, G.A. (eds) Drinking Water Microbiology. Brock/Springer Series in Contemporary Bioscience. Springer, New York, NY. https://doi.org/10.1007/978-1-4612-4464-6_6

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• Published: 17 March 2020

Microbiological quality of water sources in the West region of Cameroon: quantitative detection of total coliforms using Micro Biological Survey method

• Rodrigue Mabvouna Biguioh 1 ,
• Sali Ben Béchir Adogaye   ORCID: orcid.org/0000-0001-9611-0842 1 ,
• Patrick Martial Nkamedjie Pete 2 ,
• Martin Sanou Sobze 3 ,
• Jean Blaise Kemogne 4 &
• Vittorio Colizzi 1  

BMC Public Health volume  20 , Article number:  346 ( 2020 ) Cite this article

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Adequate supply of safe drinking-water remains a critical issue in most developing countries. The whole western region of Cameroon doesn’t have a sustainable continuous water supply system, which leads most people to use potentially contaminated water sources to meet their daily water needs. Previous, studies carried out in similar areas of Cameroon have highlighted the poor bacteriological quality of water sources used as drinking-water by the local populations.

This study used the Micro Biological Survey method, a rapid colorimetric test for the quantitative detection of Coliforms in water samples. 22 water sources (12 improved and 10 unimproved) were identified; 1 water sample of 50 ml was collected in sterile plastic tubes, immediately kept in a refrigerator box and transported to the laboratory for analysis. 1 ml of each sample was inoculated in the Coliforms Micro Biological Survey (Coli MBS) vials initially rehydrated with 10 ml of sterile distilled water. The Coli MBS vials were closed, shaken for about 30 s for homogenization and then incubated at 37 °C. From the initial red color of the Coli MBS vials, changes in color of the reaction vials were monitored at three different time intervals (12 h, 19 h and 24 h), corresponding to three levels of contamination.

The average distance (8.7 m) of the latrines from the nearest water source was less than the minimal recommended distance (15 m) to ovoid external contamination. The pH of water samples ranged from 5.5 to 8.3 and the maximum temperature found (26 °C) was almost at level favorable to outbreaks of waterborne diseases such as cholera. The presence of Total Coliforms was detected in 90.91% of the samples. 40% of samples were positive 12 h after the analysis beginning. High level of contamination was observed in unimproved water sources, 50% after 12 h corresponding to Total Coliforms concentration of 10 < x < 103 CFU/ml and the other samples after 19 h (Total Coliforms concentration: 1 < x < 10 CFU/ml).

This study revealed the poor microbiological quality of water used by local populations of our study sites. There is need to conduct further qualitative microbiology studies to isolate potential germs involved in outcome of diarrheal diseases.

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Safe drinking-water is an essential resource for human life, a basic human right and one of the key components of effective health protection policy [ 1 , 2 ]. It is known that drinking-water is one of the main transmission pathways for diarrheal diseases [ 2 ]. It is also established that improving the bacteriological quality of drinking-water significantly reduces the risk of waterborne diseases [ 3 ]. Thus, every effort should be made to achieve a satisfactory drinking-water supply to all in terms of adequacy, safety and accessibility [ 2 ].

Most developing countries face high population growth which poses a considerable challenge for local authorities who are not able to meet basic needs of populations whose most crucial problem is sustainable access to save drinking-water [ 2 , 3 ]. Ensuring availability and sustainable management of water sources and sanitation for all, remains one of the most important Sustainable Development Goals governments need to achieve [ 4 ]. According to the World Health Organization (WHO), safe drinking-water does not represent any significant risk to health over a lifetime of consumption, including different sensitivities that may occur between life stages [ 2 ]. Therefore, microbial, chemical and other acceptability aspects of drinking-water should feet with WHO guidelines for drinking-water quality [ 2 ].

Supply of safe drinking-water for human is a critical problem in African countries [ 5 , 6 , 7 ], more importantly in remote areas due to the hyper centralization of public management services [ 8 , 9 ]. As in other parts of the country, but less in the Central or Littoral regions, the West Cameroon does not have a continuous water supply system, leading to majority of people to use surface, well, borehole and river water as alternative source of drinking-water and for other water needs [ 8 , 10 ]. Studies carried out in similar areas of Cameroon have highlighted the poor bacteriological quality of these water sources [ 11 , 12 , 13 , 14 ].

