Summary:

Investigations with wastewater from small abattoir were carried on hybrid constructed wetland systems. Mean COD of wastewater reached 3000 gO₂∙m^-3 and concentration of Ntot was about 400 g∙m^-3. The main problem was sufficient removal of NO₃-N and Ntot. In order to intensify denitrification, a part of effluent from the vertical bed was recirculated to the settling tank. Effectiveness of Ntot removal on the plant raised along with the rise of recirculation level and obtained for 100, 150 and 200 % respectively 85,7; 91,9 and 96,6 %. The main contamination of wastewater from small fruit-and- vegetable processing plant consist of organic substance (to 10000 gO₂∙m^-3 as COD). The bed with vertical flow built of various fractions of sand and with fully developped reeds was found very effective in its removal. Sufficient results were obtained with loading of the bed up to 90gCOD∙m^-2∙d^-1.