Abstract
This research demonstrated the feasibility of incorporating, at regular intervals, non‐aerated conditions in aerobic sludge digestion. This paper (Part II) details the benefits realized in terms of supernatant quality (NO levels reduced by 2 orders of magnitude; PO4 levels reduced by one‐half to one‐third). Monitoring the oxidation‐reduction potential (ORP) revealed characteristic profiles where slope changes correlated well with the (dis)appearance of ammonia, nitrates and dissolved oxygen. An overall rating system was developed which suggested that anoxic‐aerobic sludge digestion out performed both lime‐control and conventional digestion modes.