Tannery Wastewater Treatment Using a Sequencing Batch Membrane Reactor

Abstract

The feasibility of a new system, SBMR (Sequencing Batch Membrane Reactor) was investigated for tannery wastewater treatment which includes high strength organic matter and a heavy metal, chromium. This system consists of a hollow fiber microfiltration unit in a SBR for solid-liquid separation, which aims to enhance sludge concentration in the reactor for stable removal of organic matter and heavy metals. The removal efficiency of COD and Total Chromium was 93.7 to 96.3% and 95.4 to 97.7%, respectively. The critical sludge concentration was found between 30,000 and 40,000 mg/l in order to keep stable filtration. Lower SRT gave lower Cr content in the sludge under constant organic loading. Higher organic loading gave lower Cr content at fixed SRT except for the longest SRT case. SRT of 20 days gave the highest ammoniacal/total nitrogen removal. A short SRT of 10 days gave adverse effect on nitrifying bacteria because of their low growth rate. Judging from the process stability in the light of the removal of organic matter, nitrogen and chromium and the flux, the SRT of 20 days was the best among 10, 20, 550 days. There must exist an appropriate combination of SRT and volumetric organic loading. When SRT of 20 days is selected, it is recommended that the volumetric organic loading be kept less than 8 kgCOD/m3d.