Using aquatic plants to remove nutrients from

aquaculture wastewater

How does aquaculture introduce nitrogen into the

environment?

• Fish feeds contain nitrogen compounds

• large amounts of waste

Mechanisms to reduce nitrogen

• Traditional separation machinery

• settling ponds

• Constructed wetlands

• hydroponics

Case Studies

Lin et al. (2003)

ammonia 57%, nitrite 90%, nitrate 68%

Mississippi State University

Ammonia 63%

Nitrite 97%

Nitrate 80%

Giant Salvinia (Salvinia molesta)

Experimental Design

• 4 aquaria all containing 30g tilapia

• 2 of the 4 aquaria containing Giant Salvinia

• water quality parameters (ammonia, nitrite, nitrate) measured weekly

• difference in nitrogen levels between tanks with aquatic plants and those without?

Nitrite

00.5

11.5

22.5

33.5

44.5

1 2 3 4 5

Test #

Nitr

ite le

vel tank 1

tank 2

tank 3

tank 4

Nitrate

0

20

40

60

80

100

1 2 3 4 5

Test #

Nit

rate

leve

l tank 1

tank 2

tank 3

tank 4

Ammonia

0

0.2

0.4

0.6

0.8

1

1 2 3 4 5

Test #

Am

mo

nia

leve

l

tank 1

tank 2

tank 3

tank 4

Conclusions/Experimental modifications

• Salvinia may be able to effect nitrogen at very low concentrations

• No effect at higher concentrations• Questionable for use in aquaculture

• Light for Salvinia• replications• extend length of experiment

References

• Posadas, B.C. 2003. Use of constructed wetlands to improve water quality in finfish production. Mississippi State University. http://www.msstate.edu/dept/crec/cwres.html

• Lin, Y-F., Jing, S-R., Lee, D-Y. 2003. The potential use of constructed wetlands in a recirculating aquaculture system for shrimp culture. Environmental Pollution. 123: 107-113.

• Seawright, D., Stickney, R., Walker, R. 1998. Nutrient dynamics in integrated aquaculture-hydroponics systems. Aquaculture. 160: 215-237

Photos• Michael, J. H. Jr. 2003. Nutrients in salmon hatchery wastewater and its removal through

the use of a wetland constructed to treat off-line settling pond effluent. Aquaculture. 226: 213-225

• Tilapia:www.sun.ac.za/kie/unistel/ aquaculture/aquastel/• Catfish: www.fish2go.com/info6.htm• Constructed wetland: http://www.msstate.edu/dept/crec/cwres.html• Shrimp: whyfiles.org/025chem_weap/ 7.html• Aquaponics(1): http://www.hamburger-umweltinst.org/biomass/mnlwide/img33.gif• Aquaponics (2): www.aquaranch.com/ aquapon.html• Salvinia: http://www.wapms.org/images/salvinia2.jpg