Intermittent　aeration　and　bio-augmentation　were　integrated　to　enhance　single-stage　partial　nitrificationanammox　(SPN/　A)　stability　over　235-day　operational　period　treating　low-strength　sewage.　The　effect　of　bio-augmentation　sludge　(with　different　abundances　of　ammonium　oxidizing　bacteria　(AOB)　and　nitrite　oxidizing　bacteria　(NOB))　was　determined.　Partial　nitrification　sludge　based　bio-augmentation　increased　the　total　nitrogen　(TN)　removal　efficiency　from　29.1%　to　70%,　followed　by　the　nitrification　sludge　(from　38.1%　to　65.4%),　then　the　denitrifying　phosphorus　sludge　(from　42.1%　to　54.4%).　The　evolution　of　bacteria　activity　and　communities　showed　that　anammox　activity　increased　with　the　enhancement　of　AOB　activity,　and　higher　AOB　abundance　led　to　higher　anammox　bacterial　abundance　despite　high　NOB　abundance.　The　enhancement　of　AOB　activity　produced　more　nitrite,　anammox　bacteria　gained　more　nitrite　than　NOB　since　intermittent　aeration　selectively　inhibited　NOB,　thus　the　reactor　stability　enhanced　substantially.　This　study　highlights　the　significance　of　enhancing　AOB　activity　to　ensure　long-term　operational　stability　of　SPN/A　processes.　(C)　2017　Elsevier　Ltd.　All　rights　reserved.