The "dual carbon" strategy is the long-term strategic direction of green and low-carbon development in our country. It has set off a wave of "peak carbon dioxide emissions · carbon neutrality" practices in the whole society, and various industries have introduced medium- and long-term plans under the dual carbon target. Therefore, implementing low-carbon transformation through technological innovation, efficient and clean use of energy, and intelligent production as soon as possible, and reducing industry carbon emissions will help provide a broader development space for the whole industry. At the same time, replacing fossil energy consumption with clean energy and establishing green power usage channels will help to further offset industry carbon emissions and empower industry green and low-carbon transformation.
So, how can the water industry achieve low carbon?
01
Water industry is closely related to carbon emissions
The water industry refers to the industrial chain composed of raw water, water supply, water conservation, drainage, sewage treatment and water resource recycling, as shown in the figure. The urban water industry is the foundation of urban development, residents' lives and industrial production. The upstream of the industry is the acquisition of raw water. The form of water resource acquisition (surface water, groundwater) and the quality of the water source directly affect the water supply cost and energy consumption; the downstream of the industry is the treatment and disposal of sewage and sludge. The water consumption, water saving situation of urban residents, and the process technology and intelligent management level of sewage plants will directly affect the comprehensive energy consumption and chemical consumption of sewage treatment.
The carbon emissions of the water supply system reach 10 million tons! Demystifying the low-carbon breakthrough road for water enterprises
A typical urban water industry system
According to statistics, in 2020, the carbon emissions of the whole process of urban sewage treatment in the country were 34.16 million t CO2, the carbon offset was 7.691 million t CO2, the net emissions were 26.469 million t CO2, and the carbon emissions of the national urban water supply system exceeded 22 million t CO2. It can be seen that the realization of carbon emission reduction in the water industry is of great significance to the early realization of "peak carbon dioxide emissions" and "carbon neutrality" in our country.
1. Water supply carbon emissions
The raw water obtained from the water source is sent to thousands of households after being transported by the original water pipe network, treated by the water plant, and transported by the water supply pipe network. During the transportation of the original water pipe network and the transportation of the water supply pipe network, it needs to be treated by multi-stage pumping stations and pump rooms. In this process, the indirect discharge of the electric energy consumed by the pump is the main form of greenhouse gas emissions.
During the treatment process of water plants, greenhouse gases are generally not directly emitted, but indirect emissions result from the energy consumption generated by the operation of the equipment, as well as the consumption of chlorine, flocculant and disinfectant in the pretreatment process.
Zhao Rongqin et al. analyzed and calculated the water supply situation and related data in Zhengzhou City, and the results showed that the carbon emission value of the water intake system relying on groundwater extraction and South-to-North Water Diversion water supply reached 0.14 kg/m3, and the energy intensity of water production and water transmission and distribution was 0.543 kW · h/m3 and 0.320 kW · h/m3, respectively. According to the conversion of CO2 emissions per unit of thermal power generation in 2020, the CO2 emissions of water production and water transmission and distribution were 0.452 kg/m3 and 0.266 kg/m3, respectively, and the contribution rate of water production to carbon emissions was greater.
2. Wastewater treatment carbon emissions
The forms of carbon emissions in domestic sewage treatment are mainly divided into direct emissions and indirect emissions. Among them, direct emissions are generally in the process of sewage treatment, due to the degradation of organic pollutants in the water, greenhouse gases such as CO2, CH4 and N2O are released into the atmosphere; indirect emissions are generally in the process of sewage treatment, including electricity, gas and chemicals used. Converted carbon emissions.
Ma Boya and others pointed out through research that compared with direct emissions, the current research on indirect emissions is more in-depth, and the technical direction is also more clear. The relevant research mainly focuses on energy conservation and consumption reduction and wastewater energy reuse. Beijing Urban Drainage Group and Shenzhen Water Group, two large-scale water companies, have separately measured greenhouse gas emissions in the wastewater treatment process. The results show that in the process of wastewater treatment, indirect emissions caused by power consumption and direct nitrogen oxide emissions generated during denitrification are the main components of greenhouse gas emissions, accounting for 80% to 90% of total emissions.
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Carbon reduction measures by well-known companies
Beikong Water Affairs:
In terms of new technology research and development, Beikong Water has developed new technologies such as AOA and aerobic granular sludge, which have made breakthroughs and have been widely used in Shandong, Guangdong, Zhejiang and other places.
In terms of energy conservation and consumption reduction in operation, Beijing Control Water has achieved significant energy conservation and consumption reduction effects by using the whole process of fine control and smart water affairs. Beijing Control Water has built a water plant information data center based on big data, a water plant production and operation system, an intensive management and control system, an analysis decision support system, and a business process-based operation mobile Internet APP application system. It has built a cloud-based smart water system.
In 2020, the cost of raw materials per ton of water in Beikong Water will decrease by 25.8%, and the savings of raw materials and electricity consumption such as carbon sources, phosphorus removers, and flocculants will be realized. The annual carbon dioxide emission reduction will be about 150,000 tons, and the remaining sludge emission reduction will be about 180,000 tons (moisture content 80%).
In terms of new energy development, Beikong Water has promoted photovoltaic, water source heat pump and other technologies and has begun to take shape. At present, the group has more than 50 water plants using photovoltaic power generation, with a total installed capacity of more than 32MW.
