Lake Tai

Coordinates
31.2580° N, 120.2051° E
Between Zheijiang and Jiangsu provinces, China

Details
Fresh water.
Its dimensions are 70 km (45 miles) from north to south and 59 km (37 miles) from east to west.
Total surface area is 2,428 square kilometers (938 square miles).
The average depth is 2 meters (6.6 ft).
It has 90 islands.

Challenge
Severe blue green algae blooms

1.Introduction

Lake Tai or Lake Taihu is China’s third largest freshwater lake.
The lake covers 2,428 square kilometers (938 square miles) and is located in the densely populated Yangtze Delta plain in Wuxi, China. The lake belongs to Jiangsu and the southern shore forms its border with Zheijang province. It provides water for forty million people.

A massive blue green algae (cyano bacteria) bloom broke out in 2007. This bloom was mainly due to the excessive runoff of agricultural fertilizers, and the discharge of nitrogen and phosphorous containing effluents into the lake.
The water supply of 2 million residents in the nearby town of Wuxi was contaminated.

Since the blue green algae outbreak in 2007, more than 1000 manufacturing plants have been closed down. Sewage water treatment plants have been installed on Lake Tai tributaries. Nutrient rich sediments are dredged from the tributary mouths and algae eating fish spawn has been introduced.
Strict discharge regulation laws have been implemented for all manufacturing plants in the region.
The water quality of Lake Tai has improved but industrial waste water and sewage management remains a major problem.

2.Challenge
Blue green algae blooms continues to be a problem in Lake Tai.
The frequency and the density of the blooms have become less since 2007. However, the blooms cause blockage of piping, and water treatment systems. Further the blue green algae can produce toxins such as microcystins and anatoxins that affect people, and livestock that swim in and drink from the algae- contaminated water.

Environmental friendly algae treatment technologies are essential to mitigate the algae blooms in Lake Tai.

3.Solution
Nitrogen, phosphorous, warm temperatures, and sunlight promote the growth of blue green algae.

Ochemate developed an environmental friendly product “Bloombuster” that kills the algae and also reduces nitrogen, phosphorous, and COD.
The physical and chemical reactions of the active ingredients of Bloombuster results in flocculation and sedimentation of the blue green algae. The algae is killed due to lysis by the active ingredients in Bloombuster.
The reaction of Bloombuster results in a precipitate that can be removed by means of filtration such as MMF, MF and UF.

Untreated Lake Tai water Bloombuster treatment

blue green algae Dosage: 200, 100, 50 and 0 ppm (left to right)

Sample Lake Tai	pH	NTU	P total, ppm	NH₃ – N, ppm	COD, ppm
Untreated	8.02	30.20	0.56	3.50	26.60
200 ppm Bloombuster	8.16	1.53	0.10	1.10	10.10
100 ppm Bloombuster	8.05	2.17	0.13	1.80	13.50
50 ppm Bloombuster	7.91	3.37	0.15	2.30	17.20

4. Conclusions
Bloombuster has proven to be very effective in removing the blue green algae in addition to the phosphorus, nitrogen, COD and turbidity reduction:
• Phosphorus reduction 70 - 85%
• Nitrogen reduction 35 - 70%
• COD reduction 35 - 65%
• Turbidity reduction 90 – 95%
The product has a long life time when applied to the Lake Tai water. It is effective for 2 hours after it has been added to the water.

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