Internship defense: Central Storage Sewer

Michiel Lecomte

2nd Master of Bioscience Engineering: Environmental Technology

Sewer system Graz

• RW-conditions: 96 combined sewer overflows

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Central Storage Sewer

• 10 km• > 100 000 m³ storage capacity

Central Storage Sewer

• Mike Urban

• Mike View

Central Storage Sewer

• Lowest cost through scenario analysis– Connection pipes– Depth and slope

Central Storage Sewer• Scenario analysis:

– + 0.5 m, + 1.0 m, 0.18% slope, 2 slopes, + 0.6 m– 10 EUR/m³ soil– ca. 97290 EUR construction costs saved

Reduced model

Big model Reduced model

3 h inputfiles (BC)

Design storm of 4h, return period = 100 years

Improved reduced model

Time series of flow rates

Energy balance (short)

• Central Storage Sewer:– 0-12000 m³: 0.02334 kWh/m³– >12000 m³: 0.006280 kWh/m³

• WWTP (2013):– Total energy needed: 12 936 256 kWh– Biogas energy produced: 9 390 834 kWh– Archimedes screw : 425 003 kWh produced– Balance: 3 120 419 kWh needed

Conclusions

• Design ZSK: connection pipes and distance below ground level changed

• Improved reduced model: starting point for further optimisation

• Archimedes screw: 63750 EUR/y• Biogas: 72.6% of total energy needs

Questions?

Nash Sutcliffe Efficiency

• Goodness of fit of hydrological model

• = individual observed values (day i)• = individual modelled values (day i)• = mean of observed values

• E: -∞ 1(McCuen et al. 2006)

Intensity Duration Frequency

• Frequently used• Probability of occurance of average rainfall

intensity

Pump 1 WWTP