Did flhrimp culture effluents have been known to release high concentrations of nutrients, lUttjloikled solids, and toxic metabolites to the environment. Since the shrimp farms release llisir effluents directly to the same water body that acts as the water source for shrimp SUilUi’o, it has caused deterioration of water quality in the receiving water source. Therefore, lF&ti(monl. of effluent before release was required and the use of biological treatment methods VVtirt Introduced to upgrade the quality of effluent.
|lx Bpecies of locally available molluscs were used to treat the effluent and 3 species showed good survival under farm conditions. Molluscs were capable of reducing 30% of suspended ptil'llcles in 48 hours. Seaweeds were used to reduce nutrients but when seaweeds were (Italy exposed to the effluent the survival rates were low[>40%]. But when effluents were permitted to flow through a settling tank prior to treatment, survival increased to 45- 50% fijld 20% nutrients were reduced in 24 hours. Use of milk fish in treatment tanks reduced the ladlinorit load by 60% at the end of the culture cycle. Use of probiotics to improve water Cjlifllity through reducing the levels of toxic metabolites were not very successful as there WM no significant difference in the water quality with respect to 6 types of probiotics tested. Tills may be due to the method of use or due to environmental conditions in the farming which do not favour the activity of these probiotics. Two probiotic types showed FSduolion of ammonia, nitrite and sulphide while one was successful in reducing only Pj11i 110 ilia.
PUi'lH.or research is required to identify better methods of upgrading water quality without damaging the environment further, to identify other suitable organisms that could be used for liTliibrit treatment, and develop probiotic species that are adapted to the prevailing Jlivli'omuental conditions in the farming areas. Development of complete recirculation iyalfliiis, incorporating biological organisms to reduce the entry of pathogens, entry of (IllPi'lors, and adverse impacts of farms on environment and adverse impacts of environment QH ftirrns would be the only solution to sustainable shrimp culture activities.