Effects of Filter Media in High-Rate Filters for Pretreating Textile Wastewater

Textile wastewater contains dyes, slurries, additives, oiling agents, acid-base substances, fiber impurities, and inorganic salts and generally exhibits harsh characteristics such as high chemical oxygen demand (COD), suspended solids (SS), color, and salinity. This study evaluated the performance of a high-rate filter (HRF) as an alternative to conventional primary sedimentation (CPS) processes. The HRF, with a significantly shorter hydraulic retention time (HRT: 0.3 h), demonstrated a performance efficiency similar to that of the CPS process, which had a longer HRT of 3.0 h. The packed depths in the HRF were 0.8 m for cylindrical plastic media (CPM) and 0.6 m for cube sponge media (CSM). This study aimed to evaluate the system’s performance in treating textile wastewater with the following characteristics: BOD 746.0 mg/L, COD 492.0 mg/L, T-N 34.7 mg/L, T-P 7.0 mg/L, SS 296.4 mg/L, and color 647.0 units. The HRF packed with CSM achieved 1-7% higher removal efficiency than the HRF packed with CPM. In particular, the CSM was significantly more effective in reducing SS and color, owing to its specific surface area being three times that of CPM. The effects of HRF with both CPM and CSM on SS and color removal were similar to those of CPS. To further enhance the filtration efficiency of the HRF with filter media, the process needs to operate at a lower filtration velocity and be coupled with coagulation.