Waterborne diseases are the second leading cause of death and infant morbidity after malaria in Bafoussam and in other main cities of the West Cameroon [ 15 ], indicating the non-achievement of bacteriological standards of drinking-water standards for human consumption [ 16 ]. Morbidity and mortality rates of diarrheal diseases are more prevalent among children under 5 [ 15 ]. Among the top 10 diseases in children under 5 including malaria, infection of the lower respiratory tract, upper respiratory tract infection, meningitis, typhoid fever, bloody diarrhea, diarrhea (non-bloody diarrhea), dysentery, parasitic worm infection and gastritis, 4 of them are related to the consumption of unsafe water and/or food [ 15 , 16 ]. The germs responsible for these diseases are generally transmitted by feco-oral route and represent a major concern in public health risk [ 16 ]. Microbiological contamination of water occurs in a context of poor waste management including faeces [ 17 ]. Contaminated water with bacteria should not be intended for human consumption. Coliforms can be used as indicator to monitor the microbiological quality of drinking-water [ 18 , 19 ] and their rapid detection is therefore crucial and should be easy to perform in order to evaluate water quality especially in resource limited countries, such as Cameroon. Preventive public health approaches for safe drinking-water must include rapid assessment of microbiological quality of water to guide monitoring of water quality and treatment. In line with this point of view, this study aimed to assess the potability of water points using Micro Biological Survey Hazard Analysis Critical Control Point (MBS-HACCP) & water Easy test® [ 20 ] in the West Cameroon.

Study area and sampling

The study was performed in West region of Cameroon (Fig.  1 ), an area of 14,000 km 2 located in the central-western part of the country with a total population estimated at 1,921,590 inhabitants [ 21 ]. Even if the region is the smallest of the country in terms of area, the West region has the highest population density (140/km 2 ). The climate is mainly cold with an average temperature varying between 15 and 22 °C, sometimes reaches 30 °C during the dry season and rainfall is moderate.

Map of the Western Region of Cameroon. Source: Wikimedia Commons. https://commons.wikimedia.org/wiki/File:West_Cameroon_divisions.png

A water source was considered as improved if the nature of its construction satisfactorily protects the water from any external contamination, especially faeces. 12 improved and 10 unimproved water sources were identified in the study area, especially in the localities of Bafoussam 1 er , Bafoussam 2 e , Foumbot, Galim and Kouoptamo (Table  1 ). At each site, 1 water sample of 50 ml was collected in sterile plastic tubes and immediately kept in a refrigerator box and transported to the laboratory for microbiological analysis.

Water sources in this study were located on areas of public accessibility and are used for free by local population. The 12 improved sources were constructed by volunteers, but they don’t have authority over these water points in terms of management and control. So, for the collection of water samples, no authorization was requested.

MBS-HACCP, water easy test and MBS method

The MBS-HACCP & water Easy test is a rapid colorimetric test for the quantitative detection of coliforms in water samples [ 20 ]. The method is based on observation of color change of the suspension formed in the analysis vial following inoculation of the test sample. The color change occurs when the water sample added in the vial contains Coliform bacteria, the greater the amount of microorganisms, the more rapid the color change and thus, a positive result (contamination). The concentration of bacteria is expressed in Colony Forming Units (CFU/ml) for the analysis water samples. The MBS method is based on the detection of bacterial metabolism and not on the replication of microorganisms, but the results (in terms of number) correspond to individual bacterial cells.

Water analysis: MBS operating procedures for quantitative detection of Total coliforms

We followed the MBS standard protocol for quantitative detection of Total Coliforms [ 20 ]. Before starting with the analysis, the MBS vials were rehydrated with 10 ml of sterile distilled water and shaken to dissolve the reagent. 1 ml of each sample was collected from plastic tubes using a sterile Pasteur pipette and inoculated in the Coli MSB vial. The vials were then closed and shaken for about 30 s for homogenization. Each analysis was done twice, the vials were incubated at 37 °C. The color changes of the Coli reaction vials were monitored using the chromatic scale provided with the tests at three different time intervals (12 h, 19 h and 24 h), corresponding to three levels of contamination. The initial color of the Coli vials is red. A color change from red to yellow after 12 h indicates a very high contamination (Total Coliforms concentration >  10 3  CFU/ml), a color change at 19 h indicates a high contamination (Total Coliforms concentration 10 < x < 10 3  CFU/ml) and a color change at 24 h corresponds to Total Coliforms concentration of 1 < x < 10 CFU/ml [ 20 ].

Description of water points

Water samples were collected in 22 sites. Improved water sources accounted for 54.55% ( n  = 12) while 45.5% ( n  = 10) were unimproved. The average distance of the latrines from the nearest water source was 8.7 m. The closest and the farthest water sources were at 1 and 100 m respectively from the nearest latrine. The pH of the water samples collected ranged from 5.5 to 8.3 and the temperature varied from 22 to 26 °C. Most of water sources were clear (90.91%) and the turbidity was noticed in both cases (Table  2 ).

