| dc.description.abstract | The NH3-N wastewater in the process of solar cell plant is generated from single source, N2 used in CVD process. The waste gas generated in the process forms NH3-N wastewater after washed by the auxiliary equipment of CVD machine. With drastic change, the ammonia nitrogen concentration in the wastewater is relatively low in the range of 236 ~ 910mg/ L. Moreover, the wastewater contains large amount of SiO2 pollutant because SiH4 is used in CVD process.
The study applies the selective function of MD film module for fractional extraction of NH3-N contained in the wastewater, which is then adsorbed by H2SO4to form (NH4)2SO4. As shown in the results, after the addition of ammonia nitrogen wastewater pH value raises to 11.4, the transition rate of NH 4+ and and and NH 3(g)3(g) 3(g) may reach may reach may reach may reach may reach may reach may reach 99% , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature , which may be increased with the temperature of of ammonia nitrogen wastewater. However, the temperature increase will add operation cost. Heating is only applicable to maintain the temperature of wastewater during seasons with low temperature, so as to retain the system processing performance.
The optimal operation range for H2SO4 is pH = 2 ~ pH =3. When the NH3-N concentration is within the low range of 323 ~ 448 mg/L, the optimal operation ratio lower than the cyclic H2SO4 flow and NH3-N waste water flow is 2:1. When the ammonia nitrogen concentration is within the high range of 672 ~ 1,210 mg/L, the operation ratio is 1:1. This can decelerate the water permeating MD, and increase the output proportion of (NH4)2SO4 to 22~24%. Higher the flow ratio within the low concentration range will result in higher system processing efficiency, and vice versa. When the flow ratio is increased, it will result in insufficient space for NH 3(g)3(g) 3(g) to permeate MD film due to the water
competition factor, and the system processing efficiency will be lowered accordingly.
After serial connection of two MDs, the system processing efficiency can reach as high as 99%, which is completely consistent with the transition rate of NH 4+ and NH 3(g)3(g) 3(g) under pH =11.4. It may provide sufficient retention time and control various operation conditions properly. Moreover, it may get extremely high efficiency of MD processing system. So it is quite suitable to the treatment of ammonia nitrogen wastewater in the solar process. | en_US |