organic nutrient pollution

Question 1

what are the sources of organic nutrient pollution

Answer 1

1) organic wastes
- sewage
- silage storage
- processing of wood and paper effluent

Question 2

list the effects of organic nutrient pollution

Answer 2

1) deoxygenation
2) pathogens
3) inorganic nutrient release

Question 3

outline how organic nutrients cause deoxygenation

Answer 3

1) flows into rivers or lakes providing food for microorganisms
2) aerobic digestion deoxygenates the water and may kill organisms such as fish or insects
3) increased food may increase microorganisms which can cover the surface inhibiting photosynthesis
4) release of inorganic nutrients from decay may cause eutrophication

Question 4

outline how organic nutrient pollution affects pathogens

Answer 4

1) sewage effluent can contain pathogens from infected individuals
2) if others come in contact with these pathogens the disease can spread
3) for example chorea

Question 5

outline how organic nutrient pollution affects inorganic nutrient release

Answer 5

1) the decay of organic nutrients may release inorganic nutrients which cause eutrophication

Question 6

what are the main groups of treatment processes for organic effluents

Answer 6

1) pre-treatment
2) primary treatment
2) secondary treatment
3) tertiary treatment
4) sludge treatment

Question 7

outline pre-treatment

Answer 7

1) screens- trap floating and suspended items such as plastic or paper time which are incinerated or placed in landfill
2) grit traps- channel widens so effluent flow decrease and grit drops to the bottom where it is removed and disposed of
3) comminutors- chop suspended faecal matter increasing surface area of later processes

Question 8

outline primary treatment

Answer 8

effluent left to stand in large tanks where faecal matter sinks to the bottom so it can be removed and treated separately

Question 9

outline secondary treatment

Answer 9

1) aeration tanks= remaining OM is broken down by bacteria in a large tank where air is mixed in by paddle wheels to prevent a shortage of oxygen for decomposition
2) secondary sedimentation tanks= effluent contains bacteria from aeration tanks, bacteria is collected in these tanks and returned as activated sludge to aeration tanks, clear effluent is returned free of pathogens and organic materials
3) trickling filter beds= an alternative process to aeration tanks where rotating arms spray effluent over large tanks containing lumps of solid material such as gravel increasing surface area for bacteria, fungi and insects to digest organic matter

Question 10

outline tertiary treatment

Answer 10

1) used if discharge site is sensitive
2) phosphates are removed by adding iron III sulphur producing insoluble iron phosphates as a fine sediment which is used in agricultural fertiliser
3) effluent can be strained through fine sieves and the remaining suspended bacteria are killed by UV light or chlorine

Question 11

what happens to the sludge removed from primary sedimentation

Answer 11

1) anaerobic digestion by microbes digest sludge in a tank for 4 weeks killing pathogens and odours, sludge is then either taken
- landfill
- dispersed into the sea
- incineration
- agricultural use

Question 12

what are the advantages of using landfill and the disadvantages of using incineration to discard sludge

Answer 12

1) simple and cheap

2) expensive as uses high energy , further waste from gases produced ie co2

Question 13

what are the advantages and disadvantages of using sludge in agriculture

Answer 13

+ reduces the need for artificial fertilizer

- may cause eutrophication