Dr. Bajnóczy Gábor Tonkó Csilla WASTEWATERS CONTAINING PLANT NUTRIENTS BUDAPEST UNIVERSITY OF TECHNOLOGY AND ECONOMICS DEPARTMENT OF CHEMICAL AND ENVIRONMENTAL PROCESS ENGINEERING FACULTY OF CHEMICAL AND BIOCHEMICAL ENGINEERING

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 phosphorus up take : soluble phosphates from the erosion of soil. CO 2 NO 3 - PO 4 ---

NUTRIENT SUPPLY OF NATURAL WATERS TROPHITY trophic phosphorus content clarity nitrogen content chlorophyll content state [μg/dm 3 ] [cm] [μg/dm 3 ] [μg/dm 3 ] oligotrophic 4 – 10 > 260 < 400 1,0 – 2,5 mezotrophic 10 – – – 600 2,5 – 8,0 eutrophic 35 – – – ,0 – 25 hipertrophic > > 25 Trophity: capacity of organic matter production of water

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

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 benthic planktonic grass carp eating fresh water seaweed option of eutrophication change

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 Can not be limited because of the chance of carbon dioxide uptake from air. Inhibition of carbon intake 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 Chironomid larvae: liveing in water, accumulates significant amount of phosphorus adult bug fly out land harvesting Sludge excavation: significant decrease of dissolved oxygen phosphorus in alga phosphorus in fish dissolved phosphorus dead alga dead fish increase of temperature increase of acidity decrease of O 2 concentration Ca ++ increase Fe +++ increase

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 PO H 2 O = (FeOH) 3 (PO 4 ) 2 + 2H +