Water: drought, ENEA's 20 tips for saving water (and energy)

28/7/2022

Rule number one: don’t waste water. A tip that is always valid, but even more so during a water emergency like the one we are currently experiencing, marked by the worst drought in 10 years. To combat water waste and make its management more sustainable, ENEA has drawn up a 20-point guide with suggestions and good practices, mistakes to avoid, and also solutions and technologies for saving water (and energy), especially in the residential sector. In short, when at home reduce leaks and waste and use it more rationally. In general, employ less water-intensive processes and systems, purification and reuse, improved efficiency and digitisation of the waterworks, but also good practices by families and schools.

20 tips for saving water

  1. Keep the water system efficient and check for hidden leaks: it is estimated that up to five litres per day are lost with a dripping tap.
  2. Close the tap tightly to prevent water from flowing unnecessarily. For example, when washing hands: in one minute you can avoid wasting at least six litres of water. If you let the water run while brushing your teeth you can waste up to 30 litres (compared to only 1.5 litres if you turn it off). Similarly, turning off the tap while shaving saves up to 20 litres.
  3. Collect unused cold water when waiting for the hot water to arrive. First do things that require cold water (e.g. brushing teeth) and then those that use hot water (e.g. shaving).
  4. The same goes in the kitchen, when preparing food or washing vegetables use basins instead of running water. It is estimated that about six litres of water per day per capita are consumed for drinking and cooking and at least 40 litres for washing dishes by hand. However, wastage can be as high as 12 litres per minute if the tap is not turned off.
  5. Reuse water from cooking pasta or washing vegetables to rinse dishes before putting them in the dishwasher or for watering plants (when not salted).
  6. Always use dishwashers and washing machines with a full load. It is estimated that for a dishwasher load (class A) without pre-wash up to 15 litres (7 litres in class A++) are used, while for a washing machine load (class A) 45 litres are used. Also prefer washing programmes with low temperatures (40-60° C). Furthermore, the installation of solar panels would avoid the consumption of electricity to heat the water needed for household appliances.
  7. Whenever possible, prefer taps with sensors or that are aerated to reduce water flow and increase washing effectiveness, taking care to maintain them (e.g. by using a scraper).
  8. Install double-button flushers to save up to 100 litres per day, considering that up to 16 litres of water are used for each use of single-button models.
  9. Use a shower instead of the bathtub to save up to 1,200 litres per year. It is estimated that an average of between 100 and 160 litres of water is consumed to take a bath in the bathtub, while a maximum of 40 litres is consumed to take a five-minute shower, and even less if you turn off the tap when you soap up.
  10. Shut off the water at the mains in the event of prolonged periods of non-use (e.g. when leaving on holiday).
  11. Install rainwater collection systems for non-drinking uses (washing toilets, washing cars) and for watering (rainwater is less hard and more agreeable to plants), avoiding watering during hot hours to reduce evaporation. Each year an average of about 800 mm of rain falls in Italy. This means that in an area of approximately 80 m2 you can collect the water needed for one person for a year.
  12. Use timed, drip or sub-irrigation systems for irrigation because of their greater efficiency.
  13. Avoid washing your car using drinking water to save 400-500 litres.
  14. Cover the surface of pools with tarpaulins to prevent evaporation.
  15. Recover condensation water from air conditioners or the dryer for domestic use, such as for ironing.
  16. Diversify the use of water according to its quality (drinking, rain, grey, black - see fig. 2).
  17. In the garden, around the plants, distribute adequate mulching[1] so as to keep as much water as possible in the soil. Also prefer plants that need less water and take care not to water impermeable areas.
  18. Where possible, use technologies for the reuse of grey water, i.e. water generated by personal hygiene. A dedicated system to recycle water from showers, washbasins and bathtubs, and in some cases, from condensation from air conditioners or boilers, ensures that it is treated for subsequent “secondary” uses such as flushing toilets, watering green areas, and washing.
  19. Install plant-based roof coverings and roof gardens. These solutions absorb up to 50% of rainwater and slow the flow of rain into the city's water system, reducing the possibility of flooding in the event of heavy rainfall. Green roofs also thermally insulate the roof, reduce particulate matter and promote a more pleasant microclimate, reducing the albedo effect.[2]
  20. On surfaces outside buildings, use drainage pavements in order to preserve the natural character and permeability of the site, encourage groundwater recharge, reduce subsidence and mitigate the heat-island effect.

