How do storm water and wastewater networks function together with the wastewater treatment plant? Theo G. Schmitt, Kaiserslautern University (Germany)

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1 Urban FG Siedlungswasserwirtschaft Water Management KfWInternational Conference on Efficient Use of Energy in Water Supply and Wastewater Disposal in Southeastern Europe and Turkey November 26-27, 2013 How do storm water and wastewater networks function together with the wastewater treatment plant? Theo G. Schmitt, Kaiserslautern University (Germany)

2 Overview Scope & objectives of urban drainage Concepts - urban drainage systems Operation: tasks, demands, experiences Future challenges Urban flood protection climate change Integrated storm water management Micro-pollutants control Sustainable sanitation Conclusions T.G. Schmitt: Urban Drainage Systems 2

3 Urban Drainage Systems Scope, Objectives & Concepts T.G. Schmitt: Urban Drainage Systems 3

4 Urban Wastewater System Kanalisiertes Urban Einzugsgebiet catchment Infiltration g Mischwasserentlastung overflow Kläranlage Combined sewer Wastewater treatment plant Groundwater Grundwasser Entwässerungs Sewer system system Natural Natürliches catchment Einzugsgebiet Gewässer r Receiving water T.G. Schmitt: Urban Drainage Systems 4

5 Objectives - Concepts Scope: Urban Settlements (residential, industrial) Sanitation - hygienic housing area collect and convey domestic & industrial sewage underground sewers (sanitary, combined) Protection against flooding and water logging collect and convey storm water roof & street drain elements underground sewers (storm, combined) Receiving water quality control reduce pollution discharge wastewater treatment storm water management T.G. Schmitt: Urban Drainage Systems 5

6 Urban Drainage Systems Combined Sewer System Seperate Sewer System T.G. Schmitt: Urban Drainage Systems 6

7 Interaction Sewer System - WWTP Seperate Sewer System Wastewater Treatment Plant Major problem: cross connections storm water in sanitary sewers causes surcharge and hydraulic overload of WWTP sewage flow in storm sewers causes pollution of receiving waters Urban Catchment Receiving Water Sanitary Sewer Storm Sewer Q WWTP = Dry Weather Flow (DWF) Q max (Runoff) WWTP infiltration water in sanitary sewers causes hydraulic overload of WWTP T.G. Schmitt: Urban Drainage Systems 7

8 Interaction Sewer System - WWTP Major problem: occurrence of combined sewer overflows need to limit flow to WWTP Intermediate storage of combined sewer flow redirect to WWTP limited storage volume due to technical and economic reasons infiltration water causes extra hydraulic load of WWTP during DWF T.G. Schmitt: Urban Drainage Systems 8

9 Interaction combined sewer system - WWTP Interface sewer system Wastewater Treatment Plant in Germany: f CSF = 3 6 cities = 6 9 towns, villages Q inflow,wwf = f CSF x Q DWF WWF wet weather flow CSF combined sewer flow DWF dry weather flow T.G. Schmitt: Urban Drainage Systems 9

10 Urban Drainage Systems Future Challenges T.G. Schmitt: Urban Drainage Systems 10

11 Urban Flood Protection climate change? Perception high uncertainty about climate change effects local hot spots of flooding no general safety factors Future needs obligatory local flood risk analysis improve adaptiveness of drainage concepts use surface features to retain surface runoff communicate local flood risks T.G. Schmitt: Urban Drainage Systems 11

12 Preserve / restore local water balance Urban areas: conventional drainage Benchmark area before development low evaporation High and fast surface runoff low infiltration blue green dream high evaporation high evaporation low surface low runoff surface runoff Minimizing adverse effects of urban drainage on local water balance! high infiltration T.G. Schmitt: Urban Drainage Systems 12

13 Micro-pollutants Concern micro-pollutants - xenobiotic substances in natural water bodies micro-pollutants Pharmaceuticals, hormones sewage Pesticides storm water discharge pathways Wastewater treatment plants Combined sewer overflows Storm sewer outlets possible effects on the aquatic environment Toxic, adverse effects on aquatic organisms Possible human health effects (hormones, mutagenic, carcinogenic, ) T.G. Schmitt: Urban Drainage Systems 13

14 Sustainable Sanitation Provide secure & financeable sanitation in developing countries Low impact urban developments Local water balance, flood protection Reduce / avoid pollutant occurrence & discharge Ecological sanitation concepts preserve natural resources (water, nutrients) reduce/limit drinking water consumption reduce discharge of wastewater pollutants recover nutrients in wastewater flow (C, N, P) exploit energy content (wastewater, sludge) reduce/limit cost of secure sanitation T.G. Schmitt: Urban Drainage Systems 14

15 Summary - conclusions Secure & well-operating urban drainage systems in developed countries Sewer system, wastewater treatment plant Integrated storm water management however: High costs, resource consumption, environmental impairments non-sustainable Major challenges & concerns Pollution of surface runoff and combined sewer overflow Flood protection & resiliency ( climate change) Emergence of micro-pollutants in natural water bodies Low impact developments in fast-growing urban areas T.G. Schmitt: Urban Drainage Systems 15

16 Urban FG Siedlungswasserwirtschaft Water Management KfWInternational Conference on Efficient Use of Energy in Water Supply and Wastewater Disposal in Southeastern Europe and Turkey November 26-27, 2013 How do storm water and wastewater networks function together with the wastewater treatment plant? Theo G. Schmitt, Kaiserslautern University

17 Combined Sewer Overflow (CSO) Scheme SE 2-7 Urban Catchment Receiving Water Overflow Structures CSO Basin WWTP 11 1 overflow structure 2 control structure 3 Wastewater treatment plant 4 Combined sewer overflow storage 5 critical combined sewer flow 6 combined sewer inflow WWTP 7 CSO - direct discharge 8 CSO - feed to combined sewer overflow (CSO) basin 9 CSO basin overflow (without treatment) 10 clarified CSO basin overflow (e.g. sedimentation) 11 WWTP effluent (treated according to BAT) T.G. Schmitt: Urban Drainage Systems 17