NMSU environmental engineers examine new method for wastewater treatment, reuse

[USA] A team of New Mexico State University graduate students and Environmental Engineering professors Nirmala Khandan and Pei Xu are developing a novel water treatment process that could render municipal wastewater into drinking water and at the same time produce algal biomass for biofuel and fertilizer.

They have a pilot-scale research project at the Jacob A. Hands Wastewater Treatment Facility in Las Cruces to develop this technology. Using a method created by Khandan, wastewater goes into two 2,000-liter bioreactors that use algae to convert carbon, nitrogen and phosphorous into biological material that once water is removed, can be used for biofuel and also fertilizer.

New Mexico State University Environmental Engineering Professor Pei Xu is leading a pilot-scale research project at the Jacob A. Hands Wastewater Treatment Facility in Las Cruces to develop a treatment process for reuse of wastewater. (Photo: Vladimir Avina/NMSU)

The algal effluent flows into an NMSU pilot-scale research facility at the plant for a new treatment process that combines both forward and reverse osmosis to separate water from algal biomass.

“Forward osmosis is an emerging treatment technology that is unique because it does not use pressure to separate the algae from the water, as in reverse osmosis,” said Xu. Forward osmosis is a natural process that draws the water through a semipermeable membrane that removes contaminants.

“On one side of the membrane we have the algal effluent which has a low salinity. On the other side of the membrane we have salty water, which naturally draws the water through the membrane by osmotic pressure gradient,” explained Xu.

The water drawn through the membrane dilutes the salty water on the other side. That water is then treated by reverse osmosis, which uses pressure to push the water through the membrane, resulting in clean, potable water. The re-concentrated saline solution is returned to continue removing fresh water from the algal effluent.

“We use forward osmosis as a pretreatment because the membrane has a lower fouling potential, where organic matter, bacteria and algae are deposited on the surface of the membrane and degrade performance of the membrane,” said Xu.

 

Photo: From left: New Mexico State University Environmental Engineering Professor Pei Xu, Program Specialist David Johnson, Ph.D. student Chathurika Bandara and Postdoctoral Researcher Xuesong Xu are monitoring the treatment process they developed to render municipal wastewater into drinking water. (Photo: Vladimir Avina/NMSU)

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