Sewage treatment system and method for natural gas purifying factory in H2S-containing gas field

The invention discloses a sewage treatment system and method for a natural gas purifying factory in H2S-containing gas field. By adopting a biological treatment process comprising pre-aeration, air floatation, hydrolytic acidification, anaerobic treatment, aerobic treatment, and precipitation, the quality of the treated water meets the primary standard of supreme permissible effluent concentration of the second category of hazardous in national integrated wastewater discharge standard. According to the invention, innovation is created based on anaerobism-aerobism of conventional purifying factory biochemical sewage treatment processes, and a sewage pretreatment step realized by hydrolytic acidification is added, thus water quality and quantity are effectively adjusted, the biodegradability of the sewage is greatly raised, and favorable conditions are created for posttreatment of the sewage; in the stage of subsequent treatment, the anaerobic-aerobic segment is changed into an aerobic-anaerobic segment, the sewage retention time is greatly reduced, the volume of treatment building is correspondingly reduced, thus the engineering investment is saved, and the workload of maintenance management is reduced.