|Application Name||Sludge Drying Reed Beds in Mojkovac|
|Application Location||Country||Montenegro||Country 2
(in case of transboundary applications)
|River Basin District Code||Tara|
|WFD Water Body Code|
|Description||The Municipality of Mojkovac is situated in the northern part of Montenegro, in Durmitor area. Mojkovac town is located on the left bank of the Tara river upstream the Tara River Gorge. The municipality of Mojkovac covers an area of 367 km2 and is one of the smallest municipalities in Montenegro having a population of 8622 inhabitants. The town Mojkovac is located at an altitude of 853 m (municipality 600 – 2253 m).|
|Application Site Coordinates
(in ETRS89 or WGS84 coordinate system)
|Latitude (WGS84): 42.96044||Longitude (WGS84): 19.5833|
|Implemented NWRM(s)||Measure #1:||Sludge drying reed beds|
|Application short description||Sludge drying reed beds (RBs) enable sewage sludge dewatering, stabilization, mineralization and hygenization. They are an alternative to mechanical treatment (e.g. belt presses, centrifuges). In the process, sludge is spread on a filter media (substrate) of an open bed after which drainage and evaporation takes place. Planted RBs enable effective dewatering of sewage sludge and produce a mineralized product that can be used as a soil amendment in agriculture and other uses.|
|Brief description of the problem to be tackled||With
the construction and expansion of municipal infrastructure (sewage and
wastewater treatment plants), the amount of sludge produced by the
wastewater treatment plants is increasing. Sewage sludge is the main
waste by-product of wastewater treatment. The excess sludge presents
biomass and microorganisms that contain organic matter, nutrients and
persistent pollutants that originate from wastewater.
RBs were constructed as a cost-effective solution to solve problems of sludge treatment, storage, and disposal in Municipality of Mojkovac. In 2004 the town of Mojkovac was equipped with a biological wastewater treatment plant with an installed capacity of 5200 P.E. Until RBs were constructed in 2016, the generated sludge was mismanaged and mainly stored on the location of WWTP with the risk of being washed to the Tara River in high intensity rainfall events. The installed filter press was never in operation due to high operational costs. The municipality had no sustainable concept to manage the accumulating sludge or possibility to dispose it safely. Dumping of increasing volumes of sewage sludge on local landfill was not possible; also, in the entire country of Montenegro there is no incineration plant. Limited financial resources and sludge disposal problems were the key drivers of search for alternative sludge treatment solutions.
|What were the primary & secondary targets when designing this application?||Primary target #1:|
|Primary target #2:|
|Secondary target #1:|
|Secondary target #2:|
|Remarks:||sludge dewatering, stabilization, mineralization and hygenization|
|Which specific types of pressures did you aim at mitigating?||Pressure #1:||WFD identified pressure||wastewater and sludge|
|Which specific types of adverse impacts did you aim at mitigating?||Impact #1:||WFD identified impact||chemical and physico-chemical quality elements|
|Which EU requirements and EU Directives were aimed at being addressed?||Requirement #1:||WFD-mitigation of significant pressure||Sludge from WWTP|
|Which national and/or regional policy challenges and/or requirements aimed to be addressed?||In
order to shape the adequate response and holistic sludge management on
local/national level, the following steps are recommended:
|Dominant Land Use type(s)||Dominant land use||3.1.1|
|Secondary land use||3.2.1|
|Other important land use||3.1.3|
|Remarks: Based on data from Corine Land Cover database, 31% of the total area falls under agricultural land (pastures, complex cultivation patterns, land principally occupied by agriculture with significant areas of natural vegetation, and natural grasslands). 65% of area is covered with forest (broad-leaved forest, coniferous forest, mixed forest, transitional woodland-shrub, and sparsely vegetated areas) and only 0.9% is urban area (continuous and discontinuous).|
|Climate zone||cool temperate dry|
|Soil type||Rendzina and distric cambisole|
|Average Slope||nearly level (0-1%)|
|Mean Annual Rainfall||1500 - 1800 mm|
|Mean Annual Runoff||> 900 mm|
|Average Runoff coefficient (or % imperviousness on site)|
|Characterization of water quality status (prior to the implementation of the NWRMs)|
