Abstract: First, a primary fluoric ion concentration detection process is performed, and a primary calcium salt addition process is performed to add calcium salt in a first reaction tank, wherein the dosage of the calcium salt in the primary calcium salt addition process is determined according to the detected fluoric ion concentration. Thereupon, a secondary calcium salt addition process is performed to add calcium salt into the second reaction tank. Following that, a solid-liquid separation process is performed to separate calcium fluoride from the wastewater, and a secondary fluoric ion concentration detection process is performed upon the wastewater after the calcium fluoride is separated. Finally, the dosage of the calcium salt in the secondary calcium salt addition process is determined in a feed back control manner according to the detected fluoric ion concentration.

Abstract: First, water in a filter is drained to a low level, and the remaining water is adjusted to an alkaline condition so as to break up the flocs in the filter media. Then, a pneumatic rinsing process is performed, by introducing air from the bottom of the filter for shaking the filter media, so as to loosen the flocs. After that, a reverse rinsing process is performed, by providing water from the bottom of the filter, so that small flocs, having a relatively small specific gravity, float up to be removed. Finally, a sterilizing process is performed upon the filter media, and the impurities remaining in the filter media are cleaned up to ensure the quality of water to be filtered.

Abstract: First, a primary fluoric ion concentration detection process is performed, and a primary calcium salt addition process is performed to add calcium salt in a first reaction tank, wherein the dosage of the calcium salt in the primary calcium salt addition process is determined according to the detected fluoric ion concentration. Thereupon, a secondary calcium salt addition process is performed to add calcium salt into the second reaction tank. Following that, a solid-liquid separation process is performed to separate calcium fluoride from the wastewater, and a secondary fluoric ion concentration detection process is performed upon the wastewater after the calcium fluoride is separated. Finally, the dosage of the calcium salt in the secondary calcium salt addition process is determined in a feed back control manner according to the detected fluoric ion concentration.