Abstract
Objective: The special-glaze-applied ceramic pieces used in this study are bisque fired ceramics manufactured by applying a special glaze. It has been suggested that cyanobacteria, which are oxygen-producing photosynthetic bacteria, may proliferate when ceramic pieces are placed in soil or water. In this study, we installed ceramic pieces in the Benten Pond (Ichikawa, Chiba, Japan) and verified the effect of the pieces on water quality.
Method: Benten Pond is a closed water system with a little flow from upstream where a water inlet pipe is located, to downstream where a drainage channel is located. We placed three sandbags filled with approximately 6 kg of ceramic pieces in the water. We observed reddish mud and oil film around the water inlet pipe that were determined to be iron oxide biomats produced by iron bacteria, and ceramic pieces of 1 kg were scattered only on the west side of the pipe.
Result: The values of Biochemical Oxygen Demand (BOD)/Chemical Oxygen Demand (COD), which are indicators of water quality, were 1.8/4.2 mg/L when the ceramic pieces were placed (November 21, 2019), the values temporarily increased during summer and decreased to 1.2/3.5 mg/L after one year. An improvement was observed in suspended solids, which dropped from 17 mg/L to 12 mg/L. The previous value of total nitrogen was 14 mg/L, which was well above the standard value. Total nitrogen decreased during the summer and then approached the previous value. Although total phosphorus increased temporarily during summer from the previous value of 0.034 mg/L, the value was 0.030 mg/L after one year. The iron oxide biomats almost disappeared in the area where the ceramic pieces were placed, and the biomats remained unchanged in the area where the pieces were not placed. Adverse events associated with the installation of ceramic pieces were not observed.
Conclusion: The installation of ceramic pieces improved the water quality and reduced iron oxide biomats. Further studies regarding the involvement of cyanobacteria are required.
