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Effective infrastructure management with wise pump selection
The Algarve region of Portugal is internationally renowned for its natural beauty, fine beaches, slow pace of life and year-round temperate climate. These factors make it a popular holiday destination and provide advantageous conditions for agriculture. As one of Europe’s sunniest regions, optimizing water usage is a high priority, as is wastewater treatment. For many “Blue Flag” beaches (the European standard for beach quality) along the 500-km coast and many natural wildlife habitats, pollution is always a major concern.
Over the past decade, considerable investment has been made in upgrading the many municipal water supply and effluent treatment plants throughout the region. This has involved the construction of a major new dam, water and wastewater treatment plants, and pumping stations; the upgrading of many existing treatment plants and pumping stations; and the construction a 454-km water supply pipeline and a 203-km wastewater gravity pipeline. In addition, for the first time, it is possible to pump water from east to west and vice versa in order to adjust demands of the complete supply system. For KSB Portugal, the 10-year investment program provided an opportunity for the company to install valves and pumps for transporting water along the pipelines and in the various stages of treatment.
A Sound Investment
Costing a little under €700 million, this infrastructure investment program has been made possible by combining the Algarve Multi-Municipal Water Supply System and Algarve Multi-Municipal Sanitation System in 2000. Jointly known as the Algarve Multi-Municipal Water Supply and Sanitation Systems (AMWS&SS), the activities of these two systems are under the management of Aguas do Algarve SA, which was established at the time of the merger, and which holds the 30-year concession from the Portuguese government.
The AMWS&SS covers all 16 counties in the region and supplies 450,000 inhabitants during the low season and approximately 1.5 million of them during the high season. Coverage includes distribution and treatment of water and household wastewater. Aguas do Algarve aims to supply adequate-quality drinking water year-round and to equip the region with a safe system in terms of public health, improving levels of assistance and promoting environmental quality—more specifically, the water quality of the Algarve’s beaches and rivers, which is an essential factor for the well being of the population and for developing the region’s economy and tourism.
Most significantly, it means that there is just one organization responsible for running an integrated water supply and wastewater treatment infrastructure for the whole of the Algarve, from east to west, with clear advantages in terms of synergies, coordination, consistency and decision processes.
Protecting the Water Supply
Before the Algarve Multi-Municipal Water Supply System was established, each municipality in the east and west regions was responsible for its own water supply pumping and piping infrastructure. Both regions had to contend with qualitative and quantitative problems concerning the public water supply, which came from underground sources and dams. Until the construction of the multi-municipal system, these sources supplied most of the permanent residents and temporary population. In addition, agriculture required considerable amounts of water for irrigation purposes.
The pressure exerted by the growing search for water was so strong that the availability of water decreased and the quality of the water supplied dropped considerably in many aquifers as a result of over-exploitation, especially during consecutive dry years. Poor quality was, to a degree, attributable to saline intrusion, which led to a sharp increase in chloride content in areas close to the sea, together with widespread pollution as a result of intensive agricultural activities. The construction of the Odelouca Dam, which opened in 2012, will increase the supply resources in the west of the region.
When designing the network, engineers had to provide a supply system that would operate to maximum capacity, taking into account projected growth and demand, until 2055. At certain times of the year, however, demand drops considerably, creating a situation in which efficiency levels decline and production costs per liter of treated water increase. To overcome this, identical pump types with varying flow capacities offering lower maintenance costs were installed. This way, when demand drops, the water treatment plant can switch to smaller-capacity pumps running at optimum performance as opposed to large pumps running at a low performance rate. In addition, almost every pump is fitted with speed control to adjust capacity to demand.
The water supply system operates four water treatment plants and 32 pumping stations along the network of treated water and raw water pipelines. The treated water pipeline runs at an average elevation of 100 meters above sea level along its 454-km length, with the individual pumping stations extracting water at pressures and volumes as required. These are controlled remotely in the main water treatment plants at Tavira and Alcantrilha using telemetry.
There are three major pumping stations: Tavira, Alcantrilha (both of which have treatment plants nearby) and Vilamoura; and each one has been equipped with a variety of KSB pumps for a range of supply applications. In the east, the main Tavira plant can treat 2.2 cu meters per second of drinking water with a further station treating 0.5 cu meters per second. In the west, the main Alcantrilha plant has a treatment capacity of 3 cu meters per second, with a second station providing a capacity of 0.125 cu meters per second. In the middle of these two subsystems is the Vilamoura reversible pumping station.
