(without cleaning) in 2 days. Although N2 flushing was applied in
the following operating condition and did effectively alleviate the
membrane fouling, the TMP again increased to 50 kPa, which is
unfavorable for the longtime operation of the membrane. Thus,
though 80% COD removal could be obtained at an HRT of 2 d, the
aggravation of membrane fouling caused by the increased flow rate
was a problem. Based on these results, the suggested operating
HRT is longer than 5 d.