Predicting impacts of water conservation with a stochastic sewer model

Population growth and climate change put a strain on water resources; hence, there are growing initiatives to reduce water use. Reducing household water use will likely reduce sewer input. This work demonstrates the use of a stochastic sewer model to quantify the effect water conservation has on sewer hydraulics and wastewater concentration. Probabilistic discharge patterns have been developed using SIMDEUM WW® and fed into hydraulic modelling software InfoWorks ICM® to produce likely flow and quality profiles for five future water use scenarios. The scenarios tested were developed to outline how commercial and political factors may change water use in future. Scenario testing revealed that 15-60% water reduction reflected a 1-48% drop in the morning peak flow. The water use reduction was predicted to increase wastewater concentrations of chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN) and total phosphorus (TPH) by 55-180%, 19-116% and 30-206% respectively. The sewer flow model was developed, calibrated and validated using a case study in the Wessex Water region of the UK and all future scenarios were compared to the validated baseline case. This wastewater flow and quality model allows scenario testing, which could help redesign future sewer networks to better prepare for water conservation strategies.