Assessing sediment removal capacity of vegetated and non-vegetated settling ponds in prawn farms

Abstract

Sediment removal capacity is assessed for a constructed mangrove wetland, and a non-vegetated settling pond that are both used for filtering water in tropical aquaculture. The assessment is performed through sediment budget analysis using data of suspended sediment concentration collected from optical backscatter sensors. The sensors were deployed at the pond's inlet and outlet. These data sets provide a measure of trapping efficiency of each pond with different flow regimes and settling areas. The tides influenced flow in the wetland but none was felt in the settling pond. The average trapping efficiency obtained for the vegetated and the non-vegetated ponds was (40±33) and (70±36)%, respectively. The deposition rate calculated for the vegetated and non-vegetated pond ranges between 13–174 g/m2 per h (average=63 g/m2 per h) and 10–19 g/m2 per h (average=14 g/m2 per h), respectively. The efficiency of vegetated and non-vegetated ponds is likely to be improved by decreasing the aspect ratio (length/width) from the current value of 6 to 1 and of 5 to 1, respectively.