WATER RECYCLED MEANS WATER SAVED

Clean water to drink is in short supply in many places around the world. Global climate change is
making a bad situation even worse. With intelligent water recycling for crop irrigation, life-saving
drops of the precious liquid can be saved. Scientists and engineers from universities and private
companies in Denmark, Italy, Switzerland, and Israel have contributed knowledge and solutions
to the problem in the EU-project SAFIR. New technology for water recycling and use in agriculture
has been tested in southern Europe and other areas with insufficient potable drinking water.
Up to 80 percent of water consumption in southern European countries such as Spain, Italy and
Greece is spent on irrigating agricultural crops. Demand placed on the all-important potable
water is increasing as potable water becomes in short supply in these areas. What to do? Should
the crops thirst? Or should people thirst?


How to recycle water for irrigation
Neither crops nor people need to go without water if the water resources available are used
sensibly. One of the methods is to treat and recycle waste and grey water and use it to irrigate
high-value agricultural crops – typically vegetables. In SAFIR, the company Grundfos Biobooster
A/S, Denmark has developed advanced, compact biological-mechanical technology for decentralized
treatment of municipal wastewater. Also, less polluted water has been treated by
a new modular system developed by CER, Italy; EAWAG, Switzerland and Netafim, Israel, that
can reduce pathogens and heavy metals in e.g. river water. Both treatment systems have been
able to deliver a sufficiently good water quality to feed the treated water into subsurface dripirrigation
systems manufactured by the company Netafim, Israel.
Recycled water typically contains some remaining particles that may stop the water flow in
the drip-tubes as well as pathogens, including bacteria. However, with Netafims self-cleaning
drip-emitters it has been demonstrated that it is possible to deliver the water underground
consistently and very uniformly to the plants. This is an important prerequisite for efficient use
of irrigation water. Further, when the water is delivered below ground and percolates through
the soil, even more of the remaining pathogens are held back. How clean the water becomes
after its journey through the soil depends on how many pathogens the recycled water contains
and on soil properties.
Scientists from other parts of the SAFIR project have quantified these processes. Experiments
where they poured water infected with various concentrations of pathogens and fecal bacteria
like E. coli, on different soil types in a so-called semi-field facility have shown that pathogens did
not reach the ground water. But what about the quality of the vegetables?

Healthy food with recycled water
The studies indicate that both treatment systems are able to reduce faecal microorganisms to
a large extent. Therefore, when the treated water is distributed to the crops via the subsurface
drip systems very few bacteria if any reach the edible parts of the vegetables. Furthermore, the
plant nutrients that are present in the polluted water can be used productively for plant growth
instead of posing a costly problem of removal.

These findings are important for consumers as well as for the vegetable farmer. With the introduction
of the ’fork to farm’ principle and the common use of product standards, vegetable
farmers need to be able to control and assure product quality – like primary producers in other
industries. The studies have also documented how contaminated the water may be before being
applied to various soil types under various conditions. This knowledge has been used by Grundfos
Biobooster A/S in their refinement of water treatment technology to evaluate how thoroughly
the water needs to be treated before being used under given conditions. This knowledge will
help minimize treatment costs. The aim is to recycle water from towns in local communities for
use in crops grown close to the towns – which would typically be the case for vegetables.
The various versions of the new water treatment and irrigation systems have been tested in Italy,
Crete, Serbia and China using different types of polluted water. Measurements carried out by
food safety experts of fecal contamination of the produce at harvest time have always shown
very low levels. Risk assessments with respect to the impact on human health confirm that the
consumer is not exposed to a higher risk than usual when eating vegetables irrigated in this
way. Finally, the cost-effectiveness of the new water treatment and irrigation systems have been
evaluated by SAFIR economists.

Household Waste Water Recycling Systems

Many people aren't aware of the economic advantages that household waste water recycling systems offer. Every time faucets are turned on and toilets are flushed, precious water is wasted. For those concerned about the environment, recycling waste water is an important issue. more