Quantification of non-stormwater flow entries into storm drains using a water balance approach

• Published in: The Science of the total environment 2014-07, Vol.487, p.381-388
• Main Authors: Xu, Zuxin, Yin, Hailong, Li, Huaizheng
• Format: Article
• Language: English
• Subjects: Applied sciences; China; Cities; Drainage, Sanitary - methods; Drainage, Sanitary - statistics & numerical data; Dry-weather flows; Environmental Monitoring - methods; Exact sciences and technology; Floods - statistics & numerical data; Non-stormwater entries; Pollution; Rain; Sewage - analysis; Sewage - statistics & numerical data; Sewerage works: sewers, sewage treatment plants, outfalls; Storm drains; Waste Disposal, Fluid - methods; Waste Disposal, Fluid - statistics & numerical data; Water balance; Water flow quantification; Water Movements; Water treatment and pollution
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2014.04.035

To make decisions about correcting illicit or inappropriate connections to storm drains, quantification of non-stormwater entries into storm drains was performed using a water flow balance approach, based on data analysis from 2008 to 2011 in a separate storm drainage system in a Shanghai downtown area of 374ha. The study revealed severe sewage connections to storm drains; meanwhile, misconnections between surface water and storm drains were found to drive frequent non-stormwater pumping discharges at the outfall, producing a much larger volume of outfall flows in a short period. This paper presented a methodology to estimate quantities of inappropriate sewage flow, groundwater infiltration and river water backflow into the storm drains. It was concluded that inappropriate sewage discharge and groundwater seepage into storm drains were approximately 17,860m3/d (i.e., up to 51% of the total sewage flow in the catchment) and 3624m3/d, respectively, and surface water backflow was up to an average 28,593m3/d. On the basis of this work, end-of-storm pipe interceptor sewers of 0.25m3/s (i.e., 21,600m3/d) would be effective to tackle the problem of sewage connections and groundwater seepage to storm drains. Under this circumstance, the follow-up non-stormwater outfall pumping events indicate misconnections between surface water and storm drains, featuring pumping discharge equivalent to surface water backflow; hence the misconnections should be repaired. The information provided here is helpful in estimating the magnitude of non-stormwater flow entries into storm drains and designing the necessary pollution control activities, as well as combating city floods in storm events. •Sewage, groundwater and river water into the storm drains were quantified.•End-of-storm pipe sewers could be effective approach for non-stormwater pollution.•The higher the river water level, the larger the amount of river water backflow.•Misconnections between surface water and storm drains should be repaired.