Every year, the United States uses enough water to fill 88 million Olympic-sized swimming pools to produce energy. This more than 58 trillion gallons of water is drawn from lakes, rivers and underground aquifers that make up our freshwater reserves, which account for just 3% of the global water supply.
As populations around the globe surge, so does the amount of freshwater consumed. Satisfying the thirst created by growing populations impacts more than just having enough water to drink and bathe in, though. When populations boom, there’s an increased demand on the energy sector to provide resources needed to power livelihoods. Extracting, pumping and delivering water for human use and treating used water for safe return into to the natural environment requires energy, and water is used in every phase of energy production.
Unless current practices change, we won’t have enough water to drink, let alone serve energy and power needs in the next two decades.
But what if we showed you how VandCenter Syd (VCS) Denmark transformed Odense, Denmark’s largest water resource recovery facility (WRRF) from a large electrical power consumer into a net producer of electricity and heat energy capable of serving more than 400,000 people – and achieved carbon neutrality and energy independence in less than a quarter of the typical timeframe for utilities?
of the Ejby Mølle WRRF’s energy is generated on its own, virtually eliminating the need for external power from the grid
people served with a biogas-driven combined heat power system and by leveraging carbon redirection to reduce process energy consumption
VCS Denmark strives to be a model for incorporating sustainability principles in its operations. Very few treatment facilities can consider themselves energy self-sufficient, let alone net energy positive – and this project is an international model in advancing sustainable water resource recovery.
Forming an ambitious goal and innovative partnership
VCS is a Danish water and used water company with more than 150 years of operational experience and a strong tradition of innovation, with a focus on implementing triple-bottom-line sustainability practices and innovative technologies to manage the water-energy nexus.
In 2009, the company implemented the Beyond Energy Neutrality program, aimed at improving resiliency and sustainability through turning the Ejby Mølle WRRF from a large electrical power consumer to a net producer of electricity and heat energy used within the City of Odense in Denmark. The plant has a 410,000-population equivalent capacity in Denmark’s third-largest city, is the company’s largest facility and is required to meet very stringent nutrient limits in its discharge into a small, local river.
Through its own efforts, VCS was able to implement changes in the facilities and operations of the plant and achieve a very impressive level of 77% energy self-sufficiency before engaging Jacobs to identify additional energy optimization opportunities (EOOs) in 2012.
Going program-wide, rather than standalone solutions
Our adopted approach aimed to develop a comprehensive electrical energy consumption profile and identify EOOs that relied primarily on relatively quick-to-implement process modifications, which would significantly reduce electrical power consumption and/or increase power generation from cogeneration. The approach also identified (but did not fully develop) more complex improvements that could be considered for future implementation.
Our team developed a plant-wide process model to identify, prioritize and develop the selected EOOs and used historical flows, solids loads and operational data (including electrical energy consumption and production) to calibrate and run the process model. We quickly and thoroughly evaluated multiple process re-configuration scenarios as well as the impact of implementing operational modifications to existing systems – making sure that the stringent effluent requirements were always met, while also measuring improvements against pre-established metrics for energy demand, energy generation and carbon footprint.
The following alternatives have been developed as part of the program:
- An ammonia-based aeration control for biological nutrient removal.
- A nitrous oxide (N2O) probe for continuous measurement of emissions from liquid processes.
- First full-scale granular sidestream deammonification process controlled to minimize N2O emissions while maximizing ammonia removal.
- First full-scale application in Scandinavia of induced granulation processes to improve biomass settleability in activated sludge bioreactors.
- First full-scale application in Scandinavia of facilities to leverage mainstream deammonification as part of a biological nutrient removal system.
Achieving self-sufficiency through energy optimization
When VCS set its goal of achieving carbon neutrality and energy independence in five years – it was optimistic. Many utilities have set similar energy self-sufficiency goals, often allowing themselves a 20- or 30- year period to study alternatives, implement solutions and then undertake significant and costly capital improvement programs. The goal of five was incredibly ambitious, yet, with help from Jacobs, VCS did it (and more) in only three, and with just a little more than $2 million in capital expenditures.
The Ejby Mølle WRRF achieved energy neutrality in 2013, primarily by leveraging carbon redirection to reduce process energy consumption while increasing energy generation from a biogas-driven combined heat power system.
And with the innovative solutions developed by the team, the plant now generates more than 150% of its energy (electrical and heat) demand by adopting sidestream and mainstream assisted deammonification capabilities. Surplus electrical energy is fed back into the power grid and hot water is used in a district heating system that serves locations up to 12 miles away. This is achieved while still maintaining full effluent compliance with total nitrogen and total phosphorus concentrations averaging less than 6.0 and 0.5 mg/L respectively, without having to rely on external carbon addition.
In 2018, the International Water Association recognized the Beyond Energy Neutrality Program as an outstanding example of innovation in the water sector. The project nabbed the in the Performance Improvement and Operational Solutions category of the association’s 2018 Project Innovation Awards.
Continuing to support VCS’ next step toward sustainable water resource recovery at the Ejby Mølle WRRF, Jacobs is helping develop a two-year industry-first demonstration program focused on how an emerging technology called membrane aerated biofilm reactor might deliver further energy savings, while reducing greenhouse gas emissions and requiring a much smaller facility footprint.
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