Dr. Joe Yelderman, professor of geology at Baylor, and Dr. Margaret Forbes, research associate of biology at Baylor, constructed five different submerged gravel wetlands and tested the contaminant-removal ability of each wetland against different dosing systems, ranging from a continuous dose to a more rapid batch dose coming out of a septic tank. The submerged wetlands rely on the gravel and plants to remove contaminants by mirroring the pollutant removal ability of nature.
“There are a lot of places where it would be nice to build a home, but if you can't put in a septic tank because the soil can't handle a drain field, you can't build a home there unless you have some sort of alternative treatment system,” Yelderman said. “Our goal was to improve the water quality coming out of the septic tank so residents could dispose of the treated wastewater into thinner soil or places where the water table is higher. It would just provide more options to them.”
In Texas, state law requires treated wastewater from a septic tank must be disposed of in the soil, however traditional septic tanks need a certain depth of soil and a certain type of soil to meet environmental standards. Once treated wastewater – known as effluent – leaves a residential septic tank, it flows into what's called a drain field, which is an arrangement of perforated pipes that carry the effluent into the soil. In theory, the soil will further decompose the effluent, making it safer for the environment. However in many areas, the water table is either too high, which means the effluent does not have a chance to fully decompose, or the type of soil can not adequately absorb the effluent, which is the case around much of north and central Texas. The end result produces contaminants like phosphorous and nitrate entering the groundwater.
After several tests on the wetlands to see what dosing system works the best with a specific wetland, the Baylor researchers found that the wetland with gravel and plants performed better, or discharged water that was cleaner, during batch dosing when compared against more continuous dosing. Yelderman said he believes the batch system performed better because of the interaction with the air in between the dosing. When the wetland dried out and was then re-wetted, the gravel and plants oxidized the wastewater better and allowed the aerobic bacteria to better decompose the organic matter. Yelderman said this process actually stressed the plants and they did not grow as large, but they adjusted to the fluctuations and sent their roots deeper.
The results also showed that the wetlands with a certain type of gravel – an expanded shale aggregate – did not perform as well as expected, however it performed as well if not better that just using “regular” gravel. Yelderman said the results also show that the majority of the wetlands significantly reduced Biological Oxygen Demand (BOD) and successfully reduced nutrients like phosphorus and ammonia.
The research was funded by the Texas Onsite Wastewater Treatment Research Council and was completed at the Baylor Wastewater Research Program research site located at the Waco Metropolitan Area Regional Sewerage System.
Matt Pene | Newswise Science News
Dispersal of Fish Eggs by Water Birds – Just a Myth?
19.02.2018 | Universität Basel
Removing fossil fuel subsidies will not reduce CO2 emissions as much as hoped
08.02.2018 | International Institute for Applied Systems Analysis (IIASA)
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...
A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.
The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...
Cardiovascular tissue engineering aims to treat heart disease with prostheses that grow and regenerate. Now, researchers from the University of Zurich, the Technical University Eindhoven and the Charité Berlin have successfully implanted regenerative heart valves, designed with the aid of computer simulations, into sheep for the first time.
Producing living tissue or organs based on human cells is one of the main research fields in regenerative medicine. Tissue engineering, which involves growing...
A team of scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg investigated optically-induced superconductivity in the alkali-doped fulleride K3C60under high external pressures. This study allowed, on one hand, to uniquely assess the nature of the transient state as a superconducting phase. In addition, it unveiled the possibility to induce superconductivity in K3C60 at temperatures far above the -170 degrees Celsius hypothesized previously, and rather all the way to room temperature. The paper by Cantaluppi et al has been published in Nature Physics.
Unlike ordinary metals, superconductors have the unique capability of transporting electrical currents without any loss. Nowadays, their technological...
02.05.2018 | Event News
13.04.2018 | Event News
12.04.2018 | Event News
18.05.2018 | Power and Electrical Engineering
18.05.2018 | Information Technology
18.05.2018 | Information Technology