Total coliforms samples contamination

Of the 22 water samples analyzed, 20 (90.91%) contained Coliforms (Fig.  2 ). Both improved and unimproved water sources were evenly contaminated with Coliforms. All water samples with yellow coloration were positive as well as 90% of clear water samples. This result was similar for the turbidity.

Coliforms detection result according to the Microbiological Survey (MBS) method. Source: Authors. Generated by QGIS version 3.4.11-Madeira (GNU GENERAL PUBLIC LICENSE Version 2, June 1991)

Total coliforms levels of contamination in water samples analyzed

Of the 20 samples positive for Coliforms, 40% ( n  = 8) were highly positive, indicating a very high level of coliforms contamination (Total Coliforms concentration >  10 3  CFU/ml). Of all positive samples, high level of contamination was observed in unimproved water sources, 50% at 12 h corresponding to Total Coliforms concentration of 10 < x < 10 3  CFU/ml and the other samples after 19 h (Total Coliforms concentration of 1 < x < 10 CFU/ml). Of all the water sources, only two samples (collected in improved water sources) were positives at 24 h (Total Coliforms concentration of 1 < x < 10 CFU/ml) (Table  3 ).

Safe drinking water is essential for life. This study aimed at analyzing the presence of bacteria, through quantitative detection of Total Coliforms in both improved and unimproved water sources in the West region of Cameroon. Inhabitants of the study area are in majority poor with limited capacities including financial to afford pipe borne water [ 8 , 15 ], they turn to health threatening and potentially highly polluted water sources which could explain why diarrheal diseases mostly occur in populations with limited financial means. This has been described by a study conducted in South Africa, which highlighted that cholera outbreak does not on results from inadequate sanitations, but also due to poverty [ 22 ].

According to the WHO guidelines for drinking-water quality, the microbial safety of drinking-water includes the prevention of the drinking-water contamination by the microorganisms or the reduction of contamination to levels not injurious to human health [ 2 ]. While ingestion of microorganisms from contaminated water and food is the main cause of diarrheal diseases [ 23 ], lack of safe drinking-water is one of the leading causes of death especially in children under 5 [ 15 , 16 ]. Total Coliforms are used as indicators of faecal pollution, the effectiveness of water filtration or disinfection, the integrity and cleanliness of water distribution systems [ 24 , 25 ]. The WHO guideline for drinking-water quality recommends the absence of Total Coliforms in drinking-water [ 2 ]. This study highlights poor quality of the water due to the presence of Total Coliforms in high concentration. In fact, of the 22 water samples collected, 20 contained coliforms which could be associated with high risks of diarrheal diseases outbreaks, such as cholera as suggested by previous studies that stipulate fecal coliform-contaminated water may contain Vibrio Cholerae [ 26 , 27 ]. Both types of water sources (improved and unimproved) were contaminated indicating a possible human or animal faecal pollution of these water points.

The minimal recommended distance between latrine and water source to avoid external contamination ranged between 15 and 50 m [ 2 , 28 ]. The average distance found in this study did not feet with this recommendation. Even though improved water sources were more closely to latrines, unimproved water points which are open water sources showed greater concentration of Coliforms. This may be explained by the nature of the improved water sources construction satisfactorily protects the water from any external contamination [ 29 ]. This is consistent with previous studies which suggest that unprotected water sources have high probability of being contaminated by fecal material carried out by run-off water mainly during rainy season [ 22 , 30 ]. Globally, the results of this study reveal poor quality of water sources used by the population. Our results are consistent with previous studies carried out in the West Cameroon and similar areas which indicated an alarming lack of safe drinking-water [ 8 , 11 , 12 , 13 , 14 ]. Water samples with a small amount of germs turned pathogenic after 24 h of incubation. This maximum incubation time does not deviate from the WHO recommendations whose procedures include membrane, filtration followed by incubation of the membranes on selective media at 35–37 °C and counting of colonies after 24 h [ 2 ].

There is no pH guide value but an optimum between 6.5 and 9.5. The average water pH found in this study was 6.5 which correspond to the lower value recommended by WHO [ 2 ]. The temperature of the samples varied between 22 and 26 °C. This indicator needs to be monitored to support preventive public health to control measures, as it has been established that outbreaks of waterborne diseases such as cholera are consistent with a rise in temperature during the dry season and the peaks are reached in the rainy season [ 30 ]. Monitoring temperature and pH variations during the seasons could help in the planning and implementation of outbreaks prevention measures.

Microbial and other water constituents can affect the appearance of the water [ 2 ]. Most samples were clear (90.91%), suggesting their good quality and acceptability based of this criterion, but the Total Coliforms analysis have shown another case of figure indicating that changes in the normal appearance of water is not a sufficient signal of the water quality.

