Elsevier

Desalination

Volume 331, 16 December 2013, Pages 26-34
Desalination

Removal of pharmaceuticals from a WWTP secondary effluent by ultrafiltration/reverse osmosis followed by electrochemical oxidation of the RO concentrate

https://doi.org/10.1016/j.desal.2013.10.010Get rights and content

Highlights

  • Removal of emerging pollutants from WWTP secondary effluent by a tertiary treatment that combines UF and RO

  • Electrooxidation as means of mineralization of micropollutants contained in the RO concentrate

Abstract

This study aims to assess the removal of emerging contaminants from municipal wastewaters using a pilot system that integrated ultrafiltration (UF), reverse osmosis (RO), and electrooxidation, which mineralized the RO concentrate. Initially, the study monitored 77 emerging contaminants in the influent and effluent of a wastewater treatment plant (WWTP). Most of the compounds were detected in significant amounts in the WWTP effluent.

A group of 12 compounds that represent the most prevalent therapeutic pharmaceutical categories was selected to monitor their removal by UF/RO. For the majority of the micropollutants, the UF removal efficiency was less than 20%. Excellent removal efficiencies were achieved with the RO treatment. As a result, the concentrations of the emerging contaminants in the RO permeate varied between 44 ng/L for naproxen and 4 ng/L for ofloxacin, and furosemide, bezafibrate and fenofibric acid were not detected. After the RO treatment, electrooxidation of the RO concentrate with boron-doped diamond electrodes reduced the total micropollutant content in the RO concentrate from 149 μg/L to less than 10 μg/L. Increasing the intensity of the electrooxidation treatment is expected to further reduce the micropollutant concentrations.

Introduction

The focus of environmental research has expanded to include both “classic” environmental pollutants and so-called “emerging contaminants”, which comprise pharmaceuticals and personal care products (PPCPs) [1], [2], [3], [4]. Concern about their presence in aquatic environments has been increasing because their presence in small concentrations has been associated with chronic toxicity, endocrine disruption and the development of pathogen resistance [5], [6], [7], [8], [9].

Because of the observed concentrations of emerging pollutants in raw wastewaters and the limited effectiveness of secondary treatments, municipal wastewater treatment plant (WWTP) effluents are the main disposal pathway for pharmaceuticals and personal care products into the environment [10], [11], [12]. In general, the total concentration of emerging contaminants in WWTP effluents ranges from ng/L to μg/L [13]. The technologies for removing emerging contaminants from WWTP effluents include ultra-violet (UV) radiation, granulated activated carbon, ion-exchange, membrane filtration and advanced oxidation processes such as ozonation, photocatalysis and the Fenton reaction [1], [5], [14], [15], [16], [17], [18], [19], [20], [21], [22].

Membrane processes are being increasingly implemented in water treatment because these technologies combine process stability with an excellent effluent quality [23], [24], [25], [26]. However, widely used microfiltration and ultrafiltration technologies have been found to filter out only a few emerging organic contaminants [27], [28], [29]. In contrast, it has been shown that nanofiltration and reverse osmosis can separate out many of these compounds [5], [21], [30], [31], [32].

While the permeate water obtained from NF/RO treatments of WWTP effluents can be employed for industrial uses that demand high quality water [24], [33], [34], [35], [36], [37], the pollutants are accumulated in a concentrate stream and an additional step is required to treat it [38], [39], [40]. In addition to conventional technologies, such as coagulation and activated carbon adsorption [41], advanced oxidation technologies, including ozonation, photocatalysis, sonolysis, and electrochemical oxidation have been proposed for eliminating contaminants from the concentrate stream [42], [43], [44], [45], [46], [47], [48]. Electrochemical oxidation, in particular has several advantages. For example, it can be used to treat RO concentrate streams with moderate to high salinity [49], which ensures excellent electric conductivity and reduces the energy consumption, and with moderate chloride concentrations, which promote indirect oxidation and disinfection pathways [39], [44], [46], [47], [48], [49], [50], [51], [52]. A few studies have shown that electrochemical oxidation with boron-doped diamond (BDD) electrodes is effective at eliminating emerging contaminants with removal percentages higher than 90% for most compounds [53], [54], [55].

In this work, an advanced tertiary treatment that includes membrane technologies and electrooxidation was proposed to treat a secondary WWTP effluent and eliminate the removed pollutants to prevent their discharge into the environment. The occurrence of numerous emerging contaminants in the WWTP influent and effluent was assessed, and the removal efficiency of some of the most prevalent pharmaceuticals and stimulants was determined by using an on-site pilot-scale integrated membrane system (UF-RO). The electrooxidation of the RO concentrate stream with boron-doped diamond electrodes was proposed for the mineralization of the retained pharmaceuticals.

Section snippets

Description of the applied tertiary treatment

The experimental work was performed on-site using the secondary effluent of the WWTP located in Vuelta Ostrera (Cantabria, Spain) as the feed water. This WWTP currently operates at 85% capacity, treating an average flow-rate of 110,000 m3/day, and utilizes a secondary treatment based on activated sludge. In this work, the applied tertiary treatment consisted of pilot-scale ultrafiltration (UF) and reverse osmosis (RO) units combined with laboratory-scale electrooxidation (ELOX). A process

Physicochemical characterization

The physicochemical characteristics of the macro-contaminants and main ionic components of the WWTP effluent and tertiary unit effluents have been included in the supplementary material (see Table S3 of the supplementary data). Because the WWTP effluent exhibited a high variability, the minimum and maximum values are given for each parameter, and the mean value of all the analyzed samples is given in brackets.

