**2. Description of the selected WWTPs**

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 WWTP are described.

#### **2.1 WWTP-A**

454 Pesticides in the Modern World - Risks and Benefits


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

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

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


people, silviculture, maintenance of wetlands, minimum flows and similar.

to disinfect the water, as a minimum (Metcalf and Eddy, 2002).

2006/11/EC).


dumping has.

• *Hazardous Organic Matter:* persistent substances which haven't been removed in the WWTP. If these substances are present with low concentrations can derive in an environmental and health problem. They are pharmaceutical products, clean and care personal products, pesticides and plasticizers. Some of these compounds have characteristics toxic, cancinogenic, mutagenic, teratogenic, bioaccumulative or endocrin disruptors, and they are part of a big group of organic compounds, called Emerging Pollutants, which are received great attention in the last years (Hernando et al., 2006). All are hazardous compounds such as Directives 80/68/EEC, 2000/60/EC and 2006/11/EC establish (Directives 80/68/EEC, 2000/60/EC,

The description of this WWTP is as follow:


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

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

#### **2.2 WWTP-B**

The description of this WWTP is as follow:


Study of the Presence of Pesticides in Treated Urban Wastewaters 457

Stages of the treatment in this WWTP are shown in the figure 4. Water which arrives to the WWTP is pumped to the sieve. The sieve operates as desander/degreaser too. After water goes to an anoxic biological reactor with agitation by which nitrogen and phosphorous is

Stages of the treatment in this WWTP are shown in the figure 5. Once sewage water arrives to the plant, it is subjected to a pretreatment. This pretreatment consists of a sieve which removes big solids and a pump that raises the water up to the degreaser/desander. Moreover, this stage has an auxiliary reactor which is used when peaks flow happens. Finally, the primary decanter removes a great part of solids. The secondary treatment consists of two biological reactors and one secondary decanter. In the first, water goes to a big lagoon in which the nitrogen is removed. In the bottom of this lagoon there are two stirrers which purpose is to avoid the decantation of solids. The residence time of water is a bit higher than in the aerobic reactor. The second part of the degradation is carried out in an aerobic reactor with two stages in series. In its interior there is a plastic layer in which the

**2.4 WWTP-D** 

**2.5 WWTP-E** 

biomass is fixed.

The description of this WWTP is as follow: - Water origin: urban and agricultural


partially removed. Next, water goes to a decanter.

Fig. 4. Diagram of stages in the WWTP-D

The description of this WWTP is as follow:


Fig. 5. Diagram of stages in the WWTP-E





Stages of the treatment in this WWTP are shown in the figure 2. Water arrives by a sewer system to the WWTP and it is subjected to a pretreatment consisting of the separations of thick solids by deflector sheets or sieves. After the degrease and desanding are carried out. This consisting of the extraction of mineral particles and the removal of greases, oils and floating material. Next obtained water goes to a primary decanter which purpose is decrease the suspension matter of the water. After this removal of matter, the biological treatment is carried out. The biological treatment is produced by bacterium layers. Finally, the biological mud is separated from water in the secondary decantation.

Fig. 2. Diagram of stages in the WWTP-B

#### **2.3 WWTP-C**

The description of this WWTP is as follow:


Stages of the treatment in this WWTP are shown in the figure 3. The sewage water arrives to the plant pass through a sieve where big solids are removed. After, water goes to the primary decanter in order to remove the suspended matter from water. Next water goes to the biological reactor which has a bacterium layer composed by stone and plastic where the organic load of water is reduced considerably. Aftherthat, the reduction of suspended matter is increased in a secondary decanter. After these processes, there is a tertiary treatment consisting of 4 lagoons. The residence time of water in lagoons is 5-6 days. The function of these lagoons is degrade the organic matter or the water and complete the disinfection by the effect of the solar radiation.

Fig. 3. Diagram of stages in the WWTP-C

#### **2.4 WWTP-D**

456 Pesticides in the Modern World - Risks and Benefits

Stages of the treatment in this WWTP are shown in the figure 2. Water arrives by a sewer system to the WWTP and it is subjected to a pretreatment consisting of the separations of thick solids by deflector sheets or sieves. After the degrease and desanding are carried out. This consisting of the extraction of mineral particles and the removal of greases, oils and floating material. Next obtained water goes to a primary decanter which purpose is decrease the suspension matter of the water. After this removal of matter, the biological treatment is carried out. The biological treatment is produced by bacterium layers. Finally, the biological


Stages of the treatment in this WWTP are shown in the figure 3. The sewage water arrives to the plant pass through a sieve where big solids are removed. After, water goes to the primary decanter in order to remove the suspended matter from water. Next water goes to the biological reactor which has a bacterium layer composed by stone and plastic where the organic load of water is reduced considerably. Aftherthat, the reduction of suspended matter is increased in a secondary decanter. After these processes, there is a tertiary treatment consisting of 4 lagoons. The residence time of water in lagoons is 5-6 days. The function of these lagoons is degrade the organic matter or the water and complete the



Fig. 2. Diagram of stages in the WWTP-B

The description of this WWTP is as follow:


disinfection by the effect of the solar radiation.

