أثر أحداث الأمطار على التقييم الكمي والنوعي لنظام الصرف الصحي: دراسة حالة لحي الشهداء بمدينة السماوة.

Rp-The impact of rainfall events on quantitative and qualitative assessment of sanitary sewers system Case study of Al-Shuhada quarter in Al- Sam.pdf

Stormwater surface runoff and its inflow to sewer systems have increased due to vast urbanization and aging of existed infrastructure. This study describes the application of stormwater management model (SWMM) for predicting the sewage quantity as well as quality of the sanitary sewer system of the study area Al-Shuhada quarter resulting from the stormwater surface runoff leakage to the sewage system during rainfall events at different return periods. Also, solutions to reduce both quantity and improve quality of sewage during rainfall events were suggested. The quantity model was manually calibrated by changing the influential subcatchment characteristic using modeled and measured discharges. Normalized mean square error NMSE (0.103) and correlation coefficient R (0.85) values were within the acceptable limits and proved that the model is valid. While in quality model, the results of sensitivity analysis indicated that possible maximum buildup was the parameter with the greatest sensitivity for model calibration. The quality model was calibrated using real rainfall event, and statistical validation coefficients of R (0.8 to 0.83) and NMSE (0.016 to 0.032) proved that the model is valid. Evaluation results of quantity model indicated that the system was very well operated at dry weather flow but flooded at some locations during the inflow of stormwater at wet weather flow. As a response to rainfall of event, increased return period from 2 to 25 years showed an increase in sanitary sewage system flooding volume and flooding manholes percentage from 1,453 m3 and 10% to 2,115 m3 and 24%, respectively. By contrast, proposing the addition of extra two sewer lines has highly reduced the flooding events. The sewage quality assessment results showed that pollutants concentration increased to their maximum level after 20 min of rainfall, and then gradually decreased to a slightly constant minimum value after 2 hours. The proposed solution of low impact development LID reduced the pollutants concentrations by 75-77%, 52-55%, and 7-10% for all pollutants at returns at five years, ten years, and twenty-five years, respectively. In conclusion, the SWMM is a very powerful tool for predicting flood volumes and how pollutant concentrations change in different precipitation intensities, and the SWMM is capable to propose solutions to reduce both floods and pollutants in sanitary sewer system.