Study On Pollution Load Source And Water Quality Control Strategy Of A Large Urban Sewage Treatment Plant

Municipal wastewater treatment plants(MWWTP) are of a principal countermeasure to control water pollution. The proportion of industrial wastewater is normally high in the influent of a civil MWWTP, since the discharge amount of industrial wastewater greatly increases in recent years with the rapid development of industrialization. Industrial wastewater comes from a complex source and usually contains a high concentration of non-biodegradable pollutants. Therefore, the influent of a MWWTP with a high proportion of industrial wastewater is usually refractory, resulting in effluent that fails to meet the emission standard. It is in urgent need to scientifically monitor and stablize the influent quality of a MWWTP in order to achieve the stringent emission standard.A large-scale MWWTP was studied in the thesis. Wastewaters from 27 primary district pumping stations, 10 first-stage pumping stations and 9 key industries were studied on the emission characteristics of chemical oxygen demand(COD), nondegradable COD(ND-COD), total nitrogen(TN), total phosphorus(TP) and heavy metals(Cu, Zn,Cr). Pollution loads from each pumping station were calculated, their devotion to the loading of the MWWTP was evaluted, based on which the principal contributors to the loading were screened. Monitoring and management strategies were then proposed in order to improve the influent quality of the MWWTP. The results are as follows:(1) The biodegradability and water quality of wastewater greatly differed among 27 primary district pumping stations. Most water quality indexes in stations of HY4#, NHQ, BZ, ZP and KHDQ seriously and high-frequently exceeded the pipenet emission standard. Stations HYB5, HYB7, HYA9 and ZAL were with wastewater of poor biodegradability, the ratio of ND-DOC in total DOC were 70%±2.5%, 86%±20.5%, 59%±13.3% and 53%±9.2%, respectively.(2) Stations BJH, ZPKJ, NHQ, HY4#, PHCQ, BZ and JSZR accounted for 57.5% of the ND-COD load of the MWWTP, being the major contributors to ND-COD. Stations JSZR, ZPKJ, PHCQ, BZ and NHQ accounted for 41.0% of the TN load of the plant, being the principal contributors to TN. Stations BZ, HY4#, NHQ and JSZR accounted for 65.4% of the TP load of the plant, being the principal contributors to TP.(3) The investigation on nine key industries revealed that ND-COD were high or TN, TP and heavy metals concentration were by far over the pipenet emission standard in most industries. Besides, some industrial wastewater was with high concentration of ND-COD although a low ND-COD/COD ratio, which still lead to a risk on the MWWTP to meet the emission standard.