Microbiology of Water and Waste Water Management Study Notes

Types of Pathogenic Microorganisms in Water

• Pathogenic Bacteria:     * Escherichia coli:         * Pathogenic Strains: Responsible for causing severe diarrhea and Hemolytic-Uremic Syndrome (HUS).         * Non-pathogenic Strain: Acts as a key indicator of fecal contamination and is considered normal gastrointestinal (GI) flora.     * Vibrio cholerae: The causative agent of cholera. It leads to severe dehydration and electrolyte imbalance.     * Salmonella: Includes S. Typhi and S. Paratyphi, which cause typhoid and paratyphoid fevers, respectively.

• Pathogenic Viruses:     * Rotavirus: A major cause of severe diarrhea, particularly in children.     * Norovirus: A highly contagious virus that cause acute gastroenteritis.     * Hepatitis A Virus: Transmitted through contaminated water and results in liver infection.

• Protozoa:     * Cryptosporidium: Causes cryptosporidiosis. Notably, it is resistant to chlorine treatment.     * Giardia lamblia: A flagellate protozoan that causes giardiasis, characterized by diarrhea and abdominal pain.

• Helminths (Parasitic Worms):     * Ascaris: Soil-transmitted roundworms that can lead to intestinal blockages.     * Schistosoma: Parasitic flatworms (blood flukes) that cause schistosomiasis, which can be chronic or acute.

Sources of Water Contamination and Modes of Transmission

• Natural Sources:     * Soil runoff occurring during heavy rainfall.     * Wildlife excreta (feces and urine) located near water sources.

• Human Activity:     * Discharge of untreated or poorly treated domestic sewage.     * Agricultural runoff containing fertilizers, pesticides, and animal waste.     * Industrial effluents consisting of heavy metals, toxic substances, and chemicals.

• Modes of Transmission for Waterborne Diseases:     * Consumption of contaminated drinking water.     * Exposure during recreational water activities (e.g., swimming pools, hot tubs).

Defined Categories and Symptoms of Waterborne Diseases

• Water Categories for Exposure:     * Recreational Water: Swimming pools, hot tubs, etc.     * Non-Recreational Water: Water not intended for drinking or water of unknown intent.     * Drinking Water: Tap water, well water, etc.

• Common Symptoms of Infection:     * Diarrhea, abdominal pain, nausea, vomiting, and dehydration.     * Systemic symptoms like headache, chills, and fever.

• Prevention Strategies:     * Water Treatment: Boiling water before use, utilizing chlorine tablets, water filters, and ensuring proper sewage disposal.     * Hygiene Practices: Handwashing with soap; proper washing of fruits and vegetables.     * Improved Sanitation: Implementing proper waste disposal systems.

Microbiology of Wastewater and Waste Water Treatment

• Wastewater Composition:     * Organic Matter: Food scraps and human waste.     * Inorganic Compounds: Heavy metals and nutrients such as nitrogen and phosphorus.     * Microbes: Includes both pathogens and beneficial decomposers (e.g., Pseudomonas and Nitrobacter).

• Biological Oxygen Demand (BOD):     * BOD is the measure of Biochemical Oxygen Demand in water, which defines water quality.     * Definition: The amount of oxygen ($mg$) required by bacteria to degrade the organic load in $1\,L$ of sewage over a period of $5$ days.     * Experimental Determination:         1. Fill BOD bottles with a diluted sample or just dilution water (control).         2. Record the initial dissolved oxygen (DO).         3. Incubate the bottles for $5$ days.         4. Record the dissolved oxygen at the end of the incubation period.

Wastewater Treatment Steps and Processes

• Primary Treatment:     * The removal of solid matter referred to as sludge through sedimentation.     * Biological activity is not significant at this stage.     * Removes about $25-35\%$ of the biologically degradable organic matter (BOD).

• Secondary Treatment:     * The biological degradation of organic matter following primary treatment.     * Microorganisms degrade the organic matter aerobically, removing up to $95\%$ of the BOD.     * Trickling Filter: A bed of rocks ($10-15\,cm$ diameter) at a $2\,m$ depth. A thick biofilm forms on the rocks to oxidize organic matter.     * Activated Sludge: Aerated system where flocs consisting of bacteria (specifically Zoogloea ramigera) embedded in EPS (slime) degrade organic carbon into $CO_2$ and microbial biomass. Retention time is usually $5-10$ hours.

• Tertiary Treatment:     * Uses physical filtration and chemical precipitation to remove remaining pathogens, residual nutrients (nitrogen/phosphorus), and all biologically degradable organic matter.     * Techniques include UV radiation and reverse osmosis.     * Result: Secondary treatment provides water for irrigation; Tertiary treatment provides drinkable (potable) water.

Sludge Digestion and Microbial Roles

• Anaerobic Sludge Digestion:     * Remaining sludge is digested anaerobically in an anoxic digester.     * High molecular weight materials are removed, typical for industrial wastewater.     * Produces methane ($CH_4$) and $CO_2$. These can be used as biofuel.     * Chemical Equations:         * $CO_2 + 4 H_2 \rightarrow CH_4 + 2 H_2O$         * $CH_3COOH \rightarrow CH_4 + CO_2$

• Role of Microbes in the Nitrogen Cycle:     * Nitrosomonas: Converts ammonia ($NH_3$) into nitrites ($NO_2^-$).     * Nitrobacter: Converts nitrites ($NO_2^-$) into nitrates ($NO_3^-$).

Indicators of Water Quality

• The Indicator Organism Concept:     * Pathogens are often too fragile or too few in number to detect directly. Indicator organisms are used instead.     * Criteria for a Useful Indicator:         * Useful for all water types.         * Always present when pathogens are present; absent when pathogens are absent.         * Correlated with the degree of pollution.         * More easily detectable than the pathogen.         * Survives longer than the pathogen and is not dangerous to laboratory personnel (normal flora).

• Key Indicator: Coliforms:     * Definition: Aerobic or facultative anaerobic, gram-negative, non-endospore forming rods that ferment lactose to acid and gas within $48$ hours at $35\,^\circ C$.     * Escherichia coli: Primary indicator of fecal contamination. If water is free of E. coli, it is generally considered free of enteric pathogens.     * Other Indicators:         * Enterococcus faecalis: Used primarily in European countries.         * Clostridium perfringens: Presence of spores in water indicates fecal contamination.

Bacteriological Examination Techniques

• Microbial Quality Standards:     * Standard plate count: < 500\,CFU/ml.     * Coliforms: < 2.2\,MPN/100\,ml.

• Standard Plate Count (Total Aerobic Count):     * Uses spread or pour plate methods.     * Count colonies on plates with $30-300$ Colony Forming Units (CFUs).     * Calculation: $\text{Number of colonies} \times \text{reciprocal of dilution} = \text{number of bacteria/ml}$.

• Multiple Tube Fermentation / MPN (Most Probable Number):     * A quantitative statistical test for low levels of fecal contamination.     * Based on coliforms fermenting lactose to produce acid and gas.     * Stages: Presumptive test (lactose fermentation), Confirmed test (Brilliant Green Bile Broth - BGBB), and Completed test (biochemical tests to identify E. coli).

• Membrane Filter Technique:     * $100\,ml$ of water is passed through a millipore filter ($0.45\,\mu m$ or $0.22\,\mu m$ holes).     * Bacteria are trapped and the filter is placed on specific media like MacConkey (pink colonies) or EMB (metallic green sheen/dark centers for coliforms).

• ONPG-MUG Test:     * A rapid test to detect enzymes specific to E. coli.     * Presence of specific color changes indicates contamination.