**1. Introduction**

452 Pesticides in the Modern World - Risks and Benefits

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**8. References** 

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The increase of the industrial activity and the consequent economic and social development have produced, at least until some years ago, a growth of big cities which leads and complicates the supply of one of the most important elements to the life, "water". Nowadays, faced with the growing water demand and the hydric resources shortage, the reuse of treated water is considered as a possible solution in order to increase existing resources. However, all effluents can`t be reused since environmental minimum flows have to be guaranteed downstream of the dumping (Ormad, 2011).

The *water reuse* is the application, before its return to the public water resources and the terrestrial maritime one to a new exclusive use of waters that, having been used by who derived them, they have been subjected to a process or processes of treatment established in the corresponding authorization of dumping and to the necessary in order to get the quality required in function of uses to which it goes to be destined. As well, reuse waters are treated wastewaters that have been subjected to an additional or complementary process which is capable to adapt its quality to the destined use. All this is carried out in *reclamation plants*, group of installations where treated wastewaters are subjected to additional treatments which can be needed in order to adapt the water quality to the destined use (Royal Decree 1620/2007).

Waters which go to be reclaimed, it is, treated wastewaters, are waters that must obey the specifications of Directive 91/271/EEC (Directive 91/271/EEC). However, in these waters can exist some substances which can be pollutants. In general, the composition of these waters mainly depends on two factors: the industrial contribution to the urban dumping and the type of water treatment in the wastewater treatment plant (WWTP). In spite of this, in general, these waters are characterized by:

	- *Non Hazardous Organic Matter*: This organic matter is mayoritary composed by compunds which haven't degraded in the WWTP. This is because they are refractary compounds or the achieved yields aren't of 100%; they are organic substances non toxic like carboxilic acids, esters, proteins, carbon hydrates, aminoacids, polihydroxilated alcohols, etc.

Study of the Presence of Pesticides in Treated Urban Wastewaters 455

application of the Directive 2000/60/EC the Decision 2455/2001 establishes the relation of Priority Hazardous Substances of the European Union which dumping to surface and

The aim of this work is the characterization of urban treated wastewaters from different treatments with the purpose of knowing the presence of pesticides in these waters and if these waters can be reused or need an additional treatment for this. All studied WWTPs are located in the Ebro river Basin (Spain). Moreover, a bibliographic revision related to the

This work has been carried out in collaboration with "Navarra Infraestucturas Locales S.A." (NILSA) by the Research Project "Regeneración de aguas depuradas mediante procesos de

The five selected WWTPs in this study are located in the "Comunidad Foral de Navarra" (Spain). Next a detailed description of the characteristics and process carried out in each


Stages of the treatment in this WWTP are shown in the figure 1. Water arrives by sewers to the WWTP. After homogenizing water in a pond, the treatment consists of the separation of big and medium solids by sieves which act as desander/degreaser too. After water passes to the primary decanter during a retention time of 3-6 hours. Decanted muds are retired to treat them. The effluent of the decanter goes to biological reactor consisting of a percolator filter with plastic layer. After the secondary decantation, water goes to a lagoon system consisting of 4 lagoons put in series. Lagoons are 2.5 meters deep. Rests of organic matter are removed and the removal of pathogen germs happens too due to the effect of the solar


groundwaters has to be limited. In this relation are included a lot of pesticides too.

pesticides mainly detected in this type of waters has been carried out.

oxidación avanzada (CTM2008-01876/TECNO)".

**2. Description of the selected WWTPs** 

The description of this WWTP is as follow:


Fig. 1. Diagram of stages in the WWTP-A

The description of this WWTP is as follow:

radiation. The residence time of water in lagoons is about 25 days.


WWTP are described.

**2.1 WWTP-A** 

**2.2 WWTP-B** 

industries


Effluents of WWTPs can be reused to urban, agricultural, industrial, recreational and environmental uses. It is expected an urban use as irrigation of private gardens, emptying of healthy apparatus, irrigation of urban green places such as parks, sport fields and similar, cleaning of streets, systems against fires and industrial cleaning of vehicles. As agricultural use, it is expected the irrigation of cultivation which is consumed in fresh form or has an industrial treatment to its consume, irrigation of pasture to animal consumption, aquaculture, irrigation of woody cultivation, cultivation of ornamental flowers, nurseries, greenhouses and irrigation of industrial and no alimentary cultivation. It is considered the reuse as industrial use as cleaning and process water, in cooling towers and evaporative condensers. It is considered recreational use the irrigation of golf courses, ponds, water masses and ornamental circulated flows in which the public access to water is blocked. Finally, to environmental use it is expected the use of water to fill aquifers by percolation or direct injection, irrigation of woods and other green places which aren't accessible to people, silviculture, maintenance of wetlands, minimum flows and similar.

To carry out all of these uses, indicated in the Spanish current legislation about reclaimed water (Royal Decree 1620/2007) it is necessary to carry out a treatment which gets the minimum criteria of quality demanded in relation with several parameters. In general, this treatment has to remove the suspension matter, the turbidity, the hazardous substances and to disinfect the water, as a minimum (Metcalf and Eddy, 2002).

On the other hand, depend on the use of reclaimed water, apart from considering the quality criteria indicated in the Royal Decree 1620/2007, other criteria included in specific fields have to be considered; for example, Directive 2006/118/EC has to be considered, directive related to the protection of groundwaters against the pollution and deterioration when the reclaimed water is destined to environmental use (Directive 2006/118/EC). This norm includes Environmental Quality Standards (EQSs) related to nitrates, salinity, metals, trichloroethylene, tetrachloroetylene and other hazardous substances such as pesticides. Also the Directive 80/68/EEC establishes that it is necessary to impede the dumping of hazardous substance of the List I and to limit the dumping of the hazardous substances of the List II, lists in which a lot of pesticides are founded, in order to guarantee an effective protection of groundwaters. In the same way, the Spanish Royal Decree 60/2011 (Royal Decree 60/2011) by which quality objectives to some pollutants are fixed and the Reglament of Public Waters is modified, establishes EQSs to Preferential Hazardous Substances of the List II. Likewise, in the application of the Directive 2000/60/EC the Decision 2455/2001 establishes the relation of Priority Hazardous Substances of the European Union which dumping to surface and groundwaters has to be limited. In this relation are included a lot of pesticides too.

The aim of this work is the characterization of urban treated wastewaters from different treatments with the purpose of knowing the presence of pesticides in these waters and if these waters can be reused or need an additional treatment for this. All studied WWTPs are located in the Ebro river Basin (Spain). Moreover, a bibliographic revision related to the pesticides mainly detected in this type of waters has been carried out.

This work has been carried out in collaboration with "Navarra Infraestucturas Locales S.A." (NILSA) by the Research Project "Regeneración de aguas depuradas mediante procesos de oxidación avanzada (CTM2008-01876/TECNO)".
