Removal of anthelmintic drugs and their photodegradation products from water with RO/NF membranes

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Abstract

Photolytic reactions are often complex, involving various competing or parallel pathways and leading to multiple reaction products. Removal of anthelmintic drugs (AD) – levamisole (LEV), albendazole (ABZ), praziquantel (PZQ), febantel (FEBA) from water and their photodegradation products with reverse osmosis (RO) and nanofiltration (NF) membranes were investigated in this work. Simulation of photodegradation of ADs was carried out under laboratory conditions with UV lamp at a wavelength of 254 nm for 4 h.

Reverse osmosis (LFC–1 and XLE) and tight nanofiltration (NF90) membranes showed good removal (>83%) of anthelmintic drugs in binary solutions and in mixture. Other nanofiltration (NF270, NF and DK) membranes had rejection between 22 and 45% for smaller drugs (LEV and ALB) and >90% for PZQ and FEBA. These results show that main rejection mechanism in binary solutions was size exclusion and in mixture additional physico-chemical interactions had influence.

After the UV treatment anthelmintic drugs were degraded into several photodegradation products (5 for LEV, 2 for ABZ, 1 for PZQ and 8 for FEBA). Reverse osmosis and NF90 membranes removed >95% of all photodegradation products (except FEBA1 around 70%) and other nanofiltration membranes between 33 and 99.99%.

Highlights

► Treatment of anthelmintic drugs (AD) in model waters with UV light for 4 h. ► We examined removal of AD and their degradation product with NF and RO. ► Excellent removal of AD with NF and RO membrane treatments. ► Degradation of compounds (up to 8% compound) after UV treatment. ► Good to excellent removal of degradation products with NF and RO.

Introduction

The fate of human and animal pharmaceuticals in the environment has attracted great attention from the public and scientific community since their occurrence was identified in aqueous samples (drinking, surface and ground waters) (Kuster et al., 2008, Daneshvar et al., 2010, Loos et al., 2010).

Anthelmintics are of huge importance for veterinary medicine and human tropical medicine. They are drugs that are used to treat infections with parasitic worms. This includes both flat worms, e.g. flukes and tapeworms and round worms, i.e. nematodes.

World Health Organization (WHO) reported the number of preschool-age children (PAC) and school-age children (SAC) who had received treatment against soil-transmitted helminthiasis (STH). The WHO recommends ABZ, mebendazole, pyrantel and LEV for the treatment of STH but most programs use either ABZ or mebendazole because dose is smaller. They reported that in 2006 more than 82 million PAC and more than 77 million SAC were treated (World Health Organization, 2008).

Over the last 20 years PZQ and ABZ were used for treatment of neurocysticercosis (most common helminthic disease of the nervous system) in developing countries of Latin America, Asia and Africa (Bonato et al., 2007).

Anthelmintic drugs have high degree of efficacy, good margin of safety and versatility of administration. They are used both in monogastric and in ruminant animals. For example, the addition of the drugs to poultry and swine feeds is usually at a range concentration of 30–150 mg kg−1 (Dusi et al., 2005).

Furthermore, once these pollutants reach the aquatic environment, they undergo biological and/or photochemical transformation leading to the formation of photodegradation products. In most cases, the identity of these photodegradation products is unknown and proper risk assessment with respect to the aquatic environment has not been conducted. Different transformation can take place, sometimes producing products that can differ in their environmental behavior and ecotoxicological profile. For example, transformation products of some pollutants are often more persistent than their corresponding parent compound (Boxall et al., 2004) and exhibit greater toxicity (Jahan et al., 2008). Also some authors (Weigel et al., 2004, Vasskog et al., 2008) found that some metabolites are often more concentrated than their parent compounds.

In the last few years a number of scientists (Pal et al., 2010, Kuster et al., 2008) were investigating occurrence of emerging contaminants in the natural aquifers, which can be sources for drinking water. UV treatment is very popular method for disinfection of potable water and in wastewater treatment. Also photochemistry plays an important role in the transformation of organic compounds, of both natural and anthropogenic origin, in surface waters (sources for drinking water). In particular, many emerging contaminants undergo photodegradation, under the natural sunlight, as their main removal pathway in surface waters. This photolytic reactions are often complex involving various competing or parallel pathways and leading to multiple reaction products that may be more toxic than the parent compound (DellaGreca et al., 2003). Because of this it is important to treat the photodegradation products.

Due to large amount of drugs used in the world it is necessary to find good and reliable treatment. The RO/NF membrane treatment processes are widely used for removal of emerging contaminants from water (Chen et al., 2004, Kiso et al., 2002, Snyder et al., 2007, Yangali-Quintanilla et al., 2010) and in water treatments. Usage of these treatments is growing every year compared to other water treatment technologies but according to our knowledge none is dealing with photodegradation products of anthelmintic drugs. In our previous work good removal of LEV, PZQ (Košutić et al., 2007) and FEBA (Dolar et al., 2011) with RO/NF membranes was presented.

This paper describes a treatment of anthelmintic drugs (LEV, ABZ, PZQ and FEBA) and their photodegradation products, for the first time, with RO/NF membrane treatment. Two reverse osmosis (LFC–1 and XLE) and four nanofiltration (NF90, NF270, NF and DK) membranes were used.

Section snippets

Chemicals

Four anthelmintic drugs (LEV, ABZ, PZQ and FEBA) were selected as organic micropollutants for study their removal with RO/NF membrane treatment. All anthelmintic drugs were kindly provided by Veterina, Kalinovica, Croatia. The purities of all drugs were ≥99%, as determined by suppliers. The chemical structures of the drug substances are given in Fig. 1 and in Table 1 their physico-chemical properties according to increase of molecular weight (MW) are presented. These compounds represent a

Membrane characterization

In Table 2 rejections of three typical inorganic salts (NaCl, CaCl2, MgSO4) and flux (with standard deviation, S.D.) are displayed. Membranes were treated with NaCl and CaCl2 to see their basic (nominal) properties. According to rejection factors of these two salts there are big differences between RO and NF membranes. For RO membranes difference among NaCl and CaCl2 are very small because the main rejection mechanism is size exclusion mechanism. For nanofiltration NF90 membrane difference was

Conclusion

Usefulness of the anthelmintic drugs is uncontested, but at the same time they pose a risk to aquatic systems and sources, especially for those intended for drinking.

Anthelmintic as emerging contaminants must be either removed from water supplies or degraded if we wish to assure that they will not contaminate aquatic environments.

According to the data from this study, nanofiltration and especially reverse osmosis membranes showed to be effective barrier for removal of selected anthelmintic

Acknowledgements

This work has been supported by the Croatian Ministry of Science, Education and Sports Projects. 125-1253008-3009 Membrane and adsorption processes for removal of organic compounds in water treatment, 125-1253008-1350 Advanced analytical methods for pharmaceuticals determination in the environment and by the Unity Through Knowledge Fund (UKF), which was established by the Croatian Ministry of Science, Education and Sports through World Bank Loan No. 7320-HR. Reduction of environmental risks

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