Life cycle assessment of two sewage treatment systems with different external carbon sources

doi:10.19965/j.cnki.iwt.2025-0278

Abstract

Abstract:

In response to China’s “dual carbon” strategic goals, this study compared the different environmental impacts of system 1(S1)—a sewage treatment system using sodium acetate as carbon source, and system 2(S2)—a sewage treatment system using anaerobic fermentation broth from kitchen waste as carbon source, to address the carbon reduction needs of sewage treatment systems. Based on the framework of life cycle assessment, a method of amplifying laboratory scale data was adopted for S2 to improve the life cycle inventory. The analysis of the resource consumption and emission inventory of the two system operation stages showed that S2 was superior to S1 in all environmental impact indicators. Therefore, using food waste acid fermentation broth instead of sodium acetate had certain environmental benefits. Electricity consumption was the main environmental impact factor for both systems, while S2 reduced global warming potential by 18.3% by replacing carbon sources. Sensitivity analysis showed that S1 was sensitive to changes of electricity consumption and photovoltaic ratio, while the transportation distance of food waste and the amount of sodium hydroxide used in S2 had a relatively small impact on the life cycle results of the sewage treatment system. When reducing the use of fermentation broth, the ozone depletion potential and non biological resource depletion potential increased most significantly. It was recommended to optimize data accuracy through pilot or actual engineering trials in the future to improve evaluation reliability.

Key words: life cycle assessment, carbon source, carbon emission reduction, food waste

摘要：

为响应中国“双碳”战略目标，针对污水处理系统碳减排需求，对比了系统1（S1，以乙酸钠为碳源）和系统2（S2，以餐厨垃圾厌氧发酵液为碳源）对环境的不同影响。基于生命周期评价的框架，针对S2采用了放大实验室规模数据的方法完善了生命周期清单，然后对两系统运营阶段的资源消耗与排放清单进行分析。结果表明，S2所有环境影响评价指标均优于S1，因此采用餐厨垃圾产酸发酵液替代乙酸钠具有一定环境效益。电力消耗为两系统主要环境影响因子，但S2通过替代碳源减少了18.3%的全球变暖潜值。敏感性分析显示，S1用电量及光伏比例变化对环境影响敏感；而S2中餐厨垃圾运输距离与氢氧化钠用量对污水处理系统生命周期的环境影响较小；减少发酵液使用量时，臭氧层耗竭潜值和非生物资源耗竭潜值增大最明显。建议未来通过中试或实际工程试验优化数据精度以提升评价可靠性。

关键词: 生命周期评价, 碳源, 碳减排, 餐厨垃圾

CLC Number:

X52
X703

Xinyu LEI, Xizhi GUO, Liang XU, Yajun LIU, Jianying WANG, Yinghui CUI, Quanbao ZHAO. Life cycle assessment of two sewage treatment systems with different external carbon sources[J]. Industrial Water Treatment, 2026, 46(3): 110-118.

雷馨雨, 郭喜志, 许梁, 刘雅君, 王剑英, 崔英辉, 赵全保. 两种不同外加碳源污水处理系统的生命周期评价[J]. 工业水处理, 2026, 46(3): 110-118.

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URL: https://www.iwt.cn/EN/10.19965/j.cnki.iwt.2025-0278

https://www.iwt.cn/EN/Y2026/V46/I3/110

Figures/Tables 12

Fig.1 Flow chart of sewage treatment system of S1（a） and S2（b）

Fig.2 Overview of magnification procedure

Fig.3 Material flow analysis of 300 t food waste anaerobic fermentation

Table 1 Summary of amplification calculation

项目	计算公式	变量
餐厨垃圾		q _{in，餐厨垃圾}=300 t/d
NaOH消耗量		q _in，NaOH=626.84 kg/d
发酵罐加热能耗	$Q r e a c t = Q h e a t + Q l o s s η h e a t$ Q _heat=C _p×m _mix×（T _r-T ₀） Q _loss=A× $k a S$ ×（T _out-T ₀）×t	效率： $η h e a t$ =0.75 比热容：C _p=3 580 J/（kg·K）反应混合物质量：m _mix=1 447 700 kg 反应温度：T _r=308.15 K 起始温度：T ₀=308.15 K 反应器表面积：A=33.04 m² 绝热材料导热系数：k _a=0.042 W/（m·K）绝热材料厚度：S=0.075 m 外部温度：T _out=299.15 K 反应时间：t=86 400 s
发酵罐搅拌能耗	$E s t i r = N p × ρ m i x × N 3 × d 5 × t η s t i r$	叶轮功率数：N _p=3.44 反应混合物密度：ρ _mix=970 kg/m³ 搅拌速度：N=0.125 s^-1 叶轮直径：d=4.22 m 反应时间：t=86 400 s 效率：η _stir=0.9
发酵液离心脱水能耗	E _离心=a×m _干物质	m _干物质=21.46 t 1 t干物质能耗*：a=10 kW·h（取值范围1~10 kW·h/t）
发酵罐泵送能耗（×6）	$E p u m p = n × m × g × ∆ h η p u m p$	传递质量：m=300 000 kg 重力加速度：g=9.81 m/s² 高差：∆h=4.2 m 效率：η _pump=0.75 输送泵数量：n _泵=6
发酵液输送能耗	E _输送=n×t×P	泵数量：n=20 工作时间：t=20 h 泵功率：P=30 kW

