News Feature | October 17, 2016

Researchers Claim New Process Cuts Electricity At Waste Plants

Sara Jerome

By Sara Jerome,

If necessity is the mother of invention, it makes sense that winery wastewater, and the challenge of treating it, continually produces innovation in the wastewater industry.

One winery in California, for instance, uses earthworms to clean its wastewater, according to The Guardian. The Chilean company BioFiltro enabled the winery to spray wastewater into “giant bins filled with earthworms” for purification, the report said. The winemaker, Fetzer Vineyards, is “the first U.S. winery to use the closed-loop biological wastewater treatment system for all its winery process wastewater,” The North Bay Business Journal reported.

Treatment plants are also looking for better ways to treat winery waste. Scientists at the Fraunhofer Institute, a German research organization focused on applied sciences, recently sought out efficient ways for waste plants to handle effluent from wine-making operations. For such treatment facilities, wine-harvesting season presents difficulties.

“When the grapes are being processed, the effluent load rises steeply — by a factor of 17 in the Palatinate town of Edenkoben, Germany,” according to a statement by the researchers.

“Whereas the load on its wastewater treatment plant doesn't exceed 7,000 person equivalents (PE) on a normal Sunday or public holiday, it can rise to as high as 120,000 PE during the harvest — 17 times as much,” the statement said. Power consumption triples at the treatment plant during harvesting season.

Many small utilities use aerobic stabilization as part of their waste treatment process. It prevents sludge from producing a bad odor, the researchers said. But it also uses a lot of energy.

These scientists say they’ve found an alternative. They call it high-load anaerobic digestion, and they say it provides a more energy-efficient way for the plant to do the job. The process was developed by researchers at the Fraunhofer Institute. One of the lead scientists on the project, Werner Sternad, described the new process.

"We converted the plant to a process based on high-load anaerobic digestion with the help of colleagues from several engineering companies. The new process implemented in Edenkoben has numerous advantages. First, it generates energy instead of merely consuming it. Second, it reduces the quantity of sludge that would otherwise have to be disposed of at great cost," he said.

The benefits of this solution, per the researchers:

  • Energy consumption is 20 percent lower because the process doesn't require a power-hungry aeration system;
  • Of the power actually consumed, 50 percent or more is generated from sewage gas on-site in two cogeneration units. This means that less than half of the electricity the wastewater plant needs is bought in;
  • Sludge disposal: In the past, the sludge had to be dewatered on a daily basis. Anaerobic digestion produces so little sludge that now the filter press runs only twice a week, except during the wine harvest, making it possible to slash costs.

The researchers say their process is ideal for treatment plants that must adapt to a wide variation in the effluent load depending on the season.

"We installed two digestion tanks, which can be operated in parallel during the wine harvest, or in series at other times of the year. This makes it possible to adapt the process flow to the volume of sludge produced and optimize sludge treatment," Sternad said.