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Joint workshop on Enhancing efficiency and sustainability of Water Supply and Sanitation presentation - Nataša Uranjek

Joint workshop on Enhancing efficiency and sustainability of Water Supply and Sanitation presentation - Nataša Uranjek, Waste water treatment in small settlements of Slovenia

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Joint workshop on Enhancing efficiency and sustainability of Water Supply and Sanitation presentation - Nataša Uranjek

  1. 1. International Workshop ENHANCING SUSTAINABILITY AND EFFICIENCY OF WSS PROVISION 15. – 16. June 2021 WASTEWATER TREATMENT IN SMALL SETTLEMENTS OF SLOVENIA Nataša Uranjek Chamber of Commerce and Industry of Slovenia Chamber of Public Utilities
  2. 2. Republic of Slovenia (2.094.060 Inhabitants) Capital city: Ljubljana (270.000) Area: 20.273 km² (46.6 km coastline) Highest mountain: Triglav 2.864 m Relief: The territory of Slovenia is geographically divided into four basic types of landscape - Alpine in the north, (42.1%), Mediterranean in the south-west (8.6%), Dinaric in the south (28.1%), and Pannonian in the east (21.2%) Forests: almost 58% of the Slovenia territory No. of municipalities: 212 2
  3. 3. AGGLOMERATIONS IN SLOVENIA 3 > AGGLOMERATION SIZE
  4. 4. AGGLOMERATIONS IN SLOVENIA - total of 1.533 agglomerations - 123 agglomerations with a total load ≥ 2.000 PE - 1.410 agglomerations with a total load of < 2.000 PE For agglomerations with a total load of < 2.000 PE: - < 50 P.E. (IAS) - < 500 PE (public system or IAS) - > 500 P.E. (public system, IAS exception) OBLIGATORY MUNICIPAL PUBLIC SERVICE: - Public infrastructure – public service providers (public companies, municipalities, concession) - For IAS – inspection and sludge removal is public service 4
  5. 5. BUILDINGS WITH TYPE OF COLLECTING SYSTEMS AND TREATMENT OF MUNICIPAL WW Source: MOP-IJSVO, cut-off date 31. December 2018 5 Sewer IAS Septic tank no discharge Septic tank – outflow WW discharges (no treatment) Unknown system Not reported State border
  6. 6. WASTEWATER COLLECTION AND TREATMENT • Total WW treatment capacity ≈ 2.680.000 P.E. • No. of public service providers: 112 • Total length of public WW network: 10.754 km • Length of network / inhabitant connected: 8,22 m • Number of UWWTP: 559 • Only 41 UWWTP capacity > 10.000 PE • 430 UWWTP capacity < 2.000 PE • 6.176 UWWTP capacity < 50 PE • Population connected: - 62,4% to WW sewage system - 60,4% to WWTP - 31,8% to individual sanitation (IAS) 6
  7. 7. PROBLEMS IN SLOVENIA DEALING WITH INDIVIDUAL OR APPROPRIATE SYSTEMS (IAS) • Legislation: • all WW should be treated by the end of 2021 • for existing facilities septic tanks can remain until the first reconstruction • Small WWTP - appropriate cleaning Appropriate cleaning 7 Parameter Unit < 50 PE >= 50 PE and < 2.000 PE COD mg O2/L 200 150 BOD5 mg O2/L (a) 30 (a) the limit value is not set Agglomeration size or WWTP capacity
  8. 8. PROBLEMS IN SLOVENIA DEALING WITH 8 Small wastewater treatment plant ≥50 PE and < 2.000 PE - Slovenia has extremely dispersed population (430 UWWTP capacity < 2.000 PE) - The versatility of the surface makes it impossible or financially unjustified to build larger WWTPs without many pumping stations - Problems to get WWTP with performance to fulfil legislation for big agglomeration, especially N and P removal - The price for such WWTP is 2-3 times higher as for secondary treatment and demands big effort from WWTP staff to operate them
  9. 9. PROBLEMS IN SLOVENIA DEALING WITH IAS 9 IAS - Small wastewater treatment plant < 50 PE (SWWTP) - Investors are individuals (price is one of the criteria and often crucial for the choice of SWWTP – not always the best) - Effluent discharge on landslide area - At the start of SWWTP operation measurements are performed (first measurements) - Treatment efficiency and measurements are made only at the start of SWWTP operation – no monitoring is required - Performance review of SWWTP operation is required every 3 years and is one of the utility company obligations - Performance review is defined in the legislation with the form but based on a visual inspection and the assessment of performance is left to the subjective decision of the individual
  10. 10. PROBLEMS IN SLOVENIA DEALING WITH IAS 10 IAS - Small wastewater treatment plant < 50 PE (SWWTP) - On the one hand, a very vague and subjective review of SWWTP performance, without measurements (at least COD) and monitoring is satisfying and on the other hand tertiary treatment is required (big agglomeration) with N and P removal - Problems to get SWWTP with performance to fulfil legislation (especially N tot, P tot) - And yet, for existing facilities septic tanks can remain until the first reconstruction
  11. 11. PROBLEMS IN SLOVENIA DEALING WITH Small WWTP ≥50 PE and < 2.000 PE and IAS Question often asked to us, operators at utility companies: What is the better solution for rural areas: - good secondary treatment with carbon removal and ammonium oxidation which we can achieve - or almost unattainable tertiary treatment by removing phosphorus and nitrogen to very ‘’hard-to-reach’’ values - is the removal of carbon and phosphorus alone sufficient to prevent eutrophication? We were told eutrophication can be prevented by removing one of the necessary nutrients, such as phosphorus. 11
  12. 12. Thank you for you attention! 12

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