A pinboard by
Vinoth Kumar Raja

Postdoctoral Researcher, University of Porto (Portugal)


Membranes – Formation, Structure, Property, Performance – For Water Treatment Applications

Micropollutants are a vast group of substances that are found in the environment at residual concentrations (i.e., between ng L-1 and µg L-1). Micropollutants include synthetic organic contaminants, namely pesticides, personal care/cosmetic products, industrial chemicals, food additives and detergents, and naturally occurring substances such as estrogens. They may create undesirable effects on ecosystems and pollute drinking water resources even when present at trace concentrations. The European Union recently defined a list of 45 priority substances/groups of substances (PSs) considered as threat to the environment in Directive 2013/39/EU. Furthermore, 17 organic compounds, among them 5 pharmaceuticals, are enlisted in a Watch List of substances for Union-wide monitoring launched by Decision 2015/495/EU. Conventional MWWTPs are the main pathway for the continuous input of these substances into the environment, because of their inability to entirely remove micropollutants at ng L-1 - µg L-1 levels before discharging into the aquatic receptacles. Therefore, upgrading the current MWWTPs with additional advanced treatment processes is a strategy that can mitigate the pollution of aquatic environment by micropollutants or other type of contaminants. In general, physical, chemical and biological treatment techniques can be used for the removal of micropollutants from wastewater. However, all these type of treatments have shortcomings, such as partial removal, need to recover the adsorbing material, membrane fouling, high pressure drop and clogging, slow mass transfer, higher energy requirement, and more importantly none of these processes can remove all the compounds of concern. Therfore, my current research empassis on the removal of micropollutants from wastewater by combining advanced treatment processes such as membrane technology and advanced oxidation processes to ensure the efficient elimination of a variety of micropollutants, overcoming some of the shortcomings of the single treatments in order to provide pollutant free water to the people.


A focus on pressure-driven membrane technology in olive mill wastewater reclamation: state of the art.

Abstract: Direct disposal of the heavily polluted effluent from olive oil industry (olive mill wastewater, OMW) to the environment or to domestic wastewater treatment plants is actually prohibited in most countries, and conventional treatments are ineffective. Membranes are currently one of the most versatile technologies for environmental quality control. Notwithstanding, studies on OMW reclamation by membranes are still scarce, and fouling inhibition and prediction to improve large-scale membrane performance still remain unresolved. Consequently, adequately targeted pretreatment for the specific binomium membrane-feed, as well as optimized operating conditions for the proper membranes, is today's challenge to ensure threshold flux values. Several membrane materials, configurations and pore sizes have been elucidated, and also different pretreatments including sedimentation, centrifugation, biosorption, sieving, filtration and microfiltration, various types of flocculation as well as advance oxidation processes have been applied so far. Recovery of potential-value compounds, such as a variety of polyphenols highlighting oleuropein and hydroxytyrosol, has been attempted too. All this research should constitute the starting point to proceed with OMW purification beyond recycling for irrigation or depuration for sewer discharge, with the aim of complying with standards to reuse the effluent in the olive oil production process, together with cost-effective recovery of added-value compounds.

Pub.: 31 Oct '12, Pinned: 27 Sep '17

Elimination of micropollutants during post-treatment of hospital wastewater with powdered activated carbon, ozone, and UV.

Abstract: A pilot-scale hospital wastewater treatment plant consisting of a primary clarifier, membrane bioreactor, and five post-treatment technologies including ozone (O3), O3/H2O2, powdered activated carbon (PAC), and low pressure UV light with and without TiO2 was operated to test the elimination efficiencies for 56 micropollutants. The extent of the elimination of the selected micropollutants (pharmaceuticals, metabolites and industrial chemicals) was successfully correlated to physical-chemical properties or molecular structure. By mass loading, 95% of all measured micropollutants in the biologically treated hospital wastewater feeding the post-treatments consisted of iodinated contrast media (ICM). The elimination of ICM by the tested post-treatment technologies was 50-65% when using 1.08 g O3/gDOC, 23 mg/L PAC, or a UV dose of 2400 J/m(2) (254 nm). For the total load of analyzed pharmaceuticals and metabolites excluding ICM the elimination by ozonation, PAC, and UV at the same conditions was 90%, 86%, and 33%, respectively. Thus, the majority of analyzed substances can be efficiently eliminated by ozonation (which also provides disinfection) or PAC (which provides micropollutants removal, not only transformation). Some micropollutants recalcitrant to those two post-treatments, such as the ICM diatrizoate, can be substantially removed only by high doses of UV (96% at 7200 J/m(2)). The tested combined treatments (O3/H2O2 and UV/TiO2) did not improve the elimination compared to the single treatments (O3 and UV).

Pub.: 14 Jun '13, Pinned: 27 Sep '17

Multicriteria assessment of advanced treatment technologies for micropollutants removal at large-scale applications

Abstract: With the introduction and discharge of thousands of new micropollutants (MPs) every year, traditional water and wastewater treatment plants may be incapable of tackling them all. With their low concentrations and diversity in nature, MP removal encounters numerous challenges. Although some MPs are effectively eliminated via conventional treatment methods, most of them can easily escape and are retained in the discharged effluent. Therefore, advanced methods such as (i) adsorption, (ii) oxidation and advanced oxidation processes (O3 and O3-based advanced oxidation processes, UV/H2O2), (iii) membrane processes, and (iv) membrane bioreactors, become an inevitable approach. Despite the unsurprisingly vast number of papers on MP treatment available at present, most of these studies were carried out at a laboratory scale while only a few pilot- and full-scale studies have experimented. Nevertheless, an in-depth assessment of real-world MP treatment methods is extremely crucial for practitioners. To date, no paper has been dedicated to look at this issue. Therefore, this paper aims to review these large-scale treatment methods. First, the paper goes through the regulations and standards which deal with MPs in water courses. It will then assess these methods in various case-studies with reference to different criteria towards serving as a reference for further practical applications.

Pub.: 16 May '16, Pinned: 27 Sep '17

Evaluation of direct membrane filtration and direct forward osmosis as concepts for compact and energy-positive municipal wastewater treatment.

Abstract: Municipal wastewater treatment commonly involves mechanical, biological and chemical treatment steps to protect humans and the environment from adverse effects. Membrane technology has gained increasing attention as an alternative to conventional wastewater treatment due to increased urbanization. Among the available membrane technologies, microfiltration and forward osmosis have been selected for this study due to their specific characteristics, such as compactness and efficient removal of particles. In this study, two treatment concepts were evaluated with regard to their specific electricity, energy and area demands. Both concepts would fulfil the Swedish discharge demands for small and medium-sized wastewater treatment plants at full scale: 1) direct microfiltration and 2) direct forward osmosis with seawater as the draw solution. The framework of this study is based on a combination of data obtained from bench- and pilot-scale experiments applying direct microfiltration and forward osmosis, respectively. Additionally, available complementary data from a Swedish full-scale wastewater treatment plant and the literature were used to evaluate the concepts in depth. The results of this study indicate that both concepts are net positive with respect to electricity and energy, as more biogas can be produced compared to conventional wastewater treatment. Furthermore, the specific area demand is significantly reduced. This study demonstrates that municipal wastewater could be treated in a more energy- and area-efficient manner with techniques that are already commercially available and with future membrane technology.

Pub.: 10 Mar '17, Pinned: 27 Sep '17