The conversion of ammonium and nitrate on the growth of the two duckweed

—— Lemna perpusilla and Spirodela oligorrhiza

Name: Wu Xuefei Major: Environmental Science

Key Words

nitrogen 氮（ N） ammonium 铵态氮（ NH4

+ ） nitrate 硝态氮（ NO3

-） duckweed 浮萍 Lemma perpusilla 稀脉浮萍 Spirodela oligorrhiza 少根紫萍

Why choose duckweed?

Content

Experimental considerations

Method

Expected result

Choose DuckweedChoose Duckweed

Why?

High removal rate of

nitrogen

Animal foodRich in protein

Growing rapidly

Harvest conveniently

Experimental Considerations

• In order to train duckweed to use ammonium in water,

• convert nitrate in the water into ammonium gradually, and see if the two kinds of duckweed can grow well

• Because duckweed prefers to absorb nitrate to ammonium, and excessive ammonium can be toxic to duckweed.

Hutner nutrient solution

nutrients Concentration (mg/L)

NH4NO3 20

CaCO3 15

MgSO4•7H2O 50

K2PO4 40

H3BO3 1.0

MnSO4•H2O 1.54

ZnSO4•7H2O 6.59

Na2MoO4•2H2O 2.52

CuSO4•5H2O 0.39

CoSO4•7H2O 0.09

FeSO4•7H2O 25

Na2EDTA 5

Footnote:NH4

+ ： NH4ClNO3

- ： KNO3

Method

0.05mmol/L N

n NH4+ ： n

NO3-

1 5:0

2 4:1

3 3:2

4 2:3

5 1:4

6 0:5

1.0mmol/L N

n NH4+ ： n

NO3-

7 5:0

8 4:1

9 3:2

10 2:3

11 1:4

12 0:5

5mmol/L N

n NH4+ ： n

NO3-

13 5:0

14 4:1

15 3:2

16 2:3

17 1:4

18 0:5

• 80% NO3-—N 20% NH4

+—N

100% NO3-—N

80% NO3-—N 20% NH4

+—N

60% NO3-—N 40% NH4

+—N 40% NO3-—N 60% NH4

+—N

20% NO3-—N 80% NH4

+—N

100% NH4+—N

Every three days

If the experiment is successful, we can certainly raise the capacity that

duckweedremoves the ammonium in wastewater.

Expected result