Use of Sewage Sludge on Sports Surfaces

The increasing production of sewage sludge is creating problems for its storage and disposal.

On the other hand, the composition of this sludge, although variable, makes it a source of organic matter and fertilising elements for use on our sports surfaces, which is the most appropriate way of disposal, as it allows it to be incorporated into the natural cycles of matter and energy.

Whether the sewage treatment plant is owned by the sports facilities or not, documentation concerning the stabilisation treatment of the sludge and analyses of heavy metal content must be provided. The treatment of the sludge must ensure, by biological, chemical or thermal means, by long-term storage or by any other appropriate procedure, a way to significantly reduce its fermentability and the health disadvantages of its use.

The sludge shall be analysed for dry matter, organic matter, pH, Nitrogen, Phosphorus and heavy metals, which shall be within the limit values as indicated below:

    Parameters (ppm) Soils with pH 7

1. Cadmium 20 40
2. Copper 1000 1750
3. Nickel 300 400
4. Lead 750 1200
5. Zinc 2500 4000
6. Mercury 16 25
7. Chromium 1000 1500

At the same time, we as end-users of the sludge will have to test our soils for pH (soils with pH below 5 are exempted from application) and heavy metals to ensure that levels are not exceeded, as shown below:

  Parameters (ppm) Soils with pH 7

1. Cadmium 1 3
2. Copper 50 210
3. Nickel 30 112
4. Lead 50 300
5. Zinc 150 450
6. Mercury 1 1.5
7. Chrome 100 150

Soil sampling shall be carried out by means of a composite sample, resulting from the mixture of 25 isolated samples for every 5 hectares of surface area of the golf course where they are to be applied; the sampling depth shall be between 10 and 25 cm.

Only perfectly treated and stabilised sludge with a maximum moisture content of 80% may be used. One of the most viable treatments for our simple golf course maintenance facilities is the conditioning with lime and/or potash to achieve and stabilise the sludge. maintain a pH of 12 or more for 3 months. It is useful to mix the sludge with aggregates or even with the remains of the pricked slurry for later use in road surfacing.

The application must take into account a minimum distance of 500 m. between application areas and dwellings and must not exceed the value of 210 kg N/ha/year.