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Please use this identifier to cite or link to this item:
http://hdl.handle.net/10174/1227
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Title: | Using clay materials to remove pharmaceuticals from waters |
Authors: | Dordio, Ana V. Palace Carvalho, A. J. Estêvão Candeias, A. J. Pinto, Ana P. Costa, Cristina |
Keywords: | clay materials pharmaceuticals sorption |
Issue Date: | Apr-2007 |
Abstract: | Pharmaceutical active compounds (PhACs) have an important role in the treatment and prevention of disease
in both human and animals. Ingested drugs are only partially absorbed by the organisms and studies have
shown that the excreted compounds are only partially removed in the sewage treatment plants (STPs) [1].
Contaminated effluents are being released from the STPs and trace amounts of PhACs have been detected in
wastewaters, surface and groundwaters worldwide [1]. Acidic pharmaceuticals like diclofenac, ibuprofen and
clofibric acid are some of the most frequently detected compounds [1]. The concentrations detected are low
(ng/L - μg/L) but, due to the very nature of these compounds, studies have shown damaging effects on the
aquatic ecosystems [1].
Several different processed natural materials can be used as filter media in water and wastewater treatment
systems. Some of these materials can additionally present functions which extend beyond the simple process
of filtration. Their surface areas can constitute a support for microbial population growth in biofilters as well
as support matrix for the development of macrophytes in sub-surface flow constructed wetland systems
(SSF-CWS) [2] which are increasingly being used in sewage tertiary treatment. The efficiency of these
biological systems in the removal of xenobiotics can be significantly enhanced by a greater capability of the
support matrix to retain contaminants by sorption phenomena, ionic exchange or other physico-chemical
processes [2].
The aim of the present work was to evaluate the efficiency of two different materials namely, Light
Expanded Clay Aggregates [LECA] (in two different particle sizes) and sand, for the removal from water of
three acidic PhACs, clofibric acid, diclofenac and ibuprofen. In addition, relationships were established
between the compounds removal efficiencies and the physico-chemical properties of each material.
A series of batch essays were carried out to study the sorption capacities of the different materials for the 3
chemical compounds. The influence of some experimental conditions, such as the contact time, the initial
PhACs concentrations (1 mg/L up to 50 mg/L) and LECA particle size, were investigated. The media were
sterilized before use in order to minimize any microbial development on the matrix and experiments were
conducted in the dark to avoid any photocatalytic degradation reactions. The mineralogical composition of
the materials was determined by X-ray diffraction and some physico-chemical properties were characterized.
Samples of the contaminants’ aqueous solutions were collected over a range of contact times with the
support matrix and the remaining concentrations in solution were determined by UV/Vis spectrophotometry.
The results show that LECA has a good sorption capacity for acidic compounds. In contrast, sand does not
exhibit any sorption capacity for any of the compounds tested. Not surprisingly, LECA with smaller particle
sizes show higher efficiencies that larger grade LECA, due to a larger available surface area. However, the
use of these smaller particle media at upper scales may present problems with hydraulic conductivities.
From the results obtained, it can be concluded that expanded clay presents important advantages as a CWS
support matrix or as a filter medium, because it has a good sorption capacity, a pH buffer capacity and an
excellent control of hydraulic permeability. On the other hand, sand does not exhibit any sorption capacity
that might enhance the performance of filters and CWS in the treatment of water contaminated with this type
of contaminants. |
URI: | http://hdl.handle.net/10174/1227 |
Type: | lecture |
Appears in Collections: | QUI - Comunicações - Em Congressos Científicos Internacionais
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