Treatment of wastewater from small slaughterhouse in hybrid constructed wetlands systems

Suitability of CW systems for treatment of wastewater from small slaughterhouse of pigs was tested. In the first part of the experiment, a system comprising two VF (vertical flow constructed wetlands) and an HF (horizontal flow constructed wetlands) was used. In the second part, VF + HF system was used with recirculation of outflow from VF to sedimentation tank in the range 100 to 200%. The experiment showed that sand and gravel beds of VF can be very effective in removal of organic substances, TSS and NH4-N from strong wastewater, BOD5reaching an average of 2500gO2m−3, TSS - 560gm−3, NH4-N - 400g Nm−3, and Ntot - 500gN-m−3. The hybrid system of 2VF + HF removed only 78.2% N24tot. Application of recirculation, depending on the extent, raised this index to as high as 85.7–96.6%. Unexpectedly low was the effectiveness of denitrification in gravel bed of HF.