Granulated Coal Ash-Used Filter Design for Efficient Removal of Nutrient Salts

Tadashi Hibino; Yuki Morimoto; Manaka Okabe; Hiroki Takata; Narong Touch
To date, granulated coal ash (GCA, a by-product from coal fired-power plants) has been widely used for improving sediment and water quality, such as removals of nutrient salts and hydrogen sulfide. These removal capacities of GCA lead us to consider that GCA can be used as a filter material in wastewater treatments. This study is aiming at examining the potential of using GCA as a filter material in wastewater treatments. One of our objectives is to examine how to use GCA for efficient removal of nutrient salts. Another objective is to propose filter design and operation of using GCA for removing nutrient salts effectively. Laboratory experiments were conducted under different conditions, such as different concentrations of nutrient salts and retention times. The experimental results showed a higher removal rate of ammonium ion when polluted water was retained in GCA filter compared to the circulating polluted water through the GCA filter. This was observed when the retention time shorter than 180 min. However, the removal rate was similar when the retention time was longer than 180 min. A higher solution pH in the retention condition was considered to partly contribute to the higher removal rate. Moreover, the absorbed quantity increased with an increase in the concentrations of nutrient salts. This pointed out that the removal of nutrient salts by GCA depends on the concentrations of nutrient salts present in the solution. According to these results, design of GCA filter and its operation were proposed. The GCA filter was divided into two different parts. The polluted water was retained in the first part for 90 min, then discharging to the second part for 90 min-retention. Compared with the filter without division (180 min-retention), 1.33-fold increases in NH4+ and 1.55-fold increases in PO43- removals were obtained owing to our proposed filter design and operation.
Granulated Coal Ash; Filter Design; Removal; Nutrient Salts; Retention
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