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Conventional Gravity Drainfields:
This type of drainfield is generally a system of trenches in which perforated pipes set underground in a bed of crushed rock that allows the effluent to seep slowly into the ground, undergoing further cleansing. The drainfield may be designed as "trenches" or a "bed". If trenches are used there are usually 2 or more parallel trenches approximately 3 ft. wide. Gravel is placed around the pipe in the trenches and covered by fabric that prevents clogging of the pipe with dirt. Beds are used when space or soil considerations indicate their use instead of a trench system. *
Cross Section of a Conventional Gravity Trench
*The number and length of the trenches or the size of the bed is determined by the number of square feet of drainfield that is specified in the Health Department permit. The requirements are based on a number of factors, some of which are the type of soil, the location of the water table, and the number of bedrooms in the house (which is an indicator of future water usage based on number of residents). Some soils are better suited to septic systems than others. Well aerated soil with good permeability is desired. Clay soil will generally have lower permeability and will require a larger drainfield than a system located in sandy soil.
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Chamber System
*Chamber System:
Chambers can be used to replace stone in the absorption field trenches. The picture above shows the installation of a plastic chamber in a trench. One advantage of the plastic chambers is their lightweight, which allows them to be easily carried to and placed in the trench. This reduces the traffic around the subsurface absorption field, thus reducing the potential for compaction, and also reduces in the number of trees that need to be removed from the field. Infiltrator Systems Inc. is a manufacture of plastic drainage chambers for on-site septic and stormwater management. Sand Filtration Inc. is a dealer for these chamber systems. Chambers have changed the septic and stormwater industries, providing cost-effective methods for handling residential and commercial wastewater. Chambers replace conventional stone and pipe drainfields. *
Shallow Gravelless Trenches
*Shallow Gravelless Drainfields:
are the ideal subsurface disposal method for highly-treated media filter effluent. They are placed in the ground at 12". Because of its exceptionally high quality, the effluent produced by media filters can be absorbed at higher rates than other wastewater and can be discharged to shallow trenches. Pressurized shallow trenches reduce installation costs and minimize site impacts, virtually eliminating the need to remove existing trees and vegetation. Moreover, shallow trenches can be smaller in total area than the gravity drainfield, usually 2/3 the size. This is due to even distribution of high quality effluent. Most importantly, shallow trenches provide additional treatment of (and nutrient removal from) effluent. In fact, our research studies indicate that an additional 50% reduction in total nitrogen occurs in shallow trenches. *
Sub-Surface Drip Irrigation System
*Drip Irrigation:
Is a flexible polyethylene dripline which has flow emitters regularly spaced along the line. With the dripline hidden about six inches below ground, effluent is distributed slowly and uniformly, reducing ponding, even in difficult soils and hilly terrain. The emitters are protected against root intrusion by the ROOTGUARD® patented process, and the dripline wall is protected from biological growth with a bactericide lining. Drip irrigation lines are easily adaptable for projects ranging in size from single family homes to large multi-million gallon per day projects. Geoflow, Inc. is a U.S. licensee for this technology. The Geoflow website is a technical one which aims to enable the potential user to understand the advantages and limitations of subsurface drip irrigation for use in agriculture, turf and landscaping, and wastewater disposal or re-use applications. **
Cross Section of A Mound
*Mounds:
One possible way of overcoming the problems in treating wastewater such as, low permeable soils, shallow permeable soils over a limiting layer, or permeable soils with high water tables, is to construct an elevated soil absorption bed called a mound. Mounds require more care than conventional systems in site selection, design, and construction. This partly is because the soil and site characteristics are marginal, and contractors are apt to be less experienced with mound construction techniques. The proper location and soil preparation are essential for a properly functioning mound. Perdue University has an excellent publication which discusses the construction steps involved in preparing the site for a mound properly, placing the fill, laying and covering the distribution network, and installing the septic tank. Because of their higher cost, mounds are installed only on sites where conventional absorption systems are not suitable. Since mounds usually are constructed on sites with very limiting soil and site conditions, good construction techniques are essential if a mound is to function properly and provide many years of trouble-free operation. **
Reed bed is a stable, engineered ecosystem and is based on complex inter relationships between plants, soils and microorganisms.
