12 wastewater microbiology

12 wastewater microbiology - CEE 266 ENVIRONMENTAL...

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Unformatted text preview: CEE 266 ENVIRONMENTAL BIOTECHNOLOGY Lecture 10 (Wastewater Microbiology and Treatment) Public Health and Water Quality  Coliforms and Water Quality   Water can be sampled for the presence of specific indicator microorganisms   The coliform group of microbes   Includes Enterobacter, E. coli, and Klebsiella pneumoniae   They are a widely used indicator for fecal contamination in water Public Health and Water Quality  Testing for Coliforms and E. coli   All tests assay the growth of organisms recovered from the water samples   Common methods for enumerating the samples   Most-probable-number (MPN) procedure   Membrane filter (MF) procedures   E. coli can be distinguished from total coliforms with defined substrates (e.g., MUGal, IBDG) Coliform Colonies Growing on a Membrane Filter Figure 36.1 Sources of Waterborne Infection  Common sources of waterborne disease transmission include   Potable water used for drinking and cooking   May be improperly treated or of low quality   May be from nonregulated sources (e.g., private wells)   Recreational water from public ponds, lakes, swimming pools, etc. Waterborne Disease Outbreaks from Drinking Water Figure 36.10a Waterborne Disease Outbreaks from Recreational Water Figure 36.10b Cholera  Cholera   Severe diarrheal disease   Caused by Vibrio cholerae   Typically transmitted through ingestion of contaminated water   Can be controlled by application of water treatment   Immunization not recommended Figure 36.11 Cholera   Pathogenesis   V. cholerae attaches to epithelial cells in the small intestine where it grows and releases enterotoxin   This enterotoxin causes severe diarrhea   Can result in dehydration and death unless treated   Diagnosis   Presence of V. cholerae in the “rice water” stools of patients   Prevention   Public health measures are very important   Treatment   Treated with oral rehydration and electrolyte replacement therapy Giardiasis and Cryptosporidiosis   Giardia intestinalis causes giardiasis, an acute gastroenteritis   Cryptosporidium parvum causes cryptosporidiosis   These organisms are found in nearly all surface waters and are highly resistant to chlorine due to cyst formation Giardiasis and Cryptosporidiosis  Giardia intestinalis   A flagellated protist that is usually transmitted to humans in fecally contaminated water   The protist cells produce a resting stage (cyst) that is resistant to desiccation and chemical disinfection   Following ingestion, cysts germinate and attach to the intestinal wall causing symptoms of infection   Many individuals exhibit no symptoms and can act as carriers The Parasite Giardia: Forms Cysts Figure 36.13a & b Giardiasis and Cryptosporidiosis  Cryptosporidium parvum   A protist that lives as a parasite in warm-blooded animals   Produces thick-walled, infective cells (oocysts) that are shed in high numbers in the feces of infected animals   The oocysts are transmitted in fecally contaminated water   Oocysts are highly resistant to chlorine and UV radiation, thus sedimentation and filtration methods are most effective at removal Cryptosporidium Figure 36.14a & b Typhoid Fever and Other Waterborne Diseases   Worldwide, the most important pathogenic bacteria transmitted by water are Salmonella typhi and Vibrio cholerae   S. typhi causes typhoid fever and has been virtually eliminated in developed countries due to water treatment Typhoid Fever and Other Waterborne Diseases  Viruses can also be transmitted in water and cause human disease   E.g., enteroviruses such as poliovirus, norovirus, and hepatitis A are shed into water in feces  Viruses can survive in water for relatively long periods but are inactivated by disinfection with chlorine Typhoid Fever and Other Waterborne Diseases   Entamoeba histolytica   A common pathogenic protist transmitted to humans primarily through contaminated water and sometimes food   Anaerobic and produces resistant cysts   Infection can be asymptomatic or lead to diarrhea and/or dysentery   If untreated, invasive cells can invade the liver and occasionally the lungs and brain   Amoebicidal drugs are not universally effective Effect of Water Purification on the Incidence of Disease Figure 36.3 Drinking Water Purification   Wastewater treated by secondary methods is not yet potable, or safe for human consumption   It requires further treatment to remove pathogens, eliminate taste and odor, reduce chemicals (e.g., iron, maganese), and decrease turbidity   A typical drinking water treatment installation purifies raw (untreated) water Aerial View of Water Purification Plant in Kentucky (USA) Figure 36.9a Schematic of a Typical Community Purification System Figure 36.9b Drinking Water Purification  Purification involves many steps   Sedimentation to remove particles   Coagulation and flocculation form additional aggregates which settle out   Filtration   Disinfection (typically with chlorine gas or UV radiation) Wastewater and Sewage Treatment  Wastewater   Domestic sewage or liquid industrial waste  Wastewater Treatment   Relies on industrial-scale use of microbes for bioconversion   Following treatment, the discharged treated wastewater (effluent water) is suitable for   Release into surface waters   Release to drinking water purification facilities Wastewater and Sewage Treatment   Wastewater treatment is a multistep operation employing both physical and biological processes   Primary, secondary, and sometimes tertiary treatments are used   Primary treatment   Uses physical separation methods to separate solid and particulate organic and inorganic materials from wastewater Wastewater Treatment Processes Figure 36.4 Primary Treatment of Wastewater Figure 36.5 Wastewater and Sewage Treatment  Secondary Treatment   Aerobic secondary treatment uses digestive reactions carried out by microbes under aerobic conditions to treat wastewater with low levels of organic materials   The trickling filter and activated sludge are the most common decomposition processes Aerobic Secondary Wastewater Treatment Processes Trickling Filter in a Treatment Facility Figure 36.7a Aerobic Secondary Wastewater Treatment Processes Aeration Tank of an Activated Sludge Installation Figure 36.7b Aerobic Secondary Wastewater Treatment Processes Wastewater Flow through an Activated Sludge Installation Figure 36.7c Wastewater and Sewage Treatment   In the activated sludge process, wastewater is mixed and aerated in large tanks and slime-forming bacteria (e.g., Zoogloea ramigera) grow and form flocks   Most treatment plants chlorinate the effluent after secondary treatment to further reduce the possibility of biological contamination Figure 36.8 Wastewater and Sewage Treatment  Secondary Treatment (cont’d)   Anoxic secondary treatment involves a series of digestive and fermentative reactions carried out by various microbes under anoxic conditions   The process is carried out in large enclosed tanks (sludge digesters or bioreactors) Sludge Digester for Anoxic Secondary Wastewater Treatment Figure 36.6a Inner Workings of an Anoxic Sludge Digester Figure 36.6b Major Microbial Processes in Anoxic Sludge Digestion Figure 36.6c Wastewater and Sewage Treatment  Tertiary Treatment   Any physiochemical or biological process employing bioreactors, precipitation, filtration, or chlorination procedures similar to those used for purification of drinking water   Reduces the levels of inorganic nutrients (e.g., phosphate, nitrate, nitrite)   Most complete method of treating sewage but it has not been widely adopted due to costs ...
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  • Fall '11
  • ShailyMahendra
  • Sewage treatment, Secondary Wastewater Treatment Processes, Anoxic Secondary Wastewater Treatment, Wastewater Microbiology and Treatment

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