Decentralize Wastewater Treatment and Disposal

CUD provides sewer services to many of it’s outlying customers through an innovative system known as Decentralized Wastewater Treatment and Disposal. The system allows for high density development (Subdivisions) in areas of the county where City sewer is not available or soil types are not conducive to conventional septic tank and drain field lines. Often referred to as the “STEP” system (an acronym for Septic Tank Effluent Pumped), CUD’s Decentralized Systems consist of five major components. The modified septic tank or “STEP” tank is a 1500 gallon septic tank is equipped with a pump and control panel located at each residence for controlled discharge of wastewater to the second component which is the wastewater collection system.

This wastewater collection system consists of water tight pipes that connects each residence to a main that conveys the wastewater to a treatment unit known as a Recirculating Sand Filter. This biological treatment process, the third component of the system, produces a high quality water for final disposal. Prior to disposal, treated wastewater is disinfected using Ultaviolet Light. This fourth component is used to kill disease causing bacteria. The fifth and final component of the system is the Drip irrigation field. Treated wastewater, called “Effluent”, is pumped under ground through a series of small pipes approximately seven inches below ground where the above vegetation root system absorbs the water and remaining nutrients.

In 2000, the first decentralized wastewater system was built in Rutherford County. While the technology was not new, it was to CUD and Rutherford County. There was and is no doubt as to the effectiveness of the treatment by sand filters for wastewater. The efficiency is well documented. The most critical part of decentralized wastewater is the soil. The soils must have the ability to let water move through the soils in an efficient manner.  Many of the soils in Rutherford County are high in clay content.  We strive to protect the soils in the drip fields at all cost.  Mowing or cutting is not allowed when the drip fields are wet.  We have not permitted the soils area to be used for recreation because we are concerned about compaction and the possibility of destroying the percolation of water through the soil.  If the percolation of the soils is destroyed, then the wastewater system will fail.