In the application of water source heat pump technology, taking the western sewage treatment plant in Qinhuangdao Harbor District as an example, the sewage treatment scale of the plant is 120,000 tons/day, and the wastewater treated water is used as the heat source of the water source heat pump to provide heating and cooling for the office building and production and living areas of the factory.
Central Water:
Promote the application of distributed energy. Distributed photovoltaic power generation projects have been operated in a number of sewage treatment plants in Bengbu, Feicheng, Qi County and other places, which have made significant contributions to reducing carbon dioxide emissions. At present, it can replace more than 20% of traditional energy. In the future, it is planned to use the latest flexible bracket method to effectively utilize the water plant site and apply it to new projects to expand the installed capacity.
Promote the utilization of wastewater resources. At present, Central Water is building the Bengbu Reclaimed Water Reuse Project, which is a key project for water ecological environment management in the Huaihe River Basin and a demonstration project for recycled water utilization and wastewater resources. The project adopts the process plan of "denitrification filter (transformation) + ultrafiltration + disinfection", which can recycle 26.90 million tons of recycled water every year, which can reduce COD emissions by about 8,800 tons and has significant environmental benefits.
The treated reused water is used for municipal miscellaneous, landscape reuse, industrial reuse, etc., which will reduce the use of tap water and wastewater discharge in Bengbu City, greatly improve the ecological water environment of the Huaihe River Basin, and increase the green coverage due to the use of recycled water, replenish artificial ponds and lakes, and improve the living environment of local residents.
Promote the energy-saving technology of water source heat pump. Sewage source heat pump technology is an air conditioning system that uses urban or industrial wastewater as a cold and heat source to provide and store energy, which can reduce the consumption of energy and water resources and produce greater economic and social benefits. The company's subordinate Zhonghuan Water Xiaotangshan Reclaimed Water Plant and Machikou Reclaimed Water Plant use wastewater source heat pump technology to extract low-grade heat energy stored in sewage to heat the plant area, realize energy recycling, and save the expenses of boiler rooms and traditional air conditioners.
The carbon emissions of the water supply system reach 10 million tons! Demystifying the low-carbon breakthrough road for water enterprises
03
The Road to Low-carbon Breakthrough for Water Enterprises
1. Building "low-carbon water" is the only way to move towards "carbon neutrality" in water
Water is an indispensable material resource for human daily life and social development. The black and odorous water produced by direct sewage discharge will increase a large amount of carbon emissions in an anaerobic environment. Carbon reduction measures in the water industry can not only directly promote the coordinated control of carbon emissions in the water environment governance process, but also effectively cover the carbon emission reduction of the whole industry's water use process.
"Low-carbon water" can reduce the unit electricity consumption and chemical dosage through the application of new technologies, thereby reducing the input of additional energy and carbon sources, and at the same time rely on the use of new energy in the factory area, by-product energy conversion and other ways to achieve the "carbon neutrality" goal of the water supply and drainage industry.
2. The key to achieving "carbon neutrality" in the water industry is management strategy and technological innovation
(1) Clarify the development goals of the stage and improve the consensus of practitioners on achieving "carbon neutrality" in the water industry.
The water industry cannot achieve "carbon neutrality" overnight. It is necessary to avoid the movement of "carbon charge", but also to avoid the "irrelevant" of the whole industry to achieve "carbon neutrality". It is necessary to clarify the stage development goals, give priority to reducing energy consumption and material consumption in the plant area, combine technological innovation and process improvement to achieve "peak carbon dioxide emissions", and then further transition to "carbon neutrality" by introducing new energy and reducing carbon emissions per unit of water treatment.
Through the establishment of phased goals and the training of practitioners, the staff of the water industry will gradually increase their awareness of the necessity and urgency of achieving "carbon neutrality", and simultaneously improve the industry's exploration of energy conservation and emission reduction technologies and management measures and enthusiasm from top to bottom and bottom to top.
The carbon emissions of the water supply system reach 10 million tons! Demystifying the low-carbon breakthrough road for water enterprises
(2) Develop low-carbon disposal technologies to promote industrial transformation and upgrading.
Further research and development of new technologies and new equipment in the process of water purification and sewage disposal, improve the efficiency of treatment operation, reduce energy consumption and drug consumption, increase the proportion of energy recovery and utilization, actively develop renewable energy including solar energy and wind energy suitable for the water industry, promote the process of unmanned, intelligent treatment equipment, realize the stable operation of water industry treatment plants, save external energy input, and reuse resources, so that the relevant treatment process can be transformed from energy consumption to energy spillover, achieve "carbon neutrality" operation, and promote the development and application of greenhouse gas emission reduction technologies.
(3) Carry out a full life cycle assessment to promote carbon emission reduction across the entire industry chain.
The whole life cycle assessment can help to clearly quantify the carbon emissions of substances flowing in each process, analyze the carbon footprint, and evaluate the greenhouse gas emission potential of the plant under different processes and technologies. The whole chain product lifecycle evaluation of the water industry should be further improved, and the whole process carbon emission evaluation of "water source - water purification disposal - end point water use - sewage disposal - drainage" should be realized, so as to provide support for the development of green and low-carbon water products and further reduce carbon emissions in the water industry.
Source: Water Purification House, Peking University Wang Pu, Cyborg Internet of Things
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