The residue that accumulates in sewage treatment plants is termed sludge (or biosolids). Sewage sludge would be the solid, semisolid, or slurry residual material that's produced like a by-product of wastewater treatment processes. This residue is normally classified as primary and secondary sludge. Primary sludge is generated from chemical precipitation, sedimentation, along with primary processes, whereas secondary sludge would be the activated waste biomass caused by biological treatments. Some sewage plants also receive septage or septic tank solids from household on-site wastewater treatment systems. Quite often the sludges are combined together for even more treatment and disposal. Treatment and disposal of sewage sludge are major factors inside design and operation of most wastewater treatment plants. Two basic goals of treating sludge before final disposal will be to reduce its volume as well as stabilize the organic materials. Stabilized sludge don't even have an ...