Conclusions

This study revealed the poor microbiological quality of the water sources used by inhabitants of West Cameroon. These poor water sources could be at the origin of waterborne disease outbreaks. Even though qualitative analysis was not performed, the MBS method detected the presence of Coliforms in almost all the water samples collected. It is also important to emphasis that the quantity of Coliforms found in the samples could indicate the presence of disease-causing bacteria such as Vibrio Cholerae . The average distance (8.7 m) between the water point and the nearest latrine doesn’t meet up with WHO recommendations (15–50 m to the nearest latrine), showing groundwater high risk of contamination by faeces infiltration. There is need for the local public health services and rural council to establish local water management committees to help in monitoring and ensure water sources do not represent a risk of waterborne disease outbreak. In addition, local populations need to be trained on simple and cost-effective of water treatment techniques. Additional qualitative microbiology studies need to be conducted to isolate germs involved in diarrheal diseases.

Availability of data and materials

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Abbreviations

Hazard Analysis Critical Control Point

Micro Biological Survey

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Mabvouna Biguioh, R., Sali Ben Béchir Adogaye, Nkamedjie Pete, P.M. et al. Microbiological quality of water sources in the West region of Cameroon: quantitative detection of total coliforms using Micro Biological Survey method. BMC Public Health 20 , 346 (2020). https://doi.org/10.1186/s12889-020-8443-0

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A study of isolation and identification of bacteria from lake water in and around Udaipur, Rajasthan

Upasana bhumbla.

1 Department of Microbiology, Geetanjali Medical College and Hospital, Udaipur, Rajasthan, India

Shipra Majumdar

2 Third Year MBBS Student, Geetanjali Medical College and Hospital, Udaipur, Rajasthan, India

Sarita Jain

A. s. dalal, introduction:.

Water is an essential nutrient which plays an important role in digestion, absorption of food and elimination of waste products by urine. Udaipur also known as ‘City of Lakes’ or even the ‘Venice of East’ due to its unique and beautiful lake system has an exceptional importance at national and international levels. The aquatic systems are mostly dominated by bacteria and fungi and in the natural environments micro-organisms have very specific roles with regard to the recycling of materials and purification of water. Presence of coliform bacteria in the water indicates the fecal pollution of water.

Water from all the three lakes were included for the assessment of their water quality parameters. Biological parameters like MPN of coliforms and presence of bacterial and cyanobacterial contaminants were read. The MPN (Most Probable Number) of Coliform was determined by the Presumptive Coliform Count (Multiple Tube Method) in 100 ml of sample water.

Conclusion:

The coliform bacteria is the primary bacterial indicator for fecal pollution in water. The purpose of study was to make people aware about the bacterial load in water bodies. Based on this, categorical representation of water was unacceptable for the purpose of swimming and bathing.

Introduction

Udaipur also known as ‘City of Lakes’, or even the ‘Venice of East, due to its unique and beautiful lake system, has an exceptional importance at national and international levels. These water bodies, which once considered as divine source of water are now increasingly being abused and severely polluted. Our fresh water bodies are contaminated with different kinds of pollutants resulting from increasing human population, urbanization and industrialization. In the context of international regulations, the contamination of water bodies by organic micro pollutants is the subject of constant interest and is always under investigation. Although the provision of safe drinking water has been one of humanity's most successful public health interventions. It is a defining aspect of a developing country's ignorance of the risks and inappropriate training of the staff and managers working on drinking water systems, which still results in unnecessary waterborne disease outbreaks in affluent communities. Disposal of domestic wastes in lakes is causing undesirable changes in physio-chemical and biological characteristics of these waters.[ 1 ] Microbes including bacteria, viruses and protozoa are the common cause of diseases in present aquatic ecosystems. Many major human diseases such as typhoid fever, cholera and other diarrheal diseases, poliomyelitis and viral hepatitis A and E are water borne. These pathogens reach water sources through fecal and sewage pollution. The aquatic systems are mostly dominated by bacteria and fungi and in the natural environments micro-organisms have very specific roles with regard to the recycling of materials and purification of water. Salmonella , Acinetobacter , Chromobacterium , Alcaligens , Flavobacterium , Staphylococcus aureus , Pseudomonas aeruginosa , Clostridium botulinum , Vibrio cholerae and Escherichia coli are the main human pathogens responsible for water contamination.[ 2 ] The presence of coliform a rod shaped, gram negative bacteria in the water indicates the fecal pollution of water because they are invariably present in the feces of human beings and other warm-blooded animals in large numbers and can be easily detected in high dilutions. This confirms the presence of E. coli in the water bodies giving a definite proof of fecal pollution thus not being suitable for bathing and drinking.[ 3 ]

The intrusion of biological agents into water systems can pose serious public health risks as these agents cannot be easily detected and can remain hidden until a widespread contamination exists.

