New Zealand’s first bioreactor sets example for United States

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In 2012, construction of the world’s first bioreactor was completed along the Waikato River in New Zealand.

The purpose of the bioreactor is to mitigate the environmental impact of the Wairakei Power Station that is situated on the river. The success of this bioreactor has made it a potential model for similar technology to be produced in the United States.

The Wairakei Power Station is a geothermal power station located in the North Island of New Zealand. The station is situated on the Waikato River, so it can utilize the river water to cool the geothermal fluid that is extracted in order to generate electricity. However, after usage in the cooling process, pollutants from the plant are introduced into the water. Releasing the polluted fluid back into the Waikato River is damaging to the natural river ecosystem, especially as a threat to local biodiversity.

In an effort to reverse the detrimental environmental impact of the plant, the Wairakei bioreactor was conceived. The bioreactor is made up of 378 km of underground pipes that house bacteria on their internal surface area.

These bacteria are sulphur-oxidising, meaning they reduce the amount of the harmful hydrogen sulfide in the cooling water by consuming the pollutant. Huge amounts of water are pumped into these pipes at a rate of 13,000 liters per second, and the bacteria, which are native to the local river environment, are able to remove up to 80 percent of the pollutant.

The United States also faces water pollution difficulties. The issue is prevalent in the highly agricultural Midwest due to runoff polluted with harmful chemicals and other nutrients from fertilizer usage.

Otherwise known as the Corn Belt, the Midwest is also home to an underground network of pipes known as tile drainage networks. Any excess water is channeled into these networks, so it can be transported to nearby streams, lakes or rivers. While these networks are useful for preventing farmers’ fields from becoming waterlogged, they also have a hugely negative impact on water quality.

The networks are vehicles for bringing runoff that is polluted with nitrogen from over-fertilization to local bodies of water. Excessive levels of nitrogen fertilizer lead to algae blooms. When the algae die and bacteria decompose them, water becomes deoxygenated as bacteria use the oxygen for fuel. As a result, bodies of water become unsustainable for life; these areas are known as dead zones.

Professor Laura Christianson of the University of Illinois is currently researching solutions to reduce nitrogen pollution using the Wairakei bioreactor as a model.

Christianson’s work is focused on woodchip bioreactors, which are trench structures meant to remove pollutant from water before it enters tile drain networks. Christianson’s idea would research the process of denitrification, wherein bacteria found in soil convert the nitrate pollutant into nitrogen gas, which is environmentally friendly as the gas comprises approximately three-fourths of the atmosphere. Thus far, wood chips have been shown to be an effective construction material for the bioreactor; however, researchers like Christianson are looking into other possible solutions.

One possible alternative is corn cobs. Research studies have shown that agricultural residues like the corn cob provide a higher rate of nitrate removal than wood chips.

Research is also being conducting into possibly expanding the scope of the bioreactor’s uses. The bioreactor could prove useful and low-cost option for treating water in fish farms. Reportedly, New Zealand researchers have shown that denitrifying bioreactors could be a viable option for treating municipal wastewater, which would remove harmful contaminants like E. coli and other bacteria and viruses.

Overall, the Wairakei Power Plant’s bioreactor has proven to be a useful model in showing how local microorganisms could provide a multi-use option for saving their local environment.

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