Improvement of Water and Wastewater Treatment Process Using Various Sound Waves—A Consideration from the Viewpoint of Frequency

Application of sound waves is one of the novel techniques for the improvement of water treatment process. In this study, various sound waves such as 1) ultrasonic wave, 2) music box, and 3) windbell were irradiated to water and wastewater for removing contaminants such as nitrate, phosphorus and BOD/COD. As a result, a possibility of improvement of water and wastewater treatment process using sound waves with various frequencies was proposed.


Introduction
Several anthropogenic processes resulting from haphazard urbanization have mounted heavy stress on water quality of urban basins in underdeveloped and developing countries (Pathak et al., 2011) [1]. And then, river water is more susceptible to pollutants and is highly polluted as a result of rapid urbanization, that is, increased loadings of diffused pollutants and exploitation of sources of rivers by foreign enterprises (multinational corporations etc.). Therefore, it is very important to protect and conserve source of a river. Regarding pollution

Experimental Methods
In previous study [5], an examination for the improvement of water treatment process using ultrasonic waves (28 KHz) was carried out. As a result, It was confirmed that ultrasonic wave affects water quality such as content of calcium (Ca), magnesium (Mg), namely, hardness, sodium (Na) and potassium (K). In addition to those, the possibility of the complete removal of impurities (BOD, COD) was supposed by the irradiation. The experimental results confirmed that the ultrasonic waves improved the water treatment process significantly by accelerating the reaction. Therefore, this time we examined a possibility of an effect of improvement of water treatment process using various sound waves with different frequency in addition to the ultrasonic waves mentioned above. Three kinds of sound waves such as 1) ultrasonic wave (35 KHz), 2) Switzerland music box (3.75 Hz -102 KHz), and 3) Japanese wind-bell (1500 Hz -8.5 KHz) were irradiated to drinking water, forest water and sea water for water softening process as for total hardness and other contaminants removal such as nitrate, phosphorus and BOD/COD etc. Figure 1 and Figure 2 show a frequency range of sound waves and appearance of the sound boxes, respectively.
Details of three types of the sound system are as follows. 1 3) Wind-bell system (called "Furin") A specification of the Japanese wind-bell is as follows: Model: Nambu-Furin, Material: Made of metal, Frequency: 1.5 KHz -8. 5 KHz, This wind-bell hung inside a basket to be played by the wind (an electric fun). (In  general, Japanese wind-bell is often made of metal or glass, and some of the famous Japanese Furins are "Edo-Furin" from Tokyo and "Nambu-Furin" from Iwate prefecture.)

Experimental Condition
In this study, the standpoint is to understand how the Hardness (Ca 2+ , Mg 2+ ), nitrate-N, phosphorus (P), and BOD/COD, those are causal substances of eutrophication and organic contamination are decreased in each water sample by irradiating ultrasonic wave, music box and wind-bell. The experimental conditions of these three types of sound boxes used in this experiment are as follows: 1)  Table 1). The analysis of water qualities was focusing nitrate, phosphorus and BOD/COD.

Analytical Method of Water Quality
The analysis of the water quality was conducted using simplified water quality analysis kit made by Kyoritsu chemical-check lab., corp., Japan. The kit was used for examining Total Hardness, pH, COD, Mg 2+ , Ca 2+ , SiO 2 , 3 4 PO − , BOD. Furthermore, ICP emission spectrometry was used to analyze for Na + and K + , respectively.

Improvement of Water Quality Using Ultrasonic Wave
An improvement of water quality using ultrasonic wave with frequency 35 KHz is shown in Table 2.
Removal rate of each substance by the ultrasonic wave is shown in Figures 3-8. The ultrasonic wave is very effective for improving the water quality for especially drinking water (hard water/soft water) and forest water. The results are as follows.
1) Nitrate: As for the removal rate of 2 NO − and 3 NO − concerning to the three samples such as the sea water, drinking water (soft water) and the forest water, high values (>50%) were obtained, respectively.
2) Phosphorus: 3 4 PO − was also confirmed to decrease larger than 50% in the forest water (2 and 3).  3) BOD/COD: BOD and COD drastically decreased especially in drinking water (hard water/softwater) and forest water. 4) Ca 2+ , Mg 2+ and TH: The removal rate of Ca 2+ and Mg 2+ was also large (>50%) in the drinking water (hard water/soft water). Along with these, TH also drastically decreased. Here, TH means total hardness defined as content of Ca × 2.5 plus Mg × 4.1. 5) Na + , K + and 4 NH + : They showed very few change.

Improvement of Water Quality Using Switzerland Music Box
An improvement of water quality using sounds by Switzerland music box with frequency 3.75 Hz to 102 KHz is shown in Table 3.
Removal rate of anions by the ultrasonic wave is shown in Figures 9-11. From Table 3 and

Improvement of Water Quality Using Japanese Wind-Bell
Third, an improvement of water quality using sounds by Japanese wind-bell with frequency 1500 Hz to 8.5 KHz in Table 4. Removal rate of anions by the ultrasonic wave are shown in Figures 12-14. From Table 4 and Figures 12-14, this case also shows almost the same tendency of the removal rate of the quality of water concerning to Nitrate ( )

Chemical Reaction under Sound Waves
All measured results are shown in Tables 3 4 PO − were observed. This estimates that these ions react to each other to make neutral chemical compounds. That is, following reactions were occurred.
By the way, for distinctive phenomenon, monovalent cations such as Na + , K + and 4 NH + show little change after irradiating in all cases. Namely, for example, next reaction never happened.      Figure 15 and Figure 16 show a removal rate of 2 NO − and 3 4 PO − by each sound wave respectively. From these figures, sound waves with a wide range of frequency have effect on improvement of water quality. Sound wave is transmitted in the transverse manner with repeating expansion and compression. It is believed that expansion and compression agitates the fluid and facilitates the reaction mentioned above which means boundary film thickness in Equation (1) is made thin. In this study, the threshold values of the work on the water improvement generated by sound wave are not obtained. It is the theme in the near future.   Furthermore, from the results mentioned above, a possibility of the improvement of water quality by murmuring sound of a natural stream was suggested. If such a phenomenon may occurs, it is confirmed that natural purification mechanism could work. This is a subject for the near future.

Conclusions
In this study, various sound waves such as 1) ultrasonic waves, 2) music box, and 3) wind-bell were irradiated to water and wastewater for removing contaminants such as nitrate, phosphorus and BOD/COD. The conclusion of the paper is as follows.
1) Various sound waves affect on the improvement of the water quality.
2) As for the removal rate of 2 NO − and 3 NO − concerning to the three samples such as the seawater, drinking water and the forest water, high values (>50%) were obtained, respectively.
3) 3 4 PO − was also confirmed to decrease more than 50% in the forest water. 4) BOD and COD was drastically decreased especially in drinking water and forest water. 5) The removal rate of Ca 2+ and Mg 2+ was also large (>50%) in the drinking water. Along with these, TH also drastically decreased. On the other hand, Na + , K + .and 4 NH + showed very few change. 6) Therefore, decreases of 2 NO − , 3 NO − and 3 4 PO − are due to the reaction with bivalent cations of Ca 2+ and Mg 2+ rather than monovalent cations such as Na + , K + and 4 NH + . 7) It is supposed that if hard water with components of Ca 2+ and Mg 2+ is properly added into a soft drinking water, and the sound waves are irradiated to them, 2 NO − , 3 NO − and 3 4 PO − could be reduced. It could be useful from the industrial viewpoint.