Water in Food Processing Flashcards
What ions does hard water contain?
Calcium and magnesium
What is temporary hardness of water due to?
Presence of bicarbonates
How is temporary hardness of water removed?
By boiling
What is permanent hardness of water due to?
Presence of sulphates and chlorides
What are the two methods of water softening?
Lime softening
- Adding slaked lime, calcium hydroxide and soda ash
Ion exchange resin
- Resin has temporarily attached sodium ions which replace calcium and magnesium ions in hard water
What are the three types of water borne pathogens?
Faecal bacteria = salmonella
Enteric viruses = norovirus
Parasites = cryptosporidium
Describe the process of portable water treatment.
- Collection
- Screening and straining (removes large particles)
- Chemical addition
- Coagulation (impurities form larger particles and settle)
- Flocculation (fine particles clump together)
- Sedimentation (floc settles to form sludge)
- Clarification (water left to allow for settling)
- Filtration (removes impurities, sludge and floc)
- Disinfection (chlorination)
What is breakpoint chlorination?
The process of adding enough chlorine so that ‘free chlorine’ is present after an hour
Describe how breakpoint chlorination is achieved.
If water contain ammonia the chlorine and ammonia form chloramines
Chloramines are broken down to N2 gas
Once all ammonia and chlorine has reacted the excess chlorine is ‘free chlorine’
Describe the process of sewage treatment.
- Collection
- Odour control
- Screening and straining
- Settlement (formation of sludge which is removed)
- Aeration (air pumped into tanks to mix water and added seed sludge)
- Final settlement
- Sand filtration
What is biochemical oxygen demand?
The amount of dissolved oxygen needed for microbial oxidation of biodegradable matter
What is chemical oxygen demand?
The amount of oxygen consumed in chemical oxidation of organic compounds
What are the four sources of water contamination?
Farmer hygiene
Manure
Unsanitary farming conditions
Contaminated flooding
