Reclaiming biodiversity

Wetland project in Tirana attempts to tackle multi-source urban pollution

By Nathan Johnson

The Albanian capital city of Tirana contributes high amount of multi-source pollution to the river which runs through it and bears its name. Not only are the banks of the Tirana River used for dumping of garbage and solid waste, but heavy nutrient pollution from sewage and urban waste runoff deposited directly into the river has eliminated nearly all biodiversity - invertebrates, fish and other aquatic life - from the river. This already serious state of environmental degradation is made even worse by numerous illegally constructed buildings on the floodplain and on filled land that has actually altered the course of the river. Levels of nitrates and suspended solids in the Tirana River are at levels well above established EU limits.

In an attempt to better understand and address this problem, UNDP/GEF and Living Water Exchange (LWE) established a demonstration project called 'Constructed Wetland for Nutrient Reductions in the Waters of the Tirana River in Albania', which ran from November 2009 to August 2010. This was, in fact, the first ever constructed wetland in the Albanian capital. The Tirana-based Institute for Environmental Policy (IEP), local scientists, the Regional Environmental Center for Central and Eastern Europe (REC) and REC Country Office Albania assisted with project implementation. Total investment in the project was just over USD 60,000, with USD 38,569 coming from the GEF and USD 21,516 in co-financing from the City of Tirana, IEP and other sources.

As with the other LWE demonstration projects taking place in the CEE region during the same time period (i.e. Moldova, Serbia and Ukraine), a peer-to-peer exchange meeting took place on September 13-15 in Tirana, which comprised of presentations, field visits, and participant feedback and discussion. This and the other exchanges focused on capacity building, possible replication of best practices, and identifying further funding opportunities for best practice replication.

Getting underway

Urban wetlands, given that they are of sufficient size and involve a proper rate of water flow, can be effective, low-cost options to reduce nutrient loading. While the Albanian project was carried out at less than optimum scale (375 square metres), it was an important first step and learning experience. The project consisted of three primary components. First, an evaluation was carried out in order to determine wetland-system effectiveness; this required the conducting of water sampling and analysis prior to and subsequent to construction and implementation to estimate water quality impacts in the first year. Second, a three-tiered wetland system was construction to remove nitrogen, phosphorous and sediment from sewage and urban runoff. Third, primary outreach efforts focused on Tirana city officials.

The Municipality of Tirana selected an area known as Bregu Lumit as the project site, an area representative of the multiple urban environmental threats to the Tirana River: filled in areas of floodplain, illegal construction along the river bank, and copious amounts of garbage and untreated sewage and solid waste. Prior to the wetland construction, volunteers from local NGOs helped to remove much of the solid waste from the site, though an unfortunate consequence of this was that illicit dumping resumed immediately upstream. Another preliminary activity took place in February 2010, namely measuring and analysing water samples taken both from the Tirana River from two sewer outfall pipes bearing a combination of sewage and urban runoff.

The construction of three, adjacent 5m-by-25m basins took place in spring 2010. The basins were built so that pipe influent would enter the first basin, overflow into the second basin, and overflow once again into the third. Wastewater would then be discharged from the third basin into the Tirana River. In theory, such a design (again, given sufficient scale and proper water-flow rates) allows particulate matter to settle in the first basin, treatment to take place in the second, and final 'polishing' of the water to occur in the third prior to discharge. To facilitate this process, various wetland plants were planted in the basins, with a local variety of cattail proving the most abundant in July 2010, during which time water samples from the basins and river were taken for measuring pollutants and other biological parameters.

Observations and assessment of outcomes

Before going into any detail about the project limitations, it should be stressed that substantial effort was need just to get this wetland demonstration off the ground. The initial legwork included: securing an agreement from the Tirana Municipality on a project site, removing all solid waste covering the project site, and building concrete walls for the basin in time to effectively grow the cattails. Given the time constraints and level of funding available, the project team carried out its tasks in highly commendable fashion. This was the result primarily of the energy and leadership provided by the IEP, with Edvin Pacara acting as project head. Bearing this in mind, it can take several years for a constructed wetland to achieve its full potential. Given that the vegetation in this particular project had only six months to grow within the project period, only limited impacts could have been achieved even in the best circumstances.

