Clokie 5 Water treatment Flashcards
Hydrologic (water) cycle:
is cyclic exchange of water between atmosphere & biosphere.
- Water precipitates as rain; falls to Earth.
- It is returned by evaporation to the air.
Microbes & water cycle uses
- Wastewater: liquid derived from domestic sewage, industry that can’t be discharged into lakes/streams due to heath, economic, environmental or aesthetic reasons
- Clean water essential to public health
- Monitor, assess, remediate quality
Water purification most important for ..
public health
• Lapses → highly significant
Microbes used to:
– Identify
– Remove
– Degrade
PATHOGENS
-caused by input of sewage into rivers
CHOLERA , TYPHOID OUTBREAKS
Cholera
Causes:
Cases:
• Causes exhaustive diarrhoea, vomiting
Vibrio cholerae occurs naturally in plankton of fresh, brackish, and salt water
• Affects 3–5 million people, 100,000–130,000 deaths a year
Typhoid
Causes:
cases:
- Salmonella enterica, serovar Typhi
- 16–33 million cases of typhoid fever occur annually
- Most deaths ~ 5 and 19 years old
- Kills 1-20% people infected
- Major problem in certain countries such as Nepal
Assessing water quality
- rapid easy test for faecal contamination rather than pathogensis per species
- Use indicator organisms
- Choose a gut commensal of animals and man
- If present in large quantities, test more sensitive
Major constituents and composition of the human gut
Enterococci & enterococcus faecalis
CURRENT STATUTORY TEST:
PRESUMPTIVE COLIFORM TEST
PRESUMPTIVE COLIFORM TEST
- Gram –ve rod that produces acid & gas from lactose in presence of bile salts at 37° C in 24 – 48 h
- Member of the Enterobacteriacea, grows at 37 ° C with β-galactosidase acivity
- MPN (most probable number) liquid culture
* MF (membrane filter)
- TUBES OF MEDIA e.g. MacCONKEY
- DURHAM TUBE FOR GAS DETECTION
- REFER TO PROBABILITY TABLES
- CONFIRM E.COLI IF ANY CHANGE
2nd way of doing test: filter, grow is sensitive though
Enterococcus
• E. faecalis 90-95% a E. faecium 5-10%
Water quality is currently monitored in EU using two groups of faecal indicator organisms
- Faecal coliforms
* Intestinal enterococci
Bacteroides:
• Anaerobic Gram-negative bacteria
most substantial portion of human gastrointestinal flora (aerotolerant anaerobes)
• faeces of humans (1010-1011 cells/gram)
• Presence of these phages in wastewaters, & surface waters, shellfish, & sediments could suggests human contamination
Detecting bacteriophages*
Results expressed as plaque forming units (PFU) per 100 ml
POTENITAL PROBLEMS W/ VIRUSES & PROTOZOA
CHLORINE RESISTANT
-> no routine tests, molecular screening being developed
Biochemical Oxygen Demand
- High BOD accelerates heterotrophic respiration.
- Can cause a massive die-off of fish & other aquatic animals.
- Microbial oxygen consumption
Goal of wastewater treatment facility :
x2
– reduce organic + inorganic materials so not support microbial growth
– Eliminate toxic materials
Efficiency of treatment is expressed in
terms of
Biochemical Oxygen Demand
1912 set water standard of
20 ppm BOD5 as max conc permitted in sewage works
BOD5
- Water under test: measure O2 => reading 1
- Sealed bottle 5 days: measure O2=> reading 2
- BOD5 = reading 1-reading 2 (mg/ l ppm)
- Indirect measure of organic material
Preliminary treatment:
removes solid debris
Primary treatment:
fine screens & sedimentation tanks remove insoluble particles
- May contain 200 BOD – 1500 BOD units
- Effluent plant 5 BOD
- Wastewater → grates, screens → settled
- Still have high BOD
- Most plants have secondary treatment
