Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - OsciLEDs (New Disruptive Platform Technology for Water Treatment and Process Intensification)

Teaser

About 4000 km3 of water is used by humans each year around the world. Only 2.5% of Earth’s water resource is fresh water, and about 70% of fresh water present in the planet is frozen in the icecaps. Currently, one in three people in the planet is already facing water...

Summary

About 4000 km3 of water is used by humans each year around the world. Only 2.5% of Earth’s water resource is fresh water, and about 70% of fresh water present in the planet is frozen in the icecaps. Currently, one in three people in the planet is already facing water shortages and 1.8 billion people will face water shortages by 2025. Water scarcity and water quality degradation are therefore forcing consumers and industry to improve levels of water usage and reuse by implementing advanced water treatment technologies.
Wastewaters contain a wide variety of substances and complex mixtures of organic matter, often disposed into public sewage with little treatment. Studies show that existing wastewater treatment plants are not able to completely remove pharmaceuticals and pathogens.
Advanced Oxidation Processes (AOPs) have emerged as a suitable route for oxidation of organic contaminants and microorganism elimination. AOPs involve the generation of highly reactive species, the hydroxyl radicals (HO•). HO• are powerful non-selective oxidants and they gather several technologies such as ultraviolet irradiation (UV), ozonation, Fenton reagent, ultrasound and photocatalysis.
Despite the fact that numerous studies demonstrated that UV-driven treatments are effective in microorganisms and chemicals’ elimination, there are major barriers to the application of AOPs for the treatment of industrial wastewaters. Firstly, conventional UV-driven applications use mercury lamps. Several drawbacks are associated with these lamps: overheating, high energy consumption, short lifetime and end of life disposal issues since mercury is a hazardous pollutant. In this context, the quest for alternative cost-effective and efficient UV irradiation sources is ongoing. Secondly, wastewater treatment employing ozone is costly to break into the wastewater treatment market, which is related to the inefficiency of current designs of gas-liquid contacting reactors.
The OsciLEDs project addresses these two technological barriers to the commercial use of UV-driven water treatment processes by combining two innovative technologies: i) a reactor with outstanding gas-liquid contacting performance and ii) UV irradiation emitted by suspended light emitting diodes.
The development of LED technology has opened the possibility of employing LEDs as novel UV irradiation sources in photoreactors. LEDs offer significant advantages over traditional UV lamps such as high electrical efficiency, lower power requirement, compactness and robustness, much longer lifetime and construction of reactors with variable geometries. Hence, UV-LEDs are emerging as new photochemical light sources for water and wastewater remediation. However, until now LED systems cannot be used in a suspended liquid system.
The results obtained along the project reveal a cost-efficient UV LED-driven reactor for the inactivation of microorganisms and removal of pollutants from water, with particular focus on the removal of pharmaceuticals, comparatively to conventional reactors.

Work performed

The OsciLEDs project started with the commissioning of the ozone/UV-driven reactor. Afterwards, experiments regarding the degradation of pharmaceuticals and the inactivation of pathogenic microorganisms were carried out. The photocatalytic oxidation of pharmaceuticals (caffeine; diclofenac; hydrochlorothiazide; trimethoprim) with UVA and UVC radiation, evaluating the diclofenac antagonistic effects and determining the quantum yields was studied. This work allowed to obtain experience in terms of photolysis and photocatalytic degradation of pharmaceuticals, assess the effect of single compound and multicomponent mixtures in kinetics and the determination of quantum yields.
In order to improve the researcher advanced knowledge on microorganism inactivation a three months secondment was performed at the Plataforma Solar de Almería (PSA, Spain). Several experiments were performed trying to reach the inactivation of two pathogenic microorganisms E. coli and E. faecalis using solar AOPs. This stay at PSA allowed the use of solar UV and heat activated sulfate processes with the aim of pathogens removal at pilot scale.
The pharmaceutical compounds previously selected were used to assess the effectiveness of ozonation in the reactor with outstanding gas-liquid contacting performance. Different experimental conditions were assessed such as concentration of pharmaceuticals, ozone flowrate, ozone concentration, pH, batch and continuous mode. With this work it was possible to improve the water ozonation intensification, higher rates of ozone utilization and the reactor when benchmarked against a bubble column allows a reduction of 5-fold to one-order of magnitude in reactor volume.
The effect of UV LEDs in real wastewater was assessed trough several experiments with agro-industrial wastewaters: winery and crystallized fruit wastewater. The treatment of crystallized fruit effluents was performed by the application of a UV-A LED photo-Fenton process. In a first step, a Box-Behnken design of Response Surface Methodology was applied to achieve the optimal operational conditions to the UV-A LED photo-Fenton process. The UV-A LED photosystem combined with Fenton and coagulation-flocculation allowed reaching a higher biodegradability.
The treatment of winery wastewater was carried out using a HSO5−/Mn+/UV process. A comparison between the performance of the HSO5−/Fe(II)/UV-A LED process and the conventional photo-Fenton demonstrated important advantages associated with the HSO5−/Fe(II)/UV-A LED process, including the absence of the costly pH adjustment and the hydroxide ferric sludge generation. The HSO5−/Mn+/UV-A LED process can be considered a promising technology for application in real scale wastewater treatment plants.
During the OsciLEDs project the researcher had the possibility of increase his professional career, enhancing his interpersonal and presentation skills, as well as the supervision capacity. The researcher benefited from the exposure to a range of transferrable skills during his stay at Loughborough University such as new technical and scientific knowledge in reactor design; microorganism’s inactivation; ozonation; LEDs technology; teaching; project application; participation in international meetings and career development courses.
The dissemination of the results targeted both academic and public audiences and a common platform providing diversified contents for specific audiences was provided by the website of the project. The dissemination of research outputs to the academic community was through: 1) peer reviewed journal articles; 2) presentation at international conferences; 3) workshops and 4) dedicated website.

Final results

The current project has moved beyond the state of the start as it is a novel cutting-edge technology. The current technology will allow reducing the presence of emerging pollutants and pathogenic microorganisms in water and wastewater. The higher efficiency of the ozone/UV LEDs photoreactor will allow the development of a cost-effective technology that can be used in water disinfection and wastewater treatment, allowing the reuse of the treated water. In addition, people in deprived areas, will have less diseases and consequently less deaths caused by water-related diseases. By developing a low cost and efficient water treatment technology, it will be potentially bought by decision-makers to implement in their countries.

Website & more info

More info: https://oscileds.webnode.pt/.