Fig. 3. Diagram of stages in the WWTP-C


**2.3 WWTP-C** 

mud is separated from water in the secondary decantation.

garages, vegetable preserved food industries and wineries

The description of this WWTP is as follow:


Stages of the treatment in this WWTP are shown in the figure 4. Water which arrives to the WWTP is pumped to the sieve. The sieve operates as desander/degreaser too. After water goes to an anoxic biological reactor with agitation by which nitrogen and phosphorous is partially removed. Next, water goes to a decanter.

Fig. 4. Diagram of stages in the WWTP-D

#### **2.5 WWTP-E**

The description of this WWTP is as follow:


Stages of the treatment in this WWTP are shown in the figure 5. Once sewage water arrives to the plant, it is subjected to a pretreatment. This pretreatment consists of a sieve which removes big solids and a pump that raises the water up to the degreaser/desander. Moreover, this stage has an auxiliary reactor which is used when peaks flow happens. Finally, the primary decanter removes a great part of solids. The secondary treatment consists of two biological reactors and one secondary decanter. In the first, water goes to a big lagoon in which the nitrogen is removed. In the bottom of this lagoon there are two stirrers which purpose is to avoid the decantation of solids. The residence time of water is a bit higher than in the aerobic reactor. The second part of the degradation is carried out in an aerobic reactor with two stages in series. In its interior there is a plastic layer in which the biomass is fixed.

Fig. 5. Diagram of stages in the WWTP-E

Study of the Presence of Pesticides in Treated Urban Wastewaters 459

Isoproturon 20 0.030 20-500 0.030-300 75-130 63-110 Diuron 20 0.030 20-500 0.030-300 82-128 70-123 3.4-Dichloroaniline 20 0.030 20-500 0.030-300 88-130 47-106 4-Isopropylaniline 20 0.030 20-500 0.030-300 80-130 60-125 Desethylatrazine 20 0.030 20-500 0.030-300 76-130 80-129 Trifluralin 20 0.015 20-500 0.030-300 70-130 70-127 Dimethoate 20 0.030 50-500 0.030-300 66-124 54-137 Simazine 50 0.030 20-500 0.030-600 75-135 64-127 Prometon 20 0.030 20-500 0.030-300 76-124 0-125 Atrazine 200 0.100 200-5000 0.100-300 78-130 75-127 Propazine 20 0.015 20-500 0.015-300 86-130 73-127 Terbuthylazine 20 0.015 20-500 0.015-300 79-130 83-128 Parathion methyl 50 0.030 50-500 0.030-300 78-139 72-130 Parathion ethyl 20 0.030 20-500 0.030-300 74-122 64-128 Alachlor 20 0.015 20-500 0.015-300 75-125 70-124 Ametryn 20 0.030 20-500 0.030-300 78-130 0-116 Prometryn 20 0.030 20-500 0.030-300 80-120 17-116 Terbutryn 20 0.030 20-500 0.030-300 80-120 13-114 Chlorpyrifos 20 0.015 20-500 0.015-300 75-120 73-116 Chlorfenvinfos 20 0.015 20-500 0.015-300 76-130 70-126 HCHs 20 0.015 20-500 0.015-300 84-124 70-120 Hexachlorobenzene 20 0.030 20-500 0.030-300 70-130 74-136 Heptachlor 20 0.015 20-500 0.015-300 75-130 58-113 Heptachlor epoxide A 20 0.015 20-500 0.015-300 85-125 62-112 Heptachlor epoxide B 20 0.015 20-500 0.015-300 84-130 58-113

Aldrin 20 0.015 20-500 0.015-300 85-125 64-126

Isodrin 20 0.015 20-500 0.015-300 85-125 66-120 α-Endosulphan 20 0.015 20-500 0.015-300 70-125 70-93 pp'-DDE 20 0.015 20-500 0.015-300 89-122 64-107 Dieldrin 20 0.015 20-500 0.015-300 70-125 62-120 Endrin 20 0.015 20-500 0.015-300 80-125 74-122 pp'-DDD + op'-DDT 40 0.030 40-1000 0.030-600 79-125 66-139 Endosulphan-sulphate 20 0.015 20-500 0.015-300 83-125 73-126 pp'-DDT 20 0.030 20-500 0.030-300 76-130 50-120 Dicofol 50 0.030 50-500 0.030-300 80-148 63-136 Methoxychlor 20 0.015 20-500 0.015-300 77-126 75-130 Metholachlor 20 0.015 20-500 0.015–300 76-115 73-128 Molinate 20 0.015 20-500 0.015–300 91-130 75-113 Tetradifon 20 0.015 20-500 0.015-300 85-130 70-116

Dichlorobenzophenone 20 0.015 20-500 0.015-300 75-120 68-126

Table 3. Results of the methodology validation of pesticides analysis.

**Calibration interval (μg L-1)** 

**Validity interval**

**(μg L-1)** Instrumental

step

Full method **Recovery interval (%)** 

> Full method

**Quantification limit (μg L-1)** 

step

**Pesticide** Instrumental

4.4'-
