CONSTRUCTED WETLANDS AS BIOFILTERS IN CLOSED RECIRCULATING TANK CULTURE SYSTEMS OF ASIAN TIGER SHRIMP (PENAEUS MONODON)
Keywords:cattail, constructed wetlands, biofilter, elephant grass, Penaeus monodon, recirculating aquaculture system, water quality
The study was conducted to monitor the real-time status of toxic compounds to P. monodon in intensive recirculating aquaculture system integrated constructed wetlands (CWs) designed with surface flow (SF), vertical subsurface flow (VF) and horizontal subsurface flow (HF), and to examine removal efficiency of contaminants in different CWs. Plants used in the system were cattail (Typha sp.), elephant grass (Pennisetum purpureum) and unplanted systems used as referenced samples. Recirculating rate per day was 50 % of total water volume in tanks. Water from culture tanks was purified by passing through SF, VF and HF then return to original tanks without water exchange in entire study period. After 72 days, concentration of NO2-N, NH4-N and NO3-N was building up over study period and was not significantly different among treatment systems (except the concentration of NO3-N). At the end of study period, NH3 concentration was below the toxic threshold for P. monodon in according to Circular No. 45/2010/TT-BNNPTNT. P. monodon grew slowly and the survival rate was as low at 30 %, 43 % and 60,5 % in the HF, SF and VF systems, respectively. The average water volume added in each tank in entire study period was 393 ± 1,7 L. Despite of low survival and growth rates, the integration of CWs in intensively recirculating shrimp systems helps to improve water quality in accordance to Circular No. 45/2010, to diminish pollutant discharging and to maximize efficiency of water use which minimizes environmental pollution.