Slaughter wastewater usually contains high concertrations of organic matter, animals fats, pathogenic microorganisms. Although many slaughterhouses apply way to use biogas tanks for waste treatment, wastewater still has high concentrations of pollutants, therefor it can not be discharged directly to the environtment. The objecttives of this study was to evaluate the effectivesness an potential of water lettuce (Pistia stratiotes L.) in removing nitrogen (N) and phosphorus (P) from wastewater of slaughterhouse. The experiment was conducted in the slaughterhouse of Can Tho City with 6 treatments including 3 levels of dilution of wastewater after biogas process (diluted 95%, 90%, 80%) and 3 replications. The result showed that the water quality was improved through indicators: pH, EC, DO, COD, TN and TP. Effect of water lettuce for wastewater treatment was highest with 80% dilution. The removal efficiency of treatment with Pistia stratiotes L.in the experiment was 67.3% COD, 78.6% COD, 78.6% TN, 64.1% TP. Pistia stratiotes L. adapted and growed well in slaughter waste water through the increasing of biomass. The growth of shoots was 21.3 shoots/m²/day to 42 shoots/m²/day. After 60 days, biomass of water lettuce increased 3 - 12 times. The ability to uptake nitrogen, phosphorus in the wastewater treatment 80% dilution was 15.12 g N/m²/year; 2.21  g P/m²/year. Using Pistia stratiotes L. to treat pollution of wastewater form slaughter-house after biogas tanks, in an effective and propective way. The rapid development of Pistia stratiotes L. create biomass can be picked up to make animal feed or fertilizer.

Keywords: biomas, dilution, slaughter waste water, Pistia stratiotes L., uptake, wastewater, treatment.