Small CommunitiesMany older communities face significant challenges for sewage disposal. Approximately 700 unsewered communities in Indiana have small lots that are poorly suited for on-site systems. Cluster systems transport wastewater via alternative sewers to either a conventional treatment plant or to a pretreatment facility followed by soil absorption of the effluent. Cluster systems can be environmentally sound, finanacially responsible solutions for small community wastewater problems, where conventional central treatment systems are not practical or affordable and where individual on-site systems are inappropriate because of site or soil limitations. Small Community Wastewater Cluster Systems (ID-265) (soon to be available on the Web) answers questions about cluster systems and obtaining funding for community systems.
EPA's Office of Wastewater Management has a Web
site for small communities.
Types of Small Community Systems
|Domestic wastewater must be properly managed to avoid public health problems. Three types of wastewater handling systems can be used in small communities.|
|Your community might need a combination of these systems, such as onsite systems in outlying areas, cluster systems in small residential subdivisions, and centralized systems in more populated or commercial areas.|
Onsite SystemsSeptic systems handle the wastewater from one residence on site. These systems are very common in small communities where homes are not close together. Septic systems consist of a tank that retains the wastewater solids and a drainage field (leachfield) where the tank effluent is distributed. In the leachfield, natural processes purify the liquid as it drains through the soil.
Conventional septic systems work best on large lots with deep, permeable soils. A variety of alternative onsite system designs are available to accommodate a range of difficult site and soil conditions. The most appropriate system depends on factors such as soil permeability, depth to water table, and depth to limiting layer.
Poorly sited, designed, installed, or maintained septic systems can result in surface ponding in yards. Surface ponding that continues for an extensive period is considered a health hazard and requires corrective action. Because maintenance is the only factor that can be controlled once an onsite system is installed, a program of periodic inspection and/or pumping is advisable. This approach, combined with public education to ensure that owners are putting only appropriate materials down the drain, is the easiest to implement. Repairs and replacements should always be done by professionals with the approval of local or state authorities, since exposure to inadequately treated sewage and hydrogen sulfide gas presents a health risk.
Although individuals usually own septic systems, a community can take a variety of steps to maintain effective systems, including:
Cluster SystemsIn some neighborhoods individual onsite systems are inappropriate, either because lots are too small or because other land characteristics make them impractical. In this situation, a cluster system might be appropriate. A cluster system normally uses low-cost alternative sewers to collect wastewater from homes in the area and transport it to a reliable, low-cost, easily operated treatment/disposal facility. This type of system can be suitable for developments or neighborhoods of up to 100 homes but is often used for smaller groupings.
Several types of alternative sewer systems can be used to collect and transport wastewater from residences to the treatment facility. The treatment facility is usually a larger version of an individual onsite system, such as subsurface soil absorption systems or sand filters.
As with any treatment system, a maintenance program is essential to
ensure proper operation of a cluster system. Compared with conventional
collection and treatment systems, cluster systems require minimal maintenance.
The maintenance program, however, should always be in place and clearly
spelled out to homeowners who use the cluster system.
Centralized SystemsIn more densely settled areas, where multiple cluster systems are needed and onsite systems are not practical, a centralized wastewater system might be necessary. Constructing conventional sewers to collect the wastewater, however, is almost never practical for small communities because of the high cost. Conventional sewers usually account for over three-quarters of the total cost of a conventional wastewater collection and treatment system. The high cost of constructing the sewer system might be acceptable on a per-household basis, however, if no lift stations are required, but alternative designs are almost always cheaper under the same circumstances. Alternative sewers--small-diameter gravity, pressure, and vacuum sewers--can save 25 to 50 percent of the capital cost of wastewater collection in small communities.
Many types of technologies are available for treating wastewater at
a centralized plant. Natural treatment technologies use natural processes
associated with soils, vegetation, or wetland environments to treat wastewater
and include land treatment, lagoons, slow sand filters, and constructed
wetlands. These systems generally require larger land areas than mechanical
systems. Wastewater must be treated (usually by sedimentation or lagoons)
before application to land, filters, or wetlands.
Information above is an excerpt from the following publication:
Planning for Small Communities, A Guide for Local Decision-Makers,
EPA/625/R-94/009, September 1994, United States Environmental Protection
Agency, Office of Research and Development, Office of Science, Planning
and Regulatory Evaluation, Center for Environmental Research Information,
26 West Martin Luther King Drive, Cincinnati, Ohio 45268, Office Of Regional
Operations and State/Local Relations, Washington, DC 20460
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