Zhang Zhiyong Water Quality Restoration of Dianchi Lake Using Water Hyacinth

1.Introduction to Dian Chi (Kun-Ming Lake) 2.Biology of water hyacinth ( ) 2.Biology of water hyacinth ( Eichhornia crassipes ) 3.Project of water quality restoration at Dian Chi using water hyacinth 4.Controlled growth areas of water hyacinth 5.Effects of water hyacinth on the water quality in Dian Chi Contents

1. Introduction to Dian Chi

 Dian Chi is a plateau lake located 5 km south- west from Kun-Ming city, Yunnan Province. It is divided by a dam into two parts. One part is called Cao Hai and the other is named Wai Hai. Location Area (km 2 ) Depth of water (m) Cao Hai (average) Wai Hai (deepest point) Tab.1-1 Basic information of Cao Hai and Wai Hai

LocationTN(mg/L)TP(mg/L) pollution level Cao Hai hyereutrophic Wai Hai eutrophic Tab.1-2 Pollution level of water at Cao Hai and Wai Hai （ data from 2006 to 2010)  Cao Hai is a deposit area of the sewage both from domestic and sewage treatment facilities of the Kun-Ming city.  Wai Hai is a deposit area of the domestic sewage both from Kun-Ming city and the rural area of nearby town.

2. Biology of water hyacinth (Eichhornia crassipes )

Water hyacinth growth fact. Water hyacinth growth fact.  It is known as one of the fast growing plants.  It grows well at temperature of 13 ℃ and above, and grows vigorously between ℃.  It can duplicate itself form 1 to 60,000 times in a period of just 8 months.

Water hyacinth can absorb large amount of N and P.  The annual yield of fresh water hyacinth at Wai Hai reaches up to 225 tons per hectare.  The composition of N and P in fresh water hyacinth of Wai Hai approximates to 1.30 ‰ and 0.43‰ respectively.  The annual amount of N and P absorbed by water hyacinth at Wai Hai is 285 kg and 97 kg per hectare respectively.  The annual yield of fresh water hyacinth at Cao Hai reaches up to 600 tons per hectare.  The composition of N and P in fresh water hyacinth of Cao Hai approximates to 1.71 ‰ and 0.44‰ respectively.  The annual amount of N and P absorbed by water hyacinth at Cao Hai is 1026 kg and 330 kg per hectare respectively. A survey in 2010 showed:

LocationYield Composition of N and P in fresh water hyacinth Annual absorption of N and P per hectare(hm) Ton/hm N（‰）N（‰）N（‰）N（‰） P （ ‰ ） N （ kg/hm ） P （ kg/hm ） Cao Hai Wai Hai Tab. 2-1 Annual absorption of N and P by water hyacinth (data of 2010) by water hyacinth (data of 2010)

The effects of water hyacinth on the water quality.  At a suitable temperature, 1 m 2 of water hyacinth can improve the water quality in a day over a cubic meter of water as follows: the concentration of TN decreases 1-2 mg/L, the concentration of TN decreases 1-2 mg/L, the concentration of TP decreases mg/L, the concentration of TP decreases mg/L, the suspended particulates reduced up to 70% in the water body. the suspended particulates reduced up to 70% in the water body.

Effects of water hyacinth on water quality Effects of water hyacinth on water quality (Sep-Oct)2010 (Sep-Oct) TN11.08mg/L6.33mg/L TP0.98mg/L0.22mg/L After 200 hectares of water hyacinth planted at Cao Hai, the water quality improved significantly, and the concentration of TN and TP decreased markedly. After 200 hectares of water hyacinth planted at Cao Hai, the water quality improved significantly, and the concentration of TN and TP decreased markedly. Tab.2-2 The concentration of TN and TP in Sep-Oct

The variation of TN in Cao Hai ( ) Months

P N absorbed bywater hyacinth absorbed by water hyacinth pollutants entering the Dian Chi sediment release PN PN The effects of water hyacinth on water quality in the Dian Chi is significant, but the behavior of N and P in the ecosystem is yet to be further studied.

