1. First IWA-Bulgarian Young Water Professionals
Conference
WASTEWATER TREATMENT TECHNOLOGIES – STATE OF
ART
Prof. D.Sc. Eng. Roumen Arsov
University of Architecture, Civil Engineering and Geodesy
Bulgarian Water Association
Sofia, 17 May 2012
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2. Wastewater Treatment technologies – State of Art
The term “Best Available Technologies” – BAT is in use more
than 20 years, but it was legally introduced by the Water
Framework Directive 2000/60/ЕС, Article 10, 2(a).
Definitions
 Technologies, insuring achievement of the standards
requirements and being proved their technical, economical and
social efficiency.
 “Best Available Technique is the most efficient and most
progressed stage in development of the applied technology of
wastewater treatment which was developed in such a scale
enabling the employment of the technology under economically,
socially and technically acceptable conditions and it is at the
same time the most effective technique for water protection”
(according to the Czech Republic governmental Decree No
227/2007).
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3. Wastewater Treatment technologies – State of Art
Principles of contemporary wastewater treatment technologies are known
for about a century and the term “contemporary” nowadays concerns
plenty of technological arrangements (layouts) and constructive
modifications of the relevant technological units, stimulated by
developments in ecological and technical standards, materials, equipment
and construction technologies
Biological Wastewater Treatment Technologies are in the core of the
contemporary Best Available Technologies (BAT), applicable to municipal
wastewater treatment
The following two main divisions of municipal wastewater biological
treatment are in use nowadays:
 Intensive Biotechnologies
 With suspended biomass
 With attached biomass
 Extensive Biotechnologies
 Constructed wetlands
 Biological lakes and lagoons
 Send bed trickling filters

Hybrid biological systems 3

4. Intensive Biotechnologies with Suspended Biomass
Principal layout of activated sludge system
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5. Intensive Biotechnologies with Suspended Biomass
Recirculation of NO3-
Aerobic
Anaerobic Anoxyc Secondar
bioreactor y
bioreaktor bioreactor
Clarifier
Recirculation of activated sludge
Principal layout of nitrogen and phosphorus biological removal
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6. Intensive Biotechnologies with Suspended Biomass
Recirculation of NO3- Al2(SO4)3
Anoxic Aerobic bioreactor Secondary
bioreactor calrifier
Recirculation of activated sludge
Principal layout of nitrogen biological removal and phosphorus chemical
precipitation
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7. Intensive Biotechnologies
with Suspended Biomass
General view of aerated tank - construction type “Carousel”
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8. Intensive Biotechnologies
with Suspended Biomass
General view of aerated tanks – construction type “Plug flow”
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9. Intensive Biotechnologies
with Suspended Biomass
Scheme of Sequencing Batch Reactor - SBR
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10. Intensive Biotechnologies
with Suspended Biomass
General view of aerated tanks – technological type SBR
(Hisarya WWTP, Bulgaria)
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11. Intensive Biotechnologies
with Suspended Biomass
Scheme of membrane biological reactor - MBR
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12. Intensive Biotechnologies
with Suspended Biomass
Membrane Biological Reactor (MBR) construction
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13. Intensive Biotechnologies
with Suspended Biomass
Scheme (left) and general view (right) of Upflow Sludge Blanket Reactor – USBR
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14. Intensive Biotechnologies
with Suspended Biomass
Scheme of granule biomass – bioreactor type USBR
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15. Intensive Biotechnologies
with Suspended Biomass
Recommended most efficient area of application of aerobic and anaerobic
biotechnologies 15

16. Intensive Biotechnologies
with Attached Biomass
Technological layout of trickling filter 16

17. Intensive Biotechnologies
with Attached Biomass
General view of trickling filter with plastic carrier
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18. Intensive Biotechnologies
with Attached Biomass
General view of trickling filter with reactive distribution system
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19. Intensive Biotechnologies
with Attached Biomass
Scheme of rotating biological contactors – RBC
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20. Intensive Biotechnologies
with Attached Biomass
General view of Rotating Biological Contactors (RBC)
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21. Intensive Biotechnologies
with Attached Biomass
Moving Bed Biological Reactor (MBBR) construction
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22. Extensive Biotechnologies
EU COMPENDIUM
for
Design and construction of
extensive wastewater
treatment technologies for
small settlements
(500 - 5000 PE)
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23. Extensive Biotechnologies with Suspended Biomass
Schemes of facultative lagoon (left) and
biological lakes cascade (right)
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24. Extensive Biotechnologies with Suspended Biomass
General view of aerobic and anaerobic biological lakes and
lagoons
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25. Extensive Biotechnologies with Attached Biomass
Scheme of send bed trickling filter
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26. Extensive Biotechnologies with Attached Biomass
Technological schemes of constructed wetlands

with vertical flow (top)

with horizontal flow (down)
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27. Extensive Biotechnologies with Attached Biomass
Scheme (left) and general view (right) of
constructed wetlands
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28. Wastewater Treatment technologies – State of Art
Driving Forces for Best Available Technologies (BAT)
Development
 Legislation
 Historical trend for pollution removal: SS, BOD, N and P (up to
now), pharmacy micro pollutants (under investigations), S (future)
 Climate change and water stress – a prerequisite for:
 Change of paradigm: from “wastewater as a problem” towards
“wastewater as a resource”
 Stimulation of wastewater recycling and reuse technologies
 Stimulation of decentralized sewer systems development
 Urine separation and treatment technologies
 Requirements for energy efficiency
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29. Driving Forces for Best Available Technologies (BAT)
Development
Is there a rational sense in wastewater reuse?

