The effect of calcium peroxide originating from oyster shell powder on control of phosphorus compounds in oceanic sediment

Abstract

This study evaluated the water quality above the marine sediment by inputting oxygen releasing compound (ORC) processed from calcined oyster shells. Presumed vital parameters such as DO, pH, ORP, chlorophyll-a and classified phosphorous compounds were monitored for 20 d. ORP decreased with time in the control bed, while it increased to a positive value as a result of the ORC effect. DO kept showing a relatively high concentration in ORC treated column. We observed an increase of chlorophyll-a and a decrease of dissolved inorganic phosphate (DIP) simultaneously, which meant the released inorganic phosphorus would convert to an organic form in the overlying water. TP rises were the lowest in the ORC column (79%), meanwhile in the control column those went up to 0.304 mg/L (85%). Also, phosphorus fractions were measured in the sediment: Fe-P decreased in control while Fe-P and Ca-P soared greatly in the ORC column. This implies that in more oxidized environment inorganic phosphate bound to Ca-species would be eliminated as solidified precipitates in the sediment pore water, and it consequently suppressed the release of phosphates to the overlying water. The results indicate that the release of phosphorus and resulting eutrophication could be effectively controlled via the local environment improved by calcined ORC.