Fig. 2 shows the results expressed as removal percentages of the main

Conclusions

A wastewater treatment scheme that integrates activated sludge, ultrafiltration, reverse osmosis and electrooxidation was used to remove emerging contaminants from municipal wastewaters. The concentrations of 77 pharmaceuticals, stimulants, personal care products and metabolites were monitored in the raw municipal wastewater and secondary treatment effluent at a WWTP in the northern Spain over a period of two years. The amount of micropollutants removed during the secondary treatment varied

Acknowledgments

Support from the CTQ2008-0690, 062/SGTB/2007/3.1, and CONSOLIDER CSD2006-44 projects and Greentech (New Indigo ERANet Programme) is gratefully acknowledged. Special thanks are given to Prof. Amadeo Fernandez–Alba and his research team (Universidad de Almeria) for the analysis of the emerging contaminants.

References (76)

  • L.H.M.L.M. Santos et al.

    Contribution of hospital effluents to the load of pharmaceuticals in urban wastewaters: identification of ecologically relevant pharmaceuticals

    Sci. Total Environ.

    (2013)
  • A. Aguinaco et al.

    Photocatalytic ozonation to remove pharmaceutical diclofenac from water: influence of variables

    Chem. Eng. J.

    (2012)
  • A. Bernabeu et al.

    Solar photo-Fenton at mild conditions to treat a mixture of six emerging pollutants

    Chem. Eng. J.

    (2012)
  • L. Prieto-Rodríguez et al.

    Treatment of emerging contaminants in wastewater treatment plants (WWTP) effluents by solar photocatalysis using low TiO2 concentrations

    J. Hazard. Mater.

    (2012)
  • M.A. Sousa et al.

    Suspended TiO2-assisted photocatytic degradation of emerging contaminants in a municipal WWTP effluent using a solar pilot plant with CPCs

    Chem. Eng. J.

    (2012)
  • B.A. Wols et al.

    Review of photochemical reaction constants of organic micropollutants required for UV advanced oxidation processes in water

    Water Res.

    (2012)
  • D.P. Grover et al.

    Improved removal of estrogenic and pharmaceutical compounds in sewage effluent by full scale granular activated carbon: impact on receiving river water

    J. Hazard. Mater.

    (2011)
  • S. Kleywegt et al.

    Pharmaceucials, hormones and bisphenol A in untreated source and finished drinking water in Ontario, Canada – Occurrence and treatment efficiency

    Sci. Total Environ.

    (2011)
  • S.A. Snyder et al.

    Role of membranes and activated carbon in the removal of endocrine disruptors and pharmaceuticals

    Desalination

    (2007)
  • J.J. Qin et al.

    Dead-end ultrafiltration for pretreatment of RO in reclamation of municipal wastewater effluent

    J. Membr. Sci.

    (2004)
  • E. Alonso et al.

    On the feasibility of urban wastewater tertiary treatment by membranes: a comparative assessment

    Desalination

    (2001)
  • C. Reith et al.

    Membranes enabling the affordable and cost effective reuse of wastewater as an alternative water source

    Desalination

    (1998)
  • E. Sahar et al.

    The use of RO to remove emerging micropollutants following CAS/UF or MBR treatment of municipal wastewater

    Desalination

    (2011)
  • Y. Yoon et al.

    Nanofiltration and ultrafiltration of endocrine disrupting compounds, pharmaceuticals and personal care products

    J. Membr. Sci.

    (2006)
  • K.V. Plakas et al.

    Removal of pesticides from water by NF and RO membranes — a review

    Desalination

    (2012)
  • P. Berg et al.

    Removal of pesticides and other micropollutants by nanofiltration

    Desalination

    (1997)
  • G. Oron et al.

    Membrane technology for advanced wastewater reclamation for sustainable agriculture production

    Desalination

    (2008)
  • G. Oron et al.

    A two stage membrane treatment of secondary effluent for unrestricted reuse and sustainable agricultural production

    Desalination

    (2006)
  • J.J. Qin et al.

    Feasibility study for reclamation of a secondary treated sewage effluent mainly from industrial sources using a dual membrane process

    Sep. Purif. Technol.

    (2006)
  • J. Qin et al.

    Pilot study for reclamation of secondary treated sewage effluent

    Desalination

    (2005)
  • M. Abdel-Jawad et al.

    Non-conventional treatment of treated municipal wastewater for reverse osmosis

    Desalination

    (2002)
  • A. Pérez-González et al.

    State of the art and review on the treatment technologies of water reverse osmosis concentrates

    Water Res.

    (2012)
  • K. Van Hege et al.

    Electro-oxidative abatement of low-salinity reverse osmosis membrane concentrates

    Water Res.

    (2004)
  • B. Van der Bruggen et al.

    Removal of pollutants from surface water and groundwater by nanofiltration: overview of possible applications in the drinking water industry

    Environ. Pollut.

    (2003)
  • A.Y. Bagastyo et al.

    Characterisation and removal of recalcitrants in reverse osmosis concentrates from water reclamation plants

    Water Res.

    (2011)
  • A.Y. Bagastyo et al.

    Electrochemical oxidation of reverse osmosis concentrate on mixed metal oxide (MMO) titanium coated electrodes

    Water Res.

    (2011)
  • M. Zhou et al.

    Treatment of high-salinity reverse osmosis concentrate by electrochemical oxidation on BDD and DSA electrodes

    Desalination

    (2011)
  • L.Y. Lee et al.

    Ozone-biological activated carbon as a pretreatment process for reverse osmosis brine treatment and recovery

    Water Res.

    (2009)
  • Cited by (193)

    View all citing articles on Scopus
    View full text