This article shows a climate change mitigation strategy by means of membranes replacement and determination methodology of carbon footprint in reverse osmosis (RO) desalination plants, valid for all the islands, and even isolated territories in the continent. This study takes the case of study of Canary Islands, where there are more than 320 desalination plants with different sizes, private, and public. The objective is to propose a new method which integrates this analysis with the replacement of membranes, from 0% to 20% per year in sea water reverse osmosis desalination plants, to reduce the carbon footprint and ecological footprint. If it is considered a replacement of 20% of the elements per year, the carbon footprint could be reduced to between 5% and 6% and even more if it is introduced low energy consumption membranes instead of high rejection elements. The factor mix in Canary Islands, according to the technological structure of the generation park that uses oil products, is around 0.678 kgCO₂/kWh, much higher than in the Spanish mainland where it is 0.263 kgCO₂/kWh. Therefore, it is estimated in Canary Islands 5,326,963 t CO₂/year can be emitted, which represents 2.4 tCO₂/person/year, 12 times more the admissible admissions per inhabitant in the Canary Islands, only considering the seawater desalination sector. This document shows the different results of the analysis of energy efficiency and the environmental footprints. This study may serve as a tool for the decision-making processes related to how to improve energy efficiency in desalination plants.

Desalination is an opportunity to get fresh water for irrigation and for drinking. Reverse Osmosis (RO) for sea water desalination is a solution for the high demand for water in Atlantic islands. The most efficient process to get desalinated water is RO; however, it is necessary to study what to do with the RO membranes used at the end of their life. This paper confirms the possibility to recycle them. The main categories of recycling by thermal processing commonly used in the industry include incineration and pyrolysis to produce energy, gas and fuel. These processes can be applied to mixed plastic waste, such as the combination of materials used in the manufacture of RO membranes. Recycling RO elements from desalination plants is shown to be an opportunity and pioneering initiatives are already underway in Europe. Energy recovery, via incineration, is feasible nowadays and it is a possibility to recycle RO membranes. On the other hand, the recycling of RO elements, via the pyrolytic industry, for fuel production could be centralized in a new industry already planned in the Macaronesia area and all obsolete osmosis membranes could be sent there for recycling. Recycling RO membranes is a very important opportunity for the environment and economy of the zone. This is a new business in water treatments with membranes, very interesting for decreasing the residues and the carbon footprint. The importance of this work is applied to sea water membranes, brackish water ones, and also wastewater tertiaries RO elements at the end of their life.

The cheese whey (95% composed of water) is an effluent produced in the cheese industry, of which more than 1.5 million tons are generated in Spain, constituting a serious environmental problem. The process starts with a new fermentative/enzymatic technology that totally converts whey, mainly composed by lactose, proteins, and salts, into a fermented product with higher added value. This new product is mainly composed by lactic acid bacteria biomass, ammonium lactate, and a protein hydrolysate. To separate valuable fractions, this fermented product is processed by a two-stage membrane system, which is a very innovative process in this type of fermented product. The first stage consists of ultrafiltration to separate all suspended solids. As a result of this stage, a product mainly constituted by lactic acid bacteria that have both agronomic applications, mainly as a biocontrol and biofertilizer/bio-stimulant, and applications in animal feeding as a probiotic, is obtained. The second stage consists of reverse osmosis used to concentrate the ultrafiltered permeate obtained earlier, leading to a microbiologically stable product and reducing transport costs. The concentrate is mainly composed of ammonium lactate and a protein hydrolysate, constituted by peptides and free amino acids, which has application both in agriculture as a bio-stimulant and in animal feeding, and the permeate is water, reusable in other industrial processes. This work demonstrates the technical feasibility of this valorization process to achieve the objective of “Waste 0” from a problematic by-product, while obtaining products with commercial utility.

A novel catalyst, composed of silver phosphate (Ag₃PO₄) deposited on a magnetic material containing titanium dioxide (TiO₂) and ferromagnetite (Fe₃O₄), was synthesized and tested with wastewater from the maintenance system of a swimming pool and from the secondary effluent of a wastewater treatment plant (WWTP). The magnetic material Ag₃PO₄@1-TiO₂-Fe₃O₄ presented a slightly lower photoactivity than bare Ag₃PO₄ but was able to remove over 64% COD from the secondary effluent of a WWTP and over 75% organic UV filters from a swimming pool wastewater. The material was easily recovered from the treated water with a magnet and could be reused at least four times. The efficiency loss after five reuses was 15%. The dissolution of silver after the photocatalytic reaction was over 80 mg·L⁻¹ for bare Ag₃PO₄ and less than 500 μg·L⁻¹ for the magnetic composites. The magnetic support prevents the dissolution of silver. The materials that contained Ag₃PO₄ showed antibacterial properties under dark conditions. The photocatalytic efficiency of Ag₃PO₄ and commercial TiO₂ was similar under sunlight, both for the removal of UV filters at µg·L⁻¹ concentrations from swimming pool wastewater, and for the removal of mild COD loads from a WWTP effluent (initial COD: 110 mg·L⁻¹).

In this paper, a new method for characterizing the dielectric breakdown voltage of dielectric oils is presented, based on the IEC 60156 international standard. In this standard, the effective value of the dielectric breakdown voltage is obtained, but information is not provided on the distribution of Kelvin forces an instant before the dynamic behavior of the arc begins or the state of the gases that are produced an instant after the moment of appearance of the electric arc in the oil. In this paper, the behavior of the oil before and after the appearance of the electric arc is characterized by combining a low-cost CMOS imaging sensor and a new matrix of electrical permittivity associated with the dielectric oil, using the 3D cell method. In this way, we also predict the electric field before and after the electric rupture. The error compared to the finite element method is less than 0.36%. In addition, a new method is proposed to measure the kinematic viscosity of dielectric oils. Using a low-cost imaging sensor, the distribution of bubbles is measured, together with their diameters and their rates of ascent after the electric arc occurs. This method is verified using ASTM standards and data provided by the oil manufacturer. The results of these tests can be used to prevent incipient failures and evaluate preventive maintenance processes such as transformer oil replacement or recovery.

This article presents a proposal of an anaerobic biodigester on a laboratory scale for introducing the monitoring and sensing techniques of the growth of microorganisms according to different parameters, where the redox potential, pH, pressure, and temperature have been measured in quasi-continuous mode. For this task, a microcontroller system was used (Atmega328—Arduino). Importantly, the design is based on flexible and open-source software, hardware, and firmware (Scilab, Arduino, Processing), facilitating its modification for other related studies. This design was developed to help engineering students to learn and to understand the operation of an anaerobic biodigester, which allows us to know various properties of the system at any time, as well as its evolution over time. In this way, property curves can be drawn and related to each other to obtain a better understanding of the biodigester operation. In this context, the relationship between the oxide-reduction reaction and microbial activity was studied so that the redox potential can be a way of measuring the growth of microorganisms in an anaerobic environment. With all this, through these parameters, it is possible to introduce to engineering students the operation of this technology used normally like a very powerful tool for the control of the carbon footprint, for example in wastewater sector, and consequently for the mitigation of the climate change.