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Environmental Processes
Removal of pharmaceuticals and illicit drugs from wastewater due to ferric dosing in sewers Jagadeeshkumar Kulandaivelu, Jianfa Gao, Yarong Song, Sohan Shrestha, Xuan Li, Jiaying Li, Katrin Doederer, Jürg Keller, Zhiguo Yuan, Jochen F. Mueller, and Guangming Jiang Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.8b07155 • Publication Date (Web): 09 May 2019 Downloaded from http://pubs.acs.org on May 9, 2019
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Environmental Science & Technology
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Removal of pharmaceuticals and illicit drugs from
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wastewater due to ferric dosing in sewers
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Jagadeeshkumar Kulandaivelu1, Jianfa Gao2, Yarong Song1, Sohan Shrestha1, Xuan Li1, Jiaying
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Li1, Katrin Doederer1, Jurg Keller1, Zhiguo Yuan1, Jochen F. Mueller2, Guangming Jiang1,3,4, *
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Australia
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Woollongabba, Queensland 4072, Australia
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Advanced Water Management Centre, The University of Queensland, St. Lucia, Queensland 4072,
Queensland Alliance for Environmental Health Sciences, The University of Queensland,
Department of Chemistry and Chemical Engineering, Sichuan University of Arts and Science,
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Sichuan, China
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NSW 2522, Australia
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* Corresponding author.
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KEYWORDS. Micropollutants, adsorption, iron sulfide, biodegradation, sewer, ferric dosing
School of Civil, Mining and Environmental Engineering, University of Wollongong, Wollongong,
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ABSTRACT. Ferric (Fe3+) salt dosing is an efficient sulfide control strategy in the sewer
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network, with potential for multiple benefits including phosphorus removal in the biological
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reactors and sulfide emission control in the anaerobic digesters of wastewater treatment plant
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(WWTP). This paper extends the knowledge on the benefit of iron dosing by exploring its
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impact on the fate of organic micropollutants (MPs) in the wastewater using sewer reactors
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simulating a rising main sewer pipe. The sulfide produced by the sewer biofilms reacted with
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Fe3+ forming black colored iron sulfide (FeS). Among the selected MPs, morphine, methadone
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and atenolol had >90% initial rapid removal within five minutes of ferric dosing in the sewer
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reactor. The ultimate removal after 6-hr of retention time in the reactor reached 93-97%.
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Other compounds, ketamine, codeine, carbamazepine and acesulfame had 30-70%
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concentration decrease. The ultimate removal varied between 35 and 70% depending on the
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biodegradability of those MPs. In contrast, paracetamol had no initial removal. The rapid
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removal of MPs was likely due to adsorption to the FeS surface, which is further confirmed by
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batch tests with different FeS concentrations. The results showed a direct relationship between
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the removal of MPs and FeS concentration. The transformation kinetics of these compounds
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in the reactor without Fe3+ dosing is in good agreement with biodegradation associated with
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the sewer biofilms in the reactor. This study revealed a significant additional benefit of dosing
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ferric salts in sewers, that is the removal of MPs before the sewage enters the WWTP.
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INTRODUCTION. Hydrogen sulfide in sewers causes serious cracking and failure of the
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concrete structure, malodor and human health problems 1, 2. Billions of dollars are expended
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every year due to the need for rehabilitation or replacement of the corroded sewer pipes3. The
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anaerobic condition in the rising main induces the growth of stratified biofilms comprising of
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sulfate-reducing bacteria (SRB) and methanogenic archaea (MA)4. The SRB reduce sulfate in
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the wastewater and produce sulfide that subsequently transfers to the gas phase in the gravity
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sewers. The H2S gas induces sewer corrosion by forming sulfuric acid on the concrete surface5.
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Chemicals are commonly used for the control of sulfide, including i) chemical oxidation of
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sulfide by the injection/addition of air, pure oxygen, nitrate salts
1, 6-8,
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peroxide, hypochlorites, chlorine and potassium permanganate
ii) pH elevation by the
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addition of alkali such as Mg(OH)2 and iii) precipitation of sulfide by forming insoluble metal
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particles through the addition of metal salts such as iron, zinc, lead and copper salts 2. Among
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the various metal salts used, iron based salts were shown to be most efficient because of its
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specificity to H2S 11. In Australia iron salts accounted for 66% of the sewage flow dosed with
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chemicals for sulfide control12.
