Bacteriology and purification of water supply
- 2. Table of contents 01 04 02 05 03 06 Introduction and Bacteriological analysis Microbial load and pathogenic bacteria in water Waterborne disease Indicator Organism in water and their appearance Bacteriological testing method Water purification methods 07 08 Purpose of water purification water safety and public awareness
- 3. Bacteriology Bacteriology in water quality refers to the study of bacteria and other microorganisms present in water, their sources, behavior, and effects on human health and the environment. Its help to determine whether water is safe for drinking, recreation, agriculture, or industrial use. Clean water should be free from pathogens and low in harmless microbial counts. Bacteria can indicate contamination, especially from sewage or animal waste The Role of Bacteriology in Water Quality Bacteriology is vital for water quality because it helps identify the presence of pathogenic bacteria, which cause infectious diseases. Water is an excellent medium for the growth and spread of these microbes, making regular bacteriological analysis a critical component of public health.
- 4. Early Detection of Health Risks and Disease Prevention Identifies Potential Contamination Signals Fecal Contamination Prevents Outbreaks Monitoring Pollution and Source Identification Pinpoints Pollution Sources Guides Remedial Action Assessing Treatment Effectiveness Verifies Disinfection Maintains Quality Ensuring Regulatory Compliance Adherence to Standards Legal and Public Trust Bacteriological Analysis Bacteriological water analysis is a fundamental process for safeguarding public health by ensuring the safety and quality of water supplies. Here's a breakdown of its importance:
- 5. Key Bacteriological Indicators Total Coliforms Significance: General indicator of water system integrity Common Use: All water supplies Fecal Coliforms E. coli Significance: Indicates recent fecal contamination Common Use: Drinking water, wastewater Enterococci Significance: Reliable in saline or recreational waters Common Use: Beaches, swimming areas Clostridium Spores Significance: Sign of past contamination or treatment failure Common Use: Post-treatment verification
- 6. Standards & Guidelines for Drinking Water WHO (2017) E. coli Standard: 0 per 100 mL Coliform Standard: 0 per 100 mL (treated water) BSTI (2021) E. coli Standard: 0 per 100 mL Coliform Standard: 0 per 100 mL US EPA E. coli Standard: 0 per 100 mL Coliform Standard: Not acceptable EU Directive 2020/2184 E. coli Standard: 0 per 100 mL Coliform Standard: Not acceptable
- 7. Factors influencing microbial load in water Source of water: Rivers and ponds have more germs than deep groundwater. Sanitation: Sewage leaks and poor waste disposal increase microbes. Agriculture: Animal waste and fertilizers wash into water. Temperature: Warm water helps bacteria grow faster. Treatment: Poor filtration or weak chlorination means more microbes survive. Pipelines: Leaks, rust, or old pipes let in contamination. Storage & handling: Dirty containers or dipping cups spread germs. Season & weather: Heavy rain or floods wash germs into water sources. Microbial load is the total number of microorganisms present in a water sample. It’s a key indicator of water quality and safety. A high microbial load usually indicates pollution, especially from fecal matter or organic waste. Microbial load and pathogenic bacteria in water
- 8. Major Pathogenic Bacteria in water Escherichia coli (E. coli) – Causes gastroenteritis and diarrheal diseases. Salmonella spp. – Responsible for typhoid fever and food poisoning. Vibrio cholerae – Causative agent of cholera, leading to severe dehydration. Shigella spp. – Shigellosis / Bacillary dysentery (bloody diarrhea, cramps, fever). Clostridium perfringens – Linked with foodborne illness and gas gangrene. Pseudomonas aeruginosa – Causes skin, ear, and lung infections (especially in weak immunity).
- 9. Sources of Pathogenic Bacteria in Water Human fecal contamination o Caused by open defecation, septic system leaks, or overflow from sewage systems. These introduce pathogens like E. coli, Salmonella, Shigella, and Vibrio cholerae into water bodies. Animal waste and agricultural runoff o Livestock manure, grazing near water sources, and manure-applied fields contribute bacteria like pathogenic E. coli, Campylobacter, and Leptospira to surface and groundwater. Stormwater and surface runoff o Rainwater washing across urban, agricultural, or pasture lands can carry pathogens into rivers, estuaries, and lakes. Combined sewer overflow during heavy rain adds to contamination. Inadequate sanitation infrastructure o Malfunctioning or poorly located septic systems and untreated wastewater increase the risk of bacterial infiltration into wells and aquifers—especially near surface-level or poorly sealed wells. Wildlife and sediment reservoirs o Direct fecal deposits from birds and wildlife, and stored pathogens in sediments can resurface during disturbances (e.g., storms), releasing bacteria like E. coli and Giardia.
