Achieving robust mainstream nitrite shunt at pilot-scale with integrated sidestream sludge treatment and step-feed

•Evaluation of two novel sidestream treatment-based strategies for nitrite shunt.•Pilot-scale systems operated for >850 days to assess the process robustness.•Solely alternating sludge treatment approach is challenged by NOB adaptation.•Robust nitrite shunt process for 1 yr. by integrating sludge treatment and step-feed.•Kinetic analysis suggests integrated strategy is key to robust nitrite shunt.