NOVELTY - Large horizontal arc-shaped methane tank comprises pre-treatment tank (5), anaerobic digestion tank, material inlet and hydraulic chamber, mixing tank (4), drying tank (13), depositing tank (14), and methane process tank. The mixing tank is connected with pre-treatment tank which is connected with material inlet (6) by pipeline. The lower end of material inlet is connected with upper end of anaerobic digestion tank (7) which comprises straight formwork, arc-shaped formwork, middle arc-shaped formwork, and small arc-shaped formwork.    USE - Large horizontal arc-shaped methane tank.    ADVANTAGE - The large methane tank is easy to maintain, and has high safety. The sewage treatment method recycles methane by multi-stage purifying, including drying, depositing, and filtering. The biogas residue is further finely processed to keep standard of national green organic fertilizer that can be circularly applied to farmland and orchard, so that problem of recycling sewage of large methane tank can be completely solved.    DETAILED DESCRIPTION - Large horizontal arc-shaped methane tank comprises pre-treatment tank (5), anaerobic digestion tank, material inlet and hydraulic chamber, mixing tank (4), drying tank (13), depositing tank (14), and methane process tank. The mixing tank is connected with pre-treatment tank which is connected with material inlet (6) by pipeline. The lower end of material inlet is connected with upper end of anaerobic digestion tank (7) which comprises straight formwork, arc-shaped formwork, middle arc-shaped formwork, and small arc-shaped formwork. The wall of anaerobic digestion tank comprises straight formwork and arc-shaped formwork. Several straight formworks form two long parallel sides of walls of anaerobic digestion tank, while several arc-shaped formworks form two arc-shaped sides of walls of anaerobic digestion tank, and several small arc-shaped formworks at two ends and several arc-shaped plates at middle formed arc-shaped tank top of anaerobic digestion tank. The lower end of anaerobic digestion tank is connected with hydraulic chamber (8) with lower end connected with upper end of drying tank. The lower end of drying tank is connected with depositing tank into which channel (15) is arranged. The depositing tank is connected with methane process tank which is connected with mixing tank by pipeline. An INDEPENDENT CLAIM is included for processing of sewage of large horizontal arc-shaped methane tank by adding dejection to mixing tank to mix; controlling to convey mixture to pre-treatment tank to preprocess through valve; adding material through material inlet to anaerobic digestion tank; carrying out anaerobic digestion; pouring produced methane to methane storing tank to store and stand by service; supplying methane through distribution pipeline (17); generating through generator (18); mixing solid and liquid with waste after producing methane through anaerobic digestion tank; feeding matter into drying tank to separate dry matter to methane residue (19) and biogas from wet matter in hydraulic chamber; feeding methane residue into residue tank (20) to finely process into green organic fertilizer to be transported to fertilizer factory (21); downwards flowing methane into depositing tank to purify; depositing and purifying through multi-stage channel; transporting into methane process sink to store; recycling methane stored via methane process tank through pipeline; transporting into mixing tank; and repeating process.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of large horizontal arc-shaped methane tank.    Mixing tank (4)    Pre-treatment tank (5)    Material inlet (6)    Anaerobic digestion tank (7)    Hydraulic chamber (8)    Drying tank (13)    Depositing tank (14)    Channel (15)    Distribution pipeline (17)    Generator (18)    Methane residue (19)    Residue tank (20)    Fertilizer factory (21)