Effect of N2-back-flushing in multichannels ceramic microfiltration system for paper wastewater treatment

The ceramic microfiltration system with periodic N2-back-flushing was operated for treating paper wastewater discharged from a company making toilet papers by recycling milk or juice cartons. Two kinds of alumina membranes with 7 channels used here for recycling paper wastewater. The optimal N2 filtration time for HC04 membrane with 0.4µm pore size was lower value of 4min than 16min for HC10 with 1.0µm pore size at fixed back-flushing time 40s, trans-membrane pressure 1.0kgf /cm2 and back-flushing pressure 5.0kgf /cm2. From the results of TMP effect at fixed filtration time and back-flushing time, the lower TMP was better on membrane fouling because high TMP could make easily membrane cake and fouling inside membrane structure. However, we could acquire the highest volume of total permeate for the reason that TMP was driving force in our filtration system to treat paper wastewater. Then the permeate water of low turbidity was acquired in our microfiltration system using multichannels ceramic membranes, and the treated water could be reused in paper process.

J/J0 0.60 0.50 0.40 0.30 0.20 FT = 16 min BT = 40 sec 0.10 0.00 HC04 Time (min) TMP = 0.5 kgf /cm2 which was the lowest condition in our experiments. Also the highest value of J/J0 could be taken at the same TMP = 0.5 kgf /cm2 as shown in Fig. 9. It means the lower TMP should reduce the membrane fouling during filtration of paper wastewater, and could maintain high permeate flux compared to initial flux. However, TMP was driving force in our filtration system, and the largest value VT of 4.52 L could be obtained at the highest TMP condition of 2.0 kgf /cm2 as shown in Table 4. The average rejection rates were above 90% for turbidity, and above 25% for CODCr, and below 1% for TDS because microfiltration membranes were used here. And the permeate water treated in our system could be reused in paper plant because its turbidity was low under 5 NTU.