Influence of bioleaching on dewaterability of cattle biogas slurry

The dewaterability of cattle biogas slurry facilitated by bioleaching was investigated through batch experiments with co-inoculation of different Acidophilic thiobacilli (Acidithiobacillus thiooxidans TS6 or Acidithiobacillus ferrooxidans LX5).The experiment was set the following 5 treatments: (1)original biogas slurry (CK), (2)4 g · L^-1 Fe²⁺(uninoculation), (3)2 g · L^-1S⁰+25 mL A.t, (4)4 g · L^-1Fe²⁺+25 mL A.f and (5)2 g · L^-1S⁰+4 g · L^-1 Fe²⁺+12.5 mL A.t+12.5 mL A.f.During bioleaching, dynamic changes of pH, ORP, Fe²⁺, Fe³⁺, total Fe, the settleability, the turbidity of the supernatant after settling for 12 h, and the dewaterability (expressed as specific resistance to filtration γ or capillary suction time, CST) of biogas slurry were monitored. Results show that specific resistance γ and CST of bioleached biogas slurry are reduced drastically for the treatments of original biogas slurry spiked with only Fe²⁺, the treatment of original biogas slurry co-spiked with Fe²⁺ and Acidithiobacillus ferrooxidans LX5, and the treatment of original biogas slurry co-spiked with Fe²⁺, S⁰ and two Acidophilic thiobacilli. Taking the dewaterability, settleability, the turbidity of the supernatant fluid after settle 12 h and economical cost into account, the treatment of original biogas slurry co-spiked with Fe²⁺ and Acidithiobacillus ferrooxidans LX5 is the most suitable pattern for cattle biogas slurry bioleaching. After bioleaching, 1.14% of organic matter, 0.09% of N, 0.05% of P, and 0.1% of K are lost in the bioleaching process, but it don't affect its fertilizer efficiency. Meanwhile, the 63.2% of Cu and 91.3% of Zn are removed from the biogas slurry, and elimination efficiencies of total coliforms in bioleached slurry exceed 99%. This study might provide a new approach for treatment and disposal of biogas slurry.