|The Evolution of Septic Systems in the US|
Because of the subject matter, sewage treatment in the United
States has always been an un-popular topic of conversation. Consequently many
people are ignorant of the need for and the mechanics of this process. The
resulting health, environmental, property and financial damages is incalculable.
Lakes, rivers, streams, wetland habitat and oceans have suffered. Homes and entire neighborhoods have been rendered worthless and unlivable. More than 1,200 Americans die every year from waterborne diseases and failing septic systems are the number one source of these outbreaks. Although this situation is now being addressed in most areas of the country, if this educational process were implemented 30 years ago a lot of needless damage could have been avoided.
Prior to WWll, the bulk of the population lived in the cities close to the work place. The city dealt with the wastewater generated by people and businesses. With the economic boom generated by WWll, the late 1940ís saw a tremendous exodus from the cities into the un-developed rural areas surrounding the cities.
Because of the rapid growth rate, sewage treatment facilities could not keep pace and these new communities were facing a major "what to do with the poop" dilemma. Eventually it was decided these new homes would temporarily utilize low-tech cesspools and in 5-7 years the high-tech marvels of modern science would be available to these homeowners that were lucky enough to live in a free democracy. You see, the cold war was not just fought with weapons of mass destruction.
However, by the mid 1960ís these communities were facing another dilemma. The expansion of sewage treatment facilities was far behind schedule and many of these cesspools were beginning to fail. In fact, many of them had failed 2 or 3 times and the trend in the suburbs was to put homes on small lots so more tax payers (homes) would fit in an area. The problem was, these small lots left no room for a replacement. The result was, in many neighborhoods, the backyards were turning into sewage swamps.
At this point many people began to realize that the smarter solution would be to improve what was currently available rather than waiting for the treatment facilities to catch-up. Much of the research was conducted by the Universities of Minnesota and Wisconsin in the north central area of the country where lakes are extremely prevalent and sport fishing/water recreation contributes to a large part of the local economy through tourism. Many of these lakes were experiencing a noticeable drop in water quality. If the quality of lakes were allowed to continue to degrade, many tourists would look for other areas to spend their vacations.
One of the first problems was cesspools provided very little in the way of treatment. The common cesspool was a pit dug in the yard and rocks or bricks without mortar were used to shore up the sidewalls, the whole affair would then have some sort of top put in place and covered with topsoil.
As wastewater was flushed down the drain it would enter the "pit" where it would migrate down through the bottom and through the sides. The thought process at that time was to dig the pit deep to avoid the sewage surfacing on the property. However, many of these disposal systems were nothing more than a direct conduit to the underground water supplies. (see figure 1)
Of course these cesspools were also prone to failure as the inside of the cesspool would become sealed with fats, oils, lint, grease, feces, etc. When this happened the sewage would come to the surface where it would find itís way into surface waters, open wells and contact with people and animals. (see figure2)
It was known however that certain types of soils were excellent mechanical filters for removal of solids but as information was gathered and theories explored it was found the naturally occurring bacteria in soils performed another valuable service, they consumed the parasites and viruses present in excrement. This, along with electrostatic processes that took place [in soils] were found to be an excellent method of purifying wastewater.
There were of course limitations to this process, the contaminated effluent had to pass through a minimum of 2 feet of dry soil. Dry soils contained oxygen which supported aerobic bacterial colonies. Aerobic bacteria were found to be approximately 20 times more effective than anaerobic bacteria that existed in saturated soils.
It was also found the best zone of treatment took place in top 26 inches of soil where oxygen levels were high. The deeper in the soil the less effective the treatment process was. Below a depth of 6 feet the treatment process was significantly hindered.
Another limitation was the permeable rates of soils. Highly plasticized clay had the obvious problem of not allowing the migration of effluent at a suitable rate. Course soils presented the opposite problem. The treatment process required a certain amount of retention time and loose soils did not allow adequate time for the processes to take place. In time, design methods were found to alleviate these problems such as bringing the proper soils to the site.
By the 1970ís the typical design of a modern septic system was comprised of a sealed tank for settling and storage of solids and a shallow trench system for treatment and dispersal of liquid. (see figure 3)
The most popular tanks were usually constructed of reinforced concrete in sizes of 500, 750, 1,000, 1,250 or 1,500 gallons. Tanks were also manufactured in steel and fiberglass or plastic composites.
The septic tank is the first step of the wastewater treatment process. All tanks (should) have inlet and outlet baffles, inspection pipes, and a manhole for cleaning.
The inlet baffle forces wastewater entering the tank to slow and allow the separation of solids, the heavier solids sink to the bottom forming the sludge layer, the lighter solids float to the surface forming the scum layer, the layer in the middle is a relatively clear layer called effluent. In the tank the bacterial breakdown of organic materials begins. The inlet baffle also prevents the floating scum layer from floating back and clogging the inlet pipe.