Review of Literature

South Rajasthan, also named as ‘Mewar’, is known for its beauty around lakes. Udaipur is well-known as ‘City of lakes’ and also for beautiful palaces in and around the city. Certain microorganisms including bacteria, viruses and parasites are well known water contaminants of which several may lead to waterborne disease and epidemics. Role of water in spreading communicable diseases is evident due to combined source of water, which is drinking as well as bathing. Contaminated water with faecal coliform severely affects the performance of humans. Contamination of water sources is counted when the man's action is adding or causing the addition of pollutants thus by altering its physical, chemical and biological characteristics to such an extent that it's utility for any reasonable purpose or its environmental value is demonstrably depreciated.

Disposal of domestic wastes in lakes of Udaipur is causing undesirable changes in physio- chemical and biological characteristics of these waters. An estimation of bacterial production is a crucial step in understanding quantitatively the function and contribution of bacteria in material cycling within given aquatic habits. Wild and domestic animals seeking drinking water can also contaminate the water through direct defecation and urination.[ 2 ] Various studies have evolved, wherein contamination of various water bodies across the country with different microorganisms is notified time and again.

Kataria et al .[ 4 ] (1997) investigated coliform count in the drinking water sources of Bhopal. Maximum probable number (MPN) in the study area exceeded the WHO limit at different sampling stations, as these were located in low-lying areas. Higher values in summer and Monsoon indicated a higher degree of pollution in the water bodies of that area.

Sinha et al [ 5 ] stated that coliform count of water in monsoon season is at peak wherein its results in poor water quality of lake water. Chatterjee et al .[ 6 ] (2007) stated that the total coliforms fluctuated between 265 and 1753 MPN/100 ml. The peak value was observed in monsoon months, which was most probably due to the flushing of faecal contaminated water from the surrounding drains and bank sides. The increasing level of MPN of coliforms was observed in summer.

Sengupta et al .[ 7 ] (2008) studied that their microbiological studies included, MPN 542 to 2400/100 ml, wherein total coliform colonies were 27.5 × 10 3 to 84.17 × 10 3 /ml. Fecal coliform ranged between 109 to 2400/100 ml for lake Pichhola, Fatehsagar, Swaroopsagar and Udaisagar. Higher values of microbial parameters give clear indication of very poor water quality.

Rajiv et al .[ 8 ] (2012) studied the river water from different parts of western Tamil Nadu, India. Samples were collected and microbial analysis was done. It stated that the number of bacterial colonies were 100-120 CFU/ml and number of fungal colonies were 30-45 CFU/ml.

The primary objective of the present study was to study the prevalence of bacterial contaminants from different water bodies in and around areas of Udaipur. Water from Pichhola, Fatehsagar and Swaroop Sagar lakes was studied along with their risk factors which were associated to it by observing various microbiological parameters.

Material and Methods

Ethical clearance.

Ethical clearance was taken from the Institutional Ethical Committee before the commencement of the study.

Sample size

150 ml of water samples were collected from-

• Fatehsagar lake (geographical location and dimensions: coordinates; 24.6°N 73.67°E, catchment area of 54 km 2 , max. length- 2.4 km, max. width- 1.6 km, surface area- 4 km 2 , average depth- 5.4 m, max. depth- 13.4 m, surface elevation- 578 m).
• Lake Pichhola (geographical location and dimensions: coordinates; 24.572°N 73.679°E, catchment area of 55 km 2 , max. length- 4 km, max. width- 3 km, surface area- 6.96 km 2 , average depth- 4.32 m, max. depth- 8.5 m).
• Swaroop Sagar lake (geographical location and dimensions: coordinates; 24.6°N 73.67°E, catchment area of 10.5 km 2 , max. length- 4 km, max. width- 2.5 km, surface area- 10.5 km 2 , max. Depth 9 m).

Design of the study

Cross-sectional study.

Sample collection

Water from Lake Pichhola, Fatehsagar and Swaroop Sagar lakes was included in the present study for the assessment of their water quality parameters. Samples were collected from pre-monsoon season in a sterilised wide mouth bottles of at least 200 ml holding capacity. The bottles were opened and immersed at a depth of 30 cm with its mouth facing the current and the samples were brought to the Microbiology department of Geetanjali Medical College and Hospital, Udaipur, for analysis. The water quality assessment included physical parameters like temperature and biological parameters like MPN of coliforms and presence of bacterial and cyanobacterial contaminants.[ 9 ]

Methodology

The MPN (Most Probable Number) of Coliform is determined by the Presumptive Coliform Count (Multiple Tube Method) in 100 ml of sample water.