- 10. Flooding & Heavy Rain o Mixes sewage with drinking water sources. It causes sudden outbreaks of cholera, dysentery, and typhoid. Pipe Leaks & Distribution System o Broken or poorly maintained pipelines allow entry of contaminated soil or sewage. Biofilm inside pipes shelters pathogens like Legionella. Household Storage Practices o Dirty containers, open storage, and unsafe handling increase contamination at point-of-use.
- 11. Modes of Transmission of Pathogenic Bacteria in Water Ingestion (Fecal–Oral Route): Drinking or swallowing water contaminated with fecal matter is the most common route for enteric pathogens such as E. coli, Salmonella, Shigella, and Vibrio cholerae. Direct Contact: Skin contacts with water containing pathogens like Leptospira (infected via broken skin) during bathing or wading can transmit disease. Inhalation of Aerosols: Breathing in fine droplets or mist from contaminated water, especially with Legionella, leads to respiratory infections like Legionnaires’ disease. Aspiration (Accidental Inhalation): Inadvertent inhalation of contaminated water such as choking on water while bathing or swimming can lead to severe infections like those caused by Naegleria fowleri. Indirect Contact via Fomites: Pathogenic bacteria can survive on objects or surfaces (fomites). If hands contact a contaminated surface and then the mouth, infection can occur.
- 12. What are Waterborne Diseases? •Waterborne diseases are infections caused by pathogens that are transmitted through contaminated water. •These pathogens include bacteria, viruses, and parasites, which can pollute water sources and cause health issues when ingested. Global Significance •Waterborne diseases are a major cause of morbidity and mortality worldwide, particularly in low- income countries. •According to the World Health Organization (WHO), contaminated water causes over 2 million deaths annually. •These diseases disproportionately affect vulnerable populations, including children under five, in regions lacking access to safe drinking water and sanitation. Waterborne disease
- 13. Bacterial Diseases •Cholera •Caused by Vibrio cholerae, this disease leads to severe diarrhea and dehydration. •It spreads through contaminated water and can be fatal if not treated promptly. •Typhoid Fever •Caused by Salmonella typhi, it results in high fever, abdominal pain, and weakness. •It is transmitted through water contaminated with feces of infected individuals. •Dysentery •Caused by Shigella or Entamoeba histolytica, it leads to severe diarrhea with blood or mucus. •It can cause dehydration and long-term digestive issues. Types of Waterborne Diseases
- 14. Viral Diseases •Hepatitis A •A liver infection caused by the Hepatitis A virus, transmitted through contaminated water or food. •Symptoms include fever, fatigue, abdominal pain, and jaundice. •Norovirus •The leading cause of gastroenteritis, it spreads rapidly through contaminated water, especially in confined environments like cruise ships or schools. •Symptoms include vomiting, diarrhea, and stomach cramps.
- 15. Causes of Waterborne Diseases Contamination Sources Sewage: •Human waste can contaminate water sources if sewage systems are not properly managed or treated. •Pathogens like E. coli, Salmonella, and Shigella are commonly found in untreated sewage. Industrial Waste: •Factories and industries often discharge pollutants, chemicals, and heavy metals into water bodies. •These pollutants can not only cause diseases but also contaminate water sources with toxins and carcinogens. Agricultural Runoff: •Fertilizers, pesticides, and animal waste from farms can wash into rivers, lakes, and groundwater. •These substances introduce harmful bacteria and toxins, promoting the spread of diseases like Giardiasis and Cryptosporidiosis. Poor Sanitation Practices: •Lack of proper sanitation facilities in both urban and rural areas can lead to contamination of nearby water sources. •Practices such as open defecation and improper waste disposal significantly increase the risk of waterborne diseases.
