Nutrients removal from integrated multi-trophic aquaculture (IMTA) water using waste stabilization ponds (WSP)

Nutrients enrichment due to waste from Keramba Jaring Apung (KJA) aquaculture is one of the main causes of eutrophication in Indonesian Lakes and Reservoirs. Integrated multi-trophic aquaculture (IMTA) is one of environmentally friendly aquaculture that currently being developed at the Research Center (RC) for Limnology - National Research and Innovation Agency (BRIN). This aquaculture would re-use its water, along with fish waste and leftover fish pellets, to grow Duckweed (Lemna sp.) in its ponds system as additional feed. However, due to closed water recirculation in IMTA ponds system, the water quality would eventually deteriorate which would be marked with high turbidity of organic solid waste and low dissolved oxygen (DO). This study aims to improve water quality from aquacultures activity, especially in nutrients (nitrogen and phosphorus) reduction, using a constructed wetland (CW) system. This system consists of waste stabilization ponds (WSP) and compartments of CW and adsorbent. During this initial stage, IMTA water was treated in the WSP for then observed for its improvements in the nutrients and other water quality parameters. This research was conducted from July to September 2019 in the Prototype Laboratory of RC for Limnology-BRIN. Parameters of DO, conductivity, pH, oxidation reduction potential (ORP), and salinity were observed using a calibrated water quality checker (WQC) Horriba © , while nutrients parameters in the form of N-NH 4 , N-NO 2 , N-NO 3 , P-PO 4 , and dissolved organic matters (DOM) were measured in the laboratory referring to the standard method of the American Public Health Association (APHA). Results showed that average values of turbidity and electrical conductivity parameters were reduced from 102 to 76 NTU and 0.21 to 0.14 mS/cm, respectively. Average nutrients reductions were also found from N-NO 2 , N-NO 3 and P-PO 4 parameters of 85.5%, 44.3% and 37%, respectively. Significant changes were observed in parameters of DO and N-NH 4 . DO was increased from 4.63 mg/L to 7.44 mg/L, while N-NH4 were reduced for 81%. Even though the experiments were not conducted during low DO conditions of water from IMTA ponds, improvements from the vital water quality parameters after treatment in the WSP were observed.