3. The research project of water quality restoration of the Dian Chi using water hyacinth

 Due to its free-floating nature, water hyacinth has to be cultivated under control.  Research in JAAS shows that a combination of stake- fixed nets and floating barrels can effectively prevent the water hyacinth from drifting away. The controlled growth of water hyacinth

 Water hyacinth should be harvested when it gets to 20 kg per square meter since the growth rate decreases as space getting crowded.  Due to the large volumeof water hyacinth, JAAS has developed a machine for harvesting and cutting. It can harvest 300 tons of water hyacinth per day and reduce the volume of the fresh water hyacinth to 1/3.  Due to the large volume of water hyacinth, JAAS has developed a machine for harvesting and cutting. It can harvest 300 tons of water hyacinth per day and reduce the volume of the fresh water hyacinth to 1/3.  After harvest and volume reduction, the water hyacinth is shipped to a dock for further processing. Machine for Harvesting and Cutting

 Water hyacinth makes a good source for its N, P, K and energy.  However, dehydration is a prerequisite before its desirable utilization since its water content is up to %.  The machine for dehydration, developed by JAAS with its processing capacity of 25 tons per hour, can reduce the water content of water hyacinth from 94% to 75-80%.  And about 200 kg of residue can be obtained from 1,000 kg of fresh plant, from which 50 kg of dry matter can be retrieved. The machine for dehydration

screw distributing bin transfer belt Grinder Suction Pump screw extruder Production line of dehydration for Water hyacinth

Products of organic fertilizers from dehydrated water hyacinth  Dehydrated water hyacinth can be directly treated by thermophilic composting.  1 kg of composted water hyacinth contains 610 g of organic matter, 17 g of N, 3.4 g of P and 4.34 g of K respectively.  JAAS has already produced the pilot organic fertilizers from dehydrated water hyacinth.

4. Distribution of planted areas of water hyacinth under control

 As water hyacinth can adsorb a large amount of N and P, and it can also intercept with blue- green algae, the location should be selected according to the flowing water from rivers having a high concentration of N and P, the wind being mild and blue-green algae blooming easily.  Based on the above criteria, suitable planting areas has been chosen in the Dian Chi, the total area of enclosures is about 22 km 2 Cao Hai about 7.33 km 2 Cao Hai about 7.33 km 2 Wai Hai about km 2 Wai Hai about km 2 Suitable planting areas of water hyacinth in Dian Chi

Distribution of water hyacinth in Cao Hai

Distribution of water hyacinth in northern Wai Hai

Distribution of water hyacinth in southern Wai Hai

5. Effects of water hyacinth on water quality restoration in Dian Chi

 The area of water hyacinthin Cao Hai is 4.93 square km, and the total area of Cao Hai is square km, so its cover rate is about 46.25% in Cao Hai.  The area of water hyacinth in Cao Hai is 4.93 square km, and the total area of Cao Hai is square km, so its cover rate is about 46.25% in Cao Hai.  The area of water hyacinthin Wai Hai is 3.10 square km, and the total area of Wai Hai is square km, so its cover rate is about 1.08% in Wai Hai.  The area of water hyacinth in Wai Hai is 3.10 square km, and the total area of Wai Hai is square km, so its cover rate is about 1.08% in Wai Hai. The cover rate of water hyacinth in the Dian Chi  As the area of Cao Hai is limited, and the cover rate of water hyacinth is high, the effect of water hyacinth on water qualityis significant, the variation of water quality in Cao Hai should be investigated in depth.  As the area of Cao Hai is limited, and the cover rate of water hyacinth is high, the effect of water hyacinth on water quality is significant, the variation of water quality in Cao Hai should be investigated in depth.  As the area of Wai Hai is large, and the cover rate of water hyacinth is extremely low, the effect of water hyacinth is weak, the variation of water quality in Wai Hai may not be of interest.

Sampling points in Cao Hai There are 4 rivers flowing into northern Cao Hai, so the area could be considered as the inlet of pollutants. Sampling points 4 、 5 、 6 locate in this area. There is an outlet of water in southern Cao Hai. Sampling points 1 、 2 、 3 locate in this area. Water flows from northern to southern in Cao Hai.

Variation of water temperature of Cao Hai in 2011

 After planting water hyacinth in northern Cao Hai, the water transparency gradually increased from 42 cm in March to 140 cm in September. However, the dissolved oxygen was decreased. From May to September 2011, the TN and TP in this area decreased by 14% and 75% respectively, although this area contains 4 inlets of pollutants. The variation of water quality of northern Cao Hai

 After planting water hyacinth in southern Cao Hai, the water transparency increased gradually from 40cm in March to 73cm in September. From March to September, the dissolved oxygen was gradually decreased, but the lowest dissolved oxygen was above 4.3 mg/L in September. This level is considered not to be dangerous to the aquatic organisms in eutrophic lakes. From May to September, the TN and TP in this area decreased by 83% and 57% respectively, demonstrating a strong water quality restoration ability of water hyacinth in this ultra eutrophic lake. The variation of water quality of southern Cao Hai

Comparison of TN in 2011 and in Compared with , TN in Cao Hai decreased obviously in 2011.

Comparison of TP in 2011 and in Compared with , TP in Cao Hai also decreased significantly in 2011.