Remediation of groundwater polluted with lindane production wastes by conductive-diamond electrochemical oxidation.

This work studies the remediation of groundwater saturated with dense non-aqueous phase liquid (DNAPL) from lindane production wastes by electrochemical oxidation. DNAPL-saturated groundwater contains up to 26 chlorinated organic compounds (COCs), including different isomers of hexachlorocyclohexane (HCH). To do this, polluted groundwater was electrolysed using boron-doped diamond (BDD) and stainless steel (SS) as anode and cathode, respectively, and the influence of the current density on COCs removal was evaluated in the range from 5 to 50 mA cm-2. Results show that current densities higher than 25 mA cm-2 lead to the complete removal and mineralisation of all COCs identified in groundwater. The higher the current density, the higher the COCs removal rate. At lower current densities (5 mA cm-2), chlorobenzenes were completely removed, and degradations above 90 % were reached for COCs with more than five chlorine atoms in their molecules. The use of BDD anodes promotes the electrochemical generation of powerful reactive species, such as persulfate, hypochlorite or hydroxyl radicals, that contribute to the degradation and mineralisation of COCs. The applied current density also influences the generation of these species. Finally, no acute toxicity towards Vibrio fischeri was observed for the treated groundwater after the electrochemical oxidation performed at 5 and 10 mA cm-2. These findings demonstrate that electrochemical oxidation with BDD anodes at moderate current densities is a promising alternative for the remediation of actual groundwater contaminated with DNAPLs.

Disinfection of polymicrobial urines by electrochemical oxidation: Removal of antibiotic-resistant bacteria and genes.

In this work, data obtained from the University Hospital Complex of Albacete (Spain) were selected as a case study to carry out the disinfection experiments. To do this, different configurations of electrochemical reactors were tested for the disinfection of complex urines. Results showed that 4-6 logs bacterial removal were achieved for every bacterium tested when working with a microfluidic flow-through reactor after 180 min (0.423 Ah dm-3). The MIKROZON® cell reached a total disinfection after 60 min (1.212 Ah dm-3), causing severe damages induced in the cell walls observed in SEM images. The concentration profiles of the electrogenerated disinfectants in solution could explain the differences observed. Additionally, a mean decrease in the ARGs concentration ranked as follows: blaKPC (4.18-logs) > blaTEM (3.96-logs) > ermB (3.23-logs) using the MIKROZON® cell. This electro-ozonizer could be considered as a suitable alternative to reduce the risk of antibiotic resistance spread. Hence, this study provides an insight into different electrochemical reactors for the disinfection of complex hospital urine matrices and contributes to reduce the spread of antibiotic resistance through the elimination of ARGs. A topic of great importance nowadays that needs to be further studied.

A review on disinfection technologies for controlling the antibiotic resistance spread.

The occurrence of antibiotic-resistant bacteria (ARB) in water bodies poses a sanitary and environmental risk. These ARB and other mobile genetic elements can be easily spread from hospital facilities, the point in which, for sure, they are more concentrated. For this reason, novel clean and efficient technologies are being developed for allowing to remove these ARB and other mobile genetic elements before their uncontrolled spread. In this paper, a review on the recent knowledge about the state of the art of the main disinfection technologies to control the antibiotic resistance spread from natural water, wastewater, and hospital wastewater (including urine matrices) is reported. These technologies involve not only conventional processes, but also the recent advances on advanced oxidation processes (AOPs), including electrochemical advanced oxidation processes (EAOPs). This review summarizes the state of the art on the applicability of these technologies and also focuses on the description of the disinfection mechanisms by each technology, highlighting the promising impact of EAOPs on the remediation of this important environmental and health problem.

Enhancement of UV disinfection of urine matrixes by electrochemical oxidation.

This work focuses on the removal of antibiotic-resistant bacteria (ARB) contained in hospital urines by UV disinfection enhanced by electrochemical oxidation to overcome the limitations of both single processes in the disinfection of this type of effluents. UV disinfection, electrolysis, and photoelectrolysis of synthetic hospital urine intensified with K. pneumoniae were studied. The influence of the current density and the anode material was assessed on the disinfection performance of combined processes and the resulting synergies and/or antagonisms of coupling both technologies were also evaluated. Results show that the population of bacteria contained in hospital urine is only reduced by 3 orders of magnitude during UV disinfection. Electrolysis leads to complete disinfection of hospital urine when working at 50 A m-2 using Boron Doped Diamond (BDD) and Mixed Metal Oxides (MMO) as anodes. The coupling of electrolysis to the UV disinfection process leads to the highest disinfection rates, attaining a complete removal of ARB for all the current densities and anode materials tested. The use of MMO anodes leads to higher synergies than BDD electrodes. Results confirm that UV disinfection can be enhanced by electrolysis for the removal of ARB in urine, considering both technical and economic aspects.

Improving the biodegradability of hospital urines polluted with chloramphenicol by the application of electrochemical oxidation.

This work focuses on improving the biodegradability of hospital urines polluted with antibiotics by electrochemical advanced oxidation processes (EAOPs). To do this, chloramphenicol (CAP) has been used as a model compound and the influence of anodic material (Boron Doped Diamond (BDD) and Mixed Metal Oxide (MMO)) and current density (1.25-5 mA cm-2) on the toxicity and the biodegradability was evaluated. Results show that a complete CAP removal was attained using BDD anodes, being the process more efficient at the lowest current density tested (1.25 mA cm-2). Conversely, after passing 4 Ah dm-3, only 35% of CAP removal is reached using MMO anodes, regardless of the current density applied. Furthermore, a kinetic study demonstrated that there is a clear competitive oxidation between the target antibiotic and the organic compounds naturally contained in urine, regardless the current density and the anode material used. During the first stages of the electrolysis, acute toxicity is around 1% EC50 but it increases once CAP and its organic intermediates have been degraded. The formation and accumulation of inorganic oxidants may justify the remaining acute toxicity. This also helps to explain the trend observed in the rapid biodegradability assays. Finally, a 60% of standard biodegradability (Zahn-Wellens test) was achieved which suggests that electrochemical oxidation with BDD anodes could be the most appropriate technology to reduce the hazard of hospital urines at the operating conditions tested.