Wastewater assimilation by semi ‐ natural wetlands 69 next to the RAMSAR area of Fuente de Piedra 70 ( southern Spain )

Urban wastewater treatment is one of the most important challenges in villages of southern Spain. This is especially outstanding in arid and semiarid regions in which wastewater are discharged to temporary streams or wetlands. The treatment plant of the Fuente de Piedra village discharges its wastewater, passing previously through four semi-natural wetlands, into Fuente de Piedra Lake, a RAMSAR wetland. In summer 2016, a very dry year, water affluent to Fuente de Piedra was limited to wastewater plant effluents without dilution. In order to study the natural assimilation capacity of the wetland system, four key points were sampled. Physico-chemical and biological indicators were analyzed (temperature, pH, conductivity, total phosphorous, total nitrogen, bacteria, phytoplankton and zooplankton). The results show very high chlorophyll a concentration (>500 mg/l) at the water inlet, which decreased to concentration lower than <20 mg/l before discharging into the RAMSAR wetland. Zooplankton, dominated by cladocerans (Daphnia sp.),was lowest in the inlet wetland and highest in the last wetland. Total nitrogen and phosphorus concentration was (14 mg/l and 5mg/l respectively) at the wastewater inlet point and decreased in the first wetland (7 mg/l and 2mg/l respectively). Fecal streptococci was highest at the inlet point (1033 ± 351 ufc/100 mL) and decreased to 1 ± 1 ufc/100 mL before entering in the RAMSAR wetland. In conclusion, during the wetlands circuit (i) phytoplankton reduce the total phosphorous and nitrogen concentration, (ii) then phytoplankton is controlled by zooplankton decreasing drastically the input of nutrient and biomass into the RAMSAR wetland, (iii) fecal bacteria decreases three orders of magnitude. Thus, the negative impact from wastewater treatment plant is reduced. The waterbirds, one of the major tourists attractive of this wetland, benefit from food and water supply in dry years, guaranteeing the possibility of bird watching during high season.


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According to the ecws-1_ECWSWordTemplate.doc. Methodology is part 4 of the article.

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However, looking in the published paper of the journal "Water" methodology is part 2, located after 54 Introduction and before Results. This is How we think the paper might be published.

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Therfore we changed now the methodology part to part 2. Thus figure numbers remain, but the order of citation 56 has been changed.       wastewater can be spilled alternatively through them or directly to the RAMSAR wetland. In 95 spring 2016, a very dry year, water affluent to Fuente de Piedra was limited to wastewater plant 96 effluents without dilution. In order to study the natural assimilation capacity of the wetland 97 system, four key points were sampled. Physico-chemical and biological indicators were analyzed 98 (temperature, pH, conductivity, total phosphorus, total nitrogen, bacteria, phytoplankton and 99 zooplankton). The results show very high chlorophyll a concentration (>500 μg l -1 ) at the water 100 inlet, which decreased to concentration lower than <20 μg l -1 before discharging into the RAMSAR 101 wetland. Total nitrogen and phosphorus concentration was (14 mg l -1 and 5 mg l -1 respectively) at 102 the wastewater inlet point and decreased in the last wetland (7 mg l -1 and 2 mg l -1 respectively).

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Fecal streptococci were highest at the inlet point (1033 ± 351 ufc/100 ml) and decreased to 1 ± 1 104 ufc/100 ml before entering in the RAMSAR wetland. In contrast, zooplankton, dominated by 105 cladocerans (Daphnia sp.) was lowest in the inlet wetland and highest in the last wetland. In

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Cultural eutrophication is an increase in the biological production caused by human activity that 118 incites changes in the community ecosystem succession, as a consequence of the increment of 119 nutrient input into a water body. The cultural eutrophication of freshwater ecosystems worldwide 120 has been recognized as a serious environmental issue for more than half a century [4,10,14,21], and it 121 remains a major water quality problem; constituting a key problem in limnology. In Europe, general 122 concerns about water quality led to the Water Framework Directive [7], which aims for ʹgood statusʹ 123 for all ground and surface waters (rivers, lakes, transitional waters, and coastal waters) in the EU.

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Apart of eutrophication, pollutants, and waterborne pathogens associated with suspended 125 sediments are also of particular concern to public health [17,22]. This is especially interesting in the

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In order to follow the assimilation capacity of the lagoon system, four sampling points were 160 sampled on 27-29 of april 2016, covering from the entrance of wastewater into the semi-natural

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Total phosphorus was high (5 mg l -1 ) at the entrance to the semi-natural wetlands system (point

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reached highest values at the entrance to the wetland system (point A) (>5x10 10 μm 3 ml -1 ) decreasing 241 to concentration arround (1.5x10 10 μm 3 ml -1 ) at the exit of the first wetland (point B, Figure 5a). Then 242 phytoplankton biovolume decreased to 4.3x10 9 μm 3 ml -1 at point C and is released with the same 243 value to the RAMSAR wetland (point D, Figure 5a).

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Fortunately, the "Laguneto" wetland is not accessible to visitors, as it is included in a protected area 306 acting as observation site of avifauna. While fecal sterptococii decreases continuously from the 307 spilling point to the releasing point into the RAMSAR wetland, fecal coliforms increased by factor 10 308 from point A to B. Part of this pollution could be produced by the birds faeces [1,8]. This wetland has 309 an elevate density of avifauna, among others Phoenicopterus roseus, and some gull species (Larus 310 ridibundus, Larus fuscus and Larus michahellis). However, both fecal bacteria decreased to values 311 lower than 200 cfu/100 ml at sampling station D, which is an excellent value for bath water, and 312 shows with concentration of 17 ± 21 and 1 ± 1 cfu/100 ml concentration close to values permitted for 313 drink water (0 cfu/100 ml) [19].

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If the wastewater treatment spill would be introduced directly into the RAMSAR wetland (red 316 arrow Figure 1) fecal bacteria would be 60 times times higher than if the wastewater is spilled 317 through the wetland system (blue arrows Figure 1).

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Thus, the use of artificial wetlands for the treatment of wastewater with lower costs of installation, 320 operation, and maintenance make them an appropriate alternative to traditional treatment plants 321 [23] or could be used, as in our case, to minimize bad function or temporally overload of treatment 322 plant capacity.

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Additionally, in our case, the spilled wastewater garantize small wetlands during dry summers,