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National Trust Property

Contaminated pond on National Trust Property in Southern England

The Problem

This pond is owned by the National Trust. An accidental spillage of cooking fat and sewage into the pond effectively “killed” it. The pond was immediatly fenced off to prevent access by mammals such as deer and badgers. The Utility company responsible for the spill contracted a specialist pollution control company and also informed the Environment Agency.

The pond has an area of approx 1200 square metres.

It was quickly agreed that the immediate concern was the large deposits of fat and sewage. Initial testing of the water showed high levels of ammonia.

The Solution

The pollution control company suggested a plan which was acceptable to the landowners, the Environment Agency and the Utility company. Firstly, as much of the solid deposits as could be, was removed through suction-extraction. This left a highly contaminated and mucky pond. Secondly, the pollution control company advised the addition of micro-organisms and contacted Bio-Systems. We suggested a high initial dose of EnBac® B600, to establish a viable biomass, followed by a regular weekly dose of EnBac® B600. Dosing began in the summer.

The Results

We advised that a pond of this size would probably take about six months to achieve water quality levels within acceptable levels. In fact this particular winter and spring were relatively cold, which meant that the bacteria were present but not very active. The contractors continued dosing weekly, knowing that it was unlikely that we would achieve acceptable water quality until the air temperatures rose. Eventually at a site visit in early May, we could show that the ammonia levels were typical for this size of pond, in this area. PH levels, BOD and COD levels all recorded within acceptable levels. The water clarity was greatly improved and we found species of fungii present that could not thrive in a high ammonia situation. It was agreed that the addition of EnBac® B600 was no longer necessary and that the safety fencing could be removed.

This was a great example where all parties – The landowner, the polluter, the Environment Agency, the pollution control specialists and Bio-Systems all worked together well to prevent further contamination and then restore the pond back to it’s former good health.