TECHNOLOGY FOCUS - ENVIRONMENT - Preferred Method: Treating the wastewater sludge in the batch tank includes retaining the sludge in the batch tank for 0.5-5 hours. Treating the wastewater sludge in the first digester includes retaining the sludge in the first digester for at least4 days. Disposing includes directing the treated sludge to a third set of digesters operating at 35degreesC for at least8 days. The wastewater sludge is treated to meet Environmental Protection Agency (EPA) Vector Attraction Reduction (VAR) standard by oversizing the first digester to increase an average retention time of the wastewater sludge; oversizing the batch tank to increase the average retention time of the wastewater sludge; providing a third digester which includes a thermophilic digester; providing a third digester which includes a mesophilic digester wherein sludge leaving the batch tank is cooled to mesophilic temperatures, e.g. 35-42degreesC and digested further in the mesophilic digester; and providing alternative VAR option downstream of the first and second digester including 40-day additional digestion test, 30-day additional digestion test, subsurface injection of biosolids, or incorporation into the soil.    TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Components: The batch tank is a plug-flow reactor which includes vertically disposed reactor vessels; a sludge feed manifold for transferring sludge from the first thermophilic digester to the reactor vessels; a valved, sludge feed pipe for transferring sludge from the sludge feed manifold to the reactor vessel, wherein the sludge feed pipe directs sludge to the top of the reactor vessel and is configured to direct sludge to the top and sides of the reactor vessel and is sized to maintain solids in suspension; a weir located adjacent the top of the reactor vessel to remove floatable sludge components; and a valved outlet pipe. The valved outlet pipe is connected to the sludge feed manifold downstream of the sludge feed pipe. The reactor vessel includes a baffle located intermediate the top and bottom. The baffle has a conical configuration with the point directed upwards in the reactor vessel. Alternatively, the baffle has a truncated conical configuration with the opening directed upwards in the reactor vessel. Each reactor vessel includes several baffles. The disposal mechanism includes a mesophilic digester for finally treating the sludge prior to disposal.