Study on the Choice of Wastewater Treatment Process Based on the Emergy Theory
Abstract
:1. Introduction
2. Materials and Methods
2.1. Emergy Analysis Method
2.2. Selection of Indicators
- (1)
- EYR (Emergy Yield Ratio): Ratio of the amount of emergy produced by a wastewater treatment system to the amount of emergy purchased from society. The core value of a wastewater treatment system is to prevent ecological and human health damage caused by the direct discharge of wastewater; therefore, its yield includes reclaimed water and dewatered sludge. It is calculated as follows:EYR = EMY/EMF
- (2)
- ELR (Environmental Load Rate): Sum of non-renewable resource emergy and purchased emergy divided by the renewable resource emergy, expressed as follows:ELR = (EMN + EMF)/EMR
- (3)
- ESI (Emergy Sustainability development Index): Sustainable development requires a high level of beneficial output for a given resource input, while maintaining a low level of environmental stress; therefore, the ESI is the ratio of the EYR to the ELR, expressed as follows:ESI = EYR/ELRESI is used to measure the sustainability of an activity [36]. A higher ESI means that the system is more effective and shows better sustainability under certain conditions.
3. Case Study
3.1. Background
3.2. Principles and Advantages of the Two Wastewater Treatment Processes
3.2.1. ABR + A2/O Process
- (a)
- The anaerobic component of the ABR tank involves a simple, low-investment process that does not require expensive influent systems and complexly designed three-phase separators, nor mechanical mixing devices and additional clarification and sedimentation tanks of conventional anaerobic digesters.
- (b)
- Good biodistribution and biosolid retention capacity with good hydraulic mixing conditions.
- (c)
- No sludge bulking.
- (d)
- A2/O tank with micro-perforated aeration pipe and high oxygen utilization.
- (e)
- The process is mature and reliable, and the treatment effect is stable.
3.2.2. ABR + CASS Process
- (a)
- Aerobic tank part does not require a secondary sedimentation tank or regulating and primary sedimentation tanks, has no secondary sedimentation tank or sludge reflux equipment, has a compact layout of wastewater treatment facilities, and has a relatively small overall area and low investment.
- (b)
- Designed with flow variation in mind, it is flexible in operation and shock resistant, achieving different treatment goals.
- (c)
- The biochemical reaction has a high driving force, good sedimentation effect, a small amount of residual sludge, and a stable nature.
3.3. Results
4. Discussion
5. Conclusions
- (1)
- As an important part of urban infrastructure and a critical link in water pollution control, wastewater treatment is a socially beneficial project, which has significance for developing the national economy and environmental protection and resource reuse. Therefore, when selecting an appropriate wastewater treatment process, its economic benefits and influence on the environment from a sustainable development perspective should be considered.
- (2)
- The emergy method, when used for wastewater treatment process selection, uses a unified standard for measuring various resources and materials for inputs and outputs and can provide a reference for wastewater treatment plants to select a suitable treatment process for themselves by comparing the indicators.
- (3)
- The results indicate that the ABR + A2/O process had higher economic efficiency with the same wastewater treatment capacity; however, the ABR + CASS process was less damaging to the environment, had lower economic input and better sustainability and ecological economy, and more favorable economic policies can make it more widely promoted.
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
References
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Item | Basic Data | Emergy Conversion Rate | Solar Energy | Reference |
---|---|---|---|---|
Solar energy (J) | 3.99 × 1013 | 1 | 3.99 × 1013 | [20] |
Wind energy (J) | 1.25 × 1010 | 6.63 × 102 | 8.29 × 1012 | [20] |
Rainwater chemical energy (J) | 5.13 × 1010 | 1.54 × 104 | 7.90 × 1014 | [20] |
Geothermal energy (J) | 2.15 × 1010 | 2.90 × 104 | 6.24 × 1014 | [20] |
Hydroelectricity (J) | 2.79 × 1012 | 1.29 × 105 | 3.60 × 1017 | [37] |
Labor service (CNY) | 9.46 × 105 | 8.61 × 1011 | 8.15 × 1017 | [28] |
ClO2 (g) | 2.89 × 105 | 6.46 × 1010 | 1.87 × 1016 | Investigation |
Polymeric aluminum chloride (g) | 2.33 × 106 | 1.64 × 109 | 3.81 × 1015 | Investigation |
Phosphide remover (g) | 3.51 × 106 | 8.61 × 108 | 3.02 × 1015 | Investigation |
Flocculant (g) | 1.57 × 106 | 1.21 × 109 | 1.89 × 1015 | Investigation |
Treatment water (g) | 5.96 × 1012 | 6.46 × 105 | 3.85 × 1018 | [38] |
Item | Basic Data | Energy Conversion Rate | Solar Energy | Reference |
---|---|---|---|---|
Solar energy (J) | 3.99 × 1013 | 1 | 3.99 × 1013 | [20] |
Wind energy (J) | 1.25 × 1010 | 6.63 × 102 | 8.29 × 1012 | [20] |
Rainwater chemical energy (J) | 5.13 × 1010 | 1.54 × 104 | 7.90 × 1014 | [20] |
Geothermal energy (J) | 2.15 × 1010 | 2.90 × 104 | 6.24 × 1014 | [20] |
Hydroelectricity (J) | 4.14 × 1012 | 1.29 × 105 | 5.34 × 1017 | [37] |
Labor service (CNY) | 9.46 × 105 | 8.61 × 1011 | 8.15 × 1017 | [28] |
ClO2 (g) | 3.00 × 105 | 6.46 × 1010 | 1.94 × 1016 | Investigation |
Polymeric aluminum chloride (g) | 4.39 × 106 | 1.64 × 109 | 7.19 × 1015 | Investigation |
Phosphide remover (g) | 5.57 × 106 | 8.61 × 108 | 4.80 × 1015 | Investigation |
Flocculant (g) | 4.27 × 105 | 1.21 × 109 | 5.15 × 1014 | Investigation |
Treatment water (g) | 5.96 × 1012 | 6.46 × 105 | 3.85 × 1018 | [38] |
Energy Indicators | ABR + A2/O | ABR + CASS |
---|---|---|
Energy flow | ||
Renewable resource capacity values | 3.61 × 1017 | 5.36 × 1017 |
Non-renewable resource capacity values | 2.74 × 1016 | 3.19 × 1016 |
Purchase of energy | 8.42 × 1017 | 8.46 × 1017 |
Yield value | 3.85 × 1018 | 3.85 × 1018 |
Evaluation indicators | ||
Energy yield ratio | 4.57 | 4.55 |
Environmental load factor | 2.33 | 1.58 |
Indicators of sustainable development in terms of energy | 1.96 | 2.88 |
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Wang, C.; Liu, C.; Si, X.; Zhang, C.; Liu, F.; Yu, L.; Chen, G. Study on the Choice of Wastewater Treatment Process Based on the Emergy Theory. Processes 2021, 9, 1648. https://doi.org/10.3390/pr9091648
Wang C, Liu C, Si X, Zhang C, Liu F, Yu L, Chen G. Study on the Choice of Wastewater Treatment Process Based on the Emergy Theory. Processes. 2021; 9(9):1648. https://doi.org/10.3390/pr9091648
Chicago/Turabian StyleWang, Cui, Changyi Liu, Xiaoxiao Si, Cuixia Zhang, Fan Liu, Li’e Yu, and Guohua Chen. 2021. "Study on the Choice of Wastewater Treatment Process Based on the Emergy Theory" Processes 9, no. 9: 1648. https://doi.org/10.3390/pr9091648