Individual study: Decreasing phosphorus discharge in fish farm ponds by treating the sludge generated with sludge drying beds
Puigagut J., Angles H., Chazarenc F. & Comeau Y. (2011) Decreasing phosphorus discharge in fish farm ponds by treating the sludge generated with sludge drying beds. Aquaculture, 318, 7-14
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Dry sludge in beds
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.