Waste water reuse in agriculture

Increased pressure on water resources due to population growth, urbanisation, water resources pollution, climate change impacts is raising interest for waste water reuse, in particular in arid or semi-arid areas.

Waste water reuse is considered a very important measure to mitigate climate change impacts and as a mitigation measure to preserve good quality of fresh water resources.

As irrigated agriculture is one of the major user of freshwater troughout the world, waste water reuse for irrigation is becoming more and more practised and studied.

“The United Nations General Assembly (2000) adopter the Millenium Development Goals (MDGs) on 8 September 2000. The MDGs that are most directly related to the use of wastewater in agriculture are “Goal 1: Eliminate extreme poverty and hunger” and “Goal 7: Ensure environmental sustainability”. The use of wastewater in agriculture can help communities to grow more food and mage use of precious water and nutrient resources. However, it should be done safely to maximize public health gains and environmental benefits.” (taken from the preface to WHO guidelines for the “SAFE USE OF WASTEWATER,

EXCRETA AND GREYWATER – Vol. 2 Wastewater use in agriculture”.) 

In the Mediterranean area, different working groups are focusing on studying waste water reuse in agriculture.

Previous works showed that there exists a disparity of reuse practices from north to south, across the Mediterranean, both in EU and non-EU countries.

So the reuse processes should be made more amenable, robust and safe, by setting basic qualitative standards and other subsidiary ones that take into account regional specificities, intended applications and government planning of integrated water supply and management (IWRM).

In several countries, the reuse of treated wastewater is still shrouded in a mist of apprehensions, possibly as a result of misconceptions, lack of knowledge and wrong stakeholder and public perception. Policies are unclear, when present, and institutional capabilities to manage wastewater reuse are often lacking (med-euwi report 2007)

The widespread practice of reuse of untreated wastewater for agricultural production with public health risks in many Mediterranean countries is a very important subject to be regulated to guarantee the safe use of treated wastewater and safe food production.

Regulatory and institutional aspects, planning, financing, implementation and operation of wastewater reuse projects are amongst the most important themes to be considered for further development, if reuse of treated wastewater is intended to be a meaningful and an acceptable alternative to the community, both in terms of sustainability and affordability.

Within the EU, at least two major environmental directives, directly or indirectly, raise the issue of wastewater reuse insofar as these directives lead towards two primary objectives:

  1. The Urban Wastewater Treatment Directive (91/271/EEC) requires that “treated wastewater shall be reused whenever appropriate” under the requirement of “minimising the adverse effect on the environment” in the light of the objective of first article of the same directive which is clearly defined as the protection of the environment from the adverse effects of wastewater discharges.
  2. On the other hand the Water Framework Directive (WFD) (2000/60/EC) refers, under Annex VI (v) to “emission controls” and under Annex VI(x) to “efficiency and reuse measures, inter alia, promotion of water efficient technologies in industry and water saving techniques for irrigation”, as two, non-exclusive list, supplementary measures. Again these measures have to be perceived in the light of the achievement of the environmental objectives laid down in Article 4, namely that of achieving good environmental status of water bodies.

Hence wastewater reuse needs to be perceived as a measure towards three fundamental objectives within a perspective of integrated water resources management:

  1. Environmental sustainability – reduction of emission of pollutants and their discharge into receiving water bodies, and the improvement of the quantitative and qualitative status of those water bodies (surface-water, groundwater and coastal waters) and the soils.
  2. Economic efficiency – alleviating scarcity by promoting water efficiency, improving conservation, reducing wastage and balancing long term water demand and water supply.
  3. For some countries, contribution to food security – growing more food and reducing the need for chemical fertilisers through treated wastewater reuse.

In addition to these objectives, the public health perspective should be considered. The most common quality standards which are followed are those by World Health Organisation (WHO) the US-EPA standards, and a few others being applied in some countries. The issue that needs to be examined carefully is whether these standards suffice in addressing safety requirements for wastewater reuse in the Mediterranean and EU, taking also into account the recent reviews conducted by WHO. Quality assurance is vital to consumer acceptance.

There is also the question whether the governing standards in some countries and within the countries are useful or constrain reuse applications unnecessarily.

Some overarching priorities were listed a priori by the Med euwi wastewater reuse working group for consideration in a policy formulation exercise:

  • Regulatory roles of institutions, to establish a basic system of good governance and compliance with environmental and health-related legislation. Linkage with related policies; land-use, Common Agricultural Policy (CAP), urban-planning.
  • Social impacts of wastewater reuse development in relation to specific sectors; agriculture and industry.
  • Cost-benefit and cost-effectiveness (including economic impacts) of the reuse process; decentralised vs. centralised facilities, etc.
  • Financing and cost recovery; putting in place economic and financial tools.
  • Stakeholder involvement as key to acceptance of a reuse policy.

It must be emphasised that these priorities are recognised across the Mediterranean for their regional significance, more so when considering the rising pressure on water resources as a result of climate change. Recommendations for potential policy formulation should therefore set strategic actions aiming towards the environmental, economic and social objectives, which, it must be emphasised, constitute also legally binding obligations for the Mediterranean EU countries.

Policy considerations are foremost. Goals have to be set and tailored for specific circumstances and situations taking into consideration the stakeholder response likely to be expected in practice. After all, the application of treated wastewater reuse will heavily depend on stakeholder acceptance and political commitment which, by and large, differs from country to country. It also involves institutional reform, and changing stakeholder behaviour by more public involvement and heightened awareness campaigning.

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