Medium: MacConkey purple broth (double strength and single strength) in tubes were the standard medium of choice. Durham's tube was used to detect gas production and bromocresol purple was used as indicator.

Procedure: Measured amount of water samples were added to tubes containing MacConkey purple broth by sterile graduated pipettes as under:

• 50 ml of water - added to one bottle of 50 ml double strength medium
• 10 ml of water - added to one bottle of 50 ml double strength medium
• 10 ml of water each - added to 5 tubes of 10 ml double strength medium
• 1 ml of water each - added to 5 tubes of 5 ml single strength medium.

Tubes were incubated at 37 degree C for 48 hrs. Positive test was indicated by a colour change in medium from purple to yellow and gas collected in Durham's tube[ 10 , 11 ]

Estimate of coliform count per 100 ml of water was calculated from the tubes showing acid and gas production using the McCrady's probability table. It gave us the Presumptive coliform count (most probable number).[ 10 , 11 , 12 ] [ Table 1 ].

Classification of quality drinking water supply according to bacteriological tests[ 9 ]

Detection of coliform bacteria does not always indicate fecal contamination, as it may have environmental contaminants too. Hence, it was further tested by differential coliform count to detect the fecal E. Coli .[ 13 ]

Samples were streaked for the growth of isolated colonies on Nutrient agar, Blood agar and MacCokey's agar. Culture plates were further incubated at 37 degree for 24-48 hrs for bacteria. Plates were examined for their morphology and same type of colonies were used for performing gram staining. Isolation of bacterial contaminants is performed by standard microbiological techniques and battery of biochemical reactions. Various biochemical reactions such as IMViC, Urease, Nitrate, Catalase, H 2 S production, Sugar fermentation tests were identified for the identification of bacterial isolates.

Water samples of 150 ml each were collected from Lake Pichhola, Fatehsagar and Swaroop Sagar Lake's water. It was observed that different bacterial colonies were isolated from the water of these three lakes. Colonies varied from circuar, irregular margins as well as rhizoidal and filamentous in shape. Different colonies obtained were subjected to gram staining and thus cocci, bacilli and coccobacilli forms were identified. It was found that maximum strains when subjected to microscopic examination revealed that gram negative bacilli were predominant followed by gram positive cocci and gram positive bacilli. The results are tabulated in Table 2 .

Morphological and cultural characteristics of the organisms isolated from lake water samples

Classification of the quality of water was based on certain bacteriological tests amongst which MPN count is major. In this study Most probable number (MPN) of water sample collected from all the 3 water bodies was estimated to be very high as much as 810 to > 1600 in May.

Quality of water for drinking was UNSATISFACTORY with the coliform count elevated grossly. Escherichia coli per 100 ml of water sample was also more than 1, which further added to correspond the contamination level in these water bodies.

The present study has clearly indicated that the areas of lake are highly contaminated with bacteria. Presence of bacteria is predominantly in all sorts of environment of human involvement, majority of them are human as well as animal pathogen. The water examined in the present study has clearly demarcated that it's loaded with indicator organisms which are indication of fecal pollution and also human interference.[ 14 ]

Nowadays, lakes are contaminated with plastics also which further adds on to water pollution and leading to serious health hazards to the community. Although micro plastic exposure via ingestion or inhalation could occur, the human health effects are still unknown. If inhaled or ingested, limited data from animal studies suggest that micro plastics may accumulate and cause particle toxicity by inducing an immune response.[ 15 , 16 ]

The present study correlates with the study of Sengupta M[ 7 ] et al ., where in the bacterial load was as high as 542 as compared to 810 in summer season.

Most common bacteria isolated in the present study was gram negative bacilli and gram positive cocci which correlated with the study of Sengupta M,[ 7 ] wherein the commonest organisms were Gram positive cocci, gram positive bacilli and gram negative bacilli, respectively.

Escherichia coli was the predominant bacteria along with Klebsiella pneumoniae and Coagulase Negative Staphylococcus (CONS) respectively were isolated in the present study which correlated with the study of Paneerselvam A,[ 2 ] who isolated Escherichia coli and Klebsiella pneumoniae as the commonest organisms respectively.

Implications

The coliform bacteria is the primary bacterial indicator for fecal pollution in water. The purpose of this study was to make people aware about the bacterial load in our water bodies. Based on this the categorical representation of water as excellent, good, satisfactory, poor or unacceptable can be designated for the purpose of swimming and bathing.

