Everything flushed down the toilet, or put down the drain in a shower or kitchen, goes to the sanitary wastewater treatment facility. After the raw sewage undergoes an initial screening for grit, sand and other inorganic solids, it enters equalization tanks that keep the system from being overloaded. From the equalization tanks the sewage moves to aeration basins, and those are where the bacteria go to work, or more accurately, to dinner. This stage of sanitary wastewater treatment is called the activated sludge process, a biological treatment that takes place in the aeration basins and depends on the lush growth of aerobic microorganisms. The microorganisms feed on both the dissolved and suspended organic material in the wastewater.
Food sources are present in the form of human waste, food waste and other simple organic material.
Along with the food from the wastes the bacteria need oxygen, supplied as compressed air that also aids in mixing the bacteria with its nourishment. All of this works very well, as long as there is a steady supply of waste and as long as nothing toxic to the bacteria finds its way into the process. Unfortunately for the wastewater treatment facility at the Laboratory, both of those problems exist. About 400,000 gallons of wastewater enter the treatment facility daily, a third of it is clean process water, the rest is sanitary waste. On the weekends, however, the sanitary waste portion of wastewater influent drops to zero, leaving only the clean process water.