Pilot-scale　studies　on　biological　treatment　of　hypersaline　wastewater　at　low　temperature　were　conducted　and　results　showed　that　seawater　salinity　had　a　strong　negative　effect　on　notronomonas　and　nitrobacter　growth,　but　much　more　on　the　nitrobacter.　The　nitrification　action　was　mainly　accomplished　by　nitrosomonas.　Bench-scale　experiments　using　two　SBRs　were　carried　out　for　further　investigation　under　different　conditions　of　salinities,　ammonia　loadings　and　temperatures.　Biological　nitrogen　removal　via　nitrite　pathway　from　wastewater　containing　30　percent　seawater　was　achieved,　but　the　ammonia　removal　efficiency　was　strongly　related　not　only　to　the　influent　ammonia　loading　at　different　salinities　but　also　to　temperatures.　When　the　ratio　of　seawater　to　wastewater　was　30　percent,　and　the　ammonia　loading　was　below　the　critical　value　of　0.15　kgNH4+-N/(kgMLSS·d),　the　ammonia　removal　efficiency　via　nitrite　pathway　was　above　90%.　The　critical　level　of　ammonia　loading　was　0.15,　0.08　and　0.03　kgNH4+-N/(kgMLSS·d)　respectively　at　different　temperatures　of　30°C,　25°C　and　20°C　when　the　influent　ammonia　concentration　was　60-80　mg/L　and　pH　was　7.5-8.0.