If this opportunity is for you please get me guide about yellow sludge.
I run membrane bioreactor for Artificial  starch wastewater treatment. operated @ SRT= 10 day hrt=12hr. after about 10day sludge color changes from brown to yellow and COD removal efficiency decreased sharply. I know that nitosamine produced in this MBR but don't know why this matter produced. Thanks if you get my guide.

Would you give us more detail about wastewater? Do you need to supplement nutrient and/or control pH before MBR?