| abstract |
Low strength wastewater such as municipal sewage is treated using an anaerobic digester. In some examples, a wastewater stream is separated into a solids rich portion and a solids lean portion. The solids lean portion is treated, for example to remove nitrogen. The solids rich portion is treated in an anaerobic digester, preferably with influent or recuperative thickening. In another example, the wastewater stream is fed to an anaerobic digester and solid-liquid separation stages downstream of the digester return active bacteria and undigested organics to the digester. Both cases may use a process train comprising treatment in an anoxic tank followed by a nitritation tank with a portion of the effluent from the nitritation tank recirculated to the anoxic tank to provide nitritation and denitritation. |