At the Tavira plant, the pumping station fulfils two duties: bringing raw water into the plant for treatment and supplying treated water to storage reservoirs along the system. The pumps in use include SNW Series large tubular casing pumps for raw water intake, and Etachrom and Etanorm pumps for treated water distribution.
The Vilamoura reversible pumping station connects the east and west systems and is unique in that it is designed to reverse the water delivery flow when necessary. This pumping station is important because, on the west side of the Algarve, water is less available than on the east, therefore, it is necessary to transfer water from east to west, usually in the summer when populations increase. The reservoirs in the east have a larger capacity than in the west, so in the event of a dry winter, the western system can be topped up. The building of the Oldelouca dam in the west will rebalance this situation when it comes on stream. Pumping from west to east, or east to west, will be possible through this reversible pumping station when there is a need, such as when maintenance is taking place in one side of the system.
Built in two stages, the Vilamoura reversible pumping station can pump water in one direction to another using a pipe and valves system. It is, in effect, a twin pumping station, with one station fitted with KSB high-pressure multistage pumps of the Multitec Series, each capable of handling 75 liters per second. The pump was selected because it offers adjustment of the suction and discharge nozzles according to the system and its low operating costs.
Depending on which way the Vilamoura station is pumping, it has to satisfy differing needs in respect of capacities and pressures. The discharge pressures may change by as much as 6 Bar, depending on demand and pumping direction. By employing variable speed, it is possible to meet the duty point and range of the demand of both the east and west parts of the system.
Along with the investment in the treated water supply, there also has been a substantial upgrade of the wastewater treatment plants along the coast. This prompted the construction of a 202-km gravity pipeline and 170-km pressurized pumped sewage pipeline, together with the upgrade of 57 wastewater treatment plants and the building and refurbishment of 159 pumping stations.
Whereas at one time each municipality had to handle its own wastewater treatment, there now is infrastructure in place for municipalities to transfer untreated and partially treated wastewater and effluent into a central gravity pipeline.
In taking over management and control of the wastewater treatment infrastructure, Aguas do Algarve inherited a highly fragmented capability, having to take over many municipal treatment systems and pumping stations. Aguas do Algarve has drawn on KSB’s considerable experience in wastewater and has installed many of its pump and mixing technologies throughout the whole development program.
The most widely specified pump is the Amarex KRT wastewater submersible pump, because it can satisfy the varying demands that occur in this region throughout the year. These pumps are used for raw sewage pumping and on treatment plants. Unlike the water supply pumps, the pumps used in the handling of untreated and treated effluent have to operate all day long, which places them under a considerable workload. Several Amamix and Amaprop agitators were installed in different treatment stages of the wastewater treatment plants.
No Red Flags
The major issue facing the pumps is sand, as this can have a serious adverse effect on impellers. To counter sand, some pumps were supplied with special wear-resistant impellers. The open design of the impeller allows the pumped effluent free passage, so clogging is minimized. This is most important during the summer, when the population soars and the nature of the raw effluent changes. Reports provided by Aguas do Algarve show that these pumps are highly reliable and offer the desired levels of operating efficiency.
“From Easter through September, there is a big challenge to keep a high level of sewage treatment capacity in order to ensure the beaches maintain their water quality and Blue Flag status,” said Vieira Pereira, maintenance coordinator engineer for Aguas do Algarve. “Our concern is not just the quality of the treatment. Because many properties are located close to the sea, it is important to maintain constant operation of the pumping stations, transferring effluent to the treatment plants to avoid coastal contamination. Pumps have to be reliable, which is why pumping stations are provided with standby pumps and designed for optimum usage. And just in case there are power supply problems, standby generating sets are installed.”
Water is a hot commodity in the Algarve. It is not blessed with abundant year-round rainfall, so its resources have to be wisely used. The upgrade in the water supply network now is ensuring that all regions receive the clean water supplies that they need. The investment in wastewater treatment infrastructure substantially reduces the risks of pollution to the sea and coastline. There also is an additional benefit: Treated wastewater is available for agricultural purposes.
Ensuring that the water is readily available where it is required and that wastewater is handled safely and efficiently can, to a large degree, be attributed to wise pump selection made by contracting engineers working for Aguas do Algarve. The company first installed KSB pumps more than 12 years ago and said that the original pumps have measured up to all expectations, as have all those subsequently installed throughout the region.