An advancement in sewage treatment technology may effectively convert residual sludge to biogas, reducing waste treatment expenses while also benefiting the environment.
A Washington State University study team evaluated a pretreatment system, adding an additional step to standard treatments and employing oxygen-containing high-pressure steam to break down sewage sludge, as reported in the journal Waste Management. They discovered that they could convert more than 85% of the organic material into biogas, which can then be converted to renewable natural gas (RNG) for the local or natural gas grid.
As a result of the new pretreatment step, the wastewater treatment facility’s anaerobic conversion of sewage sludge increased from its previous rate of less than 50% to 98%, and total methane production increased.
Birgitte Ahring, professor at the Gene and Linda Voiland School of Chemical Engineering and Bioengineering, who led the experiment, said, “It was proved to be incredibly efficient, and that’s quite exciting.” “This may be relevant, and in Washington State, we could start exploring it. There are several benefits to not wasting garbage and instead using its potential.”
Sludge from sewage systems is not a popular product. Anaerobic digestion, which uses bacteria to break down the waste, is used by about half of the wastewater treatment facilities in the U.S. but is ineffective. Biosolids, the residual sludge, are often disposed of in landfills. Large quantities of power are also used by wastewater treatment plants to clean up municipal effluent. They often use the most power in a small town.
“They could consume fewer fossil fuels if they could produce their electricity or, for some of the larger facilities, renewable natural gas and contribute it to the natural gas grid. Here, we’re starting to discuss the concept of the circular economy “said Ahring, a faculty member at WSU Tri-cities’ Bioproducts, Sciences and Engineering Laboratory.
Before the anaerobic digestion procedure, the WSU research team processed the sludge at high pressure and temperature for the study. The material’s polymers are broken down by the little quantity of oxygen acting as a catalyst in the high-pressure environment. For many years, WSU researchers have been analysing this pretreatment procedure while utilising it to disintegrate straw and other woody materials. They were pleasantly delighted since they weren’t sure the technique would work given the differing protein and lipid makeup of sewage sludge.
Ahring said, “This is not a very high-tech answer. “It’s a solution that works well even on a small scale. If the efficiency is low, adding the additional expenditures to the process is not justifiable.”
Smaller towns, many of whom are determined to decrease trash and its climate effect, may find the technology to be very useful. The WSU team is collaborating with Pacific Northwest National Laboratory (PNNL), which is doing a techno-economic study of the novel method, as well as Clean-Vantage, a Richland-based clean technology start-up firm operating in the pretreatment field.
In order to better illustrate the procedure, the researchers are now scaling up the work in a pilot facility at WSU Tri-cities. Additionally, they are researching a novel bioprocess to effectively transform biogas into more valuable renewable natural gas. The production of renewable natural gas might enable rural towns to manufacture local transportation fuel for their municipal cars, even though the biogas can be utilised to generate power.