Size and function of the constructed wetland: One of the keys to effective nutrient removal in a constructed wetland is that water be allowed sufficient residence time - generally some time period between three and seven days. Given the amounts of hydraulic waste and pollutant loads entering from two pipes, the demonstration wetland area is far too small to achieve optimal results. With wetland inflow estimates in the range of 0.2 to 1 cubic metre per second (cms), and assuming average wetland water depth of half a metre over the 375 square-metre area, the residence time is only around 3 and 15 minutes. In some cases, this brief duration is sufficient to allow limited nutrient removal by biomass, but very little else by way of treatment is possible. The proportions of a wetland of similar design to that of the demonstration project would need to nearly 300 times larger to provide optimal treatment: i.e. approximately 10,000 square metres, or roughly one full hectare. In other words, according to the LWE project report published in November 2010, "the system was severely under-designed for the flow received."

The project report lists three general ways of improving performance of the demonstration project wetland in Tirana: decrease flow into the wetland, expand the size of the wetland, and/or redesign the wetland base to assure a more circuitous flow and better interaction with vegetation and substrate. If the project wetland continues at its current size, water inflow, should be brought down drastically to less than 10% of current inflow - and, ideally, closer to just 5%. At a minimum, one of the pipes could be entirely diverted from the wetland. This would result in something of a devil's bargain: direct discharge of wastewater into the river, while allowing the wetland to better fulfil its nutrient-reducing capability.

Another, preferable option, though much more difficult logistically, would be to expand the wetland to between 2,500 and 5,000 square metres to much more effectively accommodate the current amount of water inflow. This option, however, is highly unlikely so long as illegal construction continues to proliferate near the project area. (Two more illegally built houses appeared during the project period alone!) A third, more compromising measure, would be to temporarily divert the water from the wetland and to redesign the wetland basin, and improving the existing baffle system, or creating 'rock piles' or other diversions or flow directors. Regardless of the course of action taken, it is recommended that above-water vegetative biomass be harvested each year.

Wetland monitoring: Project time constraints allowed for only two opportunities to monitor water samples, prior to basin construction period and after establishing the vegetation. In February 2010, a first set of samples was taken from both pipes and the river; the second set was taken in July from each of the three basins and the river. There were indications that some pollutant parameters went down during the period, and that phosphate content appeared to increase, but these limited results are far too inadequate to draw any firm conclusions.

While an urban wetland offers valuable opportunities to study a biotic community, the project team concluded that it is more important at this time to keep monitoring focused on pollutants and wetland effectiveness in removing them. The key pollutants to monitor in this case are phosphorous, nitrogen, ammonium, nitrite, nitrate, suspended solids, and faecal and total coliform. At a minimum, monitoring should take place quarterly, although it is recommended to carry out this work, if possible, on a monthly basis.

Another key monitoring element is that of water flow into and out of the wetland system, and this should take place monthly. If this is not possible, then weir's can be fitted at each pipe to calculate based on the height of flow through the weir. Continuous flow monitoring is best of all, but is costly and prone to acts of vandalism.

Municipal wastewater treatment in a constructed wetland: The project team concluded that it is critical to convince local and national governments that 'constructed wetlands are not intended to provide disinfection.' Constructed wetlands can be very useful in reducing nutrients and suspended solids from municipal wastewater, but only after primary treatment and disinfection takes place. Without such treatment, the modest reductions and pathogen filtering taking place in the demonstration wetland is not enough to make the Tirana River safe for human contact.

While the Tirana River suffers unusually heavy pollution, this consideration does raise the larger issue of whether or not constructed wetland systems are appropriate for treating wastewater in cities at least the size of Tirana (pop. 600,000). The project team insists that the Albanian capital must introduce some form of centralised sewage treatment. Ongoing efforts to remove pollutants from the course of the river should also take place at points both upstream and downstream from Tirana.

The demonstration project wetland constructed in Tirana, while insufficient in itself as a water-treatment solution, can indeed provide a valuable service as a demonstration and research site, especially if certain of the aforementioned adjustments and improvements take place. Any information collected from the site can then be passed on to assist smaller communities in Albania and throughout the region interested in developing similar projects. Constructed or restored wetlands can serve most effectively as a "final component of a multi-step treatment system that reduces nutrient and suspended solids in runoff from diffuse sources," the final project report concludes.

While Tirana's local government is not as responsive as it should be to illegal construction and other environmental concerns, the Minister of the Environment for Albania agreed to host a ministerial-level meeting during the first quarter of 2011 to discuss how to foster cooperation to address nutrient pollution in the region. This will hopefully clear the way for future wetland initiatives in Albania.