The outlet baffle prevents scum from leaving the tank. If the scum layer reaches the outlet pipe, the pipe will become plugged. Scum in the drainfield will clog soil pores and destroy its ability to treat wastewater.
Inspection pipes of 4- or 6-inch PVC (plastic) material should be located above the inlet and outlet baffles to allow for inspection of pipes and baffles. Clogs in the inlet or outlet pipes can be unplugged through the inspection pipes. When operating properly, the septic tank is always "full' to the level of the bottom of the outlet pipe. Some installations may have two tanks in a row or one large tank with two compartments.
The manhole in the cover of the septic tank is a large entrance (20"-24") through which the tank should be cleaned. The manhole is often buried below ground level. It may be raised from the cover of the tank with concrete or plastic rings for easier access. It is usually located in the center of the tank; however, some manufacturers locate it closer to the inlet end of the tank. There may be more than one manhole, in which case they are usually located at the ends of the tank.
A typical drainfield is a trench or series of trenches approximately 3 feet wide and 3 feet deep. Two feet of gravel are poured into the trench, 4 inch plastic pipe with Ĺ inch holes is placed on top of the gravel, 6 more inches of gravel is placed over the pipe and covered with a geo-tech fiber to prevent soil from migrating down and clogging the gravel. Top soil is then used to cover the trenches with a slight crown to encourage rain run-off.
As the effluent travels through this distribution pipe, gravity draws it through the gravel-bed where the large openings between the pieces of gravel create an excellent environment for naturally occurring aerobic bacteria that begin consuming the disease-causing pathogens. The drainfield also acts as a reservoir. At the interface of the trench sidewalls and bottom, a biomat of dead and living bacteria forms and slows the rate at which the effluent drains from the field.
The remaining pathogens are removed in the 2-3 feet of soil surrounding the drainfield. A portion of the nitrogen and phosphates are wicked-up by the plant life covering the field and the remaining nitrogen is changed to a gas form and/or diluted. Approximately 30% of the liquid is returned to the atmosphere through evaporation.
In America, each of the 50 states has the ability to establish their own code requirements as to what they consider adequate standards per sewage treatment. Naturally some parts of the country are more advanced than others and in some areas, the regulations have been relaxed to encourage development (tax dollars) even though it is known the sewage is being inadequately treated.
Many contractors that design and install systems learned their trade from their fathers, who learned it from their fathers. Years ago the purpose of on-site systems was to dispose of waste water, not treat it. Many contractors still adhere to this theory. At the same time, many inspectors, by their own admission, are not trained to inspect on-site systems for defective installations. A fair number of systems, because of faulty designs, will fail with-in 3-5 years of use.
Homeowners are never given any information on the proper way to use a septic system. Even people that have had their systems replaced multiple times are seldom provided information (by the contractor) to prevent future problems or are provided errant information by the contractor and friends.
Even the purpose of on-site treatment systems has never been explained. Many homeowners are under the impression that septic systems are a temporary solution as the city sewer is only a few years away and therefore have no incentive to [long term] protect them.
Most homeowners are not aware of the damages from failing septic systems because septic systems are not sexy environmental news stories. Often they are passed over by the news agencies in favor of high impact news. Subsequently, homeowners feel their failed system is only an inconvenience to them.
By providing education at each level, these problems are significantly reduced. When contractors are required to go through a training program and certification process, there is a better chance that the systems being installed will be proper systems.
If the regulators that inspect these systems are also required to participate in this certification process, they will be much more qualified to catch and correct any errors before they pose problems for the homeowners. By providing education [to the homeowners that operate those systems] on how to properly use those systems, failure rates drop significantly.
CONTRACTOR TRAINING AND CERTIFICATION CLASSES
These one, two or three day seminars are performed by Dave Gustafson of the University of Minnesota Extension Service in association with the NAWT (National Association of Waste Transporters). These seminars/certification classes have been performed as both voluntary and mandatory process for contractors in several states. To learn more about this program contact: Dave Gustafson
311 Bio Systems Ag Engineering
1390 Eckles Avenue
St Paul, MN 55108
Providing homeowners with clear and accurate information on the proper operation of a septic system (and denouncing the many myths and misconceptions that are so prevalent with on-site waste water treatment systems) these damages are dramatically reduced without cost to the city, county or state.
The reason is simple, when a homeowner learns they may be drinking today what they had for dinner last night, they more often than not will replace their failing system on their own. Zoning officials have noticed a rush for up-grade permits following these classes. When they learn how to use them, they donít fail.
These nation-wide classes have been performed by James vonMeier as a pilot program for the University of Minnesota Extension Service. Contact:
14622 268th Avenue
Zimmerman, Minnesota 55398
1-763-856-3800 Fax 1-763-856-3888 www.septicprotector.com
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