Comparing Suppression Effect of Bottom Ash, Granulated Coal Fly Ash, and Sea Sand against Nutrient Release from River Sediment

摘要

In stagnant water area such as a lake or tidal river, environment pollution caused by nutrient release from sediment has become a problem. Sand capping, that is one of the countermeasure for nutrient release, has a problem of depletion of sand capping material. So it is necessary to consider substitute for sand capping material. In this study, we examined suppression effect of bottom ash and granulated coal fly ash less than 2 mm as sand capping material in test tubes and compared them with sea sand. As a result, each phosphorus concentration of control, bottom ash, granulated coal fly ash, and sea sand was 1.78, 0.15, 0.14, 0.12 mg-P/L, respectively (p < 0.01). This result shows bottom ash and granulated coal fly ash can suppress nutrient release such as phosphorus and nitrogen as strongly as sea sand. And we conducted experiments using bottom ash with the phosphorus adsorbent (urchin shell and lanthanum oxide). As a result, we clarified that bottom ash with the phosphorus adsorbent can reduce phosphorus release better than using only bottom ash or phosphorus adsorbent (p < 0.05). Additionally, there is the possibility that sand capping layer made of bottom ash can be thinned with the phosphorus adsorbent.