Wastewater to Energy in Urumqi
By Nina Cambadelis 14 July, 2015
Veolia's Cambadelis shares a case study on gains for the plant & community from turning wastewater into energy
Biogas from the digestion of sewage sludge is an important renewable energy field. By implementing proven, effective and energy-efficient technologies of decontamination and of production of this fuel gas, Veolia significantly reduces the energy balance and carbon footprint of wastewater treatment plants it operates, as in Urumqi in China, a region sensitive to water stress and water quality.
Urumqi treatment in the age of recovery
Located in the Northwest of China, capital of the autonomous province of Xinjiang, the city of Urumqi is experiencing rapid economic development since the early 1990s. As a consequence, an explosion of water demand occurred and was coupled with a strong growth in the need for wastewater treatment. In this context, the municipality has chosen Veolia to upgrade and operate the Hedong wastewater treatment plant.
Energy is produced through the recovery of sewage sludge
Key in adapting to climate change
This is a key project with regards to the ability to adapt to the challenges of climate change, in terms of energy efficiency, carbon footprint and stress on water resources.
The Urumqi plant produces energy through the recovery of sewage sludge. It is also a solution of adaptation in terms of wastewater reuse for irrigation purposes, which reduces pressure on local water resources.
Renovation works allowed wastewater treatment capacity to double, from 200,000 to 400,000 m3 per day
These dimensions of mitigation and adaptation are a good illustration of an integrated project, on a collection area populated with 1.5 million inhabitants. Renovation and construction works started in early 2010 and allowed wastewater treatment capacity to double, increasing from 200,000 to 400,000 m3 per day. The plant is equipped with facilities that enable the production of electricity and heating. It uses 6 sludge digesters and in 2014, 985.318 m3 of gas have been produced monthly.
Biogas generated from sludge covers 50% of electricity needs of the site
This green source of energy is also used effectively. Studies have been conducted to ensure an optimal solution, both economically and environmentally, taking into account the operating/ working conditions and the weather. In practice, biogas is used as fuel for boilers that provide heating to the plant facilities, so as either to generate electricity and heat via 3 co-generators, thus covering 50% of the electricity needs of the site, or to feed the blowers that are equipped with gas engines, from which the heat is also used. The strategy and procedures implemented have allowed the plant to ensure a biogas production that is both reliable and profitable throughout the year.
In this context, with its international expertise in biogas production, hygiene and safety standards, or advanced equipment, Veolia has been able to respond to the major challenges related to technology and security, while at the same time training employees and delivering/ empowering them with a proven technical and operational expertise. These are the skills on which the joint venture will build in order to develop a scenario in case the city faces a power shortage or an obligation to further reduce its dependency on fossil fuels.
The plant minimizes dependency on fossil fuel, reduces the volume of sludge & can result in savings of 80% of CO2 emissions
Creating value from wastewater, the plant manages not only to minimize its dependency on fossil resources, but also to reduce the volume of sludge. It thus significantly reduces its carbon footprint, saving 80% of CO2 emissions in 2014 (70% in 2011). This interesting gain is coupled with the possibility to reuse wastewater for irrigation, which has required the development of processes to improve and stabilize the quality of the treated water. All these advantages make the treatment plant of Urumqi exemplary in terms of energy production, carbon footprint and water reuse.
|Launch Date: Contract signed in 2005 with the city of Urumqi for a period of 23 years. The entire plant has been operational since early 2010.Solution Partners: KUNLUN Urumqi Environmental Protection Group Co (formerly Urumqi Urban Construction Investment Company), Veolia partner in the Urumqi Hedong Veolia Water Company Limited joint venture.|
Weak points for solution deployment
Due to past uncertainty and technical difficulties, the former 4 digesters had not been used for a long time when Veolia took over the operations. Same abandon was to be noticed for the blowers. Refurbishing, commissioning and safely operating gas holder over the long term is both a technical and social challenge to overcome. Veolia took advantage of its worldwide expertise in biogas production, health and safety standards, and advanced equipment to overcome technical and safety challenges, while at the same time training and empowering employees with technical and operational knowledge.
Challenges came from abandoned equipment & matching plant & weather conditions for efficient biogas use
Another challenge is related to the efficient use of biogas according to the weather and the plant’s operating conditions. Extensive studies have been conducted within the joint venture in order to develop a strategy and specific procedure that guarantee reliable, economically viable and environmentally friendly use of biogas throughout the year.
Key figures illustrating solution deployment and results
- A collection area populated with 1.5 million inhabitants
- 50% of the energy needs of the site covered via self-production
- 2700 m3 of sludge treated daily
- 985.318 m3 of biogas produced per month in 2014
- 80% of CO2 emissions saved in 2014
Performance, impact and results
Environmental: Environmental footprint mitigated with the reduction of the volume of sewage sludge and its use as a source for green energy production (80% of CO2 emissions saved in 2014). Adaptation solution to climate change in a region sensitive to water stress, particularly with the reuse of treated wastewaters for irrigation purposes.
Social/societal: Renovated gas installation, safe and long-term commissioning and operation. Training of the employees.
Economic: Collection and treatment of 1.5 million inhabitants’ wastewaters. 50% coverage of the site’s electricity needs thanks to self-production.
Technical: Doubling of the plant’s processing capacity (from 200,000 to 400,000 m3/ day), reliable and cost-effective biogas production throughout the year, thanks to 6 sludge digesters producing 985,318 m3 of biogas per month.
Projected short and medium term results
“This solution … fully participates to the principles of the Circular Economy & therefore benefits not only the site and the client but also the local environment and the local residents.”
This solution, turning wastewater into a resource, fully participates to the principles of the Circular Economy and therefore benefits not only the site and the client but also the local environment and the local residents. This solution mitigates the impacts of the climate change over the long term.
Indeed in reducing its use of fossil resources but also in producing and using green energy, the sites secures its energy supply and use over the long term. Besides, the valorization of the sludge prevents the site to transport it to the landfill and to generate C02 emissions. Remaining sludge is finally reused by local farmers as fertilizer which, indirectly, helps local stakeholders to reduce their own emissions.
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