Nitrogen and phosphorus esothermal adsorption characteristics of four filter materials and pollutants removal performance of filled columns

Selection of filter materials in constructed wetlands used for eutrophic water treatment was studied. Volcanic rock, ceramsite, composite soil and gravel were chosen for experiment. Esothermal adsorption tests demonstrated that volcanic rock and ceramsite had good adsorption capacity of ammonia nitrogen while composite soil and ceramsite had good adsorption capacity of total phosphorus (TP). Continuous operation effect for filled columns of volcanic rock, ceramsite, composite soil, gravel and their combinations showed that adsorption capacity of ceramsite was not as large as that of volcanic rock, but in the later experiment period, ceramsite showed better removal performance because of degradation of microorganisms. The average removal efficiency of TP in the composite soil column reached 82.4%. Finally, ceramsite, composite soil and gravel were chosen as filter materials for constructed wetland. Composite soil was used to remove organic matters and phosphorus, ceramsite was used to remove nitrogen and organic matters, and gravel played a role in supporting and water distribution.