Transcript 1. dia - Budapest University of Technology and Economics

BUDAPEST UNIVERSITY OF TECHNOLOGY AND ECONOMICS
FACULTY OF CHEMICAL AND
BIOCHEMICAL ENGINEERING
DEPARTMENT OF CHEMICAL AND
ENVIRONMENTAL PROCESS
ENGINEERING
WASTEWATERS CONTAINING PLANT
NUTRIENTS
Dr. Bajnóczy Gábor
Tonkó Csilla
WASTEWATERS CONTAINING PLANT NUTRIENTS
There is no one special element regulating the growth of plants
Apart from the microelements three elements regulate the plants activity
Three elements : carbon,
nitrogen, phosphorus
Photosynthesis of hydrophytes:
utilize dissolved carbon-dioxide content of
water
The necessary nitrogen is taken up
by the hydrophytes in nitrate form.
blue algae : nitrogen from the air is
consumable
CO2
NO3
PO4
---
-
phosphorus up take :
soluble phosphates
from the erosion of soil.
NUTRIENT SUPPLY OF NATURAL WATERS
TROPHITY
Trophity: capacity of organic matter production of water
trophic
state
phosphorus content
[μg/dm3]
clarity
[cm]
oligotrophic
4 – 10
> 260
mezotrophic
10 – 35
eutrophic
35 – 100
hipertrophic
> 100
160 – 260
nitrogen content chlorophyll content
[μg/dm3]
[μg/dm3]
< 400
1,0 – 2,5
400 – 600
2,5 – 8,0
60 – 160
600 – 1500
8,0 – 25
< 60
> 1500
> 25
Racial diversity and large number of individuals in oligotrophic waters
can not be formed due to the low nutrient content. The sludge is negligible.
Mezotrophic waters:
decreased transparency but better conditions for aquatic life
grass carp
eating fresh water
seaweed
option of eutrophication change
benthic
eutrophic waters: possibility of diverse aquatic life
classified into two categories
a.) benthic: good clarity and presence of higher-order hydrophytes
b.) planktonic: poor transparency and dominant species: algae
Simultaneous presence of the two types is possible
planktonic
Hypertrophic waters:
Well supplied by nutrients, very poor transparency ,hydrophyte or algae blooming is possible,
Diverse aquatic life but the system is very unstable.
Large amount of dead organic material may cause lack of oxygen.
EFFECT OF PLANT NUTRIENTS TO NATURAL WATERS
NATURAL WATER
excess nutrient intake
growth of aquatic plants
benthic eutrophication
alga blooming
planktonic eutrophication
more diverse wildlife,
increased number of
species
decay of large amount of dead biomass →
→ reduction of water’s oxygen content
wildlife change,
decrease of oxygen claiming
species
INHIBITION OF EXCESSIVE EUTROPHICATION
Inhibition of carbon intake
Can not be limited because of the chance of carbon dioxide uptake from air.
Inhibition of nitrogen intake
Due to nitrogen-cycle unlimited amount nitrogen is carried by rainwater in nitrate form
Rational use of fertilizers may help!
Inhibition of phosphorus intake
The only way at present to reduce the phosphorus content of waste waters.
The human activity is mainly responsible of the ≈ 70% of phosphorous content
of natural waters.
PHOSPHORUS-CYCLE AND REMOVAL FROM NATURAL WATERS
harvesting
adult bug fly out land
phosphorus in
alga
dead fish
Fe +++ increase
Ca ++ increase
decrease of O2 concentration
increase of acidity
dead alga
increase of temperature
dissolved phosphorus
Chironomid larvae: liveing in water,
accumulates significant amount of
phosphorus
Sludge excavation:
significant decrease of
dissolved oxygen
phosphorus in
fish
REDUCTION OF PHOSPHORUS LOADING
Main resources: municipal wastewater → phosphorus content from water
softeners in washing powders
Claim of environment: phosphorus-free water softener in detergents!
Phosphorus elimination of municipal wastewaters
Biological wastewater treatment: phosphorus content is reducible about 20 – 30 %.
Removal of residual phosphorus: by chemical processes precipitating in form of
iron, calcium or aluminium salts.
3 Fe 3+ + 2 PO43- + 3 H2O = (FeOH)3(PO4)2 + 2H+