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Reed Beds:
Traditional septic systems provide anaerobic (without oxygen) treatment and a small amount of aerobic (with oxygen) treatment. Media Filter systems however provide advanced treatment and a great deal of aerobic treatment. Solids settle out of the sewage in septic tank. Septic tank effluent flows to the Media Filter and is further polished by the reed beds. Reed beds provide both aerobic and anaerobic treatment zones within the soil matrix. This is a highly complex and efficient process whereby the plants transfer oxygen to the subsurface microbes. These microbes use this oxygen to live and to in turn break down harmful bacteria and contaminants. Close to the roots of aquatic plants there are 10 to 100 billion organisms. Approximately 2,000 types of bacteria and some 10,000 types of fungi live in root-permeated soil that is charged with wastewater. Reed beds consists of a PVC lined area that contains all effluent and prevents it from finding its' way to surrounding soils or to the water table until it is completely treated. The effluent at the end of the reed bed is discharged to the ground. Reed Beds, since they are completely lined, can be installed in wet, rocky, dry or sloping sites subject to having a suitable area for discharging treated effluent. **
Wetlands - can uptake nutrients because of plant/insect/microbial action.
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Direct Discharge:
Today many large city and town wastewater systems are aging and must be repaired or replaced. Some still pipe their sewage effluent directly into a watercourse without first treating it. This said, direct discharge only makes sense when it is treated to an acceptable level and when the receiving body of water is the source body of water, or in cases where there is no other reasonable alternative. Our preferred alternative is treating wastewater to an acceptable level first and then further polishing it by some method of outlined above. **
Clifford, Ontario lagoon in background with sand filter
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Lagoons:
Are a type of wastewater treatment system in themselves. Lagoons are built to store and treat wastewater. Wastewater lagoons have been used as a process for wastewater treatment for centuries. In the 1920's artificial ponds were designed and constructed to receive and stabilize wastewater. By 1950, the use of lagoons (ponds) had become recognized as an economical wastewater treatment method for small municipalities and industries. Lagoons can serve as a very effective treatment process although they require considerable land area. Extensive research over the past 40 years has led to a greater understanding of the biological principles behind this natural treatment process. Research has shown us that by carefully configuring the lagoon to take advantage of the biological principles, improved treatment can be obtained. Wastes in sewage are broken down by microorganisms. Oxygen is required for the microorganisms to treat the sewage. Lagoon water should be green because microscopic plants (algae) produce part of the oxygen. Another source of oxygen available to lagoon water occurs at the water surface where oxygen enters from the atmosphere. This exchange is enhanced substantially when the wind is blowing. Wastes are broken down into gases and residual solids which settle to the bottom of the lagoon. Properly sized and maintained lagoons usually have little or no odor. However, during spring and fall turnover in lagoons, odors may be present for a few days. Odors are also likely when the natural biological system is upset. This can be caused by overloading, chemicals entering the system which disrupt the natural processes or extended cloudy weather, especially in spring. Sunlight is essential for algae to produce oxygen, therefore the lagoon surface should not be shaded. Bacteria and other organisms consume oxygen and give off carbon dioxide that is used by algae in their growth. This type of treatment is often used in conjunction with single and multiple pass sand filters. Note: If you are a design Engineer, Sand Filtration Inc. has products to reduce nutrient and algae levels in lagoons. Click Here if you would like to find out more. *Note: Before a permit is issued, on any disposal method, a site evaluation must be performed which identifies these criteria by boring holes at several locations on the lot and examining the soil in these holes. The location of any surface water, such as a lake, and underground water supplies, such as wells, must be identified.
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