NOVELTY - Treating a sludge, the sludge comprising solids and ammonia, the process comprises: (a) separating the sludge into a solids fraction and a liquid fraction, the liquid fraction comprising ammonia; (b) treating the liquid fraction to produce an ammonium salt solution; and (c) combining the solids fraction with the ammonium salt solution.    USE - The processes and apparatus are useful for treating a sludge; for making a fertilizer pellet; for recovering ammonia from a liquid; and for removing ammonia from a liquid (all claimed).    ADVANTAGE - The process and apparatus are highly efficient, environment friendly and effectively produce fertilizer pellet.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are:    (1) an apparatus for treating sludge comprising: (a) one or more of a mechanical dewatering device and a dryer configured to receive the sludge and to output a solids fraction and a liquid fraction; (b) an ammonia recovery system to receive the liquid fraction and output an acidic ammonium salt solution; (c) a pellet making machine to receive the solids fraction and the acidic ammonium salt solution and to combine them into pellets;    (2) a fertilizer pellet comprising solids extracted from anaerobic digester sludge and at least 2% by dry weight of ammonium salts precipitated from an acidified liquid comprising ammonia extracted from liquids, vapors or gasses previously removed from the anaerobic digester sludge;    (3) a process of making the fertilizer pellet comprising combining dried solids extracted from anaerobic digester sludge with an acidified liquid comprising ammonia previously removed from the anaerobic digester sludge;    (4) a process comprising steps of (a) recovering fibers and a filtrate from an anaerobic digester sludge; (b) recovering solids and a liquid from the filtrate; and (c) recovering ammonia from the liquid; and    (5) a process for removing ammonia from a liquid comprising steps of: (a) flowing the ammonia through a series of sequential stages; (b) blowing bubbles, for example of air, into the liquid in the stages; and (c) flowing air across the surface of the liquid in the stages.