A Preliminary Study On Diagnostic Techniques For Old Town Drainage System Performance

The study selected drainage pipelines in center old town of Changzhou as research object, 24h online samplings and laboratory analysis were conducted to investigate the water quantity and quality change from Jan 2009 to Apr 2010, According to the results of analysis, the following contents were considered: (1) the regularity of sewage water quantity and quality change, besides pollution concentration change in runoff when rain occurred and its affect on water quantity and quality in sewer pipelines; (2) pollution of illicit discharge, the method to characterize illicit discharge and infiltration/inflow which was based on the combination of quatity and quality; (3) develope a diagnostic techniques for old town drainage system performance, which provides foundation for upgrading the drainage system.The result showed that: (1) daily change of water quantity and quality in sewer pipelines showed two apparent peaks. One at noon time and the other at night. For instance, the maximum pollutant concentration in main pipe were: COD 427mg/L, NH3-N 20.2mg/L, TN 46mg/L, TP 3.06mg/L and SS 76mg/L. The minimum pollutant concentration appears at the wee hours, water quality was in low range of general sewage pollutant concentration all-day. Water quantity in sewer system was increasing when raining; water quality showed different change trend: COD and SS firstly raised and then were diluted while TN, NH3-N and TP were stable. (2) in Jan 2009, there was highest pollutant concentration from vents along river bank, pollution load was highest in Apr 2009. Key vents were: VIâ‘¢, VIâ‘¡and IVâ‘¢, discharge regularity of each vent was similar between midweek and weekend, combining with traceability work, we identified that the pollution of VIâ‘¢was most likely caused by public toilets'illicit discharge in a school, and sewage in IVâ‘¢was most likely discharged from multi sources, partly from catering and partly from infiltration which was in low concentration. (3) data analysis which was based on combining quatity and quality evaluation characterized pipelines which occurred illicit discharge and infiltration, the results confirmed with practical situation. Pollution of VIâ‘¡was mainly affected by infiltration and mixing with toilet water, pollution of IVâ‘¢was mainly affected by infiltration and mixing with catering water, sewer pipeline in Taoyuan Road occured serious leakage, it is urgent to reform. (4) proposed a set of multi-level analysis and evaluation of effective collaborative diagnostics for drainage system performance, mainly including site investigation,data analysis and diagnosis system. The application synthesis give recommendations which is aimed at the most effective method for upgrading the old town drainage system and carrying out sewer interception project, renovation plan based on combining quatity and quality evaluation reaches highest comprehensive intercerption performance.