NOVELTY - Microbiological detoxification, solidification, and hazard-free treatment of toxic metal substrate sludge includes adding toxic metal substrate sludge into a bioreactor; acidifying the substrate sludge; separating; refluxing the settled substrate sludge; dehydrating the remaining settled substrate sludge to obtain acid substrate sludge; adding organic carbon source into acid waste liquid; controlling the ratio of chemical oxygen demand (COD)/sulfate ion; regulating pH of the waste liquid; adding acid-resistant sulfate reducing bacterium; performing anaerobic treatment; and settling.    USE - Microbiological detoxification, solidification, and hazard-free treatment of toxic metal substrate sludge (claimed).    ADVANTAGE - The processed substrate sludge meets the needs of engineering filling and landfill. The method achieves complete detoxification; has no secondary pollution, less technical equipment, and low energy consumption; and is suitable for industrial operation.    DETAILED DESCRIPTION - Microbiological detoxification, solidification, and hazard-free treatment of toxic metal substrate sludge comprises: (A) adding toxic metal substrate sludge into a bioreactor 1, where sludge contains 5-15% solid, 2-4 g/L sulfur powder, and Acidithiobacillus caldus FD97 with inoculation amount of 5-10%; processing for 10-15 days at 20-30 degrees C in a ventilated environment; acidifying the substrate sludge until the pH is 2.5-3.0; and separating solid and liquid of the processed substrate sludge in a sedimentation tank 1; (B) refluxing the settled substrate sludge of 5-10% in the sedimentation tank 1 into the bioreactor 1 to replace the A. caldus FD97 for inoculation; feeding substrate sludge to be processed, which contains 5-15% solid and 2-4 g/L sulfur powder; and circulating and processing; (C) dehydrating the remaining settled substrate sludge of 90-95% in the sedimentation tank 1 to obtain acid substrate sludge, which is capable of generating acid toxic metal waste liquid and is nearly free from toxic metal; (D) adding organic carbon source into the acid waste liquid of step (C); controlling the ratio of COD/sulfate ion (SO42-) at 1.0-3.0; regulating pH of the waste liquid at 3.0-5.0 by alkaline material; continuously pumping the waste liquid into bioreactor 2 at 0.2-2.0 ml/minute; adding acid-resistant sulfate reducing bacterium into bioreactor 2 at an inoculation amount of 15-30%; performing anaerobic treatment at 20-40 degrees C; settling the water from the bioreactor 2 in sedimentation tank 2; directly discharging the obtained supernatant liquid; and settling the little solid phase for recycling metal; and (E) adding alkali slag in the acid substrate sludge of step (C); regulating pH of the substrate sludge at 6.5; adding solidifying agent, i.e. cement, into the substrate sludge at 0.2-0.4 mass ratio; uniformly mixing; maintaining for 1 day by conventional method at room temperature; demolding; and maintaining for 10-15 days to obtain stable substrate sludge solidified material.