Nitrogen and Phosphorus Removal from Effluent of Sewage Treatment Plant Using Water Lettuce (Pistia stratiotes)

Although our country has wastewater treatment plant, the main problem is it
cannot be classified as world class standard. It means some compounds which can
harm the environment still exist in the river although wastewater was treated by
treatment plant. For example the amount of the nutrient components which are
nitrogen and phosphorus still contain in our UTP sludge treatment plant eftluent.
The main effect is the rivers become toxic to aquatic organisms and polluted to
environment life.

Eutrophication is frequently a result of nutrient pollution (means an increase
in chemical nutrients typically compounds containing nitrogen or phosphorus in an
ecosystem) such as the release of sewage eftluent and run-off from lawn fertilizers
into natural waters (rivers or coasts), where the water becomes cloudy, colored a
shade of green, yellow, brown, or red and then the river becomes toxic to aquatic life
like fish. Beside that, human society is impacted as well, where health-related
problems can occur where eutrophic conditions interfere with drinking water
treatment. The main problem which occurs before deciding to have this project is
because our UTP Sewage Treatment Plant (STP) effiuent still discharged to the
nearest river with nitrogen and phosphorus compounds. If we don't take any action
to remove this type of compounds, this problem maybe can cause eutrophication to
occur.

Nitrogen exists in many forms because of the high number of oxidation states
it can assume. In ammonia and organic nitrogen compounds, which are forms most
closely associated with plants and animals, its oxidation state is -3. At the other
extreme, when nitrogen is in the nitrate form, its oxidation state is +5 [2]. The
presence of nitrogen in a wastewater discharge can be undesirable as free ammonia it
is toxic to fish and many other aquatic organisms; as ammonia it is an oxygenconsuming
compound which will reduce the dissolved oxygen in the river. In all
forms, nitrogen can be available as a nutrient to aquatic plants and consequently
contribute to eutrophication. Where the nitrate ion it is a potential public health
hazard in water consumed by infants [2].
The standard criteria limit for Nitrate-nitrogen in the river according to US
Environmental Protection Agency is 10 mg/L, but according to State of the
Minnesota River the limit is 6.5 mg/L.