NOVELTY - Complete recycling of sludge comprises e.g. opening valve a (21) and valve b (22), closing valve c (23) and connecting a sludge hydrolysis reacting tank (5) with a flocculating settling tank (7), filtering the sludge and feeding into the sludge regulating tank, measuring the chemical oxygen demand (COD) value, feeding the sludge into the sludge hydrolysis reacting tank, adding sodium hydroxide solution to maintain the pH, feeding the sludge hydrolysis liquid into a flocculating settling tank, centrifuging, calculating the COD dissolving rate, dehydrating and storing the precipitate.    USE - The recycled sludge, containing inorganic and little organic matter, is useful for preparing fertilizers.    ADVANTAGE - The method: achieves complete recycling and zero discharge of the sludge; solves the problem of processing the sludge in a sludge plant; reduces the cost of water disposal and reduces environmental pollution.    DETAILED DESCRIPTION - Complete recycling of sludge comprises: (i) opening valve a (21) and valve b (22), a closing valve c (23) and connecting a sludge hydrolysis reacting tank (5) with a flocculating settling tank (7), before processing the sludge, (ii) filtering the sludge by a mechanical sieve and feeding into a sludge regulating tank, stirring for 30 minutes till the water content is 96-98%, the density is 1.005 metric tonne/m3, and measuring the chemical oxygen demand (COD) value, (iii) feeding the sludge into the sludge hydrolysis reacting tank by a sludge lifting pump, adding sodium hydroxide solution (5%) into the sludge hydrolysis reacting tank, in a volume ratio of sodium hydroxide solution to the sludge at 1:10, stirring till the pH of the sludge hydrolysis reacting tank reaches 12-14 and controlling the temperature at 70 degrees C, stirring for 24 hours, adding sodium hydroxide solution drop wise using a sludge hydrolysis chemical dosing system, maintaining the pH of the sludge hydrolysis reacting tank at 12-14, stirring for 24 hours to obtain a sludge hydrolysis liquid, (iv) feeding the sludge hydrolysis liquid into a flocculating settling tank, opening a calcium chloride dosing system, simultaneously, adding calcium chloride solution (30%), precipitating for 3 hours in the flocculating settling tank, and separating the supernatant containing biological flocculants from the precipitate, (v) processing the supernatant containing the biological flocculants by a hydrolysis regulating tank, measuring the COD value, and calculating the COD dissolving rate, (vi) centrifuging the supernatant containing biological flocculants in a front centrifuge, for 5 minutes at 6000 revolutions/minute to obtain a crude flocculating liquid which is fed into the liquid storage tank, feeding the precipitate obtained from centrifuging into an inorganic solid product storing tank, (vii) allowing the crude flocculating liquid to stand in the liquid storing tank for 24 hours, delivering the crude flocculating liquid into a flocculating liquid-acetone mixing tank, adding acetone into the tank in a volume ratio of 2:1, reacting for 15 minutes and stirring at 200 revolutions/minute, (viii) centrifuging the mixture in a rear centrifuge for 15 minutes at 15000 revolutions/minute to obtain the precipitate, which is a flocculant crude product stored in a flocculant coarse product tank, and (ix) storing the precipitate separated from the flocculating settling tank in a flocculating settling storing tank, centrifuging and dehydrating in a dehydrating device at 8000 revolutions/minute till the water content is 70%, and storing the precipitate in an inorganic solid product storing tank together with the residual solid separated from the front centrifuge.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic representation of the device used for complete recycling of sludge.    Sludge hydrolysis reacting tank (5)    Flocculating settling tank (7)    Valve a (21)    Valve b (22)    Valve c (23)