- 17. Common Symptoms: Diarrhea Vomiting Dehydration Abdominal Pain Long-Term Health Impacts: Malnutrition Stunted Growth in Children Chronic Diseases Symptoms and Health Impacts of Waterborne Diseases Prevention and Control of Waterborne Diseases Water Purification Methods: Boiling Filtration Chlorination Importance of Proper Sanitation and Hygiene Practices: Sanitation Hygiene Encouraging Safe Water Practices
- 18. Indicator organisms are specific microorganisms used to assess the microbiological quality of water and detect potential contamination. These organisms serve as indirect markers for the possible presence of pathogenic microbes. For nearly a century, they have been used to monitor wate r safety, evaluate treatment effectiveness, and ensure compliance with public health standards. Indicator Organism in water and their appearance
- 19. Why Use Indicator Organisms Direct pathogen testing is costly and time-consuming. Indicators are easier to detect and quantify. Strong correlation with the presence of fecal contamination. Provide early warning for waterborne disease risk. It is not practical to test for pathogens in every water sample collected. Instead, the presence of pathogens is determined with indirect evidence by testing for an "indicator" organism such as coliform bacteria. Coliforms come from the same sources as pathogenic organisms. Purpose: They signal possible contamination by pathogens without directly testing for every harmful microbe.
- 20. Common Indicator Organisms include: Total Coliforms Fecal Coliforms Escherichia coli (E. coli) Fecal Streptococci Enterococci
- 21. The IMViC test is a series of four individual biochemical tests used to differentiate among members of the Enterobacteriaceae family. The acronym IMViC stands for: Indole Test (I): Determines the ability to produce indole from tryptophan. Methyl Red Test (M): This test detects the production of acid from fermentation of glucose. Voges-Proskauer Test (V): VP test is a etects acetone production from glucose fermentation. Citrate Utilization Test (C): Tests the ability to use Na-citrate as the sole carbon source. Conclusion Indicator organisms are essential for water safety monitoring. Their appearance in lab tests helps identify contamination quickly. Regular testing ensures public health protection.
- 22. Bacteriological testing of water is crucial for ensuring its safety for human consumption and other uses. The following methods are widely used, each with a different approach to detecting and quantifying bacteria. Bacterial culture test Laboratory technique to grow and identify bacteria from samples Procedure: Sample collection under sterile conditions. Inoculation on appropriate media (nutrient agar, blood agar, MacConkey agar, etc.). Incubation at optimal temperature (usually 35–37°C). Observation of colony growth, morphology, and biochemical tests. Purpose: Confirms presence of pathogens, aids diagnosis, and guides treatment Bacteriological testing method
- 23. Colony morphology The visible appearance of bacterial colonies on solid media, used for preliminary identification. Procedure Inoculation – Spread bacteria on a solid medium (nutrient agar). Incubation – Incubate at 35–37°C for 24–48 hrs. Observation – Examine colonies for: 1. Shape (circular, irregular) 2. Size (small, medium, large) 3. Margin (entire, undulate, lobate) 4. Elevation (flat, raised, convex) 5. Color & Opacity Purpose:- To observe visible characteristics of bacterial colonies and helps in preliminary identification and distinguishing bacterial species
- 24. Procedure Plate preparation – Use medium that is selective and/or differential. Inoculation – Spread or streak bacterial sample. Incubation – 35–37°C for 24 hrs. Observation – Analyze growth and reactions: Selective → only certain bacteria grow. Differential → colony color/appearance indicates species (e.g., lactose fermenters → pink, non-fermenters → colorless). Selective and differential media Special growth media designed to support certain bacteria (selective) and distinguish species based on biochemical reactions (differential). Purpose To isolate specific bacteria by inhibiting unwanted species (selective) and differentiate bacteria based on biochemical or metabolic characteristics (differential)
- 25. Gram staining Gram staining is a differential staining technique used to classify bacteria into two main groups: 1. Gram-positive 2. Gram-negative. It's a fundamental procedure in microbiology for identifying and distinguishing bacterial species based on their cell wall properties. Processes Prepare a smear of bacteria on glass slide, heat-fix. Add Crystal Violet (primary stain) → all cells purple. Add Iodine (mordant) → forms CV-I complex. Wash with Alcohol/Acetone (decolorizer): Gram-positive retain purple. Gram-negative lose color. Add Safranin (counterstain) → Gram-negatives turn pink Purposes: Differentiate bacteria into Gram-positive and Gram-negative for identification & treatment.
