This category of wastewater treatment systems includes many types of alternative treatment technologies designed to treat all of the liquid waste generated from a residence. The system is installed much like a traditional septic tank, commonly having a treatment tank similar in size. The primary difference from a septic tank is the internal design and associated mechanical and electrical components that enhance treatment.

In many respects, these systems are like miniature municipal treatment plants designed for a single family rather than an entire city or community. The unique design and components used in these systems accelerate the treatment process through the creation of an optimum environment for microorganisms that digest the waste, and for collection and storage of the resulting byproducts. The effluent generated by the tank is far superior in its treatment level to that of a septic tank, which allows for greater flexibility in disposing of the treated effluent.

Rather than being sent to a traditional drain field, as is needed with a typical septic tank in order to provide additional treatment of the waste, the treated effluent from an alternative system may be used for surface irrigation, discharged to a smaller drain field, or discharged directly to a drainage ditch or open waterway. If the treated effluent is discharged directly to the surface, most systems will include a disinfection device to reduce the microorganisms present in the treated effluent. This provides for additional measures of public health protection.