1. SOROCA PROJECT LAUNCH WORKSHOP
Soroca WWTP Project - Constructed Wetlands
as a Locally Appropriate Technology
Dr. Konrad Buchauer
Soroca, Moldova

2. Reasons for choosing Constructed Wetlands
Table of Contents
Reasons for choosing Constructed Wetlands
Constructed Wetlands – Technology and Construction
Project Implementation of Soroca WWTP

3. Local Conditions <> Conclusions
1. Reasons for Choosing Constructed Wetlands (CWs)
Local Conditions <> Conclusions
LOCAL CONDITION
CONCLUSION
(1) Treatment targets:
Carbon removal (BOD, COD, SS)
Enhanced nutrient removal (N, P)
Hygiene?
Carbon removal of CWs is equivalent to convent. technologies.
N removal – with a properly designed CW – can be brought to similar levels as with convent. technologies nowadays.
P removal in CWs decreases over time, yet an acceptable mean elimination rate of 50% is considered feasible.
Soroca WWTP shall be based upon 2-stage CWs. These systems feature superior pathogen removal, as compared to convent. technologies.
Properly designed 2-stage CWs enable enhanced nutrient removal and even have better hygienic effluent quality than conventional technologies.

4. Local Conditions <> Conclusions
1. Reasons for Choosing Constructed Wetlands (CWs)
Local Conditions <> Conclusions
LOCAL CONDITION
CONCLUSION
(2) Cold winter temperatures and snowfall
Latest design criteria take due consideration of cold temperatures.
There exist about 20 years of practical experience with CWs in Central Europe under climate zones comparable to Moldova (France, Austria, Germany, Switzerland, etc.).
CWs, of course, look different in winter time, but nonetheless work satisfactorily.
summer winter
Properly designed 2-stage CWs will continue working properly in winter time.

5. Local Conditions <> Conclusions
1. Reasons for Choosing Constructed Wetlands (CWs)
Local Conditions <> Conclusions
LOCAL CONDITION
CONCLUSION
(3) Limited financial resources, limited scope for a strong increase in water & wastewater tariffs
Cost for CWs:
Investment cost = US$ 3 million
O&M cost = US$ 0,04 million/year
Cost for (optimised) Activated Sludge system:
Investment cost = US$ 5,1 million
O&M cost = US$ 0,30 million/year
CWs will reduce the financial burden on Soroca and lead to considerable lower W&WW tariffs than convent. technologies.
(4) About 10 hectare of land are available for the WWTP
The land requirement for 2-stage CWs is estimated to about 5 ha at present. Hence there is sufficient land available, offering even scope for further expansions.

6. Local Conditions <> Conclusions
1. Reasons for Choosing Constructed Wetlands (CWs)
Local Conditions <> Conclusions
LOCAL CONDITION
CONCLUSION
(5) Lack of skilled operators
The Soroca WWTP project will include staff training. Even though CWs are easy to operate, this is considered indispensable and will safeguard proper operation practices according to the latest know-how.
By contrast, the operation of convent. techn., such as AS, poses much higher challenges to operators. The difficulties not only relate to compliance with effluent criteria, but also to human safety. A relatively short training would not be sufficient for such a task. Typical WWTP operator training programmes in Central Europe take years, and are targeting professionals only (electrician, etc.).
CWs can be satisfactorily operated by local staff after appropriate training.

7. Local Conditions <> Conclusions
1. Reasons for Choosing Constructed Wetlands (CWs)
Local Conditions <> Conclusions
LOCAL CONDITION
CONCLUSION
(6) Unreliable power supply
The CWs as such operate without electric energy. The wastewater flows through the plant by gravity. No aeration, recirculation pumping, etc is required.
By contrast, the operation of convent. techn., such as AS, is fully dependant on permanent and strong power supply.
CWs will be able to cope with unreliable power supply.

8. ● favourable -- unfavorable
1. Reasons for Choosing Constructed Wetlands (CWs)
Summary: Technol. Appropriateness under Local Cond.
2-stage CW
Convent. Technol.
ENVIRONMENT
BOD / COD / SS removal ●
Nutrient (N / P) removal
Coliform / Helminth removal --
COST
Investment
O & M
Wastewater tariff
TECHNOLOGY
Ease of operation, requirement for skilled operators
Land requirement
Dependence on permanent power supply
● favourable -- unfavorable

9. Technologies for Constructed Wetlands
2. Constructed Wetlands – Technology and Construction
Technologies for Constructed Wetlands
(1) Horizontal subsurface flow (HF)
(2) Vertical subsurface flow (VF)
(3) Free water surface (FWS)
(4) 2-stage (hybrid) CWs
Suggested for Soroca:
Combination of (1) + (2)
Source: SWAMP 2005

10. 2-stage CWs: French system with 2 VF
2. Constructed Wetlands – Technology and Construction
2-stage CWs: French system with 2 VF
Flow scheme
Nr. of 2-stage CWs in France
Sources: Molle et al. 2004, Lienard 2003

11. 2-stage CWs as compared to 1-stage CWs: Advantages
2. Constructed Wetlands – Technology and Construction
2-stage CWs as compared to 1-stage CWs: Advantages
Approximately 50% of land requirement, as compared to 1–stage CWs.
Better treatment efficiency, particularly better nutrient and pathogen removal.
20 years of practical experience.
No pre-treatment required, apart from screening (French system).
No need for separate sludge treatment ( French system).

12. 2. Constructed Wetlands – Technology and Construction
Construction steps 1 2 3 4 5 6
Source: Austria, BOKU 2005

13. Consultant’s Key Tasks
3. Project Implementation of Soroca WWTP
Consultant’s Key Tasks
Other 2-stage CW options
French CW system with 2-stage VF
Analysis and definition of prevailing wastewater flow rates and load
Optimization of treatment technology
Detailed design & Bidding Docs
Supervision of construction works
Staff training
Assistance during start-up & initial 6-month operation period

14. Time Schedule 3. Project Implementation of Soroca WWTP
Design and Bidding Docs
Construction period
Staff training
WWTP start-up
1st know-how dissemination workshop in Soroca 2011