As Government finished its 4 anniversary, to meet the standards of “Swachh Bharat Abhiyan”, one really needs to monitor the microbial quality of water at regular intervals. To check the contamination of water with these pathogens, regular cleaning and proper sewage disposal plants should be implemented.

This present study has strongly implicated that the microbiological standards of lake water must be developed to a large extent to confirm the health standards. Also the slogan which states Green city -clean city, my dream city can only be achieved when clear cut evaluation is done to protect and use of these water bodies for various purposes.

Financial support and sponsorship

Conflicts of interest.

There are no conflicts of interest.

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Recognising a legacy for the community – Dr Sarah Hooper reviews ‘Chemical Disinfection and Sterilisation’

Posted on May 16, 2024   by Microbiology Society

In 2020, the Microbiology Society was generously left with an extensive and wide-ranging selection of scientific works by long-standing member,  Dr Bernard Dixon . Bernard was a well-known scientific communicator, perhaps most notably as the Editor of  New Scientist  in the 1970s.  

We were honoured that Bernard chose to leave his rare collection to us and Council agreed that the majority would be sold to a specialist book collector. The revenue generated was donated to our  Unlocking Potential fund , the first grants from which have gone on to support ten microbiologists facing career-limiting challenges.

We retained a selection of the microbiology titles and recently invited Council members to select and review a book of their choice. We are releasing these reviews as a special series, in recognition of all those who choose to  leave  the Society a legacy, as well as those who support our fundraising activity, including the Unlocking Potential Fund, in other ways.

We need the help of more people across our community to support others who might, in turn, one day provide solutions to global challenges. You can find out about  leaving the Society a legacy  or  donating to Unlocking Potential  or you can get in touch to talk to us about the Society’s fundraising activities.

In the second blog of this series, Council member Dr Sarah Hooper of Cardiff Metropolitan University, UK reviews ‘Chemical Disinfection and Sterilisation’ by S. Rideal and E. K. Rideal, published by Edward Arnold & Co London, 1921:

“Modern science becomes daily more specialised” as penned by Rideal, S., and Rideal E. K., in 1921 still resonates profoundly. Their book beckons readers to embark on a journey into the “mysterious country wherein lies the secrets of the laws which govern the actions of germicides on microorganisms”.  As I delved into their insights, I found myself captivated by the blend of historical approaches to disinfection and the enduring principles that remain relevant in contemporary microbiology.

Even a century later, amid the lingering shadow of the COVID-19 pandemic, the discourse on disease transmission and containment from the 1920s feels eerily familiar. The authors' recognition of asymptomatic individuals as "dangerous...disease carriers" and the challenges of adhering to quarantine or lockdown regulations echo sentiments that persist today. It's a reminder that while our tools have advanced, the challenges of infectious disease management endure.

The recommended methods for room sanitation outlined in the text may raise eyebrows in modern health and safety circles. From the casual use of formalin to disinfect rooms, deemed non-poisonous beyond mild irritation, to the hazardous handling of phenol for similar purposes, these practices highlight the stark evolution in safety standards over the decades. Sharing these anecdotes at a recent lab meeting evoked both amusement and gratitude for the strides we've made in chemical safety and responsible handling.

Opening a chapter on internal disinfection, I couldn't help but feel a sense of caution. The recommendations presented were a curious blend of innovation and antiquity, including the use of sulphuric orangeade as a prophylactic measure during cholera season. Another intriguing suggestion involved an elaborate handwashing procedure using a paste of bleaching powder, washing soda, and water. Doctors of the era were advised to scrub their hands for five minutes using this concoction. Thankfully, this has been surpassed by chlorhexidine or povidone-iodine-containing soaps, offering efficacy without the harmful side effects.

Amid the antiquated practices, there are timeless gems of wisdom regarding disinfection. Strategies like ozone decontamination and topical hypochlorous acid application, touted in this book for their efficacy, are now experiencing a resurgence of interest in light of antimicrobial resistance. It's a testament to the enduring relevance of century-old principles of disinfection and the nature of scientific innovation.

As we navigate the complexities of modern microbiology, it's humbling to recognise the foundation laid by our predecessors. Their insights, though rooted in a different era, continue to shape our understanding, and guide our research endeavours. Perhaps, in another century, future microbiologists will look back at our innovations with the same mix of awe and familiarity, realising that the solutions to tomorrow's challenges may lie in the wisdom of the past.

Review kindly provided by Sarah Hooper.