9, 10
ozone, hydrogen
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The iron salt dosing in the sewers is effective in the control of dissolved sulfide by the
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formation of iron sulfide particles 2, 13-15. These studies showed that the mechanism responsible
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for the removal of sulfide includes the precipitation reaction of Fe2+ ions with sulfide forming
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ferrous sulfide (FeS), while Fe3+ ions oxidizes sulfide chemically to elemental sulfur, with itself
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being reduced to Fe2+, which subsequently precipitates sulfide (Equation 1&2). The continuous
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dosing of iron salts for two months significantly inhibits the SRB and MA production in the
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long run, leading to reduced demand for iron salts 2.
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2𝐹𝑒3 + + 𝑆2 ― → 2𝐹𝑒2 + + 𝑆0
(1)
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𝐹𝑒2 + + 𝐻𝑆 ― → 𝐹𝑒𝑆↓ + 𝐻 +
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(2)
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Further studies found that FeS particles formed in the sewer network can be oxidized in the
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aerobic activated sludge reactor. This enables phosphorus removal at a ratio of 0.44 and 0.37
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mg-P/mg of Fe2+ and Fe3+ added to the sewer network13. The iron dosing (e.g. 5–20 mg-Fe/L)
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to the sewer network was also demonstrated to provide iron for H2S emission control in the
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anaerobic digester by forming iron sulfide particles 16. Previous studies have demonstrated the
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multiple benefits of iron salts dosed into sewers, including sewer corrosion and odour control,
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phosphorus removal and biogas desulfurization 17.
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Iron salt was shown to be an effective coagulant for the removal of MPs such as
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pharmaceuticals and personal care products (PPCPs) in the drinking water treatment systems
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and WWTPs
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traditional secondary treatment processes. The MPs thus find their way in the aquatic
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environment and can have adverse effects on aquatic organisms
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WWTP, MPs go through the sewers with sewage flow and there is very limited understanding
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about their fate and transformation in the sewers. Some recent studies focused on the biological
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transformation of organic MPs in the sewer network due to the presence of biofilms 23-25. Also,
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there are a couple of studies focused on the biodegradation of pharmaceuticals and illicit drugs
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in the sewer network 26, 27.
18-20.
Organic MPs are ubiquitous in wastewater, and are recalcitrant to the
21, 22.
Before entering the
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However, no study has systematically investigated the impact of iron salt dosing on the
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removal of MPs in the sewer network. Considering the coagulating nature of iron salt and the
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adsorbing nature of iron sulfide particles
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it is hypothesized that there can be additional
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removal of some MPs due to iron dosing on top of in-sewer biodegradation.
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Collectively speaking, ferric dosing is one of the most widely used strategy to control sewer
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odor corrosion and odor, with additional beneficial effects on the downstream WWTP. The
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main objective of this study is to investigate the fate and removal of selected organic MPs from
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wastewater due to ferric dosing and biological processes in the sewer network. Experiments
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using laboratory-scale rising main sewer reactors were carried out with selected MPs,
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including pharmaceuticals and illicit drugs in the wastewater. To understand the removal
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mechanisms of MPs, batch tests were conducted with different levels of iron sulfide precipitate
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that was identified and characterized with advanced electron microscopic analysis.
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2. MATERIALS AND METHODS
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2.1. CHEMICALS. The reagent grade ferric chloride (FeCl3.6H2O) was purchased from Sigma
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Aldrich (NSW, Australia). All the drugs and pharmaceuticals were purchased from Cerilliant
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(Texas, US), Provet (Australia) and Sigma Aldrich (NSW, Australia). The selected MPs include
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ketamine, methadone, morphine, codeine, carbamazepine, atenolol, paracetamol and
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acesulfame and their properties are presented in Table S1. The compounds were selected to
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represent the hydrophobic and hydrophilic MPs in the wastewater. The octanol-water
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partition coefficient is arranged in the ascending order in Table S1 (Acesulfame being
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hydrophilic and methadone hydrophobic). Spiking solutions were prepared in Milli-Q water
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before being spiked in to the reactors. Liquid Chromatography grade methanol was purchased
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from Merck, Germany. Deionized water was produced by a Milli-Q system (Millipore, 0.22
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μm filter, 18.2 mΩ·cm−1).
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2.2. WASTEWATER CHARACTERISTICS. The wastewater used in this study was collected
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from a local sewer wet well (St. Lucia, Brisbane, Queensland) every week and was stored in
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the cold room at -4 °C. The sewage typically contained sulfate at concentrations of 10-25 mg-
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S/L, sulfide at
