Hydroponic rafts may be a solution to Chinese water pollution.

Curtis Chan
December 14, 2011

For Rachel Brennan and a group of Penn State faculty and students, the sight was almost otherworldly.

college students standing in and around a wooden boat on a lake
Rachel Brennan

CHANCE students prepare to take water samples in a boat on Lake Taihu.

This past summer, a group of 38 students and faculty from Penn State and Jiagnan University journeyed to Lake Taihu in Wuxi, China, as part of a united research effort to study the country’s third-largest freshwater lake. For the team, it was a sobering look at the price China has paid for its meteoric economic growth and expansion.

The experience was part of the embedded field course Biology 497C, “Global Environmental Sustainability: A Field Study in China,” co-taught by Brennan, an associate professor of civil and environmental engineering in University Park, and led by Jacqueline McLaughlin, associate professor of biology at Penn State Lehigh Valley.

“I think it was eye-opening to take [the students] out of Pennsylvania,” says Brennan. “It’s lush here. We’ve got trees and water. It’s relatively clean. There’s biodiversity. There’s lots of animals. We go there and it’s just wiped completely out— much higher population, more pollution.”

Lake Taihu is located in one of China’s most industrialized regions, Jiangsu Province. According to Brennan, the 870 square-mile lake was once renowned for its beauty. “It had these nicknames that implied it was a ‘pearl.’ It was supposedly beautiful 20 years ago,” she says. But as China became increasingly industrialized, lakes such as Taihu started to host more and more factories. “The effluents from approximately 1,300 factories, as well as domestic sewage, were essentially discharged without treatment into this huge lake,” Brennan says.

The water’s high phosphorus and nitrogen content resulted in crippling algae blooms. The algae on the surface was half a meter thick. According to McLaughlin, in 2007 the Chinese were pulling 10,000 pounds of algae from the lake daily.

three students in lab, one student filling a flask
Jackie McLaughlin

CHANCE students test water quality in the lab in China.

“In 2007, everything was dying,” Brennan confirms. “The residents had been using the water in the lake as their drinking water source. They couldn’t use that anymore. They had to import all of this bottled water.’

A government-mandated clean-up campaign has used algae-salvage ships, lake-bottom dredging, factory relocation, and other methods to help repair the lake. All of that effort still leaves plenty of contaminants, however.

This summer, the Penn State students and faculty teamed with their counterparts at nearby Jiangnan University to conduct real-world experiments on the lake’s water quality and surrounding land use. What the team found were nutrient levels still indicative of a eutrophic state, making the water unsafe for human consumption.

Rachel Brennan

Rachel Brennan

One avenue of remediation the Chinese have recently started exploring is the use of simple ecological systems that clean and filter polluted water. Such systems use a combination of plants, bacteria, and other organisms to clean water through bioremediation, mimicking what marshes and wetlands do.

For the Chinese, Brennan says, employing nature to clean water is relatively uncharted territory. “They’re starting to develop artificial floating islands with plants like water lilies and other macrophytes that have really long, complex root structures. These roots extend down into the water and provide a huge surface area for beneficial bacteria to grow. These bacteria can facilitate the removal of nitrogen and phosphorus from the water,” she explains. “The plants themselves also can absorb a lot of metals.”

Essentially, she adds, these experimental systems are hydroponics, with plants pulled together into rafts to filter the water circulating around them.

Jackie McLaughlin

Jackie McLaughlin

Brennan, whose own research includes investigating advanced ecological restoration methods for cleaning wastewater, believes natural methods might offer the Chinese a viable solution to pollution in Lake Taihu and beyond. “An ecological system may work for them because it’s decentralized and you don’t need a huge infrastructure,” she says.

Her team found the lake's condition has improved over the past few years. “We evaluated it and agree that it is still in a high state of eutrophication, McLaughlin says,”but their technologies are working to lessen the problem.”

Brennan says the Chinese are keenly interested in continuing their collaboration with Penn State, perhaps having some of her graduate researchers continuing to work on the lake.

Adds McLaughlin, ”They never thought of using ecological systems. There could be hydroponic rafts everywhere.“

Rachel Brennan, Ph.D., is associate professor of civil and environmental engineering at University Park. Jacqueline McLaughlin, Ph.D., is associate professor of biology at Penn State Lehigh Valley. This summer’s research on Lake Taihu was part of the embedded field course Biology 497C, “Global Environmental Sustainability: A Field Study in China,” and the University's “Connecting Humans and Nature through Conservation Experiences” (CHANCE) program.

Last Updated December 14, 2011