An antenna apparatus capable of main beam direction switching is provided that achieves high gain with a small, planar configuration. According to the invention, oxygen is artificially and periodically added to the waste water, for example in that air is periodically blown into a pipe of the sewage system by means of an air pump. The first step performs supply of the first and second process gases to the process field. In addition, a plurality of active devices is disposed at the sides of the electrodes in the liquid crystal lens, in which the active devices are electrically connected to the electrodes.