The effluent from the MBR is yellow
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A small-scale MBR laboratory unit was set up; after allowing the sludge to undergo anaerobic aeration for two days, water was introduced to the system. The sludge concentration was over 7000, and the domestic wastewater used was of my own preparation with a COD level of around 400, while the inflow rate was 1 L/h. The water quality of the water discharged after it was made to flow was yellowish; the yellowing wasn’t severe, but it was more noticeable than that of ordinary tap water. Tests showed that the COD level of the discharged water was around 20–30. The membrane filaments were also checked; there is no leakage. I would like to ask why the water quality is yellowish – what could be the possible reasons?
It may be due to iron ions in the water, or sludge disintegration caused by excessive aeration.
Has yellowing occurred in previous instances? It’s possible that the wastewater contains certain pigments, and the filtration precision of MBR membranes is generally that of ultrafiltration, which does not provide effective retention of pigments; therefore, nanofiltration is usually used for decolorization