The use of septic tanks to treat wastewater goes back to the middle of the nineteenth century. Frenchman J .L. Mouras first made a masonry tank to receive wastewater from a home in the town ofVesoul, France. After twelve years of operation, the tank was found to have only a small amount of solids in it. Mouras had expected that the tank would be very full, so he concluded that some process must be taking place that reduced the volume of solids. He and A. Moigno, a priest and scientist, experimented with the tank to learn more about processes taking place in the tank. Mouras patented the tank in 1881.
Use of septic tanks in the United States began about 1883 in Boston, Massachusetts. There, Edward S. Philbrick designed a two-chamber, round, verticalcylindrical tank with a dosing siphon.
Although these early developments showed promise, on-site wastewater disposal remained at a crude level well into the twentieth century in both Europe and the US. During the early part of this century, city-dwellers were served by large central collection systems and had no need for on-site wastewater disposal. Rural dwellers relied on privies and other simple waste disposal means because few farms had indoor plumbing.
Since the first quarter of this century, most development work on improving onsite systems has been done in the US. By the middle of the 1920s, Henry Ryon of the New York State Department of Health began to study methods to improve onsite system performance. He realized that the most critical part of the system is the treatment and disposal field. To help ensure adequate soil absorption, he developed the percolation test. This test has been widely used to help determine the level of soil absorption possible for an on-site system, although it has been more recently shown to provide inconsistent and unrealistic information.
The next big effort to improve on-site wastewater management occurred in the late 1940s. Until that time, only the percolation test and a few guidelines were used to determine soil and site suitability for on-site system installation. Rural electrification gave farm families indoor plumbing and the opportunity to install on-site wastewater disposal systems. Soldiers returning from World War II spawned a housing boom in suburban areas where on-site systems were the only choice for wastewater disposal. However, because of the lack of knowledge of onsite system operation, failures were common. The explosion in housing growth and the growing threat to public health brought about the first study of on-site systems by the US Public Health Service in 1946.
Since that landmark study, many studies have been conducted on conventional, modified conventional, alternative, innovative, and experimental on-site systems. The research has pointed out that the most critical part of the conventional on-site system is the treatment and disposal field. We now have better ways to determine the suitability of a site for an on-site system, and we know more about improving the performance of on-site systems. The next section presents some of the findings from the research done on on-site systems.
From the North Carolina Onsite Guidance Manual