Necessary water for food production - 1000 m3/PE.year

Necessary water for drinking - 1 m3/PE.year

Municipal wastewater production – 30 - 60 m3/PE.year
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30. Driving Forces for Best Available Technologies (BAT)
Development
There is a rational sense in water resources pollution
prevention, because
Untreated wastewater would pollute the following natural
water resources volumes (in BOD5 base):
 About 11 000 – 20 000 m3/PE.year in sensitive zones
 About 5 000 – 10 000 m3/PE.year in less sensitive zones
Therefore, 1 PE would pollute from 90 to 750 times more
natural water resoursece than these used for potable
needs (100 – 180 l/cap.d)
Necessity of wastewater recycling and reuse stimulates
technologies development for their treatment
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31. Driving Forces for Best Available Technologies (BAT)
Development
Scheme of general concept for wastewater recycling and reuse
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32. Driving Forces for Best Available Technologies (BAT)
Development
General view of infiltration ponds (California)
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33. Driving Forces for Best Available Technologies (BAT)
Development
Scheme of urine separation system
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34. Driving Forces for Best Available Technologies (BAT)
Development
Tendency for WWTPs energy efficiency
General view of co-generation devices for biogas utilization
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35. Driving Forces for Best Available Technologies (BAT)
Development
What is the share of the wastewater energy potential in
respect to overall energy consumption per 1 PE?
(some figures by K. Svardal & H. Kroiss, WS&T, 2011)
 Specific power consumption on the base of focil fuel - 5-10 kW/PE
 Specific power in human food consumption - 0,11 kW/PE
 Specific power in polluted wastewater - 0,0225 kW/PE
 Only 5 % of wastewater heat recuperation is economically feasible
Therefore wastewater can not be considered as a reliable source of
energy since they content no more than 0,44 % of domestic energy
consumption of 1 PE
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36. Driving Forces for Best Available Technologies (BAT)
Development
What is the share of the wastewater energy potential in
respect to overall energy balance of the WWTP
(some figures by K. Svardal & H. Kroiss, WS&T, 2011)
 Specific power for aeration at the big (over 50 000 PE) WWTPs,
depending of the technology applied – 1,0-1,9 W/PE (3 - 15 W/m3)
 Total specific power at the big (over 50 000 PE) WWTPs, depending
of the technology applied – 1,7-3,1 W/PE
 Specific power in polluted wastewater - 22,5 W/PE
 Specific electric power which could be obtained by biogas
utilization, depending of the technology applied – 0,9-2,1 W/PE
(with 25-37% co-generators efficiency)
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37. Стремеж към енергийна ефективност
What is the share of the wastewater energy potential in
respect to overall energy balance of the WWTP -
continuation
(some figures by K. Svardal & H. Kroiss, WS&T, 2011)
 Therefore at big WWTPs (over 50000 PE), utilization of the biogas
for electricity production is technically possible and economically
feasible, for covering of the vast of the power needs
 Generated electricity production could be increased by:
 Increasing of organic content of the sludge, treated in the high rate
digesters by stimulation of primary sedimentation
 Optimization of design of the high rate digesters
 Increasing of the co-generators efficiency
 At the middle sized and small WWTPs (under 20 000 PE) the
energy balance is negative - (from -27 to -32 W/PE), which makes
biogas capture and utilization economically infeasible
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38. Wastewater Treatment technologies – State of Art
BASIC FEEDBACK AND CONCLUSIONS
 “Best Available Technologies” (BAT) are these, which are implemented in
the current practice, based on advanced technological achievements
 Technological processes, applied with the BAT are known for about a
century and the term “new” concerns mainly the plenty of technological
modifications, based on developments in legislation, materials,
construction technologies and equipment
 The most power factors influencing BAT development is legislation
 Ecological and technological standards developments are the most
influencing factors for stimulation of the BAT development in comparison
with these of “climate change” and “wastewater as energy and fresh water
resource
 Trends towards achievement of the WWTPs energy efficiency is a
contemporary imperative
 The WWTP energy consumption depends mainly on the pollution load
rather than on wastewater flowrate ( Briscoe, Wasser-Abwasser, 1995)
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39. Wastewater Treatment technologies – State of Art
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