Biogas, Solar and Geothermal Energy—The Way to a Net-Zero Energy Wastewater Treatment Plant—A Case Study

Minimizing grid energy consumption in wastewater treatment plants: Towards green energy solutions, water sustainability, and cleaner environment

Wastewater treatment plants (WWTPs) consume significant amount of energy to sustain their operation. From this point, the current study aims to enhance the capacity of these facilities to meet their energy needs by integrating renewable energy sources. The study focused on the investigation of two primary solar energy systems in As Samra WWTP in Jordan. The first system combines parabolic trough collectors (PTCs) with thermal energy storage (TES). This system primarily serves to fulfill the thermal energy demands of the plant by reducing the demands from boiler units, which allows more biogas for electricity generation. The second system is a photovoltaic (PV) system with Lithium-Ion batteries, which directly produces electricity that will be used to cover part of the electrical energy demands of plant. To assess the optimal configuration, two distinct scenarios have been formulated and compared to the current case scenario (SC#1). The first scenario focuses on maximizing the net present value (NPV) and minimizing the levelized cost of electricity (LCOE). The second scenario is centred on minimizing the levelized cost of heat (LCOH). The findings indicate that both scenarios succeeded in reducing the reliance on the grid to a value that reach 1 %. Moreover, they both reduced biogas percentage in energy production from 88 % to approximately 65 % through the integration of the PV system. In terms of thermal demand, SC#2 reduced the reliance on biogas boiler units from 100 % to 25 %, while SC#3 achieved an even more impressive reduction to just 8 %. The best LCOE value was attained in SC#2, at 0.0895 USD/kWh, with an NPV of 10.54 million USD. Conversely, SC# 3 yielded an LCOH value of 0.0432 USD/kWhth compared to 0.0534 USD/kWhth USD for SC#2. Despite their relatively high capital and operating costs, SC#2 and SC#3 managed to substantially decrease the annual electricity expenditure from approximately 2 million USD to 86,000 USD and 0 USD, respectively.

Sustainability assessment of retrofitting alternatives for large and old wastewater treatment plants in Seoul

Old wastewater treatment plants (WWTPs) must be upgraded to alleviate the problems associated with aging and reduce their total environmental impacts. To enhance the environmental sustainability in retrofitting large and old WWTPs, the decision-making process for selecting the most appropriate alternative is complicated. In this study, evaluation criteria were proposed to select the most sustainable alternatives for mid- to long-term retrofitting plans for a large WWTP with the treatment capacity of 1.6 M m³/d, which is initially built in 1987. An analytic hierarchy process was applied to estimate the weights of each criterion. Fourteen experts evaluated the relative importance of criteria through pairwise comparisons. In order to assess the current retrofitting opinions, three retrofitting alternatives were constructed: A focused on energy sufficiency; B expanded the bioreactor capacity and enhancement of the facility for incinerating the sludge leaving the anaerobic digestor; C emphasized the treatment of contaminants of emerging concerns (CECs). A achieved the highest score (0.623) owing to the environmental benefits associated with recycling and first flush stormwater treatment. C exhibited the second highest score (0.612) as the focus on CECs removal. B corresponded to the lowest sustainability (0.426), with the lowest scores pertaining to effective land use and first flush stormwater treatment.

A Flexible-Reliable Operation Model of Storage and Distributed Generation in a Biogas Power Plant

This paper presents a novel methodology for planning and operating biogas energy systems based on the transactive energy concept to determine multilevel operating regimes for distributed generation. The developed model is used to manage the production, storage, and dispatch of biogas energy systems to meet the load demands of the biogas producer and support the operation of the distribution network operator. An Integer Linear Programming (ILP) is fitted to optimize the biogas production of the biogas producer, including the operation of the biogas storage systems and their interaction with the network operator. The model’s objective is to maximize benefits for the participating agents in a transactive energy context. The model’s effectiveness is validated using seven case studies involving biogas systems having different operating ranges and modes to achieve enhanced flexibility and reliability for the system operation with a large proportion of intermittent energy resources. The simulation results showed that the approach could effectively manage the operation of biogas systems and their interaction with the network operator. The developed model is suitable for systems fostering net metering charging and real-time pricing.