Phosphorus release from phosphate waste rocks deposited in Xiangxi River watershed of Three Gorges Reservoir
ZHANG Meng-zhou1,2, XU Zeng-he1, LIANG Bing3
1. College of Resources and Civil Engineering Northeastern University, Shenyang 100014, China;
2. College of Civil Engineering and Architecture Liaoning Technical University, Fuxin 123000, China;
3. College of Mechanics and Engineering Liaoning Technical University, Fuxin 123000, China
As the research object to phosphate waste rocks deposited within Xiangxi River watershed of Three Gorges Reservoir, Deionized water and artificial acid rain (pH=4.5) were selected as percolation solution of dynamic column leaching experiments. The phosphorus leaching characteristics under natural and acidic leaching conditions were compared and analysed. The results showed that the leachate pH of phosphate waste rock would maintain weak alkalinity (pH=7.0~9.0), while under the acidic condition the leachate pH would change from weak alkalinity (pH=8.0~9.0) to weak acidity (pH=6.0~7.0) when Liquid-to-Solid ratio (L/S) reached 0.5mL/g. The total phosphorus (TP) concentration of leachate was mainly dominated by pH of leaching environment, which increased with decrease of liquid pH. And the increase of leaching time won't dilution effect on the formation of TP concentration in the leaching liquid. The phosphate waste rocks would release phosphorus with a constant rate when the pH of leaching environment remained stable, while the accelerated released period would be formed during the pH of leaching environment changed from acidity to alkalinity. The leachate TP concentration would exceed the TP emission limit of the III type water area which stipulated by GB 8978~1996. The phosphate waste rocks deposited within Xiangxi River watershed should be managed as the II type industry solid waste in order to reduce the phosphorus pollution risk of Xiangxi Bay
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