The data

According to ENEA estimates, in homes the energy needed to produce hot water accounts for about 25% of the total energy used, while the average consumption of water for civil use (residential and tertiary) accounts for about 20% of total consumption, with a per capita water supply (net of leaks) of about 200 litres per inhabitant per day.

"One of the biggest problems in our country is the lack of infrastructure and the low efficiency of the waterworks", emphasises Luigi Petta, Head of the ENEA Laboratory of Technologies for the Efficient Use and Management of Water and Wastewater. “Despite its high supply of water – guaranteed by 7,594 watercourses, 324 lakes, over 1,000 underground aquifers and 526 dams that collect about 11% of rainfall – the Italian water network loses an average of 41.2% of the water supplied,[3] with peaks of 48% in national macro-environments. Even in the most virtuous areas this percentage never falls below 20%, compared to much lower values in Europe (6.5% in Germany)”. According to ENEA estimates, the efficiency and digitisation of the water network could save up to 25% of energy.

It is also crucial to save water used for production. In our country in particular, freshwater withdrawals for agriculture account for around 50% of total water consumption. This means that in order to deal with water shortages such as these that damage agricultural production, it is essential to make irrigation more efficient by using techniques with greater efficiency (subsurface irrigation, under-irrigation, drip irrigation) and to focus on research and technological innovation to encourage the re-use of treated wastewater. To achieve this objective, ENEA has developed a technologically advanced prototype[4] able to monitor the quality of purified effluents in real time and establish their optimal destinations, including first of all the irrigation of cultivated fields, with benefits in terms of greater water availability, nutrient intake, the consequent reduction of chemical fertilizers, and improving the environmental sustainability, quality and safety of the purification chain.

"Water is a precious resource. The problems related to its availability, whether due to lower rainfall on a seasonal basis, drought, or excess demand compared to the available usable water, affect many areas in Italy and Europe and call for actions at the local and multi-sectoral level, to be planned over the long term, avoiding the use of logic based on emergency responses”, Petta emphasises. "Moreover, increasing urbanisation and rising living standards are further critical factors that make optimal, careful management of the resource necessary”.

Figure 1 - Energy costs of water
Energy costs of water consumption per person or year Water (litres) Oil
Shower 25.000 320
Bath 50.000 620
Traditional tap 40.000 240
Water-saving tap 23.400 150
Traditional washing machine 4.700 55
Low-consumption washing machine 2.600 40
Traditional dishwasher 7.300 250
Low-consumption dishwasher 3.650 160
Figure 2 - Uses of water according to its types
Water type Characteristics Use
Drinking water Water that meets legally established criteria Cooking, drinking and personal hygiene
Grey water Soapy water collected at specific points of use (sink, shower) which, treated locally, can be reused. House cleaning, office cleaning, flushing and gardening
Rainwater Water collected from roofs used after simple treatment processes Gardening, car washing, flushing, washing machines.
Black water Wastewater that cannot be treated and reused locally, to be sent to the centralised sewerage treatment plant No local use

For more information:

Luigi Petta, ENEA - Head of the Laboratory of Technologies for the Efficient Use and Management of Water and Wastewater, luigi.petta@enea.it

 


[1] Mulching is an operation that is carried out in agriculture and gardening by covering the soil around plants with a layer of material in order to prevent weed growth, maintain moisture in the soil, protect the soil from erosion and the action of driving rain, prevent the formation of a so-called surface crust, decrease compaction, maintain soil structure and mitigate soil temperature.

[2] The albedo is the reflective power of a surface, i.e. the fraction of light, or solar radiation in general, incident and reflected in all directions.

[3] ARERA data for the year 2021.

[4] The results were obtained as part of the Value CE-IN project coordinated by ENEA, financed by the Emilia-Romagna Region and the Development and Cohesion Fund and conducted in cooperation with the Hera Group, the University of Bologna and Irritec.

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