Athens, the capital of Greece, is a major urban area of approximately 5,000,000. Athens is in a water scarce area: Western Greece is the wet part of the country while Eastern Greece (where Athens is situated) is much drier with most of the demand for water and almost all the population. This spatial and temporal imbalance led to the development of a very long water supply system that presents challenges for both real-time control and long term planning – as well as security. Water distribution is also a challenge due to urbanisation (of the suburbs) and de-urbanisation (of the centre), coupled with a significant elevation difference leading to pressure-energy-leakage challenges. The waste water system of Athens is a collection, transport and (end of pipe) treatment system of mostly separate sewers (approximately 97%). Measures have been taken to recover energy from wastewater (100% of the waste water) but there is no nutrient recovery from waste water. Sewage sludge is thermally recycled in 100%. Reuse options are restricted by the location of the centralised treatment plant on the island of Psytalia. Solid waste management in Athens is also a challenge due to the sheer volume of generated waste (at 450 kg per person per year multiplied by 5 million inhabitants). Currently, co-generation plant (heat and power) from biogas operates at the Ano Liosia sanitary landfill with an installed capacity of 23.5 MW. Municipality-organised recycling schemes operate for approximately 21% of the waste, with 77% landfilled (compared to an EU average of approximately 40%).
Genoa is a city in Northern Italy, with a population of 600,000, challenged with climate change features: long drought periods and the increased frequency of flash floods. Genoa and the Liguria Region have experienced many flooding events in the last ten years. Research activities have been carried out to improve management of water services and minimize service failures. The Genoa water company, Mediterranea delle Acque, has specific expertise on the procedures to identify optimal and integrated real-time management strategies applied to water resources and to define decision support standards for allocation of water sources in a competitive uses context. To control leakage and reduce water consumption, in-situ monitoring systems with smart high frequency metering devices and technologies are installed at users connections and across the network. These devices improve urban water networks monitoring and efficiency. Subsequently a model based on statistic leakage assessment integrated with the monitoring network, is used to assess leakage levels. In the urban drainage system, separated sewers for storm water runoff are present; in waste water treatment plants, no nutrients are recovered, but a great amount of the sludge is used as fertilizer (92%). The co-energy produced is 1286 662 KWh. In the waste and remediation field Regione Liguria has recently adopted a global regional waste plan divided into several sections concerned with municipal solid waste, special waste, reclamation, and introduced Environmental Reporting, including: Framework, Context Planning, Monitoring Plan and Non-technical summary.
Helsinki. The Metropolitan capital area of Finland with a population of 1,200,000. Surface and groundwater quality is good and abundant. Flooding is occasionally a concern. The main drinking water source is Päijänne lake 120 km north of Helsinki and the untreated water is delivered via a tunnel to Helsinki region where it is purified to drinking water quality. Water distribution network encompasses 7600 km of which 4900 km is waste water distribution. Per-capita consumption has decreased since its peak consumption in the 1970s from 400 l/d to is ca 155 l/ thanks to water-saving household appliances and improved showers, as well as by a general change of attitudes. The wastewater is processed by two wastewater treatment plants. The treatment is conducted by means of a biochemical process that produces sludge and biogas as by-products. The sludge is processed into soil, and the gas is utilised as an energy source. The treated wastewater is drained through a tunnel into the sea. Situated on the Baltic sea, which suffers severely from eutriphication; nutrient removal is of high concern. Helsinki Water was merged into the Helsinki Regional Environmental Service, HSY a couple of years ago. This waste and water authority is administrated by the same organisation which is a municipal Enterprise.
Istanbul forms the largest urban agglomeration in Europe and is classified as a megacity (a city with a population of over 10 million people). Furthermore, Istanbul is one of the most rapidly growing cities in Europe. The annual population growth is 2,8%. Providing water to this vast number itself is already a problem but the city faces further problems regarding water management. Watersheds used currently are threatened by urbanization, pollution and industry. Therefore, their protection and improvement is a prime concern for water managers of the city, who have to consider population increase and uncertainty of precipitation (extreme events such as drought and flood) due to climate change. Moreover, the watersheds within the borders of the city are not enough to meet the current demand. The majority of resources are located on the Asian side in contrast to the urban density, the water reservoirs are linked into an integrated system including water from adjacent catchment areas of other cities connected to secure water supply for the city at a high cost. The Melen Project is a good example of this. Water from Düzce city is transported to Istanbul via a pipeline of 151 km in length, which begins from the Asian side, passes under the Bosphorus Strait with a 5.5 km long tunnel and 135 m under the sea and reaches the European side of the city. Regarding drought conditions, provision of water from another city would create conflicts between Istanbul and that city, which must also be considered by the water authorities. In Istanbul, the share of wastewater treated increased from 9% in 1993 to 95% in 2004. Although the storm water and sewage system have been implemented separately in recent years, a major portion of them are still combined which affects drinking water quality. In principle, the sewage system consists of separate sanitary sewer and storm water drains, however, in reality there are illegal cross-connections so that untreated wastewater reaches the storm water drains and contributes to the pollution of drinking water reservoirs. In addition, uncontrolled domestic and excavation wastes are other problems for watersheds. Along with population, growing industry is another factor for deteriorating quality of watersheds, and availability of drinking water. A good example of this is the Küçükçekmece Watershed, which has not been used since 1997 due to industrial wastes.