环氧丙烷生产废水处理改造工程设计

Design of Propylene Oxide Wastewater Treatment Reconstruction Project

天津某大型化工企业以烧碱、环氧丙烷为主要产品，在环氧丙烷生产过程中排出大量的皂化废水。由于2008年天津市污水排放标准的颁布，需对企业一座4×10^4m^3／d污水处理厂进行提升改造。原工艺为初沉池／活性污泥曝气池／二沉池／接触氧化池／终沉池，改造工程将活性污泥曝气池改造为缺氧-好氧（AN／O）池，设计水力停留时间HRT（缺氧）：HRT（好氧）=1：3，混合液回流比R=0—100％，MLSS≥10g／L；处理工艺末端增加混凝过滤工艺。另外工程设计总进水量为1667m^3／h，其中缺氧-好氧（AN／0）工艺进水量为l500m^3／h，余下167m^3／h直接进入接触氧化池，为接触氧化处理段微生物提供养分。经过3年的运行，出水指标一直稳定达到天津市《污水综合排放标准》（DB12／356-2008）二级排放标准。

A large chemical company in Tianjin mainly produces caustic soda, propylene oxide, and a large quantity of saponification wastewater is discharged when propylene oxide is produced. Due to the enactment of Tianjin local standards for wastewater discharge in 2008, a wastewater treatment plant with capacity 40 000 m^3/d was upgraded. The original process was primary sedimentation tank/activated sludge aeration tank/secondary settling tank/contact oxidation tank/final settling tank. The activated sludge aeration tank was transformed to anoxic/aerobic （AN/O） tank, with anoxic HRT ： aerobic HRT of 1 ： 3, mixed liquor recycle ratio of 0 to 100% and MLSS≥10 g/L. Coagulation and filtration process was added at the end of the treatment process. In addition, the total influent amount was 1 667 m^3/h, in which the influent amount of anoxic/aerobic tank was 1 500 m^3/h, and the remainder of 167 m^3/h di- rectly flowed into contact oxidation tank to provkte the nutrient for microorganisms in contact oxidation tank. After three-year operation, the sewage indicators the second level criteria specified in Integrated Wastewater Discharge Standard （ DB 12/356 - 2008 ） of Tianjin City.