Alternative Septic Systems

Sometimes standard septic systems may not work properly especially if water has surfaced in the backyard. If a septic system had been built along a hillside that had been graded and then backfilled with topsoil. This may cause problems because fill is generally less permeable than the original soil and it is likely that the previously installed trenches were too small to accommodate the load of household wastewater. Water may seep up to the ground surface, particularly in the winter months.

Because the treatment trenches at the valley site were failing to accept household sewage, the home-owners needed a system that would significantly reduce the pathogens present in the sewage before the sewage was discharged to the drainfield. At this location, either an aerobic tank or a recirculating sand filter (RSF) system would be appropriate. Experimental studies have shown that an RSF is very effective at treating wastewater. The treated effluent is dispersed from the sand filter through a drainfield trench system.

An RSF was installed into the existing system between the septic tank and the drainfield. Wastewater moves from the house into a septic tank where solids settle out and some of the organic matter decomposes.
Liquid effluent then moves to the recirculation tank and from there to the sand filter. The effluent is pumped repeatedly through the sand filter for treatment and then flows out via gravity overflow to the drainfield. The system was designed to recirculate effluent through the filter at least five times before it is discharged into the trenches for final treatment.When wastewater enters the system from the house, an equal amount is forced out into the drainfield. A gravity overflow system ensures that the recirculating tank does not drain completely and dry out, which would kill the bacteria in the tank and allow the system to freeze in the winter.

Samples were collected from the recirculating tank to verify the system was properly treating the waste- water. Usually, homeowners contract with a professional to collect and analyze samples. For the next two years, however, the University of Minnesota will conduct the sampling.
RSFs require regular observation and maintenance to make sure the timer control is working properly. If the timer control fails, the RSF will not treat wastewater, although there may be no obvious signs untreated sewage is reaching the drainfield. Eventually, however, sewage would come to the surface.
If you are considering an alternative system, it is extremely important you estimate typical flows from your household and make sure the system you install is properly sized, designed, inspected, and maintained.