Table 1 Summary of amplification calculation

项目	计算公式	变量
餐厨垃圾		q _{in，餐厨垃圾}=300 t/d
NaOH消耗量		q _in，NaOH=626.84 kg/d
发酵罐加热能耗	$Q r e a c t = Q h e a t + Q l o s s η h e a t$ Q _heat=C _p×m _mix×（T _r-T ₀） Q _loss=A× $k a S$ ×（T _out-T ₀）×t	效率： $η h e a t$ =0.75 比热容：C _p=3 580 J/（kg·K）反应混合物质量：m _mix=1 447 700 kg 反应温度：T _r=308.15 K 起始温度：T ₀=308.15 K 反应器表面积：A=33.04 m² 绝热材料导热系数：k _a=0.042 W/（m·K）绝热材料厚度：S=0.075 m 外部温度：T _out=299.15 K 反应时间：t=86 400 s
发酵罐搅拌能耗	$E s t i r = N p × ρ m i x × N 3 × d 5 × t η s t i r$	叶轮功率数：N _p=3.44 反应混合物密度：ρ _mix=970 kg/m³ 搅拌速度：N=0.125 s^-1 叶轮直径：d=4.22 m 反应时间：t=86 400 s 效率：η _stir=0.9
发酵液离心脱水能耗	E _离心=a×m _干物质	m _干物质=21.46 t 1 t干物质能耗*：a=10 kW·h（取值范围1~10 kW·h/t）
发酵罐泵送能耗（×6）	$E p u m p = n × m × g × ∆ h η p u m p$	传递质量：m=300 000 kg 重力加速度：g=9.81 m/s² 高差：∆h=4.2 m 效率：η _pump=0.75 输送泵数量：n _泵=6
发酵液输送能耗	E _输送=n×t×P	泵数量：n=20 工作时间：t=20 h 泵功率：P=30 kW

Table 2 Data list of two sewage treatment systems

单元名称	物质	输入		输出
单元名称	物质	S1	S2	S1	S2
预处理	电力/（kW·h）	21 672	21 672
	栅渣/m³			300	300
	进水水量/t	300 000	300 000
生物处理	电力/（kW·h）	55 764	55 764
	聚铝/t	29.98	29.98
	乙酸钠/t	69.107 1
深度处理	电力/（kW·h）	22 578	22 578
	聚铝/t	7.33	7.33
	聚丙烯酰胺/t	0.19	0.19
	次氯酸钠/t	16.87	16.87
	乙酸钠/t	5.66
污泥处理	电力/（kW·h）	18 988.4	18 988.4
	石灰/t	1.46	1.46
	三氯化铁/t	0.99	0.99
	聚丙烯酰胺/t	0.20	0.20
	污泥/t			207.58	207.58
	污泥平均运输距离/km	35	35
排海除臭	电力/（kW·h）	52 224	52 224
排海除臭	出水水量/t			299 624.22	299 729.01
发酵液生产	电力/（kW·h）		9 599.98
	餐厨垃圾/t		159.37
	餐厨垃圾平均运输距离/km		62
	废油/t		10.68
	氢氧化钠/kg		332.996
	氯化钠/kg		0.64
	水/m³		202.93
	蒸汽/m³		6 086.30
	发酵液/t				179.55
	粗油脂/t				10.04
	CO₂/kg				461.46
	CH₄/kg				93.52
	H₂/kg				0.67
	惰性杂质/t				12.75
	污泥/t				8.89
污染物质量	COD/t	59.875	59.875	9.825	9.825
	SS/t	31.075	31.075	1.725	1.725
	BOD/t	19.078	19.078	0.752	0.752
	NH₃-N/t	6.587	6.587	0.074	0.074
	TP/t	1.124	1.124	0.079	0.079
	TN/t	8.648	8.648	3.385	3.385
其他污染物排放	CH₄（污水处理）/t			1.251	1.251
其他污染物排放	N₂O（污水处理）/t			0.228	0.228

Fig.4 Comparison of characterization results of environmental impact between the two systems

Fig.5 Comparison of standardized results of environmental impact assessment indicators between the two systems

Fig.6 Proportion of GWP contribution factors of the two systems

Fig.7 Proportion of MAETP contribution factors of the two systems

Fig.8 Sensitivity of electricity consumption （a） and photovoltaic power generation ratio （b） to each environmental impact indicator in the life cycle of S1

Fig.9 Sensitivity of transportation distance of food waste（a） and consumption of sodium hydroxide（b） to each environmental impact indicator in the life cycle of S2

Fig.10 Sensitivity of proportion of food waste fermentation broth to each environmental impact indicator

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