In areas with high water tables where connecting to a municipal sanitary sewer is not an option, a recirculating sand filter is one option. While more expensive than the traditional trench system, it treats effluent water from the septic tank to protect the ground water in the area. It requires minimal space and does not require destroying existing landscaping according to the University of Minnesota Extension.
This system requires a traditional septic tank where biological action breaks down organic material flushed into the system. In the traditional system, gravity flow from the tank distributes effluent water to the drainfield in trenches under the lawn. With the recirculating sand filter, the effluent water drains to a concrete tank. A pump forces the water through a series of pipes in a pile of sand where it drains and collects back in the pump tank. The system disperses the treated effluent into a traditional drainfield.
Holding tanks offer a lower initial investment but require greater maintenance costs. They do not treat sewage on-site. It is pumped from the tank for transportation to a sewage treatment facility. Switching to low flow fixtures reduces the maintenance costs associated with the holding tank system.
According to the University of Minnesota Extension estimates from 2000, the 25 year cost of installation and operation of a traditional septic system is $6,300 and a sand filter is $22,000. A holding tank system averages $70,000.