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This review article addresses wastewater treatment methods in the red meat processing industry. The focus is on conventional chemicals currently in use for abattoir wastewater treatment and energy related aspects. In addition, this article discusses the use of cleaning and sanitizing agents at the meat processing facilities and their effect on decision making in regard to selecting the treatment methods. This study shows that cleaning chemicals are currently used at a concentration of 2% to 3% which will further be diluted with the bulk wastewater. For example, for an abattoir that produces 3500 m3/day wastewater and uses around 200 L (3%) acid and alkaline chemicals, the final concentration of these chemical will be around 0.00017%. For this reason, the effects of these chemicals on the treatment method and the environment are very limited. Chemical treatment is highly efficient in removing soluble and colloidal particles from the red meat processing industry wastewater. Actually, it is shown that, if chemical treatment has been applied, then biological treatment can only be included for the treatment of the solid waste by-product and/or for production of bioenergy. Chemical treatment is recommended in all cases and especially when the wastewater is required to be reused or released to water streams. This study also shows that energy consumption for chemical treatment units is insignificant while efficient compared to other physical or biological units. A combination of a main (ferric chloride) and an aid coagulant has shown to be efficient and cost-effective in treating abattoir wastewater. The cost of using this combination per cubic meter wastewater treated is 0.055 USD/m3 compared to 0.11 USD/m3 for alum and the amount of sludge produced is 77% less than that produced by alum. In addition, the residues of these chemicals in the wastewater and the sludge have a positive or no impact on biological processes. Energy consumption from a small wastewater treatment plant (WWTP) installed to recycle wastewater for a meet facility can be around $500,000.

Groundwater pumping systems using photovoltaic (PV) energy are increasingly being implemented around the world and, to a greater extent, in rural and electrically isolated areas. Over time, the cost of these systems has decreased, providing greater accessibility to freshwater in areas far from urban centers and power grids. This paper proposes a novel sustainability analysis of the groundwater pumping systems in Tenerife Island as an example of a medium-size isolated system, analyzing the current status and the business-as-usual projection to 2030, considering the water reservoirs available and the final use of water. The 2030 projection focused on the PV deployment, evaluation of the levelized cost of electricity (LCOE), and the availability of the groundwater resource. HOMER software was used to analyze the LCOE, and ArcGIS software was used for the visual modeling of water resources. As a result, the average LCOE for a purely PV installation supplying electricity to a pumping system in Tenerife is 0.2430 €/kWh, but the location and characteristic of each pumping system directly affect the performance and costs, mostly due to the solar availability.

The current geopolitical landscape of the European Union has made it clear that the energy sector must be a top priority in EU policy, especially in light of the sudden escalation of Russian–Ukrainian conflicts. Energy efficiency has been used as the first tool of EU policy to tackle energy and climate crises, given the issues surrounding energy vulnerability and the need to limit gas emissions that contribute to climate change. The white certificate mechanism in Italy has played a pivotal role in encouraging measures to achieve the country’s energy-saving goals. Given the high energy requirements of Wastewater Treatment Plants (WWTPs), especially for aeration in the biological section, this paper examines the replacement of the air distribution system for a large WWTP as a viable intervention. In order to provide economic perspective for the plant, both the discounted Payback Period (dPBP) and the Net Present Value (NPV) were calculated for the investment. When viewed through an economic lens, the dPBP metric exhibits values that span from less than 1 year to nearly 4.5 years. Additionally, the investment’s cost-effectiveness was emphasized by the NPV, which, depending on the factors considered, can exceed 17.5 million euros. Finally, given the centrality of the theme of climate change, the avoided greenhouse gas emissions generated by the efficiency intervention were calculated, according to the GHG Protocol, resulting in a quantity of avoided emissions equivalent to over 57,770 tonnes of CO2e. These results highlight important achievements in terms of both the cost-effectiveness of the plant and the reduction of greenhouse gas emissions.

In the examined heat engine, reverse electrodialysis (RED) is used to generate electricity from the salinity difference between two artificial solutions. The salinity gradient is restored through a multi-effect distillation system (MED) powered by low-temperature waste heat at 100 °C. The current work presents the first comprehensive economic and environmental analysis of this advanced concept, when varying the number of MED effects, the system sizing, the salt of the solutions, and other key parameters. The levelized cost of electricity (LCOE) has been calculated, showing that competitive solutions can be reached only when the system is at least medium to large scale. The lowest LCOE, at about 0.03 €/kWh, is achieved using potassium acetate salt and six MED effects while reheating the solutions. A similar analysis has been conducted when using the system in energy storage mode, where the two regenerated solutions are stored in reservoir tanks and the RED is operating for a few hours per day, supplying valuable peak power, resulting in a LCOE just below 0.10 €/kWh. A life-cycle assessment has been also carried out, showing that the case with the lowest environmental impact is the same as the one with the most attractive economic performance. Results indicate that the material manufacturing has the main impact; primarily the metallic parts of the MED. Overall, this study highlights the development efforts required in terms of both membrane performance and cost reduction, in order to make this technology cost effective in the future.

This study analyzes a buffer tank simulated in both continuous operation mode and heating mode using CFD techniques. The analysis is focused in the thermal behavior of the tank, especially in parameters such as heat exchanged, heating time, and temperature distributions into the tank, in order to propose a better design. The results of the different simulations show that the tank heats water extremely slowly and extremely evenly when producing domestic hot water (DHW), which negatively affects the thermal stratification that is critical for rapidly reaching the DHW temperature. Therefore, the main problem of the tank is an inefficient heat exchange and a poor distribution of temperature. In order to overcome these operational limitations, a new design is proposed by installing a tube inside the tank that encloses the heating coil and sends hot water directly to the tank top region such that high-temperature DHW is rapidly provided, and thermal stratification is improved. Several simulations are performed with different open and closed configurations for the outlets of the inner tube. The different results show that the heating times significantly improve, and the time needed to reach the 45 °C set point temperature is reduced from 44 to 15 min. In addition, the simulations in which the opening and closing of the water outlets are regulated, the outlet DHW temperature is kept within 45–60 °C, which prevents overheating to unsafe use temperatures. Furthermore, the results of the simulation in continuous operation mode show a clear improvement of thermal stratification and an increase in the heat transmitted to the inside of the tank.

Hydrothermal liquefaction (HTL) is an effective technology for bio-crude production. To date, various co-liquefaction studies were performed with contrasted (different composition) biomasses in subcritical water. Therefore, the present study investigated co-hydrothermal liquefaction of similar kinds of lignocellulosic biomasses (wheat straw, eucalyptus, and pinewood) in supercritical water under equal ratios at 400 °C with catalytic medium (K2CO3). The lower bio-crude and higher solid yields were obtained in co-liquefaction experiments, as compared to liquefaction of individual feedstocks. On the other hand, higher carbon recovery and higher HHVs were noticed in co-liquefaction-derived bio-crudes. Gas chromatography with mass spectrometry (GC-MS) results showed that organic compounds were detected in all bio-crudes in the order of phenol derivatives > ketones/aldehydes > aromatics > carboxylic acids/esters. The aqueous phase from all samples contained higher TOC in the range of 19 to 33 g/L, with alkaline pH. In short, the co-liquefaction slightly improved the bio-crude quality with a significant reduction in bio-crude energy recovery. This reflects that co-liquefaction of lignocellulosic feedstock is not favorable for enhancing bio-crude yield and improving the overall process economics of HTL.