The drain received combined effluent. 80 percent from a busy restaurant via a catering grease trap and 20 percent from a large septic tank servicing several public toilets. The existing soakaway was built to professional standards in loamy soil overlying decomposed sandstone or gravel. It comprised 19mm of clean crushed aggregate placed into a Bidum geo-textile blanket and fed by a slotted delivery pipe.

Initially indications were that there was a blockage before the soakaway but rodding revealed that the pipe was clear for the majority of its length. The overlying topsoil was removed to expose the aggregate, which was found to be white with congealed fats, oils and greases (FOG). The FOG was so thickly deposited that the stones had to be prized apart with a pick.

To facilitate the continued running of the attraction it was decided to construct a new soakaway adjacent to, and abutting, the existing one to serve the system while the existing soakaway was allowed to bioremediate. A trial depression was scratched into the surface of the aggregate to expose the slotted pipe and 100ml of BIO-SYSTEMS DF60 was poured onto the stones.

Three days later wastewater from the slotted pipe was flowing readily through the aggregate and spilling over into the new trench. The stones had been de-contaminated sufficiently to prevent them coagulating and there was a marked reduction in the white fog scum that had previously coated them.

  Stones coated in FOG

After DF60 treatment  

Based on the success of this trial portion, the entire length of the old soakaway was treated.

Regular dosing with DF60 prevents the formation of FOG as the comprising hydrocarbons – complex fats from food wastes – are constantly degraded to natural gasses and water. Routine DF60 dosing in the future will ensure the soakaway functions as it should.