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LEVEL 2

MODULE 8.2: WATER

Strengthen your action plan with more ambitious measures

Setting more ambitious targets

-    It is important to set new targets in order to advance with your ambitions. Your previous SEAP probably did not have any targets on water and energy. Now is the time to fix this! When setting targets you need to understand what the potential solutions are – and the impact on reduced energy and/or water demand.
-    The following solutions can be addressed for improving water and energy efficiency:

  • Identifying plant improvements and operational changes:

    • Proper equipment sizing – to optimize energy demand. Match the pumps to the intended duty, and design systems with lower capacity and total head requirements. Where pumps are dramatically oversized, these reduce speed with gear, belt drives, or slower motor speed. For example by using two smaller pumps instead of one larger pump excess pump capacity can be turned off. Correctly size pipes and automate controls where ever possible to improve energy efficiency and ease monitoring. Idle or turn off non-essential equipment, especially during periods of peak power demand.

      • Through these measures the City of Lausanne , famous for its public fountains, was able to reduce 230.000 kWh per year only by applying more efficiency to three fountains.

    • Install high-efficiency motors - optimise pump system efficiency by replacing old pumps with newer ones. Replace older standard efficiency motors with premium efficiency motors. Premium efficiency motors are 2-10% more efficient than standard motors.
    • Providing for regular maintenance of pumps - collect proper data and create a pump curve, properly maintain pumps. Motor maintenance savings can range 2-30% of total motor system energy.
    • Install variable-speed technologies to improve system efficiency – e.g. introduce Variable Frequency Drives (VFDs) to match speed to load requirements for pumps. VFDs can offer motor energy savings between 10-50% with payback of 1-8 years.  Eliminate pump discharge throttling as this could provide savings close to 50% of pumping energy.
    • Reduce energy requirements for water distribution by introducing demand driven distribution and pressure management measures- By reducing pumping pressure in the water supply network at non-peak periods, for example between the hours of 23.00 to 07.00 - when the demand for water is the lowest - substantial saving in energy can be achieved. Also, the amount of water that leaks through large fractures as well as small undetected holes in the distribution network can be reduced drastically. The pressure management system also reduces the frequency of pipe busts in the network thus saving on maintenance costs.

      • See example from Zaragoza Spain and an informative video on demand driven distribution.

    • Natural treatment systems can provide substantial benefits in energy consumption and operational costs. Although selecting less energy intensive (natural) water, wastewater treatment and sludge drying methods should comply with national standards for treatment levels. Also natural treatment systems tend to take-up more built up area and availability of adequate land should be taken into consideration.

      • See case study on of constructed wetlands in Bulgaria and some information on constructed wetlands from France.

  • Conserving water - water is precious! Water saved is energy saved. Average water loss in cities can be as high as 40%. There are many different measures that can be implemented in your SEAP in this area:

    • Take up a rigorous leak detection & repair/replacement programme to avoid non-revenue water losses.
    • Install water efficient devices in operations and provide accurate metering at consumer end to determine demand and supply.
    • Promote water conservation to consumers via an effective information and education campaigns (example from Zaragoza as well as the two winners of the UK water efficiency award 2012 GabiH20 and Combined Water and Energy Efficiency).
    • Promote water saving gadgets to consumers, e.g. low flush toilets, water saving shower head, etc..
    • Efficiently manage high-volume users, such as sport parks, swimming pools and commercial utilities and promote water saving at a large scale.

      • Take a look at the example from Malta.
      • Explore this link for more information and resources on water loss reduction.

  • Using renewable energy (RE) sources:

    • The switch to clean, sustainable and secure energy sources is essential.  Setting a target for this can help to raise the level of ambition.
    • Where possible introduce (local or regional) RE in non-operational energy consumption. For example, when providing water services you can use green energy for lighting, running computers, heating and cooling systems. Lighting accounts for 35-45% of a building’s energy use and uses up to 2% of a plant’s total electricity load. By installing occupancy sensors a 10-20% of lighting energy reduction can be achieved with average payback period of 1 year.
    • RE can also be used in water management operations, in any area where energy is needed: from water purification (also desalination) to pumping.

Exploring renewable energy and water management operations

-    The greatest opportunities for introducing RE for water management operations are at design phase of a project. The latest systems can reduce energy use by 10-40% and thus can reduce greenhouse gas (GHG) emissions drastically. Following are some examples of RE use in water management systems.

  • Renewable energy from blackwater  can contribute to green homes and even green districts. Experts name wastewater from toilets “blackwater”. It consists of a large proportion of organic matter and has a high phosphate and nitrogen concentration. The chemical energy bound in the organic material can be utilised through anaerobic treatment and digested in biogas plants. In order to efficiently access this source of energy, blackwater needs to be separated from wastewater streams already in buildings or districts. This means a fundamental change in wastewater infrastructure and treatment, but can save much energy since the (energy) intensity within the purification process is decreased. Moreover, the concentrated blackwater  can be converted into electricity and heat through a combined heat and power (CHP).

    • Read how the European Green Capital of 2011, Hamburg in Germany, implements this innovative approach in its districts.

  • Energy recovery from greywater is often untapped potential. Greywater is used water that is not extremely polluted, with the most relevant sources within households for heat water recovery come from showers (41%) and other sinks (27%), followed by washing machines (12%) and dish washers (10%).

    • Get inspired by reading through the best practice catalogue on heating with wastewater heat. Don’t forget that you can reverse the process and could apply the technological system for cooling as well.

  • Solar sludge drying is an innovative new technology that has evolved for treatment of municipal sludge. Traditionally, sludge was mostly treated and disposed in landfills or incinerated. The incineration of sludge is highly energy intensive, while solar sludge drying reduces energy consumption substantially.

    • To understand this look at an example of a newly installed unit in Mallorca, Spain.

  • Saving energy through cooling with water :   
  • Energy cogeneration from wastewater treatment plants: Modern wastewater treatment plants are no longer seen as energy consumers but are rather becoming energy producers. Energy is recovered from various digestion processes during wastewater treatment to produce biogas and/or electricity.

    • Some good examples of such technology are the treatment plants of the cities Eisenhüttenstadt (generates an excess of 1,800 kWh el./h) and Stockholm (annual biogas production of 400,000 m3). The main water treatment plan of Vienna, Austria, even became energy self-sufficient.

  • Pumped-storage hydroelectricity (PSH) is power generation by hydroelectric power plants by using the concept of load balancing. In this method potential energy is stored in the form of water that is pumped back from a lower elevation reservoir to a higher elevation using low-cost off-peak electric power is used to run the pumps. During periods of high electrical demand, the stored water is released through turbines to produce electric power. Although the energy losses during the pumping operations makes the plant a net consumer of energy overall, the system increases revenue by selling more electricity during periods of peak demand, when electricity prices are highest. Moreover energy storage through water stabilises the power grid and allows in particular wind turbines (even in low demand periods) to generate as much energy as possible.

  • Tidal energy production : is a segment of RE that is gaining popularity for energy production along coastal areas. As tidal currents are highly predictable, the system is seen as a reliable source of energy. The advantages of using tidal energy: no greenhouse gas emissions and no other waste in energy production, reliable but limited electricity production (only during tidal surge - ten hours a day), inexpensive to operate and maintain, etc. Nevertheless, tidal power plants also have their disadvantages, such as, expensive to build, highly location specific and can have environmental effects - impact on fish, marine mammals and birds.

 

 

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