Sand bioreactors have a reputation of producing extremely high quality effluent even with fluctuating waste loading. Sometimes an individual reactor is plagued with poor performance. Poor performance is usually the result of short circuiting through the bioreactor. Short circuiting can occur along the edges of the bioreactor if it is neglected and allowed to pond. Short circuiting may also occur along discharge, vent, or inspection pipes that extend through the sand. Diversion collars placed around the pipes, just below the sand surface, can be retrofitted if this begins to happen. Another source of short circuits is channels through the sand. Channels seldom form if the wastewater is applied in small doses. Though rare, it is difficult to predict which bioreactors will form channels. Channeling has been observed in one filter when all the other filters in the system, built at the same time, in the same way, with the same materials, do not form channels. Try to eliminate the channels through a four-step process.
Check switches and timers in the application systems to make sure the bioreactor is receiving only small doses of wastewater spaced throughout the day.
Till the surface of the filter with a rototiller or moldboard plow.
Remove all of the sand from the bioreactor and put it back in again.
As a last resort, replace the sand with new sand.
With open sand bioreactors dosed with septic tank effluent, odors should not be a problem. However, nearby neighbors may become concerned. One way to avoid conflicts is to reset the timer to dose during the night or when neighbors are not around.