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• Published: 06 May 2024

Venus water loss is dominated by HCO + dissociative recombination

• M. S. Chaffin   ORCID: orcid.org/0000-0002-1939-4797 1   na1 ,
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Despite its Earth-like size and source material 1 , 2 , Venus is extremely dry 3 , 4 , indicating near-total water loss to space by means of hydrogen outflow from an ancient, steam-dominated atmosphere 5 , 6 . Such hydrodynamic escape likely removed most of an initial Earth-like 3-km global equivalent layer (GEL) of water but cannot deplete the atmosphere to the observed 3-cm GEL because it shuts down below about 10–100 m GEL 5 , 7 . To complete Venus water loss, and to produce the observed bulk atmospheric enrichment in deuterium of about 120 times Earth 8 , 9 , nonthermal H escape mechanisms still operating today are required 10 , 11 . Early studies identified these as resonant charge exchange 12 , 13 , 14 , hot oxygen impact 15 , 16 and ion outflow 17 , 18 , establishing a consensus view of H escape 10 , 19 that has since received only minimal updates 20 . Here we show that this consensus omits the most important present-day H loss process, HCO + dissociative recombination. This process nearly doubles the Venus H escape rate and, consequently, doubles the amount of present-day volcanic water outgassing and/or impactor infall required to maintain a steady-state atmospheric water abundance. These higher loss rates resolve long-standing difficulties in simultaneously explaining the measured abundance and isotope ratio of Venusian water 21 , 22 and would enable faster desiccation in the wake of speculative late ocean scenarios 23 . Design limitations prevented past Venus missions from measuring both HCO + and the escaping hydrogen produced by its recombination; future spacecraft measurements are imperative.

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Oxygen production from dissociation of Europa’s water-ice surface

Isotopic fractionation of water and its photolytic products in the atmosphere of Mars

Dry late accretion inferred from Venus’s coupled atmosphere and internal evolution

Data availability.

Tables containing all reactions used in the model, including their adopted rate coefficients and computed column rates, are provided in a supplementary PDF file accessible on the journal website. These rates are also accessible in the archived code repository listed below, which also includes our adopted photo cross-sections and all other source data used in our model. Model densities for all species, computed rates for reactions shown in Fig. 2 , assumed temperature and escape probabilities and computed photo rates are provided in Excel format in the online version of the paper; this file also includes data for our illustrative water-inventory timelines.  Source data are provided with this paper.

Code availability

All model code is available at github.com/emcangi/VenusPhotochemistry . The version of the model used to prepare the manuscript is archived on Zenodo at https://doi.org/10.5281/zenodo.10460004 .

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Acknowledgements

M.S.C., E.M.C., B.S.G. and R.D.E. were supported by NASA Solar System Workings grant 80NSSC19K0164 and Planetary Science Early Career Award grant 80NSSC20K1081. E.M.C. was also supported by NASA FINESST award 80NSSC22K1326. M.S.C. and E.M.C. thank M. Landis for helpful discussions about water delivery.

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These authors contributed equally: M. S. Chaffin, E. M. Cangi

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Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO, USA

M. S. Chaffin, E. M. Cangi, B. S. Gregory, J. Deighan & R. D. Elliott

Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA

R. V. Yelle & H. Gröller

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Contributions

M.S.C. oversaw the study, performed final model calculations and the photochemical equilibrium calculation and wrote the initial text of the paper. E.M.C. developed the H-bearing and D-bearing photochemical model and nonthermal escape calculation originally used at Mars with a reaction network provided by R.V.Y. and performed initial model calculations for Venus. B.S.G. developed and ran the Monte Carlo model to generate escape probability curves. R.D.E. initially developed the Monte Carlo escape model with support from J.D. and H.G. H.G. performed pilot studies of HCO + -driven loss in the Mars atmosphere. All authors contributed to the interpretation and presentation of model results.

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Correspondence to M. S. Chaffin .

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Extended data figures and tables

Extended data fig. 1 model densities for all species..

The six panels function only to separate species for clarity.

Extended Data Fig. 2 Key photochemical model inputs.

a , Temperature profiles for neutrals, ions and electrons adapted from the inputs in ref.  28 . b , Adopted eddy diffusion profile and molecular diffusion coefficients for H and O atoms.

Extended Data Fig. 3 Implications of HCO + -driven loss for Venus ocean scenarios.

a , Escaping H production rates for the two most important processes in our model. b , Schematic water loss history of Venus.

Supplementary information

Supplementary information.

This file contains Supplementary Methods and Supplementary Tables. Merged PDF containing tables of reactions used in the model, assumed reaction rate coefficients and computed equilibrium model column rates.

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Chaffin, M.S., Cangi, E.M., Gregory, B.S. et al. Venus water loss is dominated by HCO + dissociative recombination. Nature 629 , 307–310 (2024). https://doi.org/10.1038/s41586-024-07261-y

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Received : 03 October 2023

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Issue Date : 09 May 2024

DOI : https://doi.org/10.1038/s41586-024-07261-y

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