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1. Product outline
The light Color Cutter G (Fig. 1), which is composed of manganese dioxide in the beta crystal structure and was developed by our company in September 2005, is the filter media that undergoes oxidation and degradation upon contact with contaminated water. This product has the capability of arsenic adsorption. Unlike the conventional activated alumina utilized for the method of adsorption, wherein pH adjustment is necessary during the removal process of arsenic, the light Color Cutter G does not require such condition. This paper provides a more specific description of our product.
 Fig. 1 Filter media for removal of arseni 2. Characteristics of lightweight Color Cutter G
The Color Cutter G treats groundwater as raw water. Groundwater possesses little turbidity. When raw water is passed through the filter layer, the particles causing the turbidity are captured and they create an additional filter effect. This event causes refining of the particle size of the product, thereby, reducing the speed of backwashing and expanding the surface area of the filter layer. The filter media can be further improved by adding various devices on the Color Cutter G. Table 1 shows the physical and chemical characteristics of the product. Table 2 indicates sample components of the filter media.
Table 1 Physical and chemical characteristics of filter media
Table 2 Sample components of filter media
The abrasion rate of the filter media is low, thus it cannot be easily broken even if various particles collide with the filter components during backwashing. Backwashing is finished by discharging the captured turbidity in the filter media. In addition, the large porosity results in some difficulties in increasing the differential pressure.
3. Experimental comparison of filter media
The experiment on the lightweight Color Cutter G as filter media was performed following the filtration conditions and flow shown in Table 3 and Fig. 2, respectively. The results revealed insufficient adsorption of arsenic by the activated alumina because of the need for a narrow pH range activity, specifically at an acidic level (Fig. 3 reference). On the other hand, our product effectively functions in the neutral region.
Table 3 Conditions of the experimental comparison of filter media
Fig. 2 Schematic flow of the experiment
Fig. 3 Variation with time of arsenic concentration
4. Mechanism of arsenic adsorption The adsorption property of manganese oxide to arsenic has been reported for many years. As regards the mechanism of activated alumina, arsenite ion is likely to be adsorbed in the negative sorption sites. In like manner, arsenic is probably adsorbed in the asperity of manganese dioxide. Some arsenic ions are also coated by the flock of aluminum hydroxide hydrolyzed by injecting the coagulant, PAC, and then removed.
5. Cost simulation
The cost simulation of the lightweight Color Cutter G in comparison to “similar products sold in the past” and activated alumina is shown in Table 4. The results showed greater expenses for the similar products than activated alumina. However, activated alumina is not frequently employed in many cases because the use of running water still costs lower. The lightweight Color Cutter G costs approximately half as low as activated alumina, even if initial and running expenses are considered. Thus, this product is easily employed for arsenic removal.
Table 4 Cost simulation considering the duration of filter media
（denomination: 1000 yen）
? The replacement time of the filter media for the lightweight Color Cutter G and similar products lasts 15,000 longer than the filter capacity and additionally, 20,000 times longer than the activated alumina.
? Amount of grouting chemicals PAC 10mg/l、NaClO 3mg/l（Lightweight Color Cutter G and similar product）
? Amount of grouting chemicals conc HCl 432mg/l (Activated alumina only)
? The actual differences in backwashing pump capacity result in the advantage of electricity cost. However, only slight differences exist, thus the comparison on electricity costs is insignificant.
? The given filter speed is SV＝10H-1 and the amount of filter treatment is 20m3/H.
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6. Specific features of the lightweight Color Cutter G
The characteristics of the lightweight Color Cutter G are described as follows:
1. Treatment is possible only by using grouting chemicals, such as filter equipment (filter media) and sodium hypochlorite, and electricity.
2. The duration of the lightweight Color Cutter G lasts relatively long.
3. The lightweight Color Cutter G is easy to maintain.
4. The speed of backwashing can be controlled because of the light specific gravity. Consequently, this property results in uncomplicated equipment for wastewater treatment, downsized backwashing tank capacity, and reduced amount of backwashing water.
5. The lightweight Color Cutter G has excellent removal capacity of manganese as well. Additionally, the product can remove low concentration of humic color by being oxidized and degraded upon contact with water.
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