Worldwide Reservoir Aeration Services

Products and Installation

We have maintained and installed progressively improved aeration systems in Bristol Water's reservoirs over the last forty years.

Blagdon is a man made reservoir of 217 hectares with the water supplied from surrounding farmland by various streams and has had four aeration systems in the following sequence:

1971 - 81: originally there was a simple air curtain, using 63mm diameter black MDPE airline, laid in the shape of an equilateral triangle. This was later improved by laying an aerator inside the triangle.

1995 - 97: Our diving survey showed the outer leg of the triangle was broken in several places. The damaged leg was removed and an aerator placed at the end of each leg, leaving the previous aerator between them. A further aerator was added later.

2001 - 2: All old aerators and air lines were removed from the Reservoir and five new Aquaerators were laid at distances of 200m, 250m, 400m, 600m and 850m from the dam Outlet Tower in the deepest areas.

2007 -8: It was discovered that the main water outlet was 2m below the Reservoir bed, thus water going to the Treatment Works, had a low DO and previous reports showed that in July each year there were large quantities of manganese in the water column.

  • A diving survey showed that silt covered the initial 6m of the apron to a depth of 2-3m.
  • Aquarius Marine's Diving Team airlifted over 30cu m of silt from the area and stacked rocks and ancient building materials along the sides of the channel before reaching the granite apron. Due to the 1.5 knot outflow current it would be necessary to bolt the Aquaerator to the Victorian granite apron to prevent movement. The granite was drilled, enabling the Aquaerator to be assembled and bolted down 13m from the 3m diameter outflow pipe grille, which is 2-3m below the surface of the reservoir bed mud deposits.
  • Another Aquaerator was laid to improve the water quality through the alternative outflow siphon.
  • The water temperature had risen to 15ºC, the DO fallen to less than 50% saturation and the Mn concentration in the outflow to the Treatment Works showed a steady rise from early April and peaked at 320?g/l by 10 May 2008. It then averaged about 70?g/l for a month and continued to rise to 100?g/l mid June, before the two Aquaerators were switched on 23 June 2008. This reduced the Mn concentrations in the main outflow dramatically to 25?g/l and less in a few days, remaining at that level through the next months July to September.
  • The water temperature of the outflow remained steady at about 18ºC and the DO rose
  • gradually to 100% by 5 Aug 2008.
  • This year, in other words, there was no need to treat the raw water for manganese removal. The following figure shows the concentrations and conditions of the water observed by Bristol Water at the Blagdon Lake Lower Outflow, as described above
Chart

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