- 26. Hydrogen sulfide method A biochemical test used to detect bacteria that produce hydrogen sulfide gas (H S) by breaking down sulfur-containing compounds. ₂ Procedure Inoculation – Stab or streak bacteria into H S-detecting medium ₂ (e.g., SIM medium or Triple Sugar Iron agar). Incubation – Incubate at 35–37°C for 24–48 hours. Observation – Check for black precipitate (ferrous sulfide) in the medium, which indicates H S production. ₂ Black color formation → H S positive ₂ No black color → H S negative ₂ Purpose: To identify H S-producing bacteria (common in Salmonella, ₂ Proteus species). It also helps in bacterial identification and differentiation from similar species.
- 27. Water purification is the process of removable of impurities, microorganisms (bacteria, algae, viruses, fungi), Parasites (Giardia, Cryptosporidium, etc.), minerals (toxic metals like lead, copper, iron, nitrate, arsenic, manganese), and contaminants from raw water. these methods are broadly classified into: Physical Methods – Use physical forces or mechanical processes like filtration, sedimentation, boiling, or reverse osmosis to remove impurities without changing the chemical composition of water. Chemical Methods – Involve chemical agents such as chlorine, ozone, or iodine to disinfect or neutralize harmful contaminants. Biological Methods – Rely on biological activity of microorganisms or biofilms to degrade, remove, or inactivate pathogens naturally. Water purification methods
- 28. Boiling Water is heated to 100°C for 5–10 minutes, killing bacteria, viruses, protozoa, and parasites, making it safe for drinking. Pros: Simple, effective, no chemicals Cons: Energy-intensive, does not remove dissolved salts or chemicals Filtration Water passes through porous materials like sand, charcoal, or ceramic to remove suspended solids, sediments, and some microbes. Examples include sand filters, ceramic filters, and activated carbon filters. Pros: Easy to use, low-cost Cons: Does not remove dissolved chemicals or heavy metals unless combined with RO Physical Methods
- 29. Sedimentation Water is stored in large tanks where heavy particles settle at the bottom due to gravity, leaving clear water above. Pros: Simple and cheap Cons: Removes only large particles, not microbes or dissolved chemicals d) Distillation Water is boiled, and the vapor is condensed back into liquid form, leaving impurities behind. This process removes salts, heavy metals, and microbes. Pros: Produces highly pure water Cons: Energy-intensive, slow
- 30. Reverse Osmosis (RO) Water is forced through a semi-permeable membrane to remove dissolved salts, chemicals, heavy metals, bacteria, viruses, and other impurities. Process: Pre-filtration: Removes large particles, sediments, and chlorine to protect the membrane. High-pressure pumping: Water is pressurized to pass through the semi-permeable membrane. Membrane filtration: Pure water passes through the membrane; dissolved salts and impurities are left behind. Collection: Clean (permeate) water is collected for use, while concentrated impurities (brine) are discharged. Post-treatment (optional): Mineral addition or UV treatment for taste and safety.
- 31. Chlorination Chlorine or hypochlorite is added to water to kill bacteria and viruses, commonly used in municipal treatment plants. Pros: Inexpensive, effective for large-scale treatment Cons: May cause odor/taste issues, can form harmful by-products if overdosed Iodine Treatment Iodine tablets or tincture are added to water in emergency or camping situations to kill bacteria and protozoa. Pros: Portable, fast-acting Cons: Not for long-term use, leaves taste, sometimes ineffective for viruses Chemical Methods
- 32. Ozone Generation: Ozone is produced from oxygen (O ) using an ₂ ozone generator (via electrical discharge or UV light). Ozone Injection: Ozone gas is bubbled or diffused into water using injectors or diffusers. Oxidation & Disinfection: o Ozone reacts with bacteria, viruses, and other pathogens, destroying them. o Oxidizes iron, manganese, and organic compounds, removing color, odor, and taste problems. Decomposition: After reaction, ozone naturally decomposes back to oxygen. Ozonation It is the process of treating water with ozone (O ) ₃ , a powerful oxidizing agent, to disinfect it and remove impurities.
