6.1 Nitrogen removal from wastewater of afertiliser and chemical manufacturer with the use of two different hybrid constructed wetland systems planted with Schoenoplectus validus

摘要

This study analyses the performance of a hybrid Free Water surface/Vertical Flow (FWS/VF) wetland in removing nitrogen from wastewater generated in a fertiliser and chemical manufacturer in Perth, Western Australia during a 14 month period. The constructed wetland currently in use at the fertiliser plant is 12,825 m~2 (135 × 95 m), planted with Schoenoplectus validus, has a vertical flow design and has been operated as FWS/VF conjugated system with a hydraulic load = 3.3 cm/d and a retention time of 18 days. Average load removal rates are: 26% for NH_4-N, 52% for NO_3-N and 32% for TN. Parallel to that, an experiment with wetland mesocosms was conducted, this experiment compared the efficiency of a FWS/VF wetland (simulation of the industry's wetland) and an alternative hybrid VF/Horizontal Flow (VF/HF) in removing nitrogen from the industry's wastewater. Systems were planted with Schoenoplectus validus. The performance in nitrogen removal for the FWS/VF mesocosm was superior to the actual wetland's performance. The best nitrogen removal rate was achieved by the VF/HF system, with the first VF stage alone removing 82.9% of ammonia in 2.88 days while the FWS/VF removed 78.2% of the ammonia in 10.8 days.