Waste oyster shells create several serious problems; however, only some parts of them are being utilized currently. The ideal solution would be to convert the waste shells into a product that is both environmentally beneficial and economically viable. An experimental study is carried out to investigate the recycling possibilities for oyster shell waste. Bulk ceramic bodies are produced from the oyster shell powder in three sequential processes. First, the shell powder is calcined to form calcium oxide CaO, which is then slaked by a slaking reaction with water to produce calcium hydroxide Ca(OH)2. Then, calcium hydroxide powder is formed by uniaxial pressing. Finally, the calcium hydroxide compact is reconverted to calcium carbonate via a carbonation reaction with carbon dioxide released from the shell powder bed during firing at 550oC. The bulk body obtained from waste oyster shells could be utilized as a marine structural porous material.

To improve the environmental management and resources, in this study, we aimed to investigate the effect of adding oyster shell powder to Hanwoo manure on its characteristics and microbial composition during the storage period. Additives were deposited on top of the manure surface at the rate of 0, 0.5, and 1% of oyster shell powder per 200 g of Hanwoo manure in a plastic container with three replicates; however, untreated manure litter served as the control. Manure characteristics (dry matter, organic matter and crude ash) and microbial composition (lactic acid bacteria, yeast, Bacillus subtilis, Salmonella, and E.coli) were evaluated at day 0, 2, 4, and 8. Manure characteristics exhibited an effect on dry matter, organic matter, and crude ash at day 2 and 8 (p<0.05), and not for day 0 and 4 (p>0.05). With the exception of yeast content at day 4 of storage, lactic acid bacteria, yeast, Bacillus subtilis, Salmonella, and E.coli exhibited no significant differences in all conditions during the storage period. Conclusively, addition of 1% oyster shell powder to Hanwoo manure resulted in slightly better manure characteristics; however, its microbial composition remained unchanged.

To evaluate the remediation performance of recycled oyster shell powders to control nutrients release from polluted sediments. Different types of recycled oyster shell powder were applied on separated bottom sediments. The first type of oyster shell powder is Calcined Oyster Shell Powder (COSP) and another consist of ultrasonicated oyster shell powder (SOSP) which were composed of calcium peroxide. The recycled oyster shell powders were improving the water quality as slow oxygen releasing compound. The experimental results indicated that the Dissolved Oxygen (DO) in the treated columns were higher than the control column. pH was increased in the both experimental columns due to the hydrolysis of CaO2. Meanwhile, recycled oyster shell powders could prevent the nutrients (nitrogen and phosphorus) release from sediments into the overlying water. In addition, the total nitrogen and total phosphorus concentrations of the COSP applied column were decreased 27% and 20% compared to the control column respectively and the SOSP applied column were decreased 33% and 27% compared to control in the overlying water. It was proved that, COSP and SOSP can effectively adsorb phosphorus from sediments and prevent phosphorus release into overlying water from bottom sediments. In conclusion, COSP and SOSP applications was increased DO in the overlying water and nutrient released controlled effectively from the sediment.

In this study, we performed a sediment elution experiment to evaluate water quality in terms of phosphorus, as influenced by the dissolved oxygen consumed by sediments. Three separate model column treatments, namely, raw, calcined, and sonicated oyster shell powders, were used in this experiment. Essential phosphorus fractions were examined to verify their roles in nutrient release from sediment based on correlation analyses. When treated with calcined or sonicated oyster shell powder, the sediment-water interface became “less anaerobic,” thereby producing conditions conducive to partial oxidation and activities of aerobic bacteria. Sediment Oxygen Demand (SOD) was found to be closely correlated with the growth of algae, which confirmed an intermittent input of organic biomass at the sediment surface. SOD was positively correlated with exchangeable and loosely adsorbed phosphorus and organic phosphorus, owing to the accumulation of unbound algal biomass-derived phosphates in sediment, whereas it was negatively correlated with ferric iron-bound phosphorus or calcium fluorapatite-bound phosphorus, which were present in the form of "insoluble" complexes, thereby facilitating the free migration of sulfate-reducing bacteria or limiting the release from complexes, depending on applied local conditions. PCR-denaturing gradient gel electrophoresis revealed that iron-reducing bacteria were the dominant species in control and non-calcined oyster shell columns, whereas certain sulfur-oxidizing bacteria were identified in the column treated with calcined oyster powder.

Bioremediation in situ is heavily dependent on the oxygenic environment which would privide the dwelling microorganism with sufficient oxygen. The situation could be easily resolved with supply of an Oxygen Releasing Compound (ORC). In this paper we prepared that sort of material out of oyster shell powder (mostly calcium carbonate) that prevails every shore areas of the country. We used two different oxidizing methods in the first step of the whole manufacturing process–conventional heating in a furnace and an ultrasound generator to obtain calcium oxide. Then that calcium oxide was further oxidized into calcium peroxide which may release oxygen under a moisturized condition. The oxygen releasing experiments were run to test the performance of our products, and to determine the gas kinetics during the experiments. Interestingly, calcium peroxide derived from ultrasound treatment was much more energy-effective as ORC than that from furnace heating although the heat derived process was better than that of ultrasound in terms of oxygen content and its releasing rate. We also found that most of the data collected from the gas releasing experiments fairly supported an ordinary 1st order kinetics to oxygen concentration, which shaped a sharp discharge of oxygen at the very early moment of each test.

The several functions of manufactured the gypsum incorporating oyster shell powder coated by submicro-silver solutionand carrried out the tests for the adsorption of formaldehyde and antibiotic actions. Several environmentally- friendlyarchitectural materials, clay and flyash were tested for the comparison of the adsorption efficiency. The mortar by solidifiedand dried was exposed in the small chamber for the 180min with 4000µg/m3 of the initial concentration of formaldehydeand observed high removal efficiency which result was not any difference in adsorption performance of other tested materials.The microbial flora analysis of oyster mortar coated by submicro-silver solution and the similarity test were performed andobserved that the densities of Aeromonas sp. Enterococcus sp., and Micrococcus sp. were decreased and the densities ofStaphylococcus sp., Escherichia sp., Bacillus sp., were taphylococcus sp, Escherichia sp., and Bacillus sp. were increased.