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본 연구는 SDI (Silt Density Index)를 통해 RO막 전처리 장치로서의 섬유여과기 적용 가능성을 평가한 것이다. 실험 대상 원수는 탁도가 0.76∼1.6 NTU인 하수처리장 방류수와 탁도가 2.2∼3.3 NTU인 해수 및 탁도가 100 NTU인 지표수이었다. 2단 섬유여과기 공정의 최종여과수인 2차 여과수의 탁도는 17% PAC 10∼30 ppm주입 시 0.07∼0.25 NTU였으며 SDI는 1.4∼2.8이었다. 하수처리장 방류수에 대해 2단 섬유여과기 pilot 여과수와 실험실 규모의 MF, UF평막 여과수의 탁도 및 SDI15를 측정하여 비교한 결과, 여과수 수질은 2단 섬유여과기 > MF > UF순으로 약간 향상하였으며, SDI15 차이는 0.7∼1.0 수준으로 크지 않았다. 따라서 2단 섬유여과 공정을 RO막 전처리 공정으로 사용할 경우 통상의 RO막 제조사가 요구하는 SDI15 5 이하를 충분히 만족시킬 수 있을 것으로 판단된다.
This study was for the evaluation of adaptability of the fiber filter as the pre-treatment of the RO membrane through SDI (Silt Density Index) measurement. The turbidity of raw waters were 0.76∼1.6 NTU for the effluent of sewer treatment plants (STP) and 2.2∼3.3 NTU for sea waters and 100 NTU for the surface water. The turbidity of the 2 nd filtrate of the serially connected two fiber filters was 0.07∼0.25 NTU and SDI15 was 1.4∼2.8 when the 17% PAC was dosed 10∼30 ppm. Results of the turbidity and SDI15 of the 2 nd filtrate of the fiber filter which were compared with them of the lab scale MF/UF disc filter for the same STP's effluents showed that filtrate quality were enhanced with a little on the order of two stage fiber filter>MF>UF, the difference in SDI15 was only 0.7∼1.0. So, the filtrate of the serially connected two stage fiber filter could satisfy SDI15 5.0 safely which was normally required for the feed water by the RO membrane supplier and it means the serially connected two stage fiber filter could be applied as the pre-treatment process of the RO membrane.
