Drainfield recovery using Microbubble aeration

Windy Acres Assisted Living:
Forest Lake, MN

Overview:
One of the two mound dispersal systems leaked to the surface at on corner of the rockbed. Waste strengths were measured and were higher than we would have liked to see (TSS 65.6 mg/L and CBOD5 324 mg/L). Experience shows that effluent from a facility of this type contains pharmaceuticals, sanitizers and such that are expected to demand oxygen beyond BOD reduction.

Solution:

  • The design update included the addition of an MBD-6 aerator rated at 2-10 lbs BOD reduction/day to reduce the effluent strength to Level C per MN Rule 7083.4030.
  • A service contract was implemented that included semi-annual visits to service the system, collecting effluent samples for laboratory analysis, measuring solids accumulation in tanks, checking on the condition of the mounds, and annual reporting to the city of Wyoming.

    Drainfield recovery using microbubble aeration


    Overview:

    This system had effluent surfacing within 8 years of being constructed.  A heavy biomat build up in the drainfield caused the failure.  The drainfield rockbed was completely full of liquid.


    Solution:

    • The University of Minnesota was consulted to confirm soil conditions and reason for failure.
    • A Microbubble aerator was installed in the septic tank.
    • Surfacing was eliminated within a month.
    • The liquid level in the rockbed was normal at 60 days.