- 33. Slow Sand Filtration Water passes slowly through a fine sand bed where particles are trapped, and a biological layer( Schmutzdecke) digests organic matter and bacteria, producing clean water. Pros: Natural, effective, low-cost Cons: Slow, needs regular maintenance Bio-sand Filter A household filter containing sand and gravel allows beneficial bacteria to grow, removing pathogens and sediments from water. Pros: Simple, inexpensive, sustainable Cons: Requires training for maintenance, slower filtration rate Biological Methods
- 34. Multi-steps in water purification
- 35. Water is essential for life. Contaminated water causes health risks, affects daily life and harm environments. Water purification ensures water is safe, usable and environment sustainable. Purpose overview Health protection Industrial and Domestic needs Environmental consideration Purpose of water purification
- 36. Health protection Clean water prevents diseases caused by bacteria, viruses and parasites. Essential for public health and reducing mortality. Removes pathogens and harmful microorganisms. Prevents cholerae , typhoid, diarrhea and other waterborne illness. Ensures safe drinking water for families and communities. Example: Villages using water purification systems see dramatic reductions in child mortality. Purified water reduces hospital visits and medical expenses.
- 37. Industrial and Domestic needs Water is used in households, industries and agriculture. Purified water ensures efficient use and long-term safety of systems and appliances. Removes minerals causing hardness, like calcium (Ca) and magnesium (Mg) Prevents scale formation in boilers, pipelines and household appliances. Ensures clean water for cooking, cleaning and industrial processes. Example: Factories using purified water reduce equipment maintenance costs. Household enjoy clean water, tasty water and longer lasting appliances.
- 38. Environmental consideration Untreated water can pollute rivers, lakes and soils. Water purification reduces environmental degradation and protects ecosystem. Treats wastewater before release, reducing chemical and biological contamination. Preserves aquatic life and biodiversity. Supports sustainable water management for future generations. Example: Communities with purification plants report clean rivers and safer agricultural. Protects wildlife and reduces the spread of waterborne pollutants.
- 39. Purpose Key Benefits Example 1. Health protection Reduce diseases Safe drinking water 2. Industrial and Domestic needs Efficient use and appliance longevity Clean water for homes and factories 3. Environmental consideration Protects ecosystem Clean rivers and biodiversity Summary of three main purposes:
- 40. Water safety refers to ensuring that water intended for drinking, cooking, recreational use is free from harmful contaminants, pathogens and chemical pollutants.
- 41. WHO Drinking Water Standard Chemical Parameters Arsenic: 0.01 mg/L Lead: 0.01 mg/L Nitrate: 50 mg/L Fluoride: 1.5 mg/L TDS: Acceptability ≤1000 mg/L. pH: 6.5 – 8.5 BSTI Drinking Water Standard Chemical Parameters Arsenic: 0.05 mg/L Lead : 0.05 mg/L Nitrate : 10 mg/L Fluoride : 1.0-1.5 mg/L TDS : 1000 mg/L pH : 6.5-8.5
- 42. WHO Perspective on Public Awareness Health Education: Communities should understand that contaminated water spreads diseases (diarrhea, cholera, typhoid, hepatitis A/E). Safe Practices: Awareness campaigns encourage boiling, filtering, chlorination, safe storage, and hand hygiene. Community Participation: WHO’s Water Safety Plan framework includes consumers in identifying risks and reporting unsafe supplies BD National / Local Initiatives (Bangladesh) Mass Campaigns: Government, NGOs (e.g., BRAC, UNICEF, WaterAid) run awareness drives on arsenic risks, boiling water, safe tube wells (green-marked), and sanitation linkages. School Programs: Teaching children about safe drinking water, handwashing, and sanitation helps spread knowledge to households. Media & Digital Outreach: Radio, TV, posters, and now social media are used to share messages like “Boil water before drinking during flood. Community Monitoring: Training villagers to test tube wells for arsenic with field kits increases awareness and ownership.
- 43. Thanks!
- 44. Q & A