Economic Assessment of Energy Consumption in Wastewater Treatment Plants: Applicability of Alternative Nature-Based Technologies in Portugal

Abstract

Understanding how to address today’s global challenges is critical to improving corporate performance in terms of economic and environmental sustainability. In wastewater treatment systems, such an approach implies integrating efficient treatment technologies with aspects of the circular economy. In this business field, energy costs represent a large share of operating costs. This work discusses technological and management aspects leading to greater energy savings in Portuguese wastewater treatment companies. A mixed methodology, involving qualitative and quantitative aspects, for collecting and analysing data from wastewater treatment plants was used. The qualitative aspects consisted of a narrative analysis of the information available on reports and websites for 11 wastewater management companies in Portugal (e.g., technologies, treated wastewater volumes and operating costs) followed by a review of several international studies. The quantitative approach involved calculating the specific energy consumption (kWh/m3), energy operating costs (EUR/m3) and energy operating costs per population equivalent (EUR/inhabitants) using data from the literature and from Portuguese companies collected from the SABI database. The results suggested that the most environmentally and economically sustainable solution is algae-based technology which might allow a reduction in energy operating costs between 0.05–0.41 EUR/m3 and 15.4-180.8 EUR/inhabitants compared to activated sludge and other conventional methods. This technology, in addition to being financially advantageous, provides the ability to eliminate the carbon footprint and the valorisation of algae biomass, suggesting that this biotechnology is starting to position itself as a mandatory future solution in the wastewater treatment sector.

Utilization of Microalgae for Urban Wastewater Treatment and Valorization of Treated Wastewater and Biomass for Biofertilizer Applications

“…Activated anaerobic sludge removal from the activated aerobic digestion sludge process was reported to require 2.3 kWh of energy per kilogram of N removed, and the recently discovered anammox process, which oxidizes ammonium under anaerobic conditions, requires 0.9 kWh of energy per kg of N [55,56]. The reported specific energy consumption for high-rate algal ponds (HRAPs) with biofertilizer production was reported to be 0.08 kWh/m 3 to 0.1 kWh/m 3 [57][58][59][60]. Depending on the nitrogen concentration (e.g., 65 mg/L) in the wastewater and the nitrogen content in microalgal strains (5%), the energy required for the efficient removal of nitrogen from urban wastewater using HRAPs is 1.23 kWh per kg N, which is 47% less energy than that previously reported, i.e., 2.3 kWh per kg N by the conventional process in the urban wastewater treatment plant.…”

Energy Harvesting Opportunities in Geoenvironmental Engineering

“…EH can also be obtained from environmental sanitation works such as biological wastewater treatment processes [27][28][29] (e.g., activated sludge, algae technology, constructed wetlands and lagoons) and solid waste composting [30][31][32]. Wastewater and water flow can also be harnessed to generate hydroelectric power [33,34] using micro-turbines and solar panels can be installed on the rooftops of water and wastewater treatment plants, as well as in solid waste management infrastructures, to generate electricity from sunlight.…”

Enhancing Nature-Based Solutions: Efficient Removal of Hydroxytyrosol in Olive Mill Wastewater Treatment for Value Creation

“…The findings of this study could serve as a decision-support tool for olive oil producers looking for sustainable and cost-effective ways to manage their wastewater. It is also important to explore the potential of microalgae-based treatment methods for other types of wastewater and evaluate their potential for broader environmental and economic benefits [6,7].…”