NOVELTY - A treatment plant (1) of waste waters and sludge from sewage comprises purifying plant comprising sewage treatment unit (3) for separating liquid sludge (20) from purified water (11), and centrifugal dehydration unit (6) for centrifuging liquid sludge from treatment unit; gas generation plant (200) comprising anaerobic digester (5); and electricity-generating set comprising gas internal combustion engine or turbine powered with biogas produced by anaerobic digester and generator connected to turbine for production of electricity.    USE - A treatment plant of waste waters and sludge from sewage.    ADVANTAGE - The waste is easy to access and the process also allows for saving on traditional waste disposal costs. The treatment process achieves great saving on disposal system in dumping ground (or incinerator) of sewage sludge and of organic solids, while obtaining clean energy from sludge and waste to cover the energy requirements of plant.    DETAILED DESCRIPTION - A treatment plant (1) of waste waters and sludge from sewage comprises purifying plant comprising sewage treatment unit (3) for separating liquid sludge (20) from purified water (11), and centrifugal dehydration unit (6) for centrifuging liquid sludge from treatment unit; gas generation plant (200) comprising anaerobic digester (5) situated between treatment plant and centrifuge to receive liquid sludge and produce biogas by anaerobic process; and electricity-generating set comprising gas internal combustion engine or turbine powered with biogas produced by anaerobic digester and generator connected to turbine for production of electricity. The gas generation plant also comprises crusher(s) for grinding urban organic solid waste; mixing and homogenization pit for mixing and homogenizing urban organic solid waste with liquid sludge from treatment unit to obtain amalgamated mixture of sludge and organic waste; and feeding unit for feeding sludge and organic waste mixture to anaerobic digester. An INDEPENDENT CLAIM is included for sewage sludge treatment process comprising:    (A) separating liquid sludge from sewage to obtain purified water to be introduced in environment, and grinding urban organic solid waste to obtain ground organic waste;    (B) mixing and homogenizing ground organic solid waste with liquid sludge to obtain amalgamated mix of organic waste and liquid sludge;    (C) anaerobically digesting amalgamated mix of organic waste and liquid sludge to produce biogas;    (D) centrifugally dehydrating liquid sludge from anaerobic digestion to obtain dehydrated sludge with dry product concentration of 25%; and    (E) feeding biogas in electricity-generating set comprising gas engine or turbine and generator connected to turbine for production of electricity.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of a treatment plant of sewage and sludge from sewage.    Treatment plant (1)    Sewage treatment unit (3)    Anaerobic digester (5)    Centrifugal dehydration unit (6)    Purified water (11)    Liquid sludge (20)    Gas generation plant (200)