As a new designed constructed wetland developed by the EC project “Water quality improvement in tropical and subtropical areas for reuse and rehabilitation of aquatic ecosystems”, Integrated Vertical Flow Constructed Wetland (IVCW) has been widely used to the rehabiliatation of the eutrophic lake. Laboratory and field researches have been carried out in this dissertation. Performance and mechanism of phosphorus removal were investigated in pilot, medium and large scale. It was discussed how to lengthen the longevity of this kind of constructed wetland and how to keep the high removal performance on phosphorus in this paper. This dissertation concentrated on:
1. Eight different combined processes of constructed wetlands were monitored mainly for their phosphorus removal abilities.Among the 8 systems, the best TP removal efficiency took place in plug flow bed-down flow chamber process. 39.68% was observed. The Down flow chamber-stabilization pond process removed the least phosphours, only 18.41% TP and 6.95% IP was removed. The best IP removal efficiency of 33.76% was observed in IVCW. Putting the plug flow after IVCW could minorly enhance the phophorus removal ability, however putting the stabilization pond after down flow chamber would decrease 20% in removing phosphorus.
2. The spatial removal differences of six different combined processes were monitored in 2 years. Phosphorus removal efficiency in the stabilization pond-down flow chamber process significantly correlated to the DO value. Phosphorus removal efficiency in the down flow chamber-stabilization pond (r2=0.840), the down flow chamber-plug flow bed (r2=0.745), the plug flow bed- down flow chamber (r2=0.728) significantly correlated to the pH value. Under the high hydraulic load of 1200mm/d, the upper layer of the combined processes accumulated more phosphorus than the bottom. Phosphorus was released from the upper section. Phosphorus removal ability in the stabilization pond-down flow chamber process decreased least, increased along the water flow direction.
3. Spatial outlet water was collected and analysed, the sequential separation of differed form phosphorus in the substrate was also performed. The accumulation of phosphorus in the substrate was mainly casued by the increase of Ca-P, Al-P.
4. Eight constructed wetland media, zeolite, anthracite, shale, vermiculite, ceramic filter, gravel, blast furnace, biomaterial ceramic were studied for their phosphorus removal abilities in green house. Blast furnace was the best choice for the high performance removing phosphorus over 85% during the experiment stage even when the inlet phosphorus concentration lower than 0.5mg/L.
5. Phosphorus removal in Guanqiao construted wetland was studied, using grass as the upflow chamber plant was a feasible choice.
6. Through the practical use of constructed wetland in Sanjiaohu Lake, the experiences of practical use in treating eutrophic lake water were acquired.
Phosphorus removal in different combined processed constructed wetlands were investigated, IVCW operates best under high hydrolic load rate and cold climate. Spatial sampling results from different combined processed wetlands revealed some important principles of combination of constructed wetland untis. Laboratory research and field research were performed on mechanisms of phosphorus in IVCW, the method avoiding the decrease of phosphorus removal rate was brought forward. In order to length the lifespan of phosphorus remove, 8 different media were investigated for their phosphorus removal ability. Blast furnace appered the best performance,. The pratical use needs further research.