Arizona State University Professor Peter Lammers and researchers at New Mexico State University are developing an energy-positive wastewater treatment method using a special kind of algae, The Guardian reports.
The researchers believe that algal systems ultimately could eliminate sewage farms’ electricity bills, which can account for up to 60 percent of operating costs today, or even generate a surplus.
Called galdieria sulphuraria, the algae grows in a witches brew, can degrade over 50 organic molecules and even photosynthesize like a plant, the researchers say. This makes ideal for use in urban sewage farms.
At a pilot site in Las Cruces, New Mexico, the researchers are working on a way to divert effluent from the city’s wastewater treatment plant into several rows of long plastic bags primed with the algae. Air enriched with carbon dioxide is pumped gently through the tubes, while plastic wing-like foils move slowly up and down to blend the mix, The Guardian reports.
Many cities around the world already have adopted anaerobic digesters, which use bacteria to break down sewage into methane. However, current digesters leave behind a gross residue of nitrogen and phosphorus.
The algae project being piloted in Las Cruces uses sunlight and carbon dioxide to grow, breaking down over 95 percent of the nitrogen and phosphates in a couple of days, according to The Guardian. The high temperatures and acid conditions also help kill bacteria, viruses and parasites, meaning sewage treated like this could require 10 times less chemical disinfectant than usual.
The algae’s photosynthetic growth means the system also creates around four times as much rich organic sludge as traditional sewage treatment, which can then be turned into biofuel oil using processes called hydrothermal liquefaction and catalytic hydrothermal gasification.
The researchers say the Las Cruces pilot is going well and a similar project in Phoenix, Arizona, is planned to commence within a month.
Scaling this up to a city-sized project presents some difficult engineering challenges, The Guardian reports, including handling the acidic wastewater, mixing the solution efficiently, recycling millions of plastic bags and collecting the algae for conversion into biofuel.
Wastewater also has applications for reuse. In Europe, researchers are looking to make plastic packaging from the fermented wastewater of processed juice, which could save the beverage industry millions while tapping into growing consumer demand for eco-friendly products. The PHBOTTLE project focuses on juice-processing wastewater because it contains high concentrations of organic substances, including fermentable sugars such as glucose, fructose and maltose.
Not all recycled wastewater is the most environmentally-friendly. Recently, over 35,600 people signed a Courage Campaign pledge to boycott several popular California produce companies after news that they may be using contaminated oil industry wastewater to grow their crops.