1. 1 II. Sewer Networks and Facilities Topic II.2. Sewerage Systems:Kinds and Features Kinds of Sewerage Systems Combined Sewer System (CSS) 1 - combined sewer overflows (CSO); 2 - wastewater treatment plant (WTP)

2. 2 Combined Sewer System (CSS)

3. 3 Kinds of Sewerage Systems Separate Sewer System (SSS) 1 - sanitary sewer network; 2 - drainage network

4. 4 Kinds of Sewerage Systems Semi-Separate Sewer System (SSSS) a - general layout б - interceptor chamber 1 - sanitary sewer network 2 - drainage network Пp.cm. - WTP

5. 5 Features of the Sewerage Systems Main Aspects (Classical interpretation of advantages and disadvantages and state of art) §Technical and Economical §Sanitary and Hygiene §Maintenance and Exploitation

6. 6 Features of the Sewerage Systems Technical and Economical Aspects: (classical interpretation) 1. Combined Sewer System (CSS) §Investments costs - 30% less 2. Separate Sewer System (SSS) §Investments costs - 30% higher 3. Semi-Separate Sewer System (SSSS) - the most expensive one

7. 7 Features of the Sewerage Systems Technical and Economical Aspects: (state of art) 1. Combined Sewer System (CSS) §Investments costs - might be higher then ones for the SSS l Deeper trenches l Higher design rainfall intensity (bigger pipes diameters) 2. Separate Sewer System (SSS) §Investments costs - might be lower then ones for the CSS l Shallow drainage network trenches l Lower design rainfall intensity (smaller drainage pipes diameters) 3. Semi-Separate Sewer System (SSSS) - the most expensive one

8. 8 Features of the Sewerage Systems Sanitary and Hygiene Aspects (classical interpretation) 1. Combined Sewer System (CSS) §Sanitary effect - the worse one l CSO impact on the receiving water l First flush effect on the CSO quality 2. Separate Sewer System (SSS) §Sanitary effect - better than the one with the CSS l Runoff is considered as a conditionally clean wastewater l Sewer is treated in the WTP 3. Semi-Separate Sewer System (SSSS) - the best one

9. 9 Features of the Sewerage Systems Sanitary and Hygiene Aspects (state of art) 1. Combined Sewer System (CSS) §Sanitary effect - no worse than one with the SSS 2. Separate Sewer System (SSS) §Sanitary effect - no better than the one with the CSS l Runoff is very polluted and usually is not treated before discharge l Untreated runoff discharge has the same effect on the receiver as the CSO one 3. Semi-Separate Sewer System (SSSS) - the best one

10. 10 Features of the Sewerage Systems Maintenance 1. Combined Sewer System (CSS) l First flush effect on the network clean up 2. Separate Sewer System (SSS) §Maintenance costs - 30 % higher l Higher total length of the network 3. Semi-Separate Sewer System (SSSS) §Maintenance costs - the highest l High total length of the network l Additional facilities (interceptor chamber)

11. 11 Features of the Sewerage Systems Exploitation 1. Combined Sewer System (CSS) - the most unfavorable l More sophisticated pumping stations l Unfavorable wastewater inflow regime at the WTP l Lower wastewater temperature at the WTP inlet 2. Separate Sewer System (SSS) - the most favorable l Avoids the unfavorable factors associated with the CSS 3. Semi-Separate Sewer System (SSSS) - between CSS and SSS