Abstract
In the European Mediterranean area, the lack of available water resources had led to consider the reclaimed urban waters as an integral part of water resources. Reclaimed urban waters could mitigate water shortage, support agriculture sector and protect rivers and groundwater resources. This work is focused on the evaluation of reclaimed urban water (RW) from Algarrobo municipality, which is located in the Malaga province in the Mediterranean coast at South-East of Spain. Wastewater in the municipal waste water treatment plant, was treated by a membrane bioreactor (MBR) as a tertiary treatment. The main goal of this work was to determine the composition of RW to be compared with fresh local water (LW) from the Algarrobo River, in order to evaluate its suitability for irrigation. Electrical conductivity (EC), pH, sodium absorption ratio (SAR), and mineral content were weekly measured from September 2017 until June 2018. Assessment of RW quality was carried out considering the limit values for each parameter as stated by the current Spanish legislation RD 1620/2007 for reuse of reclaimed water and European Directive for water reuse (EU 91/271/EEC, Annex I). The MBR facility was also focused on preserving essential minerals for plant nutrition to use them for crop fertilization instead of commercial fertilizers. The average content of nitrogen, phosphorous and potassium were, respectively, 72%, 65% and 46% of the amount needed for the Hoagland 1/4 strength solution that was used in this study for irrigation of tomato, avocado and mango crops. From this study it appears that it is possible using membrane technology, to treat urban wastewater in order to supply a good quality of water for irrigation. Water analysis has also proved MBR to be efficient for removal of microbiological pollutants, inorganic compounds, some trace elements and heavy metals. The assessment of RW shows that the evaluated parameters of water-quality are within the range of values stated by Spanish legislation and the current European Directive for secure use of reclaimed water for irrigation.
Highlights
Water stress due to climate change and the overexploitation of water resources are two of the most serious and widespread environmental problems worldwide [1]
It was not possible to calculate the removal efficiency for potassium, because we did not have information about the content of potassium in wastewater before treatment with the membrane bioreactor (MBR), without these data the calculations cannot be done. From this study it appears that it is possible, through ultrafiltration using membrane technology, to treat in a single operation urban wastewater in order to supply a good quality of water for irrigation purposes
The analyses of water from the MBR plant have proved that this technology is efficient enough for removal of microbiological pollutants, inorganic compounds, some trace elements and heavy metals
Summary
Water stress due to climate change and the overexploitation of water resources are two of the most serious and widespread environmental problems worldwide [1]. One fifth of the Mediterranean population constantly suffers from a shortage of water, and during summer lack of available water affects up to 50% of population in Mediterranean region, which includes Spain, Portugal, Italy, Cyprus, Greece, Malta and Southern France [2]. Reclaimed urban water (RW) is the domestic wastewater that has received tertiary treatment and disinfection. The application of RW is of great importance to ease the water shortage and reduce further pollution by sewage. The use of RW has become a common and international trend as an unconventional supply for rivers with water shortages and for agricultural purposes [3]. RW may meet certain water quality standards, it is still urban sewage and carries some risk. Current water reclamation technology can ensure >99.99% pathogen removal [4]; the likelihood of human disease occurring through the use of RW is extremely low
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