『Abstract
　The potential of ferrihydrite-modified diatomite as a phosphorus co-precipitant was investigated at a laboratory scale. Ferrihydrite-modified diatomite was demonstrated to effectively remove phosphorus from lake water as well as strongly bind phosphorus in sediment under anoxic conditions. Phosphorus removal from the lake water proceeded primarily through phosphorus adsorption onto ferrihydrite-modified diatomite and further phosphorus consumption by stimulated diatom growth. a total phosphorus removal efficiency of 85％ was achieved when lake water was dosed with 250 mg/L ferrihydrite-modified diatomite; the residual total phosphorus concentration was 17.0μg/L, which falls within the range for oligotrophic phosphorus levels. During a 30-day anoxic incubation period, total phosphorus concentrations in lake water treated with 400, 500, or 600 mg/L of ferrihydrite-modified diatomite slightly decreased and maximum total phosphorus concentrations remained below 15μg/L. Addition of ferrihydrite-modified diatomite resulted in a marked increase in the iron-bound phosphorus fraction, a pronounced decrease in labile phosphorus and organic-bound phosphorus fractions, and stable aluminum-bound phosphorus, calcium-bound phosphorus, and residual phosphorus fractions in the anoxic sediments. Comparable iron-bound phosphorus concentration in the sediment treated by 400 mg/L of ferrihydrite-modified diatomite relative to that of the sediment treated by the combination of 400 mg/L of ferrihydrite-modified diatomite and alum solution at the concentration less than 532 mg/L indicated that ferrihydrite-modified diatomite exhibited a stable phosphorus-binding capacity when dosed at a similar amount. Ferrihydrite-modified diatomite had the potential to be used as an effective phosphorus coprecipitant.

Keywords: Ferrihydrite-modified diatomite; Phosphorus removal; Phosphorus release; Phosphorus co-precipitant』

1. Introduction
2. Materials and methods
　2.1. Preparation of ferrihydrite-modified diatomite
　2.2. Water and sediment samples
　2.3. Phosphorus removal from lake water
　2.4. Anoxic incubation of ferrihydrite-modified diatomite treated sediments
　2.5. Anoxic ferrihydrite-modified diatomite and alum treated sediment incubation
　2.6. Parameter measurements
3. Results and discussion
　3.1. Removal of phosphorus from lake water
　3.2. Anoxic incubation of lake water and sediment treated by ferrihydrite-modified diatomite
　3.3. Anoxic incubation of lake water and sediment treated by ferrihydrite-modified diatomite and alum
4. Conclusions
Acknowledgments
References