|Comment on any specific site characteristic that influences the effectiveness of the applied NWRM(s) in a positive or negative way||Positive impact: The efficiency of the system is influenced by climate, which positively affects the sludge drying rate.|
|Negative way: In winter the load on the system needs to be adjusted and dosing regime changed.|
|Project scale||Large (e.g. watershed, city, entire water system)||Sludge from WWTP with capacity of 5200 P.E. for Mojkovac municipality|
|Time frame||Date of installation/construction (MM.YYYY)||2014-2016|
|Expected average lifespan (life expectancy) of the application in years||At least 30 years|
|Responsible authority and other stakeholders involved||Name of responsible authority/ stakeholder||Role, responsibilities|
|Ministry of Sustainable Development and Tourism of Montenegro||Project initiator|
|Government of the Republic of Slovenia||Provision of funds / donor|
|United Nations Industrial Development Organization||Procurement and project implementation|
|Municipality of Mojkovac||WWTP Owner|
|Public utility||WWTP Operator|
|The application was initiated and financed by||Ministry of Sustainable Development and Tourism of Montenegro, UNIDO; Government of the Republic of Slovenia|
|What were specific principles that were followed in the design of this application?||Treatment efficiency, long-term biosolids accumulation and storage, potential of biosolids reuse, acceptable operational costs, functionality, usability, aesthetic benefit, impact on public perception & acceptability|
|Area (ha)||Number of hectares treated by the NWRM(s)|
|Text to specify|
|Design capacity||2500 P.E.|
|Reference to existing engineering standards, guidelines and manuals that have been used during the design phase||Reference||URL|
|Main factors and/or constraints that influenced the selection and design of the NWRM(s) in this application?||The biggest limitation in the application of reed bed technology is area required for installation. It is a land-intensive technology. As there was enough space on the property owned by the municipality, the technology was applied without additional problems (land acquisition or through time-consuming administrative processes).|
|Impact category||Impact description||Impact quantification|
|Parameter value; units
|% change in parameter value as compared to the state prior to the implementation of the NWRM(s)|
|Runoff attenuation / control|
|Peak flow rate reduction||RBs in Mojkovac can in theory retain 324 m3/day during rainfall event, which is more what a 4 hours rainfall event would bring. Thus, they contribute to flood efficient drainage of the area.||324 m3/day|
|Impact on groundwater||The system has no direct impact on groundwater because the beds are sealed with waterproof membrane|
|Impact on soil moisture and soil storage capacity|
|Restoring hydraulic connection|
|Water quality Improvements||Negative effects of municipal wastewater runoff on water quality is reduced.|
|WFD Ecological Status and objectives|
|Reducing flood risks (Floods Directive)|
|Mitigation of other biophysical impacts in relation to other EU Directives (e.g. Habitats, UWWT, etc.)|
|Soil Quality Improvements||Application of natural dewatered sludge from RBs to the soil can be a source of beneficial nutrients (N, P) for agriculture, but only after laboratory analyses confirm the material is suitable and applies all local (legislative) restrictions and conditions.||Produced around 1.000 tons of biosolids, which can be used as soil amendment|
|Greenhous gas emissions||In RBs system the organic matter is decomposed by various microbial reactions. This process generates gases such as CO2 and CH4 emitting to the atmosphere although emitted, when compared to energy demanding systems RBs produce less. The comparison between the two carbon footprints from transportation between RBs and mechanical dewatering shows that the RBs has 4 times lower impact.||Carbon footprint of sludge transportation for 20 years: 12008 kgCO2/20Y|
|What are the benefits and co-benefits of NWRMs in this application?||
The technology enables a long-term and sustainable storage of sludge
with low operating and maintenance costs. It can completely replace
dehydration which currently represents significant (operating) cost on
existing wastewater treatment plants.
With this technology different types of sewage sludge can be treated. Sludge is stored in the reed beds normally between 8 to 10 years. Due to parallel operation of physical (drying) and biological processes (mineralisation) the treatment results in significant sludge volume reduction.
The end result of the process is a compost-like material that can be reused as fertilizer in agriculture, cover layer for landfills or construction material.
Value in € (Total + possible breakdown)
|Capital:||193.000,00 €||Project documentation, construction, operation staff training, dissemination|
|Land acquisition and value:||0 €||Land owned by the Municipality|
|Operational and Maintenance:||5.400,00 €/year||Labor costs
Electricity consumption costs
Maintenance costs of mechanical equipment
Replacement costs and repairs
Sludge disposal – biosolids reuse
|Were financial compensations required? What amount?||Was financial compensation required: No, it was 100% grant capital cost.|
|Total amount of money paid (in €): -|
|Compensation schema: -|
|Comments / Remarks: -|
|Economic costs||Actual income loss: -|
|Additional costs: -|
|Other opportunity costs: -|
|Comments / Remarks: There is no economic cost.|
|Which link can be made to the ecosystem services approach?||
Management of sewage sludge in Montenegro is defined by a Regulation on
detailed conditions, which have to be met for municipal sewage sludge,
quantities, volumes, frequency and methods of analyses of municipal
sewage sludge for approved purposes, and conditions that have to be met
for soil that will receive the sludge (“Official Gazette of Montenegro,
No. 89/09 from 31.12.2009). The regulation was adopted on the basis of
European sewage sludge Directive 86/278/EEC.
It is recommended to analyze sludge once per year.
For biosolids reuse sludge must comply with national regulations (limit values for soil to which sludge is applied and limit values for sludge, Maximum annual load of heavy metals to land, on ten years basis).
Sludge analyses include: heavy metals, organic matter, organic pollutants (PAH, PCBs), percentage of dry matter, pathogens.
Soil analysis include: heavy metals (cadmium, copper, nickel, lead, zinc, mercury and chromium).
Regular maintenance works of RBs consists of:
|What are the administrative costs?|
|Which assessment methods and practices are used for assessing the biophysical impacts?|
|Which methods are used to assess costs, benefits and cost-effectiveness of measures?||“Unit value transfer method” for assessing direct and indirect benefits of RBs in Mojkovac had been used.|
|How cost-effective are NWRM's compared to "traditional / structural" measures?||
Capital expenditures in RBs are app. 30% higher than in mechanical
dewatering, but on the other hand, operational expenditures of RBs are
much lower. RBs with biosolids use can reduce operational cost for 73%
per year compared to mechanical dewatering and incineration.
The investment in RBs may be more expensive, but maintenance is incomparably cheaper.
|How do (if applicable) specific basin characteristics influence the effectiveness of measures?||Basin characteristics do not influence the effectiveness of measures.|
|What is the standard time delay for measuring the effects of the measures?||Efficiency can begin to be measured after the first growing season as the plants grow.|
|What were the main implementation barriers?||
|What were the main enabling and success factors?||
Ministry of Sustainable Development and Tourism of Montenegro together
with Municipality of Mojkovac had overcome financial barrier by
obtaining a grant (100% non-refundable donation from
Municipal support of the technology was crucial for the start of the project. A close collaboration between the municipality, ministry, public utility and technology experts resulted in the successful construction of RBs. After the completion of the construction, and during the commissioning/start-up phase, there was a strong emphasis on dissemination (video, project presentation) to promote general RBs adoption. RBs in Mojkovac demonstrate good practice, which may stimulate frequent implementation of the technology, but challenges remain still.
In Mojkovac, a considerable effort was invested so the contractor would understand the RBs technology and system functioning. Construction mistakes were prevented with the implementation of technological supervision.
Training and knowhow transfer were provided for the staff in charge of the O&M of the WWTP Mojkovac. Training included theoretical and onsite practical training. During the first year of operation, contractor stayed in close contact with operating staff in order to observe plant growth and optimize operation.
In Mojkovac, RBs competed with mechanical dewatering, but won support of decision-makers due to low operational costs and longevity of the solution for sludge storage.
|Financing||Government of the Republic of Slovenia through UNIDO – 100% grant|
|Flexibility & Adaptability||The solution can adjust depending on the load and the location of the WWTP and this will not incur in increase of cost or duration. Technology is resilient.|
beds are land intensive technology. Limiting factors usually are: RBs
area requirements, spatial planning process and its administrative
risks, land cost and legislation.
Generally, technology is more likely to be adopted and implemented by smaller settlements and cities where the price of land is low or land is already owned by state or municipality.
|Source Type||Project Report|
Alenka Mubi Zalaznik
Tea Erjavec Haložan
|Source Title||Construction of a reed bed filter for the treatment of sludge in Mojkovac, Montenegro - Final report|
|Year of publication||June 2016|
|Key People||Name / affiliation||Contact details|
|Alenka Mubi Zalaznik||alenka(at)limnos.si|
|Source Title||Interviews with public utility GRADAC d.o.o., Municipality of Mojkovac, Ministry of Sustainable Development and Tourism of Montenegro|
|Year of publication|
|Key People||Name / affiliation||Contact details|
|Alenka Mubi Zalaznik||alenka(at)limnos.si|