Abstract
Continuous measurement systems are widely spread in sewers, especially in non-pressure systems. Due to its relatively low costs, turbidity sensors are often used as a surrogate for other indicators (solids, heavy metals, organic compounds). However, little effort is spent to turbidity sensors in pressurized systems so far. This work presents the results of one year in-situ turbidity/total suspended solids (TSS) monitoring inside a pressure pipe (600 mm diameter) in an urban region in northern Germany. The high-resolution sensor data (5 s interval) are used for the determination of solids sedimentation (within pump pauses) and erosion behavior (within pump sequences). In-situ results from sensor measurements are similar to laboratory results presented in previous studies. TSS is decreasing exponentially in pump pauses under dry weather inflow with an average of 0.23 mg/(L s). During pump sequences, solids eroded completely at a bed shear stress of 0.5 N/m². Sedimentation and erosion behavior changes with the inflow rate. Solids settle faster with increasing inflow: at storm water inflow with an average of 0.9 mg/(L s) and at diurnal inflow variation up to 0.6 mg/(L s) at 12:00 a.m. The results are used as calibration data for a sediment transport simulation in Part II.
Highlights
The physical characterization of sewage is indispensable for optimization efforts in all areas of wastewater management
If the total suspended solids (TSS) sensor measures a value immediately when the pump starts, it takes 5 s of pumping until the value is recorded. Within these 5 s, some sediments are already eroded. This means that a shorter measuring interval is recommended for the erosion process in later studies
The pressure pipe and the determination and characterization of settling and erosion behavior based on pressure pipe and the determination and characterization of settling and erosion behavior based on high-resolution sensor sensor data
Summary
The physical characterization of sewage is indispensable for optimization efforts in all areas of wastewater management. Pumping processes are usually necessary in sewage and storm water transport. Because of their frequent use, all related processes offer high optimization potential, to name only a few: sediment transport, energy consumption, and storm water management. The main key to process understanding and optimization lies in data quality and quantity. Advanced optimization tools (e.g., numerical simulations) are especially data greedy. Quality and quantity varies with the data collection method: either ex-situ or in-situ. Experiments simulate real world conditions as accurately as possible and subsequently transfer the results into a representative model region. Most stream tests try to simulate more-or-less real-life conditions
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