Septic System

Imhoff System

The Imhoff two-chamber septic system, named for German engineer Karl Imhoff, was developed about 20 years later. The Imhoff system is the same basic design of systems used in the early 21st century. Wastewater is pumped into a tank. The solids, which are heavier, fall to the bottom of the tank. What is left is wastewater that includes gases, grease, and other waste products. The gases in the wastewater naturally break down the solids and other materials in the wastewater and purify it as it goes through the system. Through the two-chamber system, this process happens more efficiently, allowing more clarified water to move through the system and not be continually mixed with new blackwater. Water is released after receiving this primary treatment to filter into leach fields, where it is treated through natural processes of filtration through the soil. The Imhoff system functions optimally with a flow-through of about 1,000–2,000 gallons per day. This means that the system works adequately for a modern U.S. household of two to three people. Various amendments have been made to the Imhoff system, in part to increase capacity, but the basic design elements remain the same.

Use

Septic systems are among the most important systems for treating waste at the individual household or cluster household level. According to the Environmental Protection Agency (EPA), the 2007 U.S. Census Housing Survey estimates that approximately 20 percent of U.S. households use septic systems for wastewater treatment. In addition, some 22 percent of newly constructed houses had septic systems. Septic systems have been applied around the world in places where centralized wastewater is not available. As smaller communities have struggled with the cost of bringing centralized wastewater treatment online, there has been increased attention to decentralized wastewater treatment options. Because of technology's reliability and widespread usage, septic systems are frequently included in decentralized management plans.

Criticisms

While many consider septic systems among the most efficient systems for water-based sanitation, there are also critics of this technology as a means of treating human waste. These critics include those who are concerned about the inappropriateness of the technology for particular environmental conditions, potential mismanagement of systems, and the cost of proper installation and management, along with those who propose technologies that better incorporate human waste into the ecological system (called “biosanitatation,” such as composting toilets or wetland treatment systems). Septic systems [Page 798]may be incorporated into some alternative wastewater management programs.

Concerns about the appropriateness of the technology for particular environmental conditions vary. Septic system technology is dependent on having the correct soil type for filtration of wastewater once it is released from the tanks into the leach field. Soils that have too much clay may be insufficiently permeable, leaving wastewater bubbling to the surface, creating a health hazard both through potential direct contact or runoff into adjacent surface water.

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