Providing evidence to improve practice

Action: Dry sludge in beds

Key messages

  • Two replicated trials in Canada found sludge drying beds removed phosphorus from freshwater fish farm sludge.

Supporting evidence from individual studies

1 

Two replicated experiments in Quebec, Canada in 2009 (Puigagut et al., 2011) found that treatment of freshwater fish farm sludge with sludge drying beds removed 95- 99% of total phosphorus (TP). The first experiment showed there was no difference in total phosphorus removed between sludge loading. The second experiment found that phosphorus leaching from sludge drying beds was 5 μg TP released per gram of total phosphorus regardless of sludge loading. For the first experiment, four sludge drying beds were set up at a rainbow trout farm; each consisted of a 1m2 reservoir filled with different types of river gravel (20cm) and a top layer of sand (20cm). Typha latifolia was planted on the sludge drying bed one year before the experiment at a density of 8 plants m2. During the experiment, the sludge drying beds were fed once a week with sludge from the fish farm at two concentrations (32 or 18 kg of dry matter per m2 year). The second experiment in a laboratory aimed to determine phosphorus leaching using 2L beakers containing 0.5L of sludge and 1.4 L of filtered pond water. Phosphate concentrations in sludge and pond water were monitored.

Referenced papers

Please cite as:

Jones, A.C., Mead, A., Austen, M.C.V.  & Kaiser, M.J. (2013) Aquaculture: Evidence for the effects of interventions to enhance the sustainability of aquaculture using Atlantic salmon (Salmo salar) as a case study. Bangor University