Wastewater treatment system produces energy and usable water

While methods have already been developed to use the bacteria from wastewater to produce energy, such methods typically do so at the expense of the water itself, which could otherwise be filtered and used for 'grey water' purposes such as irrigation and toilet flushing.

The new system is set up like a typical microbial fuel cell, a bacterial battery that uses electrochemically active bacteria as a catalyst where a traditional fuel cell would use platinum.

In this type of system, the bacteria are attached to the electrode. When wastewater is pumped into the anode, the bacteria 'eat' the organic materials and release electrons, creating electricity.

The anode is a dynamic membrane, made of conductive carbon cloth. Together, the bacteria and membrane filter out 80 to 90 per cent of organic materials leaving water clean enough to be released into nature or further treated for non-potable water uses.

Lead researcher professor Zhen He said that the waste materials in wastewater are full of organic materials and can be used as food by bacteria and converted into things we can use.

“Biogas is the primary source of energy we can recover from wastewater; the other is bioelectricity,” he added.

While the amount of electricity created is not enough for major applications, such as powering a city, it could help to offset the substantial amount of energy used in a typical US water treatment plant.

“In the US, about 3 to 5 per cent of electricity is used for water and wastewater activity,” He said. Considering the usage by a local municipal plant, He believes his system can reduce energy consumption significantly.

“Typically, the process consumes about 0.5 KWH of electricity per cubic meter,” He said. Based on bench scale experiments, “We can reduce it by half or more of that.”

However, the primary goal of the system isn’t electricity production; rather, it’s about wastewater treatment and nutrient recovery.

“We can also recover nutrients like nitrogen or phosphorus for fertiliser. We can use it to feed plants. It’s only when we don’t use it, then it becomes waste,” He said. “Wastewater is a resource in the wrong location.”

Last month, another team from Hong Kong proposed a new technique for collecting microplastics from wastewater, allowing them to be removed from the environment for recycling.