Evaluating the potential impact of energy-efficient ammonia control on the carbon footprint of a full-scale wastewater treatment plant

Abstract

An assessment was performed for elucidating the possible impact of different aeration strategies on the carbon footprint of a full-scale wastewater treatment plant. Using a calibrated model, the impact of different aeration strategies was simulated. The ammonia controller tested showed its ability in ensuring effluent ammonia concentrations compliant with regulation along with significant savings on aeration energy, compared to fixed oxygen set point (DOsp) control strategies. At the same time, nitrous oxide emissions increased due to accumulation of nitrification intermediates. Nevertheless, when coupled with the carbon dioxide emissions due to electrical energy consumption for aeration, the overall carbon footprint was only marginally affected. Using the local average CO2 emission factor, ammonia control slightly reduced the carbon footprint with respect to the scenario where DOsp was fixed at 2 mg·L−1. Conversely, no significant change could be detected when compared against the scenarios where the DOsp was fixed. Overall, the actual impact of ammonia control on the carbon footprint compared to other aeration strategies was found to be strictly connected to the sources of energy employed, where the larger amount of low CO2-emitting energy is, the higher the relative increase in the carbon footprint will be.

A Critical Review on Methodologies for the Energy Benchmarking of Wastewater Treatment Plants

“…Particularly, per each methodology, a brief description is reported along with the main advantages and limitations for comparison purposes. [20, [65][66][67] Looking at Table 3, several tools and methodologies have been specifically designed and tested at WWTPs.…”

“…Plant-wide modeling is a simulation tool that enables the prediction of WWTP performance and provides detailed information about influent and effluent quality as well as energy consumption [65,66]. Modeling allows for the easy comparison of various strategies to achieve energy-neutral conditions.…”

Deep Learning-Based Multiobjective Optimization for Balancing Effluent Quality, Operational Cost, and Greenhouse Gas Emissions in Wastewater Treatment Plant Control

“…The carbon footprint of a wastewater treatment plant (WWTP) is an important measure of its climate change impact. It typically includes indirect carbon dioxide (CO 2 ) emissions from electricity consumption and other production activities as well as methane (CH 4 ) and nitrous oxide (N 2 O) emissions . Direct CO 2 emission, which is considered to be of biological origin, is excluded here.…”

Critical Analysis of the GreenMetric World University Ranking System: The Issue of Comparability

“…This fraction changes according to the country where the HEI is located. A clear example of how changing the CO 2 emission factor for electrical energy strongly affects the overall carbon footprint can be found in the work of Boiocchi et al [30]. Furthermore, the list of carbon dioxide emission sources recommended should be extended by including the contributions emitted due to the treatment and handling of waste, wastewater and drinking water fluxes coming to and leaving the institution.…”

“…For instance, an HEI may employ all kinds of sophisticated technologies for optimizing the treatment of waste and wastewater with and without the purpose of recycling and reuse while increasing the amount of CO 2 emitted due to the amount and source of the energy employed by the same technologies. The evidence of CO 2 emissions due to power consumption by these technologies is numerous [30][31][32][33][34][35][36][37][38]. Additionally, nitrous oxide, a strong greenhouse gas with a global warming potential about 300 times stronger than CO 2 , can be emitted during the typical biological nitrogen removal processes for domestic wastewaters, according to the treatment system's design and operational patterns [38][39][40][41].…”