 own homes in suburban areas, but while there are many benefits that go along with suburban living, some communities face serious problems. This neighborhood is experiencing the results of inadequate onsite wastewater treatment. The soils on their properties are unsuitable, or the groundwater table is too high for their septic tank systems to provide sufficient treatment. When this occurs throughout a neighborhood or a community, a typical solution is to rebuild conventional gravity sewers that lead to a centrally located treatment plant. This solves the wastewater treatment problem, but construction can be disrupted and unaffordable. So what are the community's alternatives? An alternative for some communities is the small diameter effluent sewer, which collects the effluent that comes out of the septic tank at each house. The small diameter effluent sewer is especially well suited for a suburban neighborhood like this one, where the houses are relatively far apart and the terrain is not too hilly. The effluent sewer is also good in a growing community because it can be tied to an existing sewer system, as long as the existing system has enough capacity. Here's the main line for the effluent sewer. Not only is the effluent sewer less disruptive to construct, it also costs less. While the cost of collection systems varies according to site conditions, in Muskingum County, Ohio, an effluent sewer costs about $5,000 per house to construct. A conventional gravity sewer would have cost about $8,000 per house. Why are these systems so different? Why does the effluent sewer cost so much less? Let's take a closer look. The conventional sewer system carries the raw sewage from your house into the main sewer in the street. These pipes must slope downhill. Roughly every 400 feet, a manhole is needed. When the main goes too deep, a pumping station is needed to lift the sewage nearer the ground surface. Eventually, it arrives at the sewage treatment plant. The basic elements of this system are sewer pipes, manholes, lift stations, and the treatment plant. First, let's look at the pipes and the manholes. The pipes must be at least 8 inches in diameter, so they won't clog. They also have to slope downward, so that the solids can keep moving. This means wide and deep excavation, which is the most costly part of sewer construction. Manholes are necessary for cleaning the sewers. Because the pipes must go deep, it's often necessary to lift the sewage with pumps. This is a typical lift station, which can give off an unpleasant odor. Such stations are also troublesome and expensive to operate and maintain. Eventually, the sewage ends up at the treatment plant, where it is partially treated. Now let's look at the effluent sewer system. It carries the raw sewage from your house through a short pipe into a septic tank. The effluent flowing out of the tank enters an effluent sewer main, which leads to a treatment plant. Lifts are not required. Simpler cleanouts are used instead. So the basic elements of the effluent sewer are septic tanks, sewer pipes, and treatment plant. Lift stations are sometimes needed, but there will be fewer of them. There are two types of effluent sewer systems, variable grade and minimum grade. The septic tank removes more than 75% of sewage solids and nearly all grease. Some solids sink to the sludge layer, while grease and other solids float to the scum layer. In time, most of the solids decompose in the septic tank. Here's a typical 1,000 gallon septic tank. Most of the septic tanks will have to be replaced with tanks that do not leak, so that the effluent sewer will not collect groundwater. Because most solids and grease stay in the septic tank, there is little danger of clogging in effluent sewers. This means that they can have small diameters and even flow uphill in some places. The effluent from the septic tank enters the effluent sewer. The overall flow must be downhill. The other type of effluent sewer is the minimum grade effluent sewer, shown in red. The minimum grade effluent sewer is more expensive than the variable grade because it never slopes uphill. Therefore, the minimum grade effluent sewer requires more excavation. Dr. James S. Gidley of the Department of Civil Engineering at West Virginia University demonstrates the operation of the effluent sewer. The blue water represents effluent continuously flowing through the sewer. This yellow water represents effluent from a single septic tank. The effluent doesn't back up into the septic tank, and it passes through the low point and beyond. If a septic tank is below the sewer, its effluent can be discharged into the sewer by a small pump. An effluent pump like this one costs only about 60 cents a month to operate. The septic tank effluent contains hydrogen sulfide. This gas has a rotten egg odor and can also corrode sewers. It can be absorbed in specially designed, low-cost soil beds. Corrosion is avoided by using corrosion resistant materials like PVC pipe throughout the effluent sewer system. On the other hand, since effluent is already partially treated in the septic tanks, the central treatment plant can be simpler. For example, septic tank effluent can be treated in a relatively simple plant like this intermittent sand filter plant. Effluent can also be treated by conventional treatment processes like this oxidation ditch. The effluent sewers can also connect with conventional sewers, leading to municipal or regional treatment plants if there is enough extra capacity in the existing sewers and at the plant. Careful design can prevent corrosion in these sewers. Now let's compare the conventional gravity sewer with the effluent sewer. The conventional sewer uses sewer pipes, manholes, lift stations, and a treatment plant. The effluent sewer, however, uses septic tanks and smaller sewer pipes placed in shallower trenches and a treatment plant that is simpler if it is built for the effluent sewer alone. Once a sewer system is in place, it must be maintained to assure proper operation. Effluent sewers differ from conventional sewers in their operation and maintenance. To keep conventional sewers from clogging, they should be cleaned every one to two years. This is a conventional sewer being cleaned. Lift stations have to be inspected frequently and cleaned several times a year. Even a small conventional sewage treatment plant can be fairly sophisticated and require several qualified full-time personnel to operate. A conventional treatment plant generates about 55 pounds of dry solids per person per year. These solids are contained in sludge and must be properly disposed of. In the effluent sewer system, most of the solids decompose in the septic tank. The tank must be pumped out once every three to five years. Most of this liquid, called septage, is applied directly to the land where the nutrients are recycled. The septage contains solids which amount to about 20 pounds per person per year. Effluent sewers carry less solid material, so they may not need flushing. However, in Australia, where effluent sewers have been operated for over 30 years, annual flushing is recommended, though rarely practiced. The high cost of sewage collection and disposal is a problem that must be solved. Small diameter effluent sewers are a proven solution. In some cases, they may cost less than half to build in conventional sewers. Also costs less to operate and maintain. Effluent sewers are an alternative you should consider. They are used